The primary feature of this release is that it supports the latest astroscrappy release. astroscrappy is a Python/C implementation of the LAcosmic cosmic ray removal algorithm.
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Years: 2021 BottomThe primary feature of this release is that it supports the latest astroscrappy release. astroscrappy is a Python/C implementation of the LAcosmic cosmic ray removal algorithm.
The Lucy mission will embark on an exploration of the Trojan asteroids with its launch in October 2021 from Cape Canaveral. Over the course of 12 years, the Lucy mission will conduct 3 Earth Gravity Assists, 1 Main Belt Asteroid flyby, and 5 of 7 different Trojan asteroids in both the L4 and L5 Lagrange point regions at Jupiter's orbital distance. The Lucy mission includes at least two flybys of binary systems. The first of these binary systems is the largest asteroid of a collisional family, Eurybates, and its recently discovered small satellite, Queta. The second is the near equal size binary system Patroclus and Menoetius, two of the largest Trojan asteroids. Lucy will fly past objects ranging in size from approximately 1 to 100 km with colors that represent both the red and less red color populations and spectral types representing the range of visible to near-IR color diversity identified in the Trojan swarms (C-, D- and P-types). The Lucy spacecraft has three scientific instruments on a 2-axis gimbaled instrument pointing platform. These instruments include a high-resolution panchromatic imager (LLORRI), a thermal emission spectrometer (LTES), and one instrument that is a combination color camera and short wave-infrared imaging spectrometer (LRalph). Additionally, two spacecraft components will contribute to the scientific return of the mission: the terminal tracking cameras which will provide wide field of view imaging, photometry, and shape model constraints for the Trojans and the telecommunication system which provides a radio science experiment to determine the mass of the Trojan asteroids, respectively. Strawman encounter scenarios will be presented.
Sputnik Planitia, Plutos gigantic, volatile ice glacier, hosts numerous scientific mysteries, including the presence of thousands of elongated pit structures. We examine various attributes of these pit structures in New Horizons datasets, revealing their length, aspect ratio, and orientation properties; we also study their reflectivities, colors, and compositions, and compare these attributes to some other relevant regions on Pluto. We then comment on origin mechanisms of the pits and also the fate of the missing volatiles represented by the pits on Sputnik Planitia. From a sample of 317 pits, we find typical length/width ratios of 2-4, with their major axis preferentially oriented approximately north-south. We also find that the floors of large pits in our sample have similar single scattering albedos and colors to dark material on crater rims and floors (i.e., possible subsurface windows) in Burney basin. We also find that the base of the three pits in our sample, large enough to study with LEISA IR spectroscopy, display both CH4 and N2 absorption features, as do the dark regions in crater windows in Burney basin. Evidence for a sublimation erosion origin for the pits is supported over both the explosion/ejecta venting and structural collapse alternatives. Finally, we find that the mass lost by the pits on Sputnik Planitia most likely lies condensed elsewhere, on Plutos surface, relocated there by volatile transport as opposed to removal by escape to space or photochemical conversion.
The journey of the New Horizons spacecraft through the solar system has afforded multiple opportunities to measure the structure of the solar plasma along the radio path from earth to the spacecraft. At a cadence of approximately once per month, when the spacecraft was not in hibernation, powerful, unmodulated microwaves were transmitted from Earth to New Horizons at a wavelength of 4.2 cm, and a frequency stability to a few parts in 1014th. The received waveforms were recorded on the spacecraft by the Radio-science EXperiment (REX) as in-phase and quadrature, narrowband samples using a frequency reference with stability of a few parts in 1013th. This process resulted in 38 individual observations of the microwave radio path during the extended mission after the Pluto Encounter. The recorded waveforms exhibit effects of multipath interference. Treating the recorded signal as the result of a superposition of EM waves propagating in low density plasma, the electron density along the radio path is obtained via a novel method exploiting the properties of superposition. This method is validated by propagating 4.2 cm microwaves from earth to the outer solar system along radial paths using plasma densities obtained from high fidelity models of the solar wind. Examples from these observations have successfully identified structure in the solar plasma both in the inner solar system as well as the outer solar system.
Stellar streams are excellent probes of the underlying gravitational potential in which they evolve. In this work, we fit dynamical models to five streams in the Southern Galactic hemisphere, combining observations from the Southern Stellar Stream Spectroscopic Survey (S 5), Gaia EDR3, and the Dark Energy Survey, to measure the mass of the Large Magellanic Cloud (LMC). With an ensemble of streams, we find a mass of the LMC ranging from ~14-19 1010 M , probed over a range of closest approach times and distances. With the most constraining stream (Orphan-Chenab), we measure an LMC mass of ${18.8}_{-4.0}^{+3.5}\times {10}^{10}\,{M}_{\odot }$ , probed at a closest approach time of 310 Myr and a closest approach distance of 25.4 kpc. This mass is compatible with previous measurements, showing that a consistent picture is emerging of the LMC's influence on structures in the Milky Way. Using this sample of streams, we find that the LMC's effect depends on the relative orientation of the stream and LMC at their point of closest approach. To better understand this, we present a simple model based on the impulse approximation and we show that the LMC's effect depends both on the magnitude of the velocity kick imparted to the stream and the direction of this kick.
Aims: Very small asteroids (VSAs, objects with diameters smaller than about 150 m) can be spun up by the YORP effect to rotation periods as short as tens of seconds. This effect has been observed for many of them. It is also hypothesised, that in the same process their spin axes are asymptotically drawn to the position perpendicular to the orbital plane. So far this effect has been observed only for one VSA and needs further verification. For that, spin axes of several other VSAs should be determined by observing their brightness variations at many different positions on the sky.
Methods: On 4 March 2021 at 9 UTC a 30-m in diameter near-Earth asteroid 2021 DW1 passed the Earth at a distance of 570 000 km, reaching the maximum brightness of V = 14.6 mag. We observed it photometrically from 2 March, when it was visible at V = 16.5 mag, until 7 March (V = 18.2 mag). During that time 2021 DW1 swept a 170 long arc in the northern sky, spanning solar phase angles in the range from 36 to 86. This made it an excellent target for physical characterisation, including spin axis and shape derivation.
Results: Convex inversion of the asteroid lightcurves gives a sidereal period of rotation Psid = 0.013760 0.000001 h, and two solutions for the spin axis ecliptic coordinates: (A) 1 = 57 10, 1 = 29 10 and (B) 2 = 67 10, 2 = 40 10. The magnitude-phase curve can be fitted with a standard H, G function with H = 24.8 0.5 mag and an assumed G = 0.24. The asteroid colour indices are g i = 0.79 0.01 mag, and i z = 0.01 0.02 mag which indicates an S taxonomic class, with an average geometric albedo pV = 0.23 0.02. The asteroid effective diameter, derived from H and pV, is Deff = 30 10 m.
Conclusions: It was found that the inclination of the spin axis of 2021 DW1 is not perpendicular to the orbital plane (obliquity = 54 10 or = 123 10). More spin axes of VSAs should be determined to check, if 2021 DW1 is an exception or a typical case.
Context. The ESA JUICE space mission, on its way to study Jupiter's environment and icy moons, will pass twice through the main asteroid belt. For this reason, the possibility to perform an asteroid flyby has been investigated.
Aims: We aim to gain insight into the physical properties of the outer main belt asteroid (223) Rosa, which has been proposed as a potential JUICE flyby target.
Methods: We report new visible and near-infrared spectroscopic observations at different rotation phases. Additionally, we perform a literature review of all the available physical properties, such as diameter, albedo, mass, and rotational period.
Results: We find that asteroid Rosa is an X-type asteroid that shows no significant spectral variability combining the new and literature spectroscopic data. Its large size and orbital semimajor axis in the outer main belt indicate that Rosa does not belong to the Themis family, while its albedo is only marginally compatible with the family. Rosa's estimated density is in agreement with those of other low-albedo X-type asteroids. Hence, we propose that Rosa is a planetesimal that accreted in the protoplanetary disk beyond the snow line.
We present a serendipitous discovery of a new stellar companion to TYC 5493-889-1 detected with the Differential Speckle Survey Instrument at the 4.3 m Lowell Discovery Telescope. We also present photometric observations of TYC 5493-889-1, and determine a spectral type of F1V and a photometric distance of roughly 320 parsecs.
The calibration and validation of scientific analysis in simulations is a fundamental tool to ensure unbiased and robust results in observational cosmology. In particular, mock galaxy catalogs are a crucial resource to achieve these goals in the measurement of baryon acoustic oscillation (BAO) in the clustering of galaxies. Here we present a set of 1952 galaxy mock catalogs designed to mimic the Dark Energy Survey Year 3 BAO sample over its full photometric redshift range 0.6 < zphoto < 1.1. The mocks are based upon 488 ICE-COLA fast N-body simulations of full-sky light cones and were created by populating halos with galaxies, using a hybrid halo occupation distribution - halo abundance matching model. This model has ten free parameters, which were determined, for the first time, using an automatic likelihood minimization procedure. We also introduced a novel technique to assign photometric redshift for simulated galaxies, following a two-dimensional probability distribution with VIMOS Public Extragalactic Redshift Survey data. The calibration was designed to match the observed abundance of galaxies as a function of photometric redshift, the distribution of photometric redshift errors, and the clustering amplitude on scales smaller than those used for BAO measurements. An exhaustive analysis was done to ensure that the mocks reproduce the input properties. Finally, mocks were tested by comparing the angular correlation function w(), angular power spectrum C, and projected clustering p(r) to theoretical predictions and data. The impact of volume replication in the estimate of the covariance is also investigated. The success in accurately reproducing the photometric redshift uncertainties and the galaxy clustering as a function of redshift render this mock creation pipeline as a benchmark for future analyses of photometric galaxy surveys.
We identify hierarchical structures in the Vela OB2 complex and the cluster pair Collinder 135 and UBC 7 with Gaia EDR3 using the neural network machine-learning algorithm StarGO. Five second-level substructures are disentangled in Vela OB2, which are referred to as Huluwa 1 (Gamma Velorum), Huluwa 2, Huluwa 3, Huluwa 4, and Huluwa 5. For the first time, Collinder 135 and UBC 7 are simultaneously identified as constituent clusters of the pair with minimal manual intervention. We propose an alternative scenario in which Huluwa 1-5 have originated from sequential star formation. The older clusters Huluwa 1-3, with an age of 10-22 Myr, generated stellar feedback to cause turbulence that fostered the formation of the younger-generation Huluwa 4-5 (7-20 Myr). A supernova explosion located inside the Vela IRAS shell quenched star formation in Huluwa 4-5 and rapidly expelled the remaining gas from the clusters. This resulted in global mass stratification across the shell, which is confirmed by the regression discontinuity method. The stellar mass in the lower rim of the shell is 0.32 0.14 M higher than in the upper rim. Local, cluster-scale mass segregation is observed in the lowest-mass cluster Huluwa 5. Huluwa 1-5 (in Vela OB2) are experiencing significant expansion, while the cluster pair suffers from moderate expansion. The velocity dispersions suggest that all five groups (including Huluwa 1A and Huluwa 1B) in Vela OB2 and the cluster pair are supervirial and are undergoing disruption, and also that Huluwa 1A and Huluwa 1B may be a coeval young cluster pair. N-body simulations predict that Huluwa 1-5 in Vela OB2 and the cluster pair will continue to expand in the future 100 Myr and eventually dissolve.
We measure the projected number density profiles of galaxies and the splashback feature in clusters selected by the Sunyaev-Zel'dovich effect from the Advanced Atacama Cosmology Telescope (AdvACT) survey using galaxies observed by the Dark Energy Survey (DES). The splashback radius is consistent with CDM-only simulations and is located at ${2.4}_{-0.4}^{+0.3}\,\mathrm{Mpc}\,{h}^{-1}$ . We split the galaxies on color and find significant differences in their profile shapes. Red and green-valley galaxies show a splashback-like minimum in their slope profile consistent with theory, while the bluest galaxies show a weak feature at a smaller radius. We develop a mapping of galaxies to subhalos in simulations and assign colors based on infall time onto their hosts. We find that the shift in location of the steepest slope and different profile shapes can be mapped to the average time of infall of galaxies of different colors. The steepest slope traces a discontinuity in the phase space of dark matter halos. By relating spatial profiles to infall time, we can use splashback as a clock to understand galaxy quenching. We find that red galaxies have on average been in clusters over 3.2 Gyr, green galaxies about 2.2 Gyr, while blue galaxies have been accreted most recently and have not reached apocenter. Using the full radial profiles, we fit a simple quenching model and find that the onset of galaxy quenching occurs after a delay of about a gigayear and that galaxies quench rapidly thereafter with an exponential timescale of 0.6 Gyr.
We calculate directly determined values for effective temperature (T eff) and radius (R) for 191 giant stars based upon high-resolution angular size measurements from optical interferometry at the Palomar Testbed Interferometer. Narrow- to wideband photometry data for the giants are used to establish bolometric fluxes and luminosities through spectral energy distribution fitting, which allows for homogeneously establishing an assessment of spectral type and dereddened V 0 - K 0 color; these two parameters are used as calibration indices for establishing trends in T eff and R. Spectral types range from G0III to M7.75III, V 0 - K 0 from 1.9 to 8.5. For the V 0 - K 0 = {1.9, 6.5} range, median T eff uncertainties in the fit of effective temperature versus color are found to be less than 50 K; over this range, T eff drops from 5050 to 3225 K. Linear sizes are found to be largely constant at 11 R from G0III to K0III, increasing linearly with subtype to 50 R at K5III, and then further increasing linearly to 150 R by M8III. Three examples of the utility of this data set are presented: first, a fully empirical Hertzsprung-Russell diagram is constructed and examined against stellar evolution models; second, values for stellar mass are inferred based on measures of R and literature values for $\mathrm{log}g> ; finally, an improved calibration of an angular size prediction tool, based upon V and K values for a star, is presented.
Despite the many successes that modern massive star evolutionary theory has enjoyed, reproducing the apparent trend in the relative number of red supergiants (RSGs) and Wolf-Rayet (WR) stars has remained elusive. Previous estimates show the RSG/WR ratio decreasing strongly with increasing metallicity. However, the evolutionary models have always predicted a relatively flat distribution for the RSG/WR ratio. In this paper we reexamine this issue, drawing on recent surveys for RSGs and WRs in the Magellanic Clouds, M31, and M33. The RSG surveys have used Gaia astrometry to eliminate foreground contamination and have separated RSGs from asymptotic giant branch stars using near-infrared colors. The surveys for WRs have utilized interference-filter imaging, photometry, and image subtraction techniques to identify candidates, which have then been confirmed spectroscopically. After carefully matching the observational criteria to the models, we now find good agreement in both the single-star Geneva and binary BPASS models with the new observations. The agreement is better when we shift the RSG effective temperatures derived from J - Ks photometry downwards by 200 K in order to agree with the Levesque TiO effective temperature scale. In an appendix we also present a source list of RSGs for the SMC which includes effective temperatures and luminosities derived from near-infrared 2MASS photometry, in the same manner as used for the other galaxies.
Little is known about Earth quasi-satellites, a class of near-Earth small solar system bodies that orbit the sun but remain close to the Earth, because they are faint and difficult to observe. Here we use the Large Binocular Telescope (LBT) and the Lowell Discovery Telescope (LDT) to conduct a comprehensive physical characterization of quasi-satellite (469219) Kamooalewa and assess its affinity with other groups of near-Earth objects. We find that (469219) Kamooalewa rotates with a period of 28.3 (+1.8/1.3) minutes and displays a reddened reflectance spectrum from 0.4-2.2 microns. This spectrum is indicative of a silicate-based composition, but with reddening beyond what is typically seen amongst asteroids in the inner solar system. We compare the spectrum to those of several material analogs and conclude that the best match is with lunar-like silicates. This interpretation implies extensive space weathering and raises the prospect that Kamo'oalewa could comprise lunar material.
We describe and test the fiducial covariance matrix model for the combined two-point function analysis of the Dark Energy Survey Year 3 (DES-Y3) data set. Using a variety of new ansatzes for covariance modelling and testing, we validate the assumptions and approximations of this model. These include the assumption of Gaussian likelihood, the trispectrum contribution to the covariance, the impact of evaluating the model at a wrong set of parameters, the impact of masking and survey geometry, deviations from Poissonian shot noise, galaxy weighting schemes, and other sub-dominant effects. We find that our covariance model is robust and that its approximations have little impact on goodness of fit and parameter estimation. The largest impact on best-fitting figure-of-merit arises from the so-called fsky approximation for dealing with finite survey area, which on average increases the 2 between maximum posterior model and measurement by $3.7{{\ \rm per\ cent}}$ (2 18.9). Standard methods to go beyond this approximation fail for DES-Y3, but we derive an approximate scheme to deal with these features. For parameter estimation, our ignorance of the exact parameters at which to evaluate our covariance model causes the dominant effect. We find that it increases the scatter of maximum posterior values for m and 8 by about $3{{\ \rm per\ cent}}$ and for the dark energy equation-of-state parameter by about $5{{\ \rm per\ cent}}$.
We present a comprehensive study of the massive binary system HM1 8, based on multi-epoch high-resolution spectroscopy, V-band photometry, and archival X-ray data. Spectra from the OWN Survey, a high-resolution optical monitoring of Southern O and WN stars, are used to analyse the spectral morphology and perform quantitative spectroscopic analysis of both stellar components. The primary and secondary components are classified as O4.5 IV(f) and O9.7 V, respectively. From a radial velocity (RV) study, we derived a set of orbital parameters for the system. We found an eccentric orbit (e = 0.14 0.01) with a period of P = 5.87820 0.00008 d. Through the simultaneous analysis of the RVs and the V-band light curve, we derived an orbital inclination of 70.0 2.0 and stellar masses of $M_a=33.6^{+1.4}_{-1.2}~\text{M}_{\odot }$ for the primary, and $M_b=17.7^{+0.5}_{-0.7}~\text{M}_{\odot }$ for the secondary. The components show projected rotational velocities vasin i = 105 14 km s-1 and vbsin i = 82 15 km s-1, respectively. A tidal evolution analysis is also performed and found to be in agreement with the orbital characteristics. Finally, the available X-ray observations show no evidence of a colliding winds region; therefore, the X-ray emission is attributed to stellar winds.
Brown dwarfs are essential targets for understanding planetary and sub-stellar atmospheres across a wide range of thermal and chemical conditions. As surveys continue to probe ever deeper and as observing capabilities continue to improve, the number of known Y dwarfs-the coldest class of sub-stellar objects, with effective temperatures below about 600 K-is rapidly growing. Critically, this class of ultra-cool objects has atmospheric conditions that overlap with solar-system worlds and, as a result, tools and ideas developed from studying Earth, Jupiter, Saturn, and other nearby worlds are well suited for application to sub-stellar atmospheres. To that end, we developed a one-dimensional (vertical) atmospheric structure model for ultra-cool objects that includes moist adiabatic convection, as this is an important process for many solar-system planets. Application of this model across a range of effective temperatures (350, 300, 250, 200 K), metallicities ([M/H] of 0.0, 0.5, 0.7, 1.5), and gravities (log g of 4.0, 4.5, 4.7, 5.0) demonstrates strong impact of water-latent heat release on simulated temperature-pressure profiles. At the highest metallicities, water-vapor mixing ratios reach an Earth-like 3% with associated major alterations to the thermal structure in the atmospheric regions where water condenses. Spectroscopic and photometric signatures of metallicity and moist convection should be readily detectable at near- and mid-infrared wavelengths, especially with James Webb Space Telescope observations, and can help indicate the formation history of an object.
We report results from new and archival observations of the newly discovered active asteroid (248370) 2005 QN173 (also now designated Comet 433P), which has been determined to be a likely main-belt comet based on a subsequent discovery that it is recurrently active near perihelion. From archival data analysis, we estimate $g^{\prime} $ -, $r^{\prime} $ -, $i^{\prime} $ -, and $z^{\prime} $ -band absolute magnitudes for the nucleus of Hg = 16.62 0.13, Hr = 16.12 0.10, Hi = 16.05 0.11, and Hz = 15.93 0.08, corresponding to nucleus colors of $g^{\prime} -r^{\prime} =0.50\pm 0.16$ , $r^{\prime} -i^{\prime} =0.07\pm 0.15$ , and $i^{\prime} -z^{\prime} =0.12\pm 0.14$ ; an equivalent V-band absolute magnitude of HV = 16.32 0.08; and a nucleus radius of rn = 1.6 0.2 km (using a V-band albedo of pV = 0.054 0.012). Meanwhile, we find mean near-nucleus coma colors when 248370 is active of $g^{\prime} -r^{\prime} =0.47\pm 0.03$ , $r^{\prime} -i^{\prime} =0.10\pm 0.04$ , and $i^{\prime} -z^{\prime} =0.05\pm 0.05$ and similar mean dust tail colors, suggesting that no significant gas coma is present. We find approximate ratios between the scattering cross sections of near-nucleus dust (within 5000 km of the nucleus) and the nucleus of Ad/An = 0.7 0.3 on 2016 July 22 and 1.8 < Ad/An < 2.9 in 2021 July and August. During the 2021 observation period, the coma declined in intrinsic brightness by ~0.35 mag (or ~25%) in 37 days, while the surface brightness of the dust tail remained effectively constant over the same period. Constraints derived from the sunward extent of the coma and width of the tail as measured perpendicular to the orbit plane suggest that the terminal velocities of ejected dust grains are extremely slow (~1 m s-1 for 1 m particles), suggesting that the observed dust emission may be aided by rapid rotation of the nucleus lowering the effective escape velocity.
Comet C/2014 UN271 (Bernardinelli-Bernstein), incoming from the Oort cloud, is remarkable in having the brightest (and presumably largest) nucleus of any well-measured comet and having been discovered at the heliocentric distance rh 29 au, farther than any Oort cloud comet. In this work, we describe the discovery process and observations and the properties that can be inferred from images recorded until the first reports of activity in 2021 June. The orbit has i = 95, with a perihelion of 10.97 au to be reached in 2031 and a previous aphelion at 40,400 260 au. Backward integration of the orbit under a standard Galactic tidal model and known stellar encounters suggests a perihelion of q 18 au on its previous perihelion passage 3.5 Myr ago; hence, the current data could be the first ever obtained of a comet that has not been inside Uranus's orbit in 4 Gyr. The photometric data show an unresolved nucleus with absolute magnitude Hr = 8.0, colors that are typical of comet nuclei or Damocloids, and no secular trend as it traversed the range 34-23 au. For the r-band geometric albedo pr, this implies a diameter of $150{({p}_{r}/0.04)}^{-0.5}$ km. There is strong evidence of brightness fluctuations at the 0.2 mag level, but no rotation period can be discerned. A coma, nominally consistent with a "stationary" 1/ surface brightness distribution, grew in scattering cross section at an exponential rate from Af 1 to 150 m as the comet approached from 28 to 20 au. The activity rate is consistent with a very simple model of sublimation of a surface species in radiative equilibrium with the Sun. The inferred enthalpy of sublimation matches those of CO2 and NH3. More volatile species, such as N2, CH4, and CO, must be far less abundant on the sublimating surfaces.
We present fundamental parameters for 110 canonical K- and M-type (1.3-0.13 M) Taurus-Auriga young stellar objects (YSOs). The analysis produces a simultaneous determination of effective temperature (Teff), surface gravity (log g), magnetic-field strength (B), and projected rotational velocity ( $v\sin i$ ). Our method employed synthetic spectra and high-resolution (R ~ 45,000) near-infrared spectra taken with the Immersion GRating INfrared Spectrometer (IGRINS) to fit specific K-band spectral regions most sensitive to those parameters. The use of these high-resolution spectra reduces the influence of distance uncertainties, reddening, and non-photospheric continuum emission on the parameter determinations. The median total (fit + systematic) uncertainties were 170 K, 0.28 dex, 0.60 kG, 2.5 km s-1 for Teff, log g, B, and $v\sin i$ , respectively. We determined B for 41 Taurus YSOs (upper limits for the remainder) and find systematic offsets (lower Teff, higher log g and $v\sin i$ ) in parameters when B is measurable but not considered in the fit. The average log g for the Class II and Class III objects differs by 0.23 0.05 dex, which is consistent with Class III objects being the more evolved members of the star-forming region. However, the dispersion in log g is greater than the uncertainties, which highlights how the YSO classification correlates with age (log g), yet there are exceptionally young (lower log g) Class III YSOs and relatively old (higher log g) Class II YSOs with unexplained evolutionary histories. The spectra from this work are provided in an online repository along with TW Hydrae Association comparison objects and the model grid used in our analysis.
The Phoenix stellar stream has a low intrinsic dispersion in velocity and metallicity that implies the progenitor was probably a low-mass globular cluster. In this work we use Magellan/Magellan Inamori Kyocera Echelle (MIKE) high-dispersion spectroscopy of eight Phoenix stream red giants to confirm this scenario. In particular, we find negligible intrinsic scatter in metallicity ( $\sigma ([\mathrm{Fe}\,{\rm\small{II}}/{\rm{H}}])={0.04}_{-0.03}^{+0.11}$ ) and a large peak-to-peak range in [Na/Fe] and [Al/Fe] abundance ratios, consistent with the light element abundance patterns seen in the most metal-poor globular clusters. However, unlike any other globular cluster, we also find an intrinsic spread in [Sr II/Fe] spanning ~1 dex, while [Ba II/Fe] shows nearly no intrinsic spread ( $\sigma ([\mathrm{Ba}\,{\rm\small{II}}/{\rm{H}}])={0.03}_{-0.02}^{+0.10}$ ). This abundance signature is best interpreted as slow-neutron-capture element production from a massive fast-rotating metal-poor star (15-20 M, vini/vcrit = 0.4, [Fe/H] = -3.8). The low inferred cluster mass suggests the system would have been unable to retain supernovae ejecta, implying that any massive fast-rotating metal-poor star that enriched the interstellar medium must have formed and evolved before the globular cluster formed. Neutron-capture element production from asymptotic giant branch stars or magneto-rotational instabilities in core-collapse supernovae provide poor fits to the observations. We also report one Phoenix stream star to be a lithium-rich giant (A(Li) = 3.1 0.1). At [Fe/H ] = -2.93; it is among the most metal-poor lithium-rich giants known. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.
We present new spectroscopic observations of the diffuse Milky Way satellite galaxies Antlia 2 and Crater 2, taken as part of the Southern Stellar Stream Spectroscopic Survey (S5). The new observations approximately double the number of confirmed member stars in each galaxy and more than double the spatial extent of spectroscopic observations in Antlia 2. A full kinematic analysis, including Gaia EDR3 proper motions, detects a clear velocity gradient in Antlia 2 and a tentative velocity gradient in Crater 2. The velocity gradient magnitudes and directions are consistent with particle stream simulations of tidal disruption. Furthermore, the orbit and kinematics of Antlia 2 require a model that includes the reflex motion of the Milky Way induced by the Large Magellanic Cloud. We also find that Antlia 2's metallicity was previously overestimated, so it lies on the empirical luminosity-metallicity relation and is likely only now experiencing substantial stellar mass loss. Current dynamical models of Antlia 2 require it to have lost over 90% of its stars to tides, in tension with the low stellar mass loss implied by the updated metallicity. Overall, the new kinematic measurements support a tidal disruption scenario for the origin of these large and extended dwarf spheroidal galaxies.
We measured the angular diameters of 44 stars with the Navy Precision Optical Interferometer, obtaining uncertainties on the limb-darkened diameter of 2% or less for all but four stars. We then used our diameters with Gaia or Hipparcos parallaxes to calculate each star's physical radius. We gathered information from the literature to determine bolometric flux and luminosity, and combined that with our diameters to produce an effective temperature. Our sample consists of mostly giant stars, and spans a wide range of spectral classes from B to M.
Sputnik Planitia, Pluto's gigantic, volatile ice glacier, hosts numerous scientific mysteries, including the presence of thousands of elongated pit structures. We examine various attributes of these pit structures in New Horizons data sets, revealing their length, aspect ratio, and orientation properties; we also study their reflectivities, colors, and compositions, and compare these attributes to some other relevant regions on Pluto. We then comment on origin mechanisms of the pits and also the fate of the missing volatiles represented by the pits on Sputnik Planitia. From a sample of 317 pits, we find typical length/width ratios of 2-4, with their major axis preferentially oriented approximately north-south. We also find that the floors of large pits in our sample have similar single-scattering albedos and colors to dark material on crater rims and floors (i.e., possible subsurface windows) in Burney basin. We also find that the base of the three pits in our sample, large enough to study with LEISA IR spectroscopy, display both CH4 and N2 absorption features, as do the dark regions in crater windows in Burney basin. Evidence for a sublimation erosion origin for the pits is supported over both the explosion/ejecta venting and structural collapse alternatives. Finally, we find that the mass lost by the pits on Sputnik Planitia most likely lies condensed elsewhere, on Pluto's surface, relocated there by volatile transport as opposed to removal by escape to space or photochemical conversion.
We present measurements of the radial profiles of the mass and galaxy number density around Sunyaev-Zel'dovich (SZ)-selected clusters using both weak lensing and galaxy counts. The clusters are selected from the Atacama Cosmology Telescope Data Release 5 and the galaxies from the Dark Energy Survey Year 3 data set. With signal-to-noise ratio of 62 (45) for galaxy (weak lensing) profiles over scales of about 0.2-20 h-1 Mpc, these are the highest precision measurements for SZ-selected clusters to date. Because SZ selection closely approximates mass selection, these measurements enable several tests of theoretical models of the mass and light distribution around clusters. Our main findings are: (1) The splashback feature is detected at a consistent location in both the mass and galaxy profiles and its location is consistent with predictions of cold dark matter N-body simulations. (2) The full mass profile is also consistent with the simulations. (3) The shapes of the galaxy and lensing profiles are remarkably similar for our sample over the entire range of scales, from well inside the cluster halo to the quasilinear regime. We measure the dependence of the profile shapes on the galaxy sample, redshift, and cluster mass. We extend the Diemer & Kravtsov model for the cluster profiles to the linear regime using perturbation theory and show that it provides a good match to the measured profiles. We also compare the measured profiles to predictions of the standard halo model and simulations that include hydrodynamics. Applications of these results to cluster mass estimation, cosmology, and astrophysics are discussed.
We present in this paper one of the largest galaxy morphological classification catalogues to date, including over 20 million galaxies, using the Dark Energy Survey (DES) Year 3 data based on convolutional neural networks (CNNs). Monochromatic i-band DES images with linear, logarithmic, and gradient scales, matched with debiased visual classifications from the Galaxy Zoo 1 (GZ1) catalogue, are used to train our CNN models. With a training set including bright galaxies (16 i < 18) at low redshift (z < 0.25), we furthermore investigate the limit of the accuracy of our predictions applied to galaxies at fainter magnitude and at higher redshifts. Our final catalogue covers magnitudes 16 i < 21, and redshifts z < 1.0, and provides predicted probabilities to two galaxy types - ellipticals and spirals (disc galaxies). Our CNN classifications reveal an accuracy of over 99 per cent for bright galaxies when comparing with the GZ1 classifications (i < 18). For fainter galaxies, the visual classification carried out by three of the co-authors shows that the CNN classifier correctly categorizes discy galaxies with rounder and blurred features, which humans often incorrectly visually classify as ellipticals. As a part of the validation, we carry out one of the largest examinations of non-parametric methods, including ~100 ,000 galaxies with the same coverage of magnitude and redshift as the training set from our catalogue. We find that the Gini coefficient is the best single parameter discriminator between ellipticals and spirals for this data set.
Reverberation mapping is a robust method to measure the masses of supermassive black holes outside of the local Universe. Measurements of the radius-luminosity (R-L) relation using the Mg II emission line are critical for determining these masses near the peak of quasar activity at z 1-2, and for calibrating secondary mass estimators based on Mg II that can be applied to large samples with only single-epoch spectroscopy. We present the first nine Mg II lags from our 5-yr Australian Dark Energy Survey reverberation mapping programme, which substantially improves the number and quality of Mg II lag measurements. As the Mg II feature is somewhat blended with iron emission, we model and subtract both the continuum and iron contamination from the multiepoch spectra before analysing the Mg II line. We also develop a new method of quantifying correlated spectroscopic calibration errors based on our numerous, contemporaneous observations of F-stars. The lag measurements for seven of our nine sources are consistent with both the H and Mg II R-L relations reported by previous studies. Our simulations verify the lag reliability of our nine measurements, and we estimate that the median false positive rate of the lag measurements is $4{{\ \rm per\ cent}}$.
We present the identification of 34 likely binary central stars (CSs) of planetary nebulae (PNe) from Kepler/K2 data, seven of which show eclipses. Of these, 29 are new discoveries. Two additional CSs with more complicated variability are also presented. We examined the light curves of all 'possible', 'likely', and 'true' PNe in every Kepler/K2 campaign (0 through 19) to identify CS variability that may indicate a binary CS. For Campaigns 0, 2, 7, 15, and 16, we find 6 likely or confirmed variables among 21 PNe. Our primary effort, though, was focused on Campaign 11 which targeted a Galactic bulge field containing approximately 183 PNe, in which we identified 30 candidate variable CSs. The periods of these variables range from 2.3 h to 30 d, and based on our analysis, most are likely to be close binary star systems. We present periods and preliminary classifications (eclipsing, double degenerate, or irradiated systems) for the likely binaries based on light-curve shape. From our total sample of 204 target PNe, with a correction for incompleteness due to magnitude limits, we calculate a binary fraction of PN central stars to be 20.7 per cent for all the observed PNe, or 23.5 per cent if we limit our sample only to 'true' PNe. However, these fractions are almost certainly lower limits due to the large angular size of the Kepler pixels, which leads to reduced sensitivity in detecting variability, primarily as a result of dilution and noise from the nebula and neighbouring stars. We discuss the binary population of CSs based on these results as part of the total known sample of close binary CSs.
Context. Recent results for asteroid rotation periods from the TESS mission showed how strongly previous studies have underestimated the number of slow rotators, revealing the importance of studying those targets. For most slowly rotating asteroids (those with P > 12 h), no spin and shape model is available because of observation selection effects. This hampers determination of their thermal parameters and accurate sizes. Also, it is still unclear whether signatures of different surface material properties can be seen in thermal inertia determined from mid-infrared thermal flux fitting.
Aims: We continue our campaign in minimising selection effects among main belt asteroids. Our targets are slow rotators with low light-curve amplitudes. Our goal is to provide their scaled spin and shape models together with thermal inertia, albedo, and surface roughness to complete the statistics.
Methods: Rich multi-apparition datasets of dense light curves are supplemented with data from Kepler and TESS spacecrafts. In addition to data in the visible range, we also use thermal data from infrared space observatories (mainly IRAS, Akari and WISE) in a combined optimisation process using the Convex Inversion Thermophysical Model. This novel method has so far been applied to only a few targets, and therefore in this work we further validate the method itself.
Results: We present the models of 16 slow rotators, including two updated models. All provide good fits to both thermal and visible data.The obtained sizes are on average accurate at the 5% precision level, with diameters found to be in the range from 25 to 145 km. The rotation periods of our targets range from 11 to 59 h, and the thermal inertia covers a wide range of values, from 2 to <400 J m2 s12 K1, not showing any correlation with the period.
Conclusions: With this work we increase the sample of slow rotators with reliable spin and shape models and known thermal inertia by 40%. The thermal inertia values of our sample do not display a previously suggested increasing trend with rotation period, which mightbe due to their small skin depth. The photometric data with asteroid lightcurves are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/654/A87
We present the four-year survey results of monthly submillimeter monitoring of eight nearby (<500 pc) star-forming regions by the JCMT Transient Survey. We apply the Lomb-Scargle Periodogram technique to search for and characterize variability on 295 submillimeter peaks brighter than 0.14 Jy beam-1, including 22 disk sources (Class II), 83 protostars (Class 0/I), and 190 starless sources. We uncover 18 secular variables, all of them protostars. No single-epoch burst or drop events and no inherently stochastic sources are observed. We classify the secular variables by their timescales into three groups: Periodic, Curved, and Linear. For the Curved and Periodic cases, the detectable fractional amplitude, with respect to mean peak brightness, is ~4% for sources brighter than ~0.5 Jy beam-1. Limiting our sample to only these bright sources, the observed variable fraction is 37% (16 out of 43). Considering source evolution, we find a similar fraction of bright variables for both Class 0 and Class I. Using an empirically motivated conversion from submillimeter variability to variation in mass accretion rate, six sources (7% of our full sample) are predicted to have years-long accretion events during which the excess mass accreted reaches more than 40% above the total quiescently accreted mass: two previously known eruptive Class I sources, V1647 Ori and EC 53 (V371 Ser), and four Class 0 sources, HOPS 356, HOPS 373, HOPS 383, and West 40. Considering the full protostellar ensemble, the importance of episodic accretion on few years timescale is negligible-only a few percent of the assembled mass. However, given that this accretion is dominated by events on the order of the observing time window, it remains uncertain as to whether the importance of episodic events will continue to rise with decades-long monitoring.
The astorb database at Lowell Observatory is an actively curated catalog of orbital elements for all known asteroids in the Solar System. astorb has heritage dating back to the 1970's and has been publicly accessible since the 1990's. Beginning in 2015 work began to modernize astorb's underlying database infrastructure, operational software, and associated web applications. We will present the latest additions to the astorb ecosystem. Recent work has involved the expansion of astorb to incorporate physical properties from a variety of sources. These data products include lightcurve properties, photometric colors, spectral types, albedos and diameters, masses and densities, dynamical families, and Main Belt source region probabilities for near-Earth objects (NEOs). The latter represent the first public access to the medium resolution (a=0.05 AU, e = 0.02, i = 2, H = 0.25 mag) NEO source region model from Granvik et al. (2018, Icarus 312, 181). The data in astorb are used to support a number of visualization and observational planning tools hosted at https://asteroid.lowell.edu. These tools include a finder chart generator (called AstFinder), flexible ephemeris calculator (AstEph), and the means for long-term observability assessment (AstObs). Direct queries to the database are facilitated for individual objects (AstInfo), and for lists of objects that meet observability criteria that are either user-defined (UpObjects) or in preset critical lists. More comprehensive access to the database will be enabled in Fall 2021 through a web-based query-building tool built upon an application programming interface (API). Lastly, we have developed a novel orbit integration scheme that is built upon the GENGA (Gravitational Encounters in N-body simulations with GPU Acceleration; Grimm & Stadel, ApJ 796, 23) hybrid symplectic integrator. By leveraging the massively parallel computing capability of a GPU we can more efficiently maintain the orbital elements in astorb. We have validated the output of GENGA against more traditional direct integrators and find the agreement to be excellent for the vast majority of astorb use cases, i.e. determining observability within months or a few years of the current epoch.
We report new observations and analyses of archival data of the newly discovered active asteroid (248370) 2005 QN137. This object was found to have a long, straight comet-like dust tail by the Asteroid Terrestrial-Impact Last Alert System (ATLAS) survey on UT 2021 July 7, yet has orbital elements (a=3.067 au, e=0.226, i=0.067 degrees) that place it unambiguously in the outer main asteroid belt, and therefore among the class of objects known as active asteroids. Using the Canadian Astronomy Data Centre's Solar System Object Image Search tool and the Mikulski Archive for Space Telescopes, we have identified several archival snapshot observations of the object obtained in 2010 and 2011 by the Pan-STARRS1 survey in g'-, r'-, i'-, and z'-band (including some obtained at orbital positions close to the object's perihelion passage on UT 2010 August 24). The object has a stellar surface brightness profile and appears inactive in each of these images, where absolute magnitudes (assuming G=0.15) estimated from photometric measurements of the object in those data (mean values of Hg=16.470.03 mag, Hr=15.980.03 mag, Hi=16.020.02 mag, Hz=15.930.09 mag) are consistent with each other over the period of observations, and therefore with inactivity during each observation. Following the discovery of activity, follow-up observations using the Lowell Discovery Telescope (LDT) and Palomar Hale Telescope show that the near-nucleus region of the comet is approximately 1.3 mag brighter in g', r', and i' (as measured using 4"-radius photometry apertures) than expected from our absolute magnitude estimates, despite the nucleus having a nearly stellar surface brightness profile as measured perpendicularly to the dust tail. The dust tail is seen in the LDT and Palomar data to extend >9 arcmin from the nucleus along the object's orbit plane as projected in the sky. We will also report results from additional upcoming LDT and Palomar observations, as well as ongoing monitoring observations conducted as part of the Las Cumbres Observatory (LCO) Outbursting Objects Key (LOOK) Project (KEY2020B-009) and the Faulkes Telescope Project's Comet Chasers school outreach program (FTPEPO2014A-004). This work is supported by NASA SSO grant 80NSSC19K0869.
NASA's New Horizons mission visited both the Pluto-system and the ~35-km-length cold classical Kuiper belt object (KBO) Arrokoth. These flybys revealed the detailed shapes and surfaces of these KBOs for the first time. We have integrated the most up-to-date shape models of Arrokoth and Pluto's ~40-km-diameter moons Nix and Hydra into the John's Hopkins Applied Physics Laboratory Small Body Mapping Tool (SBMT; Ernst et al., 2018; sbmt.jhuapl.edu). In addition, we have projected the images and other data collected by New Horizons onto these shapes. We will report results from analysis of this new data collection. Crater measurements were performed on the 3D surfaces and compared with those collected on the "flat", unprojected images. We also compare our new crater measurements to those for other small bodies in both the inner and outer solar system. We also undertook a study of the effects of lighting geometry and image resolution on the results. Our preliminary results confirm the relatively shallow size-frequency distribution slope found for the smaller craters on Arrokoth (a differential slope of approximately -2; Spencer et al., 2020; Singer et al., 2020). We also find a differential slope for all craters on the martian moon Phobos of -2.4 similar to some previous measurements (e.g., Basilevsky et al. 2014). We use Phobos as a comparison to Arrokoth because it is a somewhat similarly-sized object (~27x24x18 km) and it was imaged by the Mars Reconnaissance Orbiter High Resolution Imaging Experiment (MRO HiRISE) camera under similar lighting conditions to Arrokoth. References: Basilevsky, A.T., Lorenz, C.A., Shingareva, T.V., Head, J.W., Ramsley, K.R., Zubarev, A.E., 2014. The surface geology and geomorphology of Phobos. Planetary and Space Science 102, 95. doi:10.1016/j.pss.2014.04.013 Ernst C.M. et al., 2018. The Small Body Mapping Tool (SBMT) for Accessing, Visualizing, and Analyzing Spacecraft Data in Three Dimensions, LPSC 49, abstract no. 1043. Singer, K.N., et al., 2020. Impact craters on 2014 MU69: Implications for Kuiper belt object size-frequency distributions and planetesimal formation. Am. Astron. Soc. Meet. Abstract no. 419.06. Spencer, J.R., et al., 2020. The geology and geophysics of Kuiper belt object (486958) Arrokoth. Science 367, aay3999. doi:10.1126/science.aay3999
Compaction cratering requires both high porosity (50%) and, depending on scale, low enough crush strength. Evidence from Arrokoth (distribution of surface slopes, neck strength limits, bilobate shape energy) and from cometary analogues (SL9 tidal breakup, 67P radio tracking) implies a density in the range 150-600 kg/m3. For a Pluto- or 67P-like composition, this implies porosities in the 70-85% range. Laboratory estimates of crush strengths at these high porosities, and for icy compositions, suggest values of order 100 kPa or less. If so, we expect the largest crater on Arrokoth, "Maryland," to have formed largely by crushing of pore space and material displacement, without substantial excavation of material. This is consistent with Maryland's stereo-revealed conical shape and lack of raised rim and ejecta blanket. In contrast, photoclinometric topographic profiles across craters an order of magnitude smaller on Arrokoth appear to possess such rims, suggesting a crush strength >10 kPa. High porosity reduces cratering efficiency in the gravity regime while compaction moves it towards strength scaling (controlled by the crush strength). Compaction also guarantees that most of a given impactor's kinetic energy is taken up as waste heat near the impact point, with momentum transferred to the rest of the body by elastic waves only. For typical cold classical encounter velocities, impactor and near-field target temperatures should reach ~100 K, warm enough to mobilize hypervolatile ices, but little else (whereas faster, hot classical or scattered disk impacts can melt water ice). Monte Carlo simulations of Maryland-forming conditions indicate that, while Arrokoth's small lobe (SL) is protected from catastrophic disruption by crush-up, the momentum imparted to SL is sufficient to break the relatively narrow neck between the 2 lobes, for typical cometary compressive and shear strengths (and assuming the Maryland impact postdates lobe merger of course). From geometry it is more likely that the SL was driven obliquely into the large lobe (LL), rather than away, with shear and compressive dissipation at the disrupted neck limiting the relative motion of SL with respect to LL to under 1 km. Unusual strength properties are not required to preserve Arrokoth's bilobate configuration.
The binary near-Earth asteroid (65803) Didymos is the target for the Asteroid Impact and Deflection Assessment (AIDA) concept with two primary spacecraft: NASA's DART (Double Asteroid Redirection Test) impactor and ESA's Hera orbiter (Cheng et al. 2018; Michel et al. 2018). DART is NASA's first planetary defense mission and will be the first demonstration of asteroid deflection by a kinetic impactor. The DART spacecraft will impact Dimorphos, the secondary in the Didymos system, and modify its orbit through momentum transfer. DART will launch in late 2021 and is scheduled to impact in September/October 2022. The DART spacecraft will carry ASI's LICIACube (Light Italian Cubesat for Imaging of Asteroids, Dotto et al. 2021) to observe the DART impact event and the resulting impact ejecta. A key scientific goal of the DART and Hera missions is to measure and characterize the deflection caused by the DART impact. The impact will change the satellite orbit period, which will be measured by ground-based facilities in the post-impact period. Hera, scheduled for launch in 2024 and rendezvous in 2026, will provide in-situ observations of the physical properties of the Didymos system and its post-impact dynamical state. We need to understand the baseline, unperturbed dynamics of the system to understand the effects of impact. The DART/Hera Observations Working Group was tasked with characterizing the Didymos-Dimorphos system properties with sufficient accuracy to measure the change in the binary orbital period to within 7.3 seconds. This measurement is a small, but observable fraction of the current orbital period of the satellite (Porb=11.92 hours). The observed period change is a critical input to the calculation of the momentum transfer enhancement parameter ("Beta"). We obtained lightcurve observations during the most recent apparition (December 2020 to March 2021) to further characterize the system. We combined these observations with past data (2003-2019) to establish the state of the system before impact to a high level of precision. We will discuss our state of knowledge from previous observations (through 2019), results from our 2020-2021 observations, and our preliminary plans for pre and post-impact observations in 2022.
The Wright Mons region is unique both on Pluto and in the imaged solar system. The region consists of a young surface (with few-to-no impact craters) and enormous rises (50+ km across and 2-7 km high) with an undulating, hummocky-like surface texture. Most indications point to the features being formed from endogenic emplacement of icy material onto the surface - i.e. cryovolcanism. We will present new morphologic measurements, new composition analysis, and new insights into the configuration of the region. We will summarize the evidence for multiple eruption events, and the we explore a set of possible volcanic analogue processes ranging from central-vent dome growth to thin-skinned folding. These features share some similarities to volcanic features across the solar system, but also many differences. The combination of materials and conditions on Pluto may lead to these distinctive morphologies.
On July 14, 2015, New Horizons made its closest approach to the Pluto system. Among its many tasks were spectroscopic observations of Charon's surface using LEISA (Linear Etalon Imaging Spectral Array), the near-infrared spectroscopic component of the Ralph instrument. The LEISA component obtains spectra in the 1.25 to 2.5 m range at a spectral resolution (/) ~240 and the 2.1-2.25 m range at / ~560. LEISA observations in the days leading up to the closest approach range in spatial scale from when Charon was less than a pixel (but still spatially resolved from Pluto) to filling the field of view. We have analyzed each LEISA scan of Charon as a disk-integrated spectrum. These spectra show absorption bands due to crystalline H2O-ice at 1.3, 1.5, 1.65, and 2.0 m. In addition, we also see absorption around 2.21 m, attributed to NH3-hydrates, other ammoniated species (e.g., NH4Cl), or their mixtures. We examine the size and shape of the 2.21 m band in detail by normalizing each spectrum with a best-fit Hapke model in the 1.9-2.5 m wavelength range. This procedure isolates the 2.21 m band from the other H2O-ice features in the spectrum. We will present our analysis of these spectra, including an examination of the band size and shape. We will compare the 2.21 m band observed on Charon with a similar band seen on Pluto's small satellites, Nix and Hydra. Finally, we will also compare the New Horizons/LEISA observations of Charon with ones obtained from Earth.
An absorbing species likely to be ammonia or an ammoniated compound (e.g., a hydrate, salt, or mineral) detected in the near-infrared reflectance spectra of some regions on Pluto is associated with geologic structures that appear consistent with effusive cryovolcanic activity (1-3). West of Sputnik Planitia, water ice carrying a red-brown pigment is prominently exposed in and around Virgil Fossae (1,2) and in Uncama Fossa and adjacent Hardie crater (3) in patterns suggestive of the effusion of a fluid that has filled some topography by flow and may have covered adjacent regions in episodes of fountaining. It has been proposed that a cryofluid consisting of water, a pigment that may consist of complex organic material, and an ammoniated substance has been ejected from a subsurface reservoir of unknown depth, volume, and lateral extent (4). Attention was drawn to the two regions cited above by their strong H2O ice absorption bands detected in the New Horizons LEISA maps of the encounter hemisphere of Pluto and their strong coloration, leading to the subsequent detection of the associated ammonia absorption band near 2.2 m. Other regions where the H2O ice absorption is strong are not strongly colored, notably Kiladze crater (lat 28.4, long 212.9), situated east of Sputnik Planitia. Using a statistical clustering technique (1) in LEISA spectra of Kiladze and surroundings, we have detected the signature of the ammoniated material, although it is less prominent than in Virgil Fossae and Uncama Fossa. Competing absorption bands of CH4 complicate extraction of the ammonia signal, but it is present at a high level of confidence. The geologic structure of Kiladze crater and surroundings is not strongly suggestive of cryovolcanic activity, and the presence of H2O ice with ammoniated material, but without the strong color, challenges the cryovolcanic interpretation of the other exposures. The wide geographic separation of Kiladze from the features west of Sputnik Planitia could, however, indicate differences in the composition of putative subsurface source reservoirs. 1. Dalle Ore, C. M. et al. 2019 Sci. Adv. 5, 29 May. 2. Cruikshank, D. P. et al. 2019 Icarus 330, 155. 3. Cruikshank, D. P. et al. 2021 Icarus 356 (113786) 4. Cruikshank, D. P. et al. 2019 Astrobiology 19 (7)
Lightcurves are powerful tools for investigating the spin rates and gross shapes of bodies throughout the Solar System, providing insights on the physical make-up of bodies without visits by spacecraft. Mutual events - eclipses and occultations - of binary bodies are doubly powerful in that their changing and interacting geometry map object shapes, sizes and mutual orbit configurations with added precision. With datasets spanning growing observing time baselines the phase space of possibilities converges, and with observations in multiple filters the distribution of surface ices can also be traced. However, interpretation of these datasets also requires modeling of both object interactions due to the individual object geometry, our Earth-based perspective, as well as the nature of the objects themselves. We present the development of such a model which uses ray-tracing to estimate the lightcurve of a binary system, including shadow-casting and bidirectional reflectance to generate comparative samples which can be iteratively referenced to actual observations of binary systems experiencing mutual events. We use the large dataset collected on (79360) Sila-Nunam from 2010-2017 both inside and outside of the mutual events to test the robustness of the model and to fully interpret this binary Cold Classical trans-Neptunian object. We also explore the predictive nature of the model for planning future observations of binary systems based on limited initial inputs. Support for this work comes from NASA Grant/Contract/Agreement No. NNX15AE04G issued through the Solar System Observations Program.
Using observations from the Lowell Observatory narrowband photometry database, we examine trends in water production among comets based on dynamical classes. Our program began in 1976, and to date includes observations of nearly 220 comets. Of these, over 190 have measured OH fluxes, which are converted to production rates for OH and are then readily converted to H2O production rates. We use these water production values for several investigations, including deriving each comet's extrapolated water production rate at perihelion, calculating the surface area required to produce the observed water production for each comet (i.e. the effective active area), and finding the fractional active area for over 50 of these objects with published nucleus sizes. Our large sample allows us to not only look at these properties within the ensemble of comets, but to also examine differences among these objects based on their dynamical ages. Clear trends emerge for each of these analyses based on the bulk division of Jupiter-family (JF) comets, presumed to mostly originate from the Kuiper belt, and non-JF comets, presumed to mostly originate from the Oort cloud. Within the non-JF comets, the dynamically younger objects overall have higher extrapolated water production rates at perihelion than do the dynamically older members. We also see a clear trend in their effective active areas, with the dynamically new comets having the largest values while the older, Halley-type comets have the smallest. Though few of the younger comets have measured nucleus sizes, this trend persists when looking at the active fractions. Taken together, this provides clear evidence for the evolution of the surfaces of these comets towards lower activity. In comparison, the JF comets have overall smaller water production rates at perihelion. They exhibit a wide range of active areas and active fractions, which we conclude is a result of the JF comets having a full range of relative ages, i.e. physical evolution of their surfaces, with objects continually being moved in from the Kuiper belt, and resulting in varying amounts of time that these comets have spent in the inner solar system. Cross-listed as presentation #105.07.
The Oort Cloud is a solar system construct, formed of billion to trillions of icy planetesimals that failed to aggregate onto and become part of one of the giant planets but were instead scattered out onto nearly hyperbolic, barely bound, multi-million year orbits. Recent work (Stern 2003; Dones+ 2004, 2015; Brasser & Morbidelli 2013; Garrod 2019), has shown that a competition between attempted aggregation frequency and successful launching a clearing solar system midplane determines the success of Oort Cloud emplacements, with the majority occurring 100-500 Myr after the start of the solar system. Only a handful of Oort Cloud comets are known to contain abundant hypervolatile majority ices (e.g., N2, CO, CH4 ices), representing a negligible (~10-3) fraction of all the known Oort Cloud comets. Yet we know that hypervolatile species existed in the protosolar nebula, since we detect them on the surfaces of the large KBOs, in the atmospheres of the giant planets, and as minority (few % vs water) species in Oort Cloud and inner-system Jupiter Family comets. This can be explained as a matter of timing. As shown in Lisse+ 2021 and Steckloff+ 2021, any small icy solar system body found in regions from the Kuiper Belt inward, including the giant planet region, will lose, via insolation heating, its hypervolatile majority ices to vacuum within 10 Myrs of the optical thinning, or "clearing", of the solar system's primordial planetary disk (PPD). Thus we expect none but the very first icy planetesimal aggregational failures lucky enough to thread the busy early midplane to transport any hypervolatiles successfully to the Oort Cloud. These lucky few, if as large as the best studied hypervolatile rich Oort comet C/2016 R2 (Rnuc ~15 km), can then endure thousands of orbits' worth (i.e. Gyrs) of hypervolatiles loss upon perihelion passage. But the vast majority of the icy planetesimals launched into Oort Cloud orbits on 100-1000 Myr timescales will contain no icy volatiles, except as minority impurities in refractory ice matrices, reproducing the situation we observe today.
Nitrogen, methane, and carbon monoxide are the most abundant substances on Pluto, Triton, Eris and Makemake. Sputnik Planitia, for example, is a giant reservoir of this mixture. Understanding this ternary phase diagram is a crucial step to understanding these outer solar system planetary bodies. This study uses experiments run in the Astrophysical Materials Laboratory at Northern Arizona University to map out this ternary system, by first starting with multiphase experiments for the three constituting binary systems (N2 + CO, CO + CH4, N2 + CH4). Notably, there are no experimental data that involve solid phases of CO + CH4 in the literature. We investigate these by using Raman spectroscopy to monitor where phase changes occur in the binary systems. In Raman, a photon is absorbed and then another photon is emitted. The Raman shift is then the difference in wavelength between those two photons, usually corresponding to a vibrational energy level. This spectroscopy method allows us to effectively monitor phase changes. The laboratory studies are being compared to a pair of distinct thermodynamic models. Computational molecular dynamics simulations are used to study the thermodynamic properties of each binary system considered. We use these simulations to predict densities, from which we quantify real solution effects, and analyze the specific molecular interactions causing the observations with pair distribution functions. The second model uses CRYOCHEM equation of state, which is based on the Thermodynamic Perturbation Theory (TPT) by coupling the Perturbed-Chain Statistical Associating Fluid Theory (PCSAFT) for the fluid part with the Lennard-Jones Weeks-Chandler-Andersen approach for the solid part. The solid-phase binary interaction parameters in this model are being fine-tuned by the laboratory data, and the model will ultimately provide the compositions and densities of the equilibrium phases for use in geophysical models. Cross-listed as presentation #114.03.
Pluto's high obliquity and eccentric orbit lead to significant changes in solar insolation over latitudes and seasons. Its microbar-pressure, nitrogen-dominated atmosphere is supported by vapor-pressure equilibrium with the surface ices. The properties and existence of the atmosphere thus depend critically on surface conditions. Models of volatile transport have been employed to anticipate Pluto's atmospheric evolution. Some models predict atmospheric contraction/collapse over the coming decades, while others show the atmosphere persisting throughout Pluto's entire orbital period. Pluto's atmosphere is of interest in terms of better understanding atmospheres (or the lack thereof) on large trans-Neptunian objects as well as the long-term evolution of icy bodies with variations in solar insolation. We have an ongoing program to predict and observe stellar occultations by Pluto, which has identified a pressure increase between 1988 and 2002, revealed waves in the upper atmosphere, detected haze in the lower atmosphere, and characterized atmospheric changes over decadal timescales. NASA's New Horizons spacecraft provided a wealth of data on Pluto's atmosphere during the 2015 flyby that can be placed into context through continued observations of ground-based stellar occultations. Here, we report on the results from the past four years of Pluto occultation observations, including measurements of atmospheric size and pressure. Additional observations are scheduled for the remainder of 2021. This work is funded by NASA grant 80NSSC21K0432.
(6478) Gault is a main-belt asteroid that was found to display cometary activity in late 2018-early 2019 [1]. During its 2018-2019 apparition, Gault experienced several activity events leading to the development of up to three distinct tails [2,3,4]. Many hypotheses such as impacts with smaller objects, YORP induced spin-up [5], sublimation of volatiles [6], or even the presence of a satellite in a highly eccentric and chaotic orbit, were considered to explain these events. In this talk we present new photometric and spectroscopic observations of Gault obtained during the 2018-2019 and 2020 apparitions. These observations were obtained both when Gault was active (during the 2018-2019 apparition) and when it was found to be inactive during the 2020 apparition. For the first time we determine an accurate rotation period with high confidence of P=2.4929 0.0003 h with a low amplitude of only 0.06 mag. This rotation period associated with a low lightcurve amplitude is consistent with a bulk density no smaller than 1.85 g cm3 in order for its activity to be triggered by the YORP spin-up mechanism. Our spectral analysis is consistent with Gault being of ordinary chondrite-like composition. Several spectra and a large datasets of broad band spectro-photometric observations obtained over the two oppositions do not show any sign of spectral variation over time. Finally, we did not find any statistically significant signal of non-gravitational accelerations due to its activity even after the addition of previously unidentified detections of Gault dating back to 1958, which increased its orbital arc by a factor of almost 2. These results were published in [7]. References: [1]: Smith K. W., Denneau L., Vincent J. B., et al., 2019, CBET, 4594 [2]: Jehin E., Ferrais M., Moulane Y., et al. 2019, CBET, 4606 [3]: Ye Q., et al., 2019, The ApJ Letters, 874, L16 [4]: Jewitt D., Kim Y., Luu J., et al. 2019, The ApJ Letters, 876, L19 [5]: Kleyna J. T., et al., 2019, The ApJ Letters, 874, L20 [6]: Ferrin I., Fornari C., Acosta A., 2019, MNRAS, 490, 219 [7]: Devogele M., Ferrais M, Jehin E, et al. 2021, MNRAS, 505, 245
Most basaltic V-type asteroids in the inner Main-Belt are located inside the collisional Vesta family and are considered parts of the fossil planetesimal (4) Vesta. Some asteroids are found outside the family and are considered Vesta fugitives, that is asteroids that migrated and have escaped the boarders of the family beyond recognition of common clustering methods. Nesvorny et al. 2008 simulated the escape paths of those objects and found that asteroids that end-up in the so-called Cell I (defined by orbital elements 2.2 < a < 2.3 AU, 0.05 < e < 0.2 and 0 deg < i < 10 deg) should maximize the Yarkovsky effect and predominantly (81%) have retrograde rotations. Asteroids that ended-up in the so-called Cell II (2.32 < a < 2.48 AU, 0.05 < e < 0.2 and 2 deg < I < 6 deg) should mostly be prograde rotators (60%). We have performed an extensive observational campaign starting in 2016 to obtain lightcurves of all V-types in both Cells larger than 5 km in diameter and model their spins and shapes. We have obtained photometry from several small and medium size telescopes (42 inch Hall telescope - Lowell Observatory, Zeiss telescope - Modra Observatory, University of Hawaii 88 inch telescope, Jacobus Kapteyn Telescope - Roque de los Muchachos Observatory, Roman Baranowski telescope - Winer Observatory, Perkins telescope - Lowell Observarory and several smaller telescopes). We modeled spins and shapes of the observed asteroids and compared their sense of rotation with the statistics obtained by Nesvorny et al. 2008.
Radiative transfer models are some of the most widely used tools for compositional analyses of planetary bodies and have the opportunity to provide a comprehensive understanding of asteroid surface properties when used in conjunction with thermal modeling. We present the limitations and sensitivities of a new implementation of Hapke radiative transfer modeling using visible to near-infrared spectroscopy as a means for characterizing and constraining the surface properties of unresolved asteroids. These spectroscopically derived properties are complimentary to constraints from thermophysical models of data at longer wavelengths. This visible and near-infrared spectroscopic approach benefits from observational requirements that are less time intensive and less reliant on specialized instrumentation, and thus has the potential to characterize a large number of near-Earth and Main Belt asteroids. Currently, our model is optimized for investigating S/Q-type asteroids whose spectra are dominated by 1 and 2 micron olivine and pyroxene absorption bands. We generate visible to near-infrared spectra using a simple three mineral model which encompasses the mineralogy range seen in ordinary chondrite meteorites for olivine, pyroxene, and iron metal, and adopts the scattering properties of well-studied S-type asteroids like Eros and Itokawa. We will discuss our findings on the sensitivities and limitations of our technique and its ability to constrain grain size properties for select ordinary chondrite meteorite samples. We will also present the spectroscopic application of our technique with comparisons to ground truth and thermal regolith constraints for Eros and Itokawa. This work is supported by the NASA NEOO program, grant number NNX17AH06G.
Titan is unique among the icy satellites in that it has a thick, opaque atmosphere and stable bodies of liquid on its surface. These two systems interact with one another via precipitation, dissolution, and evaporation. This is akin to what we see on Earth, but methane (CH4), ethane (C2H6), and nitrogen (N2) are the dominant species rather than water. The presence of three primary species, as opposed to one, creates a more complex system and may give rise to unique geochemical features within the lakes. To better understand the potential processes occurring in and around Titan's lakes, we are mapping how the addition of N2 to the CH4-C2H6 system at constant vapor pressure affects the temperature at which ice first appears. This study is built on recent work completed in the Northern Arizona University Astrophysical Materials Lab, which focused on mapping the CH4-C2H6 phase diagram at low temperatures and pressures using Raman spectroscopy [1]. We first condense a liquid CH4-C2H6 hydrocarbon (HC) mixture into the cell and then introduce N2 vapor to the sample to maintain a constant vapor pressure. To best capture effects at Titan conditions, we are running experiments at both 1.38 and 1.50 bar. Due to dissolution rates, more N2 must be added to the sample with decreasing temperature, or in experiments with more CH4, to maintain constant vapor pressure. While this does change the liquid composition of the sample as the experiment progresses, the total HC ratio remains the same. We use visual inspection and Raman spectroscopy to collect data and compare our results to the CH4-C2H6 system using a pseudo binary phase diagram and also to a model created using CRYOCHEM 2.0. Thus far, we have found that phase changes can be sensitive to pressure, even within our range of 1.38 - 1.50 bar. We also find that at both pressures, C2H6-rich mixtures up to ~0.2 methane HC ratio exhibit a first ice temperature depression that follows the trend of the binary liquidus. The first ice temperature then transitions to a flat line of 81.50.5 K at 1.38 bar. While we are still conducting experiments at 1.50 bar, the CRYOCHEM 2.0 model indicates we should see a flat line form at ~82.5 K. [1] Engle A.E. et al. (2021) PSJ, 2, 118. Cross-listed as presentation #405.02.
We present observations of five stellar occultations for (11351) Leucus and reports from two efforts on (21900) Orus. Both objects are prime mission candidate targets for the Lucy Discovery mission. Combined results for Leucus indicate a very dark surface with pV = 0.037 0.001, which is derived from the average of the multichord occultations. Our estimate of the triaxial ellipsoidal shape is for axial diameters of 63.8 36.6 29.6 km assuming that the spin pole is normal to the line of sight. The actual shape of the object is only roughly elliptical in profile at each epoch. Significant topography is seen with horizontal scales up to 30 km and vertical scales up to 5 km. The most significant feature is a large depression on the southern end of the object as seen from a terrestrial viewpoint. For this work we developed a method to correct for differential refraction, accounting for the difference in color between the target object and the reference stars for astrometry derived from ground-based images.
We report observations of the Jupiter Trojan asteroid (3548) Eurybates and its satellite Queta with the Hubble Space Telescope and use these observations to perform an orbital fit to the system. Queta orbits Eurybates with a semimajor axis of 2350 11 km at a period of 82.46 0.06 days and an eccentricity of 0.125 0.009. From this orbit we derive a mass of Eurybates of 1.51 0.03 1017 kg, corresponding to an estimated density of 1.1 0.3 g cm-3, broadly consistent with densities measured for other Trojans, C-type asteroids in the outer main asteroid belt, and small icy objects from the Kuiper Belt. Eurybates is the parent body of the only major collisional family among the Jupiter Trojans; its low density suggests that it is a typical member of the Trojan population. Detailed study of this system in 2027 with the Lucy spacecraft flyby should allow significant insight into collisional processes among what appear to be the icy bodies of the Trojan belt.
The Lucy Mission is a NASA Discovery-class mission to send a highly capable and robust spacecraft to investigate seven primitive bodies near both the L4 and L5 Lagrange points with Jupiter: the Jupiter Trojan asteroids. These planetesimals from the outer planetary system have been preserved since early in solar system history. The Lucy mission will fly by and extensively study a diverse selection of Trojan asteroids, including all the recognized taxonomic classes, a collisional family member, and a near equal-mass binary. It will visit objects with diameters ranging from roughly 1 km to 100 km. The payload suite consists of a color camera and infrared imaging spectrometer, a high-resolution panchromatic imager, and a thermal infrared spectrometer. Additionally, two spacecraft subsystems will also contribute to the science investigations: the terminal tracking cameras will supplement imaging during closest approach and the telecommunication subsystem will be used to measure the mass of the Trojans. The science goals are derived from the 2013 Planetary Decadal Survey and include determining the surface composition, assessing the geology, determining the bulk properties, and searching for satellites and rings.
The Lucy Mission accomplishes its science during a series of five flyby encounters with seven Trojan asteroid targets. This mission architecture drives a concept of operations design that maximizes science return, provides redundancy in observations where possible, features autonomous fault protection, and utilizes onboard target tracking near closest approach. These design considerations reduce risk during the relatively short time-critical periods when science data is collected. The payload suite consists of a color camera and infrared imaging spectrometer, a high-resolution panchromatic imager, and a thermal infrared spectrometer. The mission design allows for concurrent observations of all instruments. Additionally, two spacecraft subsystems will also contribute to the science investigations: the Terminal Tracking Cameras will obtain wide field-of-view imaging near closest approach to determine the shape of each of the Trojan targets and the telecommunication subsystem will carry out Doppler tracking of the spacecraft to determine the mass of each of the Trojan targets.
The Double Asteroid Redirection Test (DART) is a Planetary Defense mission, designed to demonstrate the kinetic impactor technique on (65803) Didymos I Dimorphos, the secondary of the (65803) Didymos system. DART has four level 1 requirements to meet in order to declare mission success: (1) impact Dimorphos between 2022 September 25 and October 2, (2) cause at least a 73 s change in its binary orbit period via the impact, (3) measure the change in binary period to an uncertainty of 7.3 s or less, and (4) measure the momentum transfer efficiency () of the impact and characterize the resulting effects of the impact. The data necessary to achieve these requirements will be obtained and analyzed by the DART Investigation Team. We discuss the rationales for the data to be gathered, the analyses to be undertaken, and how mission success will be achieved.
Examination of the opposition geometry properties show that Ryugu's surface regolith is commensurate with laboratory studies of the photometric behavior of powdered carbonaceous chondrites. The regolith is consistent with a broad grain size distribution that contains a fine-grained component.
Pluto's fly-by by the New Horizons spacecraft in July 2015 has revealed a dark reddish equatorial region, named Cthulhu, covered by a dark, non-icy material whose origin and composition have yet to be determined. It has been suggested that this material could form from the sedimentation of photochemical aerosols, originating from dissociation and ionisation processes in Pluto's high atmosphere (similarly to aerosols forming Titan's haze). This hypothesis is here further investigated by comparing New Horizons spectra collected both in the visible and the near-infrared to laboratory reflectance measurements of analogues of Pluto's aerosols (Pluto tholins). These aerosols were synthesised in conditions mimicking Pluto's atmosphere, and their optical and reflectance properties were determined, before being used in Hapke models. In particular, the single scattering albedo and phase function of Pluto tholins were retrieved through Hapke model inversion, performed from laboratory reflectance spectra collected under various geometries. From reconstructed reflectance spectra and direct comparison with New Horizons data, some of these tholins are shown to reproduce the photometric level (i.e. reflectance continuum) reasonably well in the near-infrared. Nevertheless, a misfit of the red visible slope still remains and tholins absorption bands present in the modelled spectra are absent in those collected by the New Horizons instruments. Several hypotheses are considered to explain the absence of these absorption features in LEISA data, namely high porosity effects or GCR irradiation. The formation of highly porous structures, which is currently our preferred scenario, could be promoted by either sublimation of ices initially mixed with the aerosols, or gentle deposition under Pluto's weak gravity.
We present here the discovery of a new class of superslow rotating asteroids (Prot 1000 h) in data extracted from the Asteroid Terrestrial-impact Last Alert System (ATLAS) and Zwicky Transient Facility (ZTF) all-sky surveys. Of the 39 rotation periods we report here, 32 have periods longer than any previously reported unambiguous rotation periods currently in the Asteroid Light Curve Data base. In our sample, seven objects have a rotation period >4000 h and the longest period we report here is 4812 h (~200 d). We do not observe any correlation between taxonomy, albedo, or orbital properties with superslow rotating status. The most plausible mechanism for the creation of these very slow rotators is if their rotations were slowed by YORP spin-down. Superslow rotating asteroids may be common, with at least 0.4 per cent of the main-belt asteroid population with a size range between 2 and 20 km in diameter rotating with periods longer than 1000 h.
The object Mayall II or G1 is the brightest globular cluster belonging to M31. Because of its extreme properties for a globular cluster, it has been speculated that G1 is the remnant nucleus of a dwarf galaxy that has been stripped by the tidal field of M31. Using the Keck DEIMOS spectrograph, we have conducted a survey for tidally stripped stars from G1, obtaining a sample of 351 stellar velocities over ~320 sq. arcmin of sky centred on G1. 13 are within $25~{\, \rm km\, s^{-1}\, }$ of the systemic velocity of G1, and exhibit spatial and velocity correlations consistent with being dynamically associated with G1, and all 13 are well outside the tidal radius of the cluster. These 13 stars could be either (i) the remnants of an almost completely evaporated stellar envelope or (ii) G1 member stars lost through tidal interaction with M31. Estimates of the implied mass-loss rate based on our data suggest a short dissolution time-scale for G1, thus favouring the stellar envelope hypothesis for the origin of the tidal tail stars, or, at the very least, an advanced stage of cluster dissolution. In either case, G1 and by extension compact stellar systems in general have likely played a significant role in building the halo of M31.
We present morphological classifications of ~27 million galaxies from the Dark Energy Survey (DES) Data Release 1 (DR1) using a supervised deep learning algorithm. The classification scheme separates: (a) early-type galaxies (ETGs) from late-type galaxies (LTGs); and (b) face-on galaxies from edge-on. Our convolutional neural networks (CNNs) are trained on a small subset of DES objects with previously known classifications. These typically have mr 17.7 mag; we model fainter objects to mr < 21.5 mag by simulating what the brighter objects with well-determined classifications would look like if they were at higher redshifts. The CNNs reach 97 per cent accuracy to mr < 21.5 on their training sets, suggesting that they are able to recover features more accurately than the human eye. We then used the trained CNNs to classify the vast majority of the other DES images. The final catalogue comprises five independent CNN predictions for each classification scheme, helping to determine if the CNN predictions are robust or not. We obtain secure classifications for ~87 per cent and 73 per cent of the catalogue for the ETG versus LTG and edge-on versus face-on models, respectively. Combining the two classifications (a) and (b) helps to increase the purity of the ETG sample and to identify edge-on lenticular galaxies (as ETGs with high ellipticity). Where a comparison is possible, our classifications correlate very well with Sersic index (n), ellipticity (), and spectral type, even for the fainter galaxies. This is the largest multiband catalogue of automated galaxy morphologies to date.
The reflection of visible/near-infrared light from Mars can vary depending on the directional scattering characteristics of surface materials. Multispectral images have been acquired in situ under different illumination/viewing angles by the Viking and Mars Pathfinder landers, the Mars Exploration Rovers (MER), the Mars Science Laboratory (MSL) Curiosity, and the Mars 2020 (M2020) Perseverance rover. We review the use of these data sets with radiative transfer models to constrain the single scattering albedo (w), phase function, surface roughness, grain size and/or porosity of martian materials.Soils at the Viking Lander sites were modeled with the initial version of the Hapke model [1], which showed wavelength-dependent backscattering phase functions [1-3] (Fig. 1). Model results suggested that variations in thickness of nanophase ferric oxide coatings could explain differences between darker and brighter rock facet colors [4]. Surfaces exhibited a strong opposition effect and smooth rock surfaces exhibited specular reflections, consistent with rocks abraded by wind [4]. Fig. 1. Viking Lander 2 red filter images: (a) Sol 045, incidence=85.1 showing pronounced specular reflection in ~20 cm rock (arrow); (b) Sol 025, incidence=29.1[4]. The Imager for Mars Pathfinder (IMP) acquired multispectral images at phase angles from near 0 to ~155. "Bright soil" materials appeared brighter and redder than "dark soil" materials, whereas "gray" rocks were interpreted to be relatively less dust-covered than "red" rocks [5]. The phase curves suggested a dominantly backscattering function, although a strong forward scattering component was observed for gray rocks. The w values of bright soils were highest in red and near-infrared bands, whereas w for gray rocks was highest at 443 nm. The single particle scattering function parameters b (asymmetry parameter) and c (backscattering fraction) were compared to those modeled from laboratory data of artificial particle types [6]. Soils and red rocks clustered at high c values, near materials with a high density of internal scatterers. The gray rocks exhibited lower c values similar to agglutinates and rough, clear spheres, consistent with smooth surfaces (possibly a coating) similar to terrestrial varnished rock surfaces [4,6]. The opposition width parameter h was relatively larger for the dark soils, implying materials with lower porosity and/or a more uniform particle size distribution. Conversely, the gray rocks' low values suggested materials with higher porosity and/or a broader particle size distribution than red rocks. The opposition effect amplitude (B0) decreased with increasing wavelength, which suggested that these materials were more opaque (more surface scattering) in blue wavelengths, and become more transparent (more internal scattering) at longer wavelengths [cf. 8]. Fig. 2. IMP images (752 nm) with acquisition times (bottom) and phase angles (sides) shown. Note shadow of IMP camera head in 16:00 and 17:00 images[5]. Spectrophotometric observations acquired throughout the MER missions by the Panoramic Cameras (Pancams) were used to investigate the surface scattering properties of the basaltic rocks and soils in Gusev crater (Spirit) and the sulfate-rich outcrop rocks, hematite-bearing spherules and basaltic sands in Meridiani Planum (Opportunity) (Fig. 3). A Hapke model [9] was used in combination with corrections for diffuse sky illumination and local surface facet orientations (derived from stereo images) to analyze photometric observations [10-13] (Fig 4.). At the Spirit site, modeled w values among all typical "Soil" units were similar except for areas subjected wind events. "Gray" rocks were less contaminated with dusty coatings than "Red" rocks and were typically more forward scattering. Gray rock surfaces were consistent with rough/irregular particles with few internal scatterers [6], whereas Red rock and most Soil surfaces exhibited more internal heterogeneity. Most Red rocks and Soils were more porous (or exhibited a less uniform grain size) than Gray rocks and generally exhibited lower macroscopic roughness values. The w values of spherule-rich soils along the Opportunity traverse varied (due to dust coatings), and outcrop rocks exhibited the highest w values. Spherule soils were typically backscattering and consistent with particles with internal scatterers and/or rough, clear spheres. Observations of large drifts were modeled with w values that exhibited a downturn toward 1009 nm, consistent with minor hydration [14]. These "Dust" deposits were the smoothest of all units studied by Opportunity and exhibited the highest h values, suggesting a more homogeneous grain size distribution and/or lower porosity. Fig. 3. MER Opportunity Pancam images of Tipuna rock on Sols 306-307 (a)09:06, (b)11:42, (c)14:46, (d) 16:08, (e) 17:05[11]. Fig 4. Example of geometric information computed from MER Spirit Pancam stereo images from the Troy area: (a) false-color image, Sol 1944, 10:32; (b) surface normal (x direction); (c) z-value; (d) incidence; (e) emission; (f) phase angle[15]. MSL has collected twenty spectrophotometric Mastcam datasets (including Navigation Camera stereo images for topography) (Fig. 5), along with five data sets using the MAHLI camera on the arm as a goniometer to acquire phase angle coverage [16]. Analyses have revealed a combination of typical effects associated with dust coatings but also changes in absorption band strengths with phase angle and phase reddening effects [e.g., 17-19]. Recently, photometric data were collected by the Perseverance Mastcam-Z camera east of the landing site (Fig. 6), imaging sand ripples, rover tracks, and rocks with variable degrees of dust and coatings, whose spectra varied with phase angle. Fig 5. MSL Mastcam false-color images (Sol 172) acquired at times shown; note enhanced visibility of light-toned veins at low phase angle [cf.18-19]. Fig 6. Perseverance Mastcam-Z false-color mosaics looking east near M2020 landing site (times 10:30(left), 17:10(right)). A common theme among these in situ studies is the dominantly backscattering nature of the martian surface, modulated by the presence of dust coatings. This photometric variability encourages ongoing refinement of radiative transfer methods to help categorize and map distinct photometric units on Mars, particularly in support of ongoing and upcoming orbital and landed missions.[1]Hapke,B.,JGR,86,3039-3054,1981[2]Guinness,E.A.,JGR,86,7983-7992,1981[3]Guinness,E.A.,etal.,JGR,92,E575-E587,1987[4]Guinness,E.A.,etal.,JGR,102,28687-28703,1997[5]Johnson,J.R.,etal.,JGR,104,8809-8830,1999[6]McGuire,A.F.,and B.Hapke,Icarus,113,134-155,1995[7]McSween,H.Y.Jr.,etal.,JGR.,111,E02S10,doi:10.1029/2005JE002477,2006[8]Domingue,D.,and B.Hapke,Icarus,99,70-81,1992[9]Hapke,B.,Theory of Reflectance/Emittance Spectroscopy,Cambridge-University-Press,455p.,1993[10]Johnson,J.R.,etal.,JGR,111,E02S14,doi:10.1029/2005JE002494,2006[11]Johnson,J.R.,etal.,JGR.,111,E12S16,doi:10.1029/2006JE002762,2006[12]Johnson,J.R.,etal.,Ch. 19,in The Martian Surface: Composition,Mineralogy,and Physical Properties,Cambridge University Press,428-450,2008[13]Johnson,J.R,etal.,Icarus,248,25-71,doi:10.1016/j.icarus.2014.10.026,2015[14]Rice,M.S.,etal., Icarus 205,375-395,2010[15]Johnson,J.R.,etal.,Icarus,357,114261,doi.org/10.1016/j.icarus.2020.114261,2021[16]Liang,W.,etal.,Icarus,335,13361,,doi.org/10.1016/j.icarus.2019.06.022,2020[17]Johnson,J.R.,etal.,LPSC,#1371,2014[18]Johnson,J.R.etal.,LPSC,#1354,2018[19]Johnson,J.R.,etal.,LPSC,#1313,2019
The 27 moons of Uranus (Figure 1) are enigmatic and remain poorly understood. Voyager 2 flew by the Uranus system in 1986, collecting fascinating images of its five largest, tidally-locked `classical' moons (Figure 2), while also discovering a bevy of small moons nestled in its ring system (e.g., [1]) (Figure 3). The surfaces of Uranus' classical moons Miranda, Ariel, Umbriel, Titania, and Oberon have been modified by endogenic activity, in particular Miranda and Ariel, which exhibit substantial evidence for geologic communication between their interiors and surfaces (e.g., [1-3]) (Figure 2). The available images therefore indicate that these classical moons are candidate ocean worlds, which have, or had, liquid H2O layers beneath their icy exteriors (e.g., [3-5]). Because the Voyager 2 flyby occurred near Uranus' southern summer solstice (subsolar latitude ~81S), the collected images are centered near the south poles of these moons, and their northern hemispheres were largely unobservable. Furthermore, only the classical moons and the largest ring moon Puck (Figure 3) were spatially resolved by Voyager 2. The other nine ring moons Cordelia, Ophelia, Bianca, Cressida, Desdemona, Juliet, Portia, Rosalina, and Belinda were not resolved. Another ring moon, Perdita, was discovered via reanalysis of Voyager 2 data [6], and two more ring moons, Cupid and Mab [7,8], were discovered by space-based telescope observations. All nine known irregular satellites, Francisco, Caliban, Stephano, Trinculo, Sycorax, Margaret, Prospero, Setebos, and Ferdinand, were not detected by Voyager 2 and were discovered later by ground-based observations (e.g., [9-11]).Voyager 2 was not equipped with a near-infrared (NIR) mapping spectrometer, and most of what we know about the compositions of Uranus' moons has been determined using data collected by ground and space-based telescopes. The surfaces of Uranus' classical moons are composed of H2O ice mixed with low albedo material that could be rich in organics and silicate minerals (e.g., [12-14]). Carbon dioxide (CO2) has been detected on the classical moons, primarily on their trailing hemispheres, in particular on Ariel [15,16] (Figure 4). Spectrally red material that could be rich in organics has been detected, primarily on the leading hemispheres of these moons (e.g., [17,18]) (Figure 4). Ammonia (NH3) has possibly been detected on the classical moons and may originate from their interiors [18,19]. Although useful, these prior observations are disk-integrated, limiting our ability to constrain the distribution of surface constituents and identify links between volatile species and geologic terrains. Much less is known about the surface compositions of Uranus' 13 ring moons and nine irregular satellites, which are mostly too faint (Vmag 19.8 - 25.8) for spectroscopic analysis using existing facilities. Spectrophotometric datasets indicate that Uranus' ring moons have dark surfaces that show hints of H2O ice features [6]. Uranus' irregular satellites have dark, reddish surfaces (e.g., [20]) but little else is known about their surface compositions, except for Sycorax, which shows hints of H2O ice [21].An orbiting spacecraft collecting data during close flybys of Uranus' ring system and classical moons would reveal the surface geologies of these moons, including on their previously unobserved northern hemispheres, determine their surface compositions, and determine whether any of the classical moons are, or were, ocean worlds. Furthermore, an orbiter could spend time looking outward to characterize Uranus' irregular satellites, providing new insight into these likely captured objects (e.g., Jewitt & Haghighipour 2007). By utilizing a Jupiter gravity assist (2030 - 2034 launch window), a mission could arrive at the Uranian system in the mid 2040's (11 years flight time), using existing chemical propulsion technology [22]. This arrival time frame would allow us to observe these moons' northern hemispheres. An orbiter making close flybys of the classical moons could search for evidence of ongoing geologic activity and characterize migration of CO2 in response to changes in subsolar heating as the Uranian system transitions into southern spring in 2050.To determine whether liquid H2O layers are present in the interiors of the classical moons, the highest priority instrument onboard an orbiter would be a magnetometer, which could detect and characterize induced magnetic fields emanating from briny subsurface oceans. Visible (VIS, 0.4 - 0.7 m) and mid-infrared (MIR, 5 - 250 m) cameras would also be vital to search for plume activity, hot spots, and other signs of geologic communication between the interiors and surfaces of these moons. A spectrometer (0.4 - 5 m) would be critical for characterizing volatile species that might result from outgassing of material or recently exposed or emplaced surface deposits. The abundant evidence for geologic activity in the recent past on Ariel and Miranda likely makes them the highest priority targets for any mission that aims to characterize Uranus' satellites.References: [1] Smith, B. A. et al. 1986, Science, 233, 43. [2] Schenk, P. M. 1991, JGR: Solid Earth, 96, 1887. [3] Beddingfield, C. B. & Cartwright, R. J. 2020, Icarus, 113687. [4] Hendrix, A. R. et al. 2019, Astrobiology, 19, 1. [5] Cartwright, R.J. et al. 2021. arXiv preprint arXiv:2105.01164. [6] Karkoschka, E. 2001, Icarus, 151, 51. [7] Showalter, M. R. & Lissauer, J. J. 2006, Science, 311, 973. [8] De Pater, I. et al. 2006, Science, 312, 92. [9] Gladman, B. J. et al. 1998, Nature, 392, 897. [10] Kavelaars, J. et al. 2004, Icarus, 169, 474. [11] Sheppard, S. S. et al. 2005, AJ, 129, 518. [12] Cruikshank, D. et al. 1977, AJ, 217, 1006. [13] Clark, R. N. & Lucey, P. G. 1984, JGR: Solid Earth, 89, 6341. [14] Brown, R. H. & Clark, R. N. 1984, Icarus, 58, 288. [15] Grundy, W. et al. 2006, Icarus, 184, 543. [16] Cartwright, R. J. et al. 2015, Icarus, 257, 428. [17] Buratti, B. J. & Mosher, J. A. 1991, Icarus, 90, 1. [18] Cartwright, R. J. et al. 2018, Icarus, 314, 210. [19] Cartwright, R. J. et al. 2020c, ApJL, 898, L22. [20] Maris, M. et al. 2007, A&A, 472, 311. [21] Romon, J. et al. 2001, A&A, 376, 310. [22] Hofstadter, M. et al. 2019, Planetary and Space Science, 177, 104680.
Asteroids, along with other small bodies are what is left of the original planetesimal disk from the planet-formation era. But not all asteroids that we observe today are planetesimals. Many of those planetesimals, during the history of the solar system, were destroyed by impacts, creating families of smaller asteroid fragments, which make the vast majority of the current main belt population. However, very few of these collisional fragments are actually linked to known families. The smaller are the sizes of the family members, the more numerous they are. Moreover, due to non-gravitational forces, known as the Yarkovsky effect, the members of these families move away from the original location with a velocity proportional to 1/D, where D is the asteroid diameter. These two facts result in that the smaller are the studied asteroids the more confusing is the picture of the original compositional distribution.Our team developed a novel methodology to identify the planetesimals in the main belt (Bolin et al., 2017, Delbo' et al., 2017, 2019, 2021), based on finding asteroid families from correlations between their 1/Diameter and their semi-major axis (this is the so-called V-shape of asteroid families). By removing all asteroids that are inside these V-shapes and thus belong to families, we revealed the planetesimal population. This new analysis has now been completed in the Inner Main Belt (IMB) between 2.1 and 2.5 au with the identification of 71 planetesimals. We started a spectroscopic survey of the identified IMB planetesimals, aiming at constraining their composition and mineralogy, information that is of paramount importance for defining the original compositional gradient of the main belt, including that of materials of high exobiological interest, such as hydrated minerals and carbonaceous compounds.The survey was mainly carried out at the 1.82m Copernico Telescopio (Asiago, Italy) for spectroscopy in the visible range, and at the 4.2m Lowell Discovery Telescope (Flagstaff, USA) and 3.2m NASA Infrared Telescope Facility (Mauna Kea, USA) for the near infrared range (0.95-2.3 micron). Few data come from unpublished observations at the 3.6m New Technology Telescope (La Silla, Chile) and the 1.22m telescope in Asiago made previously by our team. The new data presented here come from 14 distinct observing runs spread out between 1999 and 2020.To complete the survey of the IMB planetesimals, we also used spectra in the visible and NIR range published in the literature. In fact, several of the identified planetesimals are relatively large and bright, and already studied in spectroscopy.After standard spectral reduction procedures, we merged the visible and near-infrared spectra (when available) of a given target to obtain a full VIS+NIR spectrum and we perform the taxonomic classification following the Bus-DeMeo taxonomy (Bus et al., 2002; DeMeo et al., 2009) using the M4AST tool (http://m4ast.imcce.fr) (Popescu et al., 2012). A visual inspection to identified the presence of absorption bands characteristic of some classes was performed to strength the taxonomic classification. In addition, we compute for each planetesimal several spectral parameters, such as spectral slopes, and center, depth and minimum of absorption bands, when present. Finally, we used the RELAB database (Pieters, 1983), to look for meteorite analogues of each planetesimal.As expected, we found that the majority of the IMB planetesimals belongs to the S-complex (about 50 %, Fig. 1). The population also includes 20% of X-complex, 18 % to C-complex and 12% of end members (D, K, L and V-type). Interestingly, our survey reveals that more than 60% of the IMB carbonaceous-rich planetesimals belong to the Ch/Cgh types, as they show features associated to hydrated materials, indicating the presence of water ice at relatively small heliocentric distances. Surprisingly, about 4% of the planetesimals belong to the D-type, which are usually located in the outer Main Belt and in the Jupiter Trojan swarms. Finally, no olivine-rich A-type planetesimal is found. A-types are supposed to be formed by the collisional exposure of a mantle of a differentiated parent body. The fact that they are absent in the IMB planetesimal population supports the aforementioned theory of the A-type origin.Here we will present the spectroscopic and compositional results of the IMB planetesimals as well as the implications for planetary formation models. Figure 1 : The spectroscopic distribution of the studied planetesimals using the Bus-DeMeo taxonomy.References : Bryce T. Bolin et al., Icarus, Volume 282, 2017, Pages 290-312 ; Marco Delbo et al., Science : 1026-1029, 2017 ; Marco Delbo et al., A&A 624 A69 (2019) ; Schelte J. Bus et al., Icarus, Volume 158, Issue 1, 2002, Pages 146-177 ; Francesca E. DeMeo et al., Icarus, Volume 202, Issue 1, 2009, Pages 160-180 ; M. Popescu et al., A&A 544 A130 (2012) ; Pieters, C. M. (1983), J. Geophys. Res., 88( B11), 9534- 9544,
Through numerical modeling, Nesvorny et al. (2008) showed that asteroids can migrate due to Yarkovsky drift and resonances to outside of the boundaries of the Vesta family. In particular, they found that objects which end up in the scattered resonances region (so-called Cell I, defined by orbital elements 2.2 AU < a < 2.3 AU, 0.05 < e < 0.2, 0 < i deg < 10 deg) typically have retrograde rotations and thermal parameters that maximize Yarkovsky drift rates. These autors also showed, that asteroids migrating to the low inclination region (Cell II defined by 2.32 AU < a < 2.48 AU, 0.05 < e < 0.2, 2 deg < i < 6 deg) should be predominantly prograde rotators.We performe photometric observations and determine spins and shapes of V-type objects in Cell I and Cell II in order to characterize the dynamical properties of these asteroids more accurately. The results of dynamical modelling show that some asteroids may have migrated to their current location from the Vesta family within ~2 Gy. There are objects, however, whose origin in another parent body may also be plausible. This may support the hypothesis that the number of differentiated basaltic objects in the inner and middle Main Belt should be much higher than previously assumed. We will present preliminary results for the first ~10 asteroids in Cell I and Cell II.
We invite observers to join an international observing campaign and obtain light curve of a selected number of the most ancient asteroids. Analysis of these data will be important to reconstruct the original state of the asteroid belt, which is a crucial problem of planetary science. This original state can be reconstructed through the identification of the oldest asteroid families. Traditional identification methods, like Hierarchical Clustering Methods (Zappala et al., 1990; HCM), have difficulties to recognise Gyr- and older asteroid families, whose members are very dispersed by the Yarkovsky effect. An innovative method, called V-shape search (Bolin et al., 2017), has been demonstrated effective (Deienno et al. 2021) to identify these aforementioned very old collisional families by searching for the signature of the size dependent dispersion of family members operated by the Yarkovsky effect.The method has already successfully identified two primordial families which likely formed before the giant planet orbital instability (Tsiganis et al., 2005) and could be as old as the Solar System and an ancient one that is ~3 Gyr-old (Delbo et al., 2017; 2019). There is evidence from observations and theoretical evolution models that there are more old families to be detected (Delbo et al., 2017; Dermott et al., 2018). However, the reliability of these V-shape families should be independently verified.A very important test of family membership is the anisotropic distribution of spin vectors of the asteroid family member, which is a fingerprint of the Yarkovsky effect evolution (Hanus et al. 2013). Namely, to test the working hypothesis that according to theories of asteroid orbital evolution under the Yarkovsky effect, members of the inward (outward) side of V-shape of a family have a statistical predominance of retrograde (prograde) objects (Fig. 1). This hypothesis has been tested (Hanus, et al., 2013) already for known families, and it is a reliable test for family membership. The observing campaign: Ancient AsteroidsFor this purpose, an international observing campaign called Ancient Asteroids has been put forward at different observatories worldwide: (University of Athens Observatory (UOAO), Greece, the BSA Observatory and Bigmuskie Observatory, Italy, the Observatoire de la Cote d'Azur (OCA), France, the Lowell Observatory in Arizona, United States, the Astronomical Institute of the Charles University in Prague, Czech Republic, the Aristotle University of Thessaloniki in Thessaloniki, Greece. The main goal of the campaign is to establish an international network of professional and amateur astronomers (Pro-Am collaboration), in order to perform photometric observations of a very specific sample of the most ancient asteroids. A special website (http://users.uoa.gr/~kgaze/research_asteroids_en.html) was developed for the purpose of the campaign, that includes guidelines for the participation, the observations and the image data evaluation and collection.In the frame of Ancient Asteroids campaign, a user-friendly web application was also developed for the target selection and observing plan preparation. The user can easily find the observable asteroids for the campaign based on the location, the time and the equipment limitations. The targets are displayed with a priority rate, in order to perform smart sampling. The user selects the favor target and an observing plan automatically is created. The contribution The obtained lightcurves from all the involved participants will be combined with data available in the literature, as well as with sparse data from space missions (Gaia, TESS, etc) and global sky surveys (PTF, LSST, ATLAS, etc). Thus, the spin state of the asteroids can be revealed. The results will be ingested to the Minor Planet Physical Properties Catalogue (MP3C) program (https://mp3c.oca.eu/catalogue/index.htm), the largest database of asteroid physical properties, which complies with the EU vision for open data. The observing campaign Ancient Asteroids has started to collect photometric observations with the contribution of amateur astronomers from Italy, France and Greece are submitted. The observations will reveal the spin state of the members, which are crucial for the testing the hypothesis of the family membership. This research will potentially lead to a better understanding of the first stages of the evolution of the Solar System, the mechanism at the origin of the formation of the asteroids and the planet formation processes. AcknowledgmentsThis work was also partially supported by the ANR ORIGINS (ANR-18-CE31-0014) and by the French National Program of Planetology (PNP). Here we make use of asteroid physical properties data from Minor Planet Physical Properties Catalog (https://mp3c.oca.eu/). ReferencesBolin, B. T. et al. (2017). Icarus, 282, 290-312.Deienno, R. et al. (2021). Icarus, 357, 114218.Delbo, M. et al. (2019). Astronomy & Astrophysics, 624, A69.Delbo, M. et al. (2017). Science, 357, 6355.Dermott, S. F. et al. (2018). Nature Astronomy, 2, 7.Hanus, J. et al. (2013). Astronomy & Astrophysics, 559.Hanus, J. et al. (2013). Astronomy & Astrophysics, 551.Tsiganis K. et al. (2005). Nature, 435, 7041.Zappala, V. et al. (1990). Astrophysical Journal, 100, 2030-2046.
Clouds and hazes play a major role in (exo)planetary atmospheres. They can absorb and reflect light from UV to thermal infrared wavelengths, changing the atmospheric emission, reflection, and transmission spectra dramatically. The organic aerosols forming the haze can act as cloud condensation nuclei. Then can also settle down onto the surface, hence participating in its composition. Dedicated laboratory experiments have been developed to produce solid materials that are analogs of haze and cloud particles, under different experimental conditions (molecular precursors, temperature, pressure, energy source). These experimental studies are key to investigating the physical and chemical processes that drive the formation of solid particles from gas and solid phase molecular precursors in planetary environments. These experiments also allow the characterization of the physical, optical and chemical properties of the laboratory-generated haze and cloud particle analogs, hence providing critical information that can be used as input parameters in models for the analysis and interpretation of observational data (e.g. optical constants, vapor pressures, spectral features, grain morphology, etc).Here, as examples of these laboratory efforts, we will present various studies that combine (1) experiments performed to produce analogs of Titan and Pluto atmospheric aerosols from gas phase molecular precursors, (2) experiments conducted to simulate the formation of benzene ice cloud particles in Titan's stratosphere, and (3) experiments carried out to characterize the haze and cloud particle analogs to provide, in particular, optical constants and vapor pressures. We will show how important these studies are for the interpretation of observational data from past, current and future (exo)planetary missions. We will also introduce the newly funded NASA Center for Optical Constants whose overarching goal is to support a stable, long-term, synergistic laboratory effort to address a critical need throughout the broader planetary science community for the development of a comprehensive database containing complex refractive indices (optical constants) of laboratory-generated analogs of organic refractory materials, and ices present in planetary atmospheres and surfaces.
2021 DW1 was discovered on 16 February 2021 by Pan-STARRS 1 on Haleakala. This ~40-m object passed the Earth at a distance of 570000 km (1.5 Lunar Distance) on 4 March at 9 UTC, reaching a brightness of V=14.6 mag. We observed it photometrically from 2 March, 4 UTC, when it was visible at V=16.5 mag, until 7 March, 9 UTC (V=18.2 mag). During that time 2021 DW1 swept a 170 deg long arc in the northern sky, spanning solar phase angles in the range from 36 to 86 deg. This made it an excellent target for physical characterization.In our campaign, we used 9 telescopes with apertures ranging from 0.3-m to 1.2-m, located in the USA, UK, Spain, Italy, Poland, Ukraine, and South Korea. This gave us a good coverage of the asteroid path. We collected a lot of data which are now being analysed. Preliminary analysis show a very short rotation period of 50 seconds and a lightcurve amplitude of about 0.3 mag, which didn't change much along the asteroid path in the sky. More results will be presented at the conference.
What long-period comets with orbital periods >250 years cause detectable meteor showers on Earth? Low-light video cameras are used to track the motion of +4 to -5 magnitude meteors in our atmosphere by triangulation and calculate the meteoroid orbit in space. In recent years, the CAMS (Cameras for Allsky Meteor Surveillance) low-light video camera network was greatly expanded and, together with other video networks, now has increased the total video meteoroid orbit database to over 2.2 million orbits. Here, we searched this database for meteor showers associated with known long-period comets. Previously, five associations were known. Now, we find 14, as well as six uncertain but likely associations. These showers show a change of longitude of perihelion with node that is a strong function of inclination. Showers of longer duration show a steeper magnitude distribution index, presumably due to aging of the meteoroid population. Showers are generally detected only if the orbital period of the comet is less than 4000 years and the Earth-Comet orbital miss distance is 0.10 AU. The lack of an associated meteor shower sets lower limits on the orbital period of poorly observed comets.
We describe the target selection procedure by which stars are selected for 2 minute and 20 s observations by TESS. We first list the technical requirements of the TESS instrument and ground systems processing that limit the total number of target slots. We then describe algorithms used by the TESS Payload Operation Center (POC) to merge candidate targets requested by the various TESS mission elements (the Target Selection Working Group, TESS Asteroseismic Science Consortium, and Guest Investigator office). Lastly, we summarize the properties of the observed TESS targets over the two-year primary TESS mission. We find that the POC target selection algorithm results in 2.1-3.4 times as many observed targets as target slots allocated for each mission element. We also find that the sky distribution of observed targets is different from the sky distributions of candidate targets due to technical constraints that require a relatively even distribution of targets across the TESS fields of view. We caution researchers exploring statistical analyses of TESS planet-host stars that the population of observed targets cannot be characterized by any simple set of criteria applied to the properties of the input Candidate Target Lists.
To properly understand the evolution of high-redshift galaxy clusters, both passive and star-forming galaxies have to be considered. Here we study the clustering environment of 21 radio galaxies and quasars at 1 < z < 2.5 from the third Cambridge catalog (3C). We use optical and near-infrared Hubble Space Telescope images with a 2' field-of-view, where the filters encompass the rest-frame 4000 A break. Passive red and star-forming blue galaxies were separated in the color-magnitude diagram using a redshift-dependent cut derived from galaxy evolution models. We find that about 16 of 21 radio sources inhabit a galaxy overdensity on scales of 250 kpc (30) projected radius. The sample shows a diversity of red and blue overdensities and also sometimes a deficiency of blue galaxies in the center. The following tentative evolutionary trends are seen: extended proto-clusters with only weak overdensities at z > 1.6, red overdensities at 1.2 < z < 1.6, and red overdensities with an increased deficit of central blue galaxies at z < 1.2. Only a few 3C sources show a blue overdensity tracing active star-formation in the cluster centers; this rarity could indicate that the powerful quasar activity may quench star-formation in the vicinity of most radio sources. The derived number of central luminous red galaxies and the radial density profiles are comparable to those found in local clusters, indicating that some 3C clusters are already mass-rich and compact.
We conducted interferometric observations with the CHARA Array of transiting super-Earth host HD 97658 and measured its limb-darkened angular diameter to be LD = 0.314 0.004 mas. The combination of the angular diameter with the Gaia EDR3 parallax value with zero-point correction ( = 46.412 0.022 mas, d =21.546 0.011 pc) yields a physical radius of R = 0.728 0.008 R. We also measured the bolometric flux of the star to be Fbol = 2.42 0.05 10-8 erg s-1 cm-2, which, together with angular size, allows a measurement of the effective temperature Teff = 5212 43 K. Our directly determined physical stellar properties are in good agreement with previous estimates derived from spectroscopy. We used our measurements in combination with stellar evolutionary models and properties of the transit of HD 97658 b to determine the mass and age of HD 97658 as well as constrain the properties of the planet. Our results and our analysis of the TESS light curve on the planet (TOI-1821) corroborate previous studies of this system with tighter uncertainties.
Stochastic field distortions caused by atmospheric turbulence are a fundamental limitation to the astrometric accuracy of ground-based imaging. This distortion field is measurable at the locations of stars with accurate positions provided by the Gaia DR2 catalog; we develop the use of Gaussian process regression (GPR) to interpolate the distortion field to arbitrary locations in each exposure. We introduce an extension to standard GPR techniques that exploits the knowledge that the 2D distortion field is curl-free. Applied to several hundred 90 s exposures from the Dark Energy Survey as a test bed, we find that the GPR correction reduces the variance of the turbulent astrometric distortions 12 , on average, with better performance in denser regions of the Gaia catalog. The rms per-coordinate distortion in the riz bands is typically 7 mas before any correction and 2 mas after application of the GPR model. The GPR astrometric corrections are validated by the observation that their use reduces, from 10 to 5 mas rms, the residuals to an orbit fit to riz-band observations over 5 yr of the r = 18.5 trans-Neptunian object Eris. We also propose a GPR method, not yet implemented, for simultaneously estimating the turbulence fields and the 5D stellar solutions in a stack of overlapping exposures, which should yield further turbulence reductions in future deep surveys.
We present here far-infrared photometry of galaxies in a sample that is relatively unexplored at these wavelengths: low-metallicity dwarf galaxies with moderate star formation rates. Four dwarf irregular galaxies from the LITTLE THINGS survey are considered, with deep Herschel PACS and SPIRE observations at 100, 160, 250, 350, and 500 m. Results from modified blackbody fits indicate that these galaxies have low dust masses and cooler dust temperatures than more actively star-forming dwarfs, occupying the lowest LTIR and Mdust regimes seen among these samples. Dust-to-gas mass ratios of ~10-5 are lower, overall, than in more massive and active galaxies but are roughly consistent with the broken power-law relation between the dust-to-gas ratio and metallicity found for other low-metallicity systems. Chemical evolution modeling suggests that these dwarf galaxies are likely forming very little dust via stars or grain growth and have very high dust destruction rates.
We use a sample of 809 photometrically classified Type Ia supernovae (SNe Ia) discovered by the Dark Energy Survey (DES) along with 40 415 field galaxies to calculate the rate of SNe Ia per galaxy in the redshift range 0.2 < z < 0.6. We recover the known correlation between SN Ia rate and galaxy stellar mass across a broad range of scales 8.5 log (M*/M) 11.25. We find that the SN Ia rate increases with stellar mass as a power law with index 0.63 0.02, which is consistent with the previous work. We use an empirical model of stellar mass assembly to estimate the average star formation histories (SFHs) of galaxies across the stellar mass range of our measurement. Combining the modelled SFHs with the SN Ia rates to estimate constraints on the SN Ia delay time distribution (DTD), we find that the data are fit well by a power-law DTD with slope index = -1.13 0.05 and normalization A = 2.11 0.05 10-13 SNe M-1 yr-1, which corresponds to an overall SN Ia production efficiency $N_{\mathrm{Ia}}/M_* = 0.9~_{-0.7}^{+4.0} \times 10^{-3}~\mathrm{SNe}~\mathrm{M}_{\odot }^{-1}$. Upon splitting the SN sample by properties of the light curves, we find a strong dependence on DTD slope with the SN decline rate, with slower-declining SNe exhibiting a steeper DTD slope. We interpret this as a result of a relationship between intrinsic luminosity and progenitor age, and explore the implications of the result in the context of SN Ia progenitors.
Determining the distribution of redshifts of galaxies observed by wide-field photometric experiments like the Dark Energy Survey (DES) is an essential component to mapping the matter density field with gravitational lensing. In this work we describe the methods used to assign individual weak lensing source galaxies from the DES Year 3 Weak Lensing Source Catalogue to four tomographic bins and to estimate the redshift distributions in these bins. As the first application of these methods to data, we validate that the assumptions made apply to the DES Y3 weak lensing source galaxies and develop a full treatment of systematic uncertainties. Our method consists of combining information from three independent likelihood functions: self-organizing map p(z) (SOMPZ), a method for constraining redshifts from galaxy photometry; clustering redshifts (WZ), constraints on redshifts from cross-correlations of galaxy density functions; and shear ratios (SRs), which provide constraints on redshifts from the ratios of the galaxy-shear correlation functions at small scales. Finally, we describe how these independent probes are combined to yield an ensemble of redshift distributions encapsulating our full uncertainty. We calibrate redshifts with combined effective uncertainties of z ~ 0.01 on the mean redshift in each tomographic bin.
We report on the discovery and validation of a two-planet system around a bright (V = 8.85 mag) early G dwarf (1.43 R, 1.15 M, TOI 2319) using data from NASA's Transiting Exoplanet Survey Satellite (TESS). Three transit events from two planets were detected by citizen scientists in the month-long TESS light curve (sector 25), as part of the Planet Hunters TESS project. Modelling of the transits yields an orbital period of $11.6264 _{ - 0.0025 } ^ { + 0.0022 }$ d and radius of $3.41 _{ - 0.12 } ^ { + 0.14 }$ R for the inner planet, and a period in the range 19.26-35 d and a radius of $5.83 _{ - 0.14 } ^ { + 0.14 }$ R for the outer planet, which was only seen to transit once. Each signal was independently statistically validated, taking into consideration the TESS light curve as well as the ground-based spectroscopic follow-up observations. Radial velocities from HARPS-N and EXPRES yield a tentative detection of planet b, whose mass we estimate to be $11.56 _{ - 6.14 } ^ { + 6.58 }$ M, and allow us to place an upper limit of 27.5 M (99 per cent confidence) on the mass of planet c. Due to the brightness of the host star and the strong likelihood of an extended H/He atmosphere on both planets, this system offers excellent prospects for atmospheric characterization and comparative planetology.
We present DES14X2fna, a high-luminosity, fast-declining Type IIb supernova (SN IIb) at redshift z = 0.0453, detected by the Dark Energy Survey (DES). DES14X2fna is an unusual member of its class, with a light curve showing a broad, luminous peak reaching Mr -19.3 mag 20 d after explosion. This object does not show a linear decline tail in the light curve until 60 d after explosion, after which it declines very rapidly (4.30 0.10 mag 100 d-1 in the r band). By fitting semi-analytic models to the photometry of DES14X2fna, we find that its light curve cannot be explained by a standard 56Ni decay model as this is unable to fit the peak and fast tail decline observed. Inclusion of either interaction with surrounding circumstellar material or a rapidly-rotating neutron star (magnetar) significantly increases the quality of the model fit. We also investigate the possibility for an object similar to DES14X2fna to act as a contaminant in photometric samples of SNe Ia for cosmology, finding that a similar simulated object is misclassified by a recurrent neural network (RNN)-based photometric classifier as an SN Ia in ~1.1-2.4 per cent of cases in DES, depending on the probability threshold used for a positive classification.
Mid-infrared photometry of the Wolf-Rayet star HD 38030 in the Large Magellanic Cloud from the NEOWISE-R mission show it to have undergone a dust-formation episode in 2018 and the dust to have cooled in 2019-20. New spectroscopy with the MagE spectrograph on the Magellan I Baade Telescope in 2019 and 2020 show absorption lines attributable to a companion of type near O9.7III-IV. We found a significant shift in the radial velocity of the C IV 5801-12 blend compared with the RVs measured in 1984 and 1993. The results combine to suggest that HD 38030 is a colliding-wind binary having short-lived dust formation episodes, like the Galactic systems WR 140 and WR 19, but at intervals in excess of 20 yr.
Context. The Centaur (10199) Chariklo has the first ring system discovered around a small object. It was first observed using stellar occultation in 2013. Stellar occultations allow sizes and shapes to be determined with kilometre accuracy, and provide the characteristics of the occulting object and its vicinity.
Aims: Using stellar occultations observed between 2017 and 2020, our aim is to constrain the physical parameters of Chariklo and its rings. We also determine the structure of the rings, and obtain precise astrometrical positions of Chariklo.
Methods: We predicted and organised several observational campaigns of stellar occultations by Chariklo. Occultation light curves were measured from the datasets, from which ingress and egress times, and the ring widths and opacity values were obtained. These measurements, combined with results from previous works, allow us to obtain significant constraints on Chariklo's shape and ring structure.
Results: We characterise Chariklo's ring system (C1R and C2R), and obtain radii and pole orientations that are consistent with, but more accurate than, results from previous occultations. We confirm the detection of W-shaped structures within C1R and an evident variation in radial width. The observed width ranges between 4.8 and 9.1 km with a mean value of 6.5 km. One dual observation (visible and red) does not reveal any differences in the C1R opacity profiles, indicating a ring particle size larger than a few microns. The C1R ring eccentricity is found to be smaller than 0.022 (3), and its width variations may indicate an eccentricity higher than ~0.005. We fit a tri-axial shape to Chariklo's detections over 11 occultations, and determine that Chariklo is consistent with an ellipsoid with semi-axes of 143.81.5+1.4, 135.22.8+1.4, and 99.12.7+5.4 km. Ultimately, we provided seven astrometric positions at a milliarcsecond accuracy level, based on Gaia EDR3, and use it to improve Chariklo's ephemeris. Tables C.1, C.2 and lightcurves are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/652/A141.
We present high-angular-resolution imaging observations of 517 host stars of TESS exoplanet candidates using the 'Alopeke and Zorro speckle cameras at Gemini North and South. The sample consists mainly of bright F, G, K stars at distances of less than 500 pc. Our speckle observations span angular resolutions of ~20 mas out to 1"2, yielding spatial resolutions of <10-500 au for most stars, and our contrast limits can detect companion stars 5-9 mag fainter than the primary at optical wavelengths. We detect 102 close stellar companions and determine the separation, magnitude difference, mass ratio, and estimated orbital period for each system. Our observations of exoplanet host star binaries reveal that they have wider separations than field binaries, with a mean orbital semimajor axis near 100 au. Other imaging studies have suggested this dearth of very closely separated binaries in systems which host exoplanets, but incompleteness at small separations makes it difficult to disentangle unobserved companions from a true lack of companions. With our improved angular resolution and sensitivity, we confirm that this lack of close exoplanet host binaries is indeed real. We also search for a correlation between planetary orbital radii versus binary star separation; but, given the very short orbital periods of the TESS planets, we do not find any clear trend. We do note that in exoplanet systems containing binary host stars, there is an observational bias against detecting Earth-size planet transits due to transit depth dilution caused by the companion star.
We present deep g- and r-band Magellan/Megacam photometry of two dwarf galaxy candidates discovered in the Dark Energy Survey (DES), Grus I and Indus II (DES J2038-4609). For the case of Grus I, we resolved the main sequence turn-off (MSTO) and ~2 mags below it. The MSTO can be seen at g0 ~ 24 with a photometric uncertainty of 0.03 mag. We show Grus I to be consistent with an old, metal-poor (~13.3 Gyr, [Fe/H] ~ -1.9) dwarf galaxy. We derive updated distance and structural parameters for Grus I using this deep, uniform, wide-field data set. We find an azimuthally-averaged halflight radius more than two times larger (~151+21-31 pc; ~ $4\buildrel{\,\prime}\over{.} {16}_{-0.74}^{+0.54}$) and an absolute V-band magnitude ~-4.1 that is ~1 magnitude brighter than previous studies. We obtain updated distance, ellipticity, and centroid parameters that are in agreement with other studies within uncertainties. Although our photometry of Indus II is ~2-3 magnitudes deeper than the DES Y1 public release, we find no coherent stellar population at its reported location. The original detection was located in an incomplete region of sky in the DES Y2Q1 data set and was flagged due to potential blue horizontal branch member stars. The best-fit isochrone parameters are physically inconsistent with both dwarf galaxies and globular clusters. We conclude that Indus II is likely a false positive, flagged due to a chance alignment of stars along the line of sight.
The analysis of current and future cosmological surveys of Type Ia supernovae (SNe Ia) at high redshift depends on the accurate photometric classification of the SN events detected. Generating realistic simulations of photometric SN surveys constitutes an essential step for training and testing photometric classification algorithms, and for correcting biases introduced by selection effects and contamination arising from core-collapse SNe in the photometric SN Ia samples. We use published SN time-series spectrophotometric templates, rates, luminosity functions, and empirical relationships between SNe and their host galaxies to construct a framework for simulating photometric SN surveys. We present this framework in the context of the Dark Energy Survey (DES) 5-yr photometric SN sample, comparing our simulations of DES with the observed DES transient populations. We demonstrate excellent agreement in many distributions, including Hubble residuals, between our simulations and data. We estimate the core collapse fraction expected in the DES SN sample after selection requirements are applied and before photometric classification. After testing different modelling choices and astrophysical assumptions underlying our simulation, we find that the predicted contamination varies from 7.2 to 11.7 per cent, with an average of 8.8 per cent and an r.m.s. of 1.1 per cent. Our simulations are the first to reproduce the observed photometric SN and host galaxy properties in high-redshift surveys without fine-tuning the input parameters. The simulation methods presented here will be a critical component of the cosmology analysis of the DES photometric SN Ia sample: correcting for biases arising from contamination, and evaluating the associated systematic uncertainty.
We present the second public data release of the Dark Energy Survey, DES DR2, based on optical/near-infrared imaging by the Dark Energy Camera mounted on the 4 m Blanco telescope at Cerro Tololo Inter-American Observatory in Chile. DES DR2 consists of reduced single-epoch and coadded images, a source catalog derived from coadded images, and associated data products assembled from 6 yr of DES science operations. This release includes data from the DES wide-area survey covering ~5000 deg2 of the southern Galactic cap in five broad photometric bands, grizY. DES DR2 has a median delivered point-spread function FWHM of g = 1.11, r = 0.95, i = 0.88, z = 0.83, and Y = 0"90, photometric uniformity with a standard deviation of < 3 mmag with respect to Gaia DR2 G band, a photometric accuracy of ~11 mmag, and a median internal astrometric precision of ~27 mas. The median coadded catalog depth for a 1"95 diameter aperture at signal-to-noise ratio = 10 is g = 24.7, r = 24.4, i = 23.8, z = 23.1, and Y = 21.7 mag. DES DR2 includes ~691 million distinct astronomical objects detected in 10,169 coadded image tiles of size 0.534 deg2 produced from 76,217 single-epoch images. After a basic quality selection, benchmark galaxy and stellar samples contain 543 million and 145 million objects, respectively. These data are accessible through several interfaces, including interactive image visualization tools, web-based query clients, image cutout servers, and Jupyter notebooks. DES DR2 constitutes the largest photometric data set to date at the achieved depth and photometric precision.
Triton is an important signpost in understanding the diverse populations of both ocean worlds and Kuiper Belt objects (KBOs). As a likely ocean world, it is unique by virtue of its kidnapped history from the Kuiper Belt: its large orbital inclination makes it the only ocean world thought to be primarily heated by obliquity tides. It is volatile-rich due to its formation in the outer solar system and its unusual surface geology may be the product of cryovolcanism. Observations from New Horizons and Cassini motivate re-examination of Triton data sets and models, with value for comparative planetology of ocean worlds and KBOs, most notably with Europa, Enceladus, Titan, and Pluto. We re-explore old data sets with the new perspective of the importance of ocean worlds in our solar system and the search for life.
Hayabusa2 is the Japanese Asteroid Return Mission and targeted the carbonaceous asteroid Ryugu, conducted by the Japan Aerospace Exploration Agency (JAXA). The goal of this mission was to conduct proximity operations including remote sensing observations, material sampling, and a Small Carry-On Impact experiment, as well as sample analyses. As of September 2020, the spacecraft is on the way back to Earth with samples from Ryugu with no critical issues after the successful departure in November 2019. Here, we propose an extended mission in which the spacecraft will rendezvous with a small asteroid with ~30 m - ~40 m in diameter that is rotating at a spin period of ~10 min after an additional ~10-year cruise phase. We introduce that two scenarios are suitable for the extended mission. In the first scenario, the spacecraft will perform swing-by maneuvers at Venus once and Earth twice to arrive at asteroid 2001 AV43. In the second scenario, it will perform swing-by maneuvers at Earth twice to reach asteroid 1998 KY26. In both scenarios, the mission will continue until the early 2030s. JAXA recently released the decision that the spacecraft will rendezvous with 1998 KY26. This paper focuses on our scientific assessments of the two scenarios but leaves the decision process to go to 1998 KY26 for future reports. Rendezvous operations will be planned to detail the physical properties and surrounding environments of the target, one of the smallest elements of small planetary bodies. By achieving the planned operations, the mission will provide critical hints on the violent histories of collisions and accumulations of small bodies in the solar system. Furthermore, the established scientific knowledge and techniques will advance key technologies for planetary defense.
In 2018 December, the main-belt asteroid (6478) Gault was reported to display activity. Gault is an asteroid belonging to the Phocaea dynamical family and was not previously known to be active, nor was any other member of the Phocaea family. In this work, we present the results of photometric and spectroscopic observations that commenced soon after the discovery of activity. We obtained observations over two apparitions to monitor its activity, rotation period, composition, and possible non-gravitational orbital evolution. We find that Gault has a rotation period of P = 2.4929 0.0003 h with a light-curve amplitude of 0.06 magnitude. This short rotation period close to the spin barrier limit is consistent with Gault having a density no smaller than = 1.85 g cm-3 and its activity being triggered by the YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack) spin-up mechanism. Analysis of the Gault phase curve over phase angles ranging from 0.4 to 23.6 provides an absolute magnitude of H = 14.81 0.04, G1 = 0.25 0.07, and G2 = 0.38 0.04. Model fits to the phase curve find the surface regolith grain size constrained between 100 and 500 $\rm {\mu }$m. Using relations between the phase curve and albedo, we determine that the geometrical albedo of Gault is pv = 0.26 0.05 corresponding to an equivalent diameter of $D = 2.8^{+0.4}_{-0.2}$ km. Our spectroscopic observations are all consistent with an ordinary chondrite-like composition (S, or Q-type in the Bus-DeMeo taxonomic classification). A search through archival photographic plate surveys found previously unidentified detections of Gault dating back to 1957 and 1958. Only the latter had been digitized, which we measured to nearly double the observation arc of Gault. Finally, we did not find any signal of activity during the 2020 apparition or non-gravitational effects on its orbit.
The Transiting Exoplanet Survey Satellite (TESS) has proven to be a powerful resource for uncovering planets, and the M-dwarfs have been established as favorable planet hosts. It has also become apparent that stellar multiplicity has wide-ranging implications for exoplanet detection and characterization, and that speckle imaging is one of the most efficient tools for probing these multi-star systems. We therefore present high-resolution imaging observations of 63 M-dwarf TOIs using speckle imagers at the 3.5m WIYN telescope, the 4.3m Lowell Discovery Telescope (LDT), and the twin 8.1m Gemini North and South telescopes. However, only one companion was detected. This finding is in contrast to the established 46% binarity rate in exoplanet host stars and the established 27% stellar multiplicity rate for field M-dwarfs. These results indicate that M-dwarf TOIs have a much lower multiplicity rate than field M-dwarfs. Our observations also imply that planet signals detected from M-dwarf TOIs are more likely to be real than those from higher-mass stars. Finally, these data support the observation that exoplanet-hosting binary stars have, in general, wider separations than field binaries.
TESS is poised to increase the number of stellar rotation period estimates by an order of magnitude, but the mission's systematics have complicated period searches. While several efforts attempt to solve this problem by removing systematics, standard methods of data reduction have shown limited success. Here I present a method to predict rotation periods from TESS full-frame image light curves using deep learning. This method relies on a training set of simulated light curves convolved with TESS galaxy light curves to emulate the instrumental noise and systematics observed in stellar signals. The simulations include surface differential rotation, spot evolution, and activity level to make the light curves as realistic as possible. Our approach allows the network to learn the difference between rotation signals and TESS systematics. With the added ability to predict uncertainty in the period, we can determine what regions of parameter space the predictions are most credible, producing a reliable set of rotation periods. I present the first set of rotation periods obtained with this method and explore TESS's insights to stellar structure and evolution through the lens of rotation.
Blanco 1, a 100 Myr open cluster in the solar neighborhood, is well known for its two 50 pc long tidal tails. Taking Blanco 1 as a reference, we find evidence of early-stage tidal disruption in two other open clusters of ~120 Myr: the Pleiades and NGC 2516, via Gaia EDR3 data. These two clusters have a total mass of 2-6 times that of Blanco 1. Despite having a similar age as Blanco 1, the Pleiades and NGC 2516 have a larger fraction of their members bound: 86% of their mass is inside the tidal radius, versus 63% for Blanco 1. However, a correlation between Blanco 1's 50 pc long tidal tails and the "kinematic tails" in velocity space is also found for the Pleiades and NGC 2516. This evidence supports the idea that the modest elongation seen in the spatial distribution for the Pleiades and NGC 2516 is a result of early-stage tidal disruption.
The recently discovered Indus stellar stream exhibits a diverse chemical signature compared to what is found for most other streams due to the abundances of two outlier stars, Indus_0 and Indus_13. Indus_13 exhibits an extreme enhancement in rapid neutron-capture (r-)process elements with [Eu/Fe] = + 1.81. It thus provides direct evidence of the accreted nature of r-process-enhanced stars. In this paper we present a detailed chemical analysis of the neutron-capture elements in Indus_13, revealing the star to be slightly actinide poor. The other outlier, Indus_0, displays a globular cluster-like signature with high N, Na, and Al abundances, while the rest of the Indus stars show abundances compatible with a dwarf galaxy origin. Hence, Indus_0 provides the first chemical evidence of a fully disrupted dwarf containing a globular cluster. We use the chemical signature of the Indus stars to discuss the nature of the stream progenitor which was likely a chemically evolved system, with a mass somewhere in the range from Ursa Minor to Fornax.
The radio thermal emission from Pluto was observed from the New Horizons spacecraft at a wavelength of 4.2 cm along two scans across the planetary disk shortly after closest approach to Pluto on 14 July 2015. The measurements were performed as part of the New Horizons Radio Science Experiment (REX) using the 2.1 m High Gain Antenna (HGA) and the spacecraft's X-Band receiver. The HGA boresight first scanned along a diametric chord across the Pluto disk and then reversed direction to traverse a chord that crossed close to Pluto's winter pole. The diametric scan reveals a "hot spot" on the Pluto nightside associated with an optically bright region centered roughly at the planetocentric coordinates 280 E, 55 S, imaged in 2002-03 with the Hubble Space Telescope. The nightside was also found to be warmer than the dayside during the polar scan. The highest emission was not observed at the maximum southern latitude, however, but rather near the outbound Pluto limb at lower latitude. The REX emission profile from the polar scan is qualitatively consistent with a bright U-shaped polar cap observed on Pluto's Charon-facing hemisphere during the recurring Pluto/Charon mutual events in the late 1980's. The REX radiometer measurements show distinct variations in microwave brightness that constrain volatile transport models and provide unique information on the thermal structure and composition on the regions in winter night during the New Horizons encounter at Pluto.
We perform a cross validation of the cluster catalogue selected by the red-sequence Matched-filter Probabilistic Percolation algorithm (redMaPPer) in Dark Energy Survey year 1 (DES-Y1) data by matching it with the Sunyaev-Zel'dovich effect (SZE) selected cluster catalogue from the South Pole Telescope SPT-SZ survey. Of the 1005 redMaPPer selected clusters with measured richness $\hat{\lambda }\gt 40$ in the joint footprint, 207 are confirmed by SPT-SZ. Using the mass information from the SZE signal, we calibrate the richness-mass relation using a Bayesian cluster population model. We find a mass trend MB consistent with a linear relation (B ~ 1), no significant redshift evolution and an intrinsic scatter in richness of = 0.22 0.06. By considering two error models, we explore the impact of projection effects on the richness-mass modelling, confirming that such effects are not detectable at the current level of systematic uncertainties. At low richness SPT-SZ confirms fewer redMaPPer clusters than expected. We interpret this richness dependent deficit in confirmed systems as due to the increased presence at low richness of low-mass objects not correctly accounted for by our richness-mass scatter model, which we call contaminants. At a richness $\hat{\lambda }=40$, this population makes up ${\gt}12{{\ \rm per\ cent}}$ (97.5 percentile) of the total population. Extrapolating this to a measured richness $\hat{\lambda }=20$ yields ${\gt}22{{\ \rm per\ cent}}$ (97.5 percentile). With these contamination fractions, the predicted redMaPPer number counts in different plausible cosmologies are compatible with the measured abundance. The presence of such a population is also a plausible explanation for the different mass trends (B ~ 0.75) obtained from mass calibration using purely optically selected clusters. The mean mass from stacked weak lensing (WL) measurements suggests that these low-mass contaminants are galaxy groups with masses ~3-5 1013 M which are beyond the sensitivity of current SZE and X-ray surveys but a natural target for SPT-3G and eROSITA.
We propose to observe the large Uranian satellites Ariel, Umbriel, Titania, and Oberon, using the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST), to investigate whether their surface compositions are modified by charged particles trapped in Uranus' magnetosphere. The large Uranian moons are candidate ocean worlds, with surfaces that are rich in CO2 ice. The origin of CO2 ice on these moons is uncertain, but it could be formed by ongoing charged particle bombardment of native H2O ice and C-rich material on their surfaces. Alternatively, CO2 ice could be native to these moons and sourced from their interiors, hinting at recent geologic activity. To investigate whether charged particles modify these four moons' surface compositions, we will collect UV spectra and conduct a series of measurements: (1) compare the near-UV (300 nm) albedos of each moon's leading and trailing hemisphere to characterize longitudinal and radial trends in charged particle irradiation; (2) measure an absorption band that spans 257 to 360 nm, attributed to trapped OH formed by charged particle irradiation of H2O ice, on each moon's leading and trailing hemisphere to characterize longitudinal and radial trends in the distribution of this feature; (3) compare the distribution of the 280-nm trapped OH band to the distribution of CO2 ice; (4) compare these new STIS spectra that would be collected over the northern hemispheres of these moons (sub-observer lat. 55 N) to archived HST/FOS spectra that were collected over their southern hemispheres (sub-observer lat. 45 S) to characterize any latitudinal trends in charged particle irradiation that might be present.
(3548) Eurybates will be the first Trojan asteroid to be explored in situ when the Lucy spacecraft flies by it in August 2027. The possibility of close-up study of Eurybates' satellite, Queta, offers a unique opportunity to test whether Eurybates' unusual properties are tied to its collisional history and, more broadly, how collisional evolution shapes small body populations. It is critical to reduce the orbital uncertainty and improve knowledge of the relative position of Queta as soon as possible to understand if there could be an impact to Lucy's encounter concept of operations and to optimize planning for the best angular resolution and lighting conditions in the brief window when observations can be made. By establishing a tighter constraint on the current orbit, it will be possible to accelerate searches for non-Keplerian motion should there be an additional satellite or satellites interior to Queta (as are commonly found in other collisional-family satellite systems). Additionally, we will use astrometric information from trailed stars in the full UVIS aperture to improve predictions for future stellar occultations. HST is required because Queta is 8.7 magnitudes fainter than Eurybates and will be observed at a separation of 0.5 arcsec - an observational regime that is unique to Hubble.
The outermost region in our Solar System retains the most pristine signatures of planetary system formation and evolution. This trans-Neptunian region and its inhabitants (trans-Neptunian objects, or TNOs) therefore offer some of the best records of the earliest stages of the formation of our Solar System. There are two very different theories for how the outermost Solar System formed and evolved, and the color distribution of very small TNOs is the diagnostic key to discriminating between these two models. We propose here 99 HST orbits to address this outstanding question in planetary system formation. We will use WFC3 and ACS in a coordinated parallel program to map most of the footprint of a JWST TNO discovery program. TNO colors will be derived by combining our HST photometry with photometry from that JWST program. We will measure the colors of at least 15 TNOs as small as 10 km and will provide a definitive test of current models of the evolution of the outer Solar System. The HST observations must be made simultaneously with the JWST observations to derive both TNO colors and parallaxes. This program can only be carried out with HST, and only by combining data from both HST and JWST. The result from this program will have broad implications across multiple fields of astronomy and showcase the unique joint capabilities of NASA's premier observatories. No other facility is capable of such sensitive measurements, and this program leverages a significant investment of allocated JWST time.
Levesque et al (2014, MNRAS, 443, 94) described the evidence that we had likely found the first identified Thorne-Zytkow object, HV 2112. In this talk, I will describe how this discovery came about, including the decades of work that laid the foundations for our work. I will also review the status of the star today: is it, or isn't it, a TZO?
Massive stars in binary systems are the progenitors to many exciting phenomena, such as TZOs and the gravitational wave events we can now detect with LIGO. The binary fraction of massive main-sequence OB stars is thought to be as high as 70% or greater. As these stars burn through their hydrogen, many of them will experience strong Roche-Lobe overflow while on the main sequence and merge. In the systems that remain, the more massive star will evolve off the main sequence and expand into a red supergiant (RSG). In binaries with close separations, the RSG will consume its companion and a merger will occur. In longer period systems, the companion will remain. Eventually, the RSG will end its life as a supernova, and the resulting system will contain an evolved star with a compact object, the progenitor to a TZO. As part of my PhD research, I characterized the RSG binary fraction as a function of metallicity in the Local Group galaxies M31, M33 and the Large Magellanic Cloud and am currently investigating the RSG merger fraction in our own Galaxy. In this talk, I'll discuss how these results help us better understand the numbers and behaviors of TZO progenitors.
The NASA Ames COsmic SImulation Chamber (COSmIC) is a unique experimental facility that can be used, among many applications, to produce solid particles from gas phase molecular precursors at low temperature (150 K) using a plasma discharge to induce the chemistry in the stream of a free jet expansion. The choice of the initial gas mixture used to produce the solid sample allows the simulation of either cold planetary atmospheres like Titan or Pluto (with N2/CH4-based initial mixtures), or circumstellar environments (with Ar/CxHy-based initial mixtures). The Ames Optical Constants Facility (OCF) allows the determination of optical constants covering a broad wavelength range with high spectral resolution for solid materials, analogs of organic refractory materials formed in planetary and astrophysical environments. The core of the OCF is a Fourier transform infrared (FTIR) spectrometer that allows the continuous characterization of solid samples in the visible to far-infrared (FIR) range (0.59-200 m, 16,950-50 cm1). Modeling of the laboratory measurements conducted with the OCF allows the determination of accurate optical constants, n and k, over the full vis-FIR range. Here we present the latest results of two studies that combined (1) experiments performed with COSmIC to produce analogs of aerosols forming in Titan's atmosphere and analogs of cosmic grains forming in circumstellar envelops, and (2) the characterization of these analogs with the OCF to provide the real and imaginary parts of their refractive indices, n + ik, to the community, from the visible to the FIR. These optical constants can be used as critical input parameters in radiative transfer, atmospheric and reflectance models to interpret observational data of, e.g., Titan's atmosphere and protoplanetary disks. Providing optical constants for various materials of different compositions allows to explore a broad range of composition by simulating mixtures of materials. We also present a new project to produce analogs of Pluto's atmospheric aerosols with COSmIC and determine their optical constants with OCF, to be used in reflectance spectra models for the interpretation of New Horizons observations of Lowell Regio, Sputnik Planitia and Cthulhu.
We report on a 5-year study of the historical literature from Galileo until today regarding the concept of a planet. Bibliometrics show that scientific productivity in astronomy grew exponentially from at least 1700 until the present except for a long period of non-growth from 1894 until 1955. Contained within that was a period of deep reduction of scientific productivity over planets and satellites lasting from 1910 until 1955, which we have labeled the "Great Depression of Planetary Science". During that period, astronomers' interests were focused largely on other, more exciting topics enabled by new technologies. Records show it was during this period that astronomers stopped using and indeed lost memory of the concept of "planet" that had been taught since Galileo. They began using in its place a folk concept of planets that had evolved during the first half 1800s in astrological and other non-scientific writings, and which had spread through the general public by the end of the 1800s. According to that folk concept, planets were defined as only the large primaries that are orderly and directly orbit the Sun because those are the bodies that suggest orderliness in the cosmos consistent with non-reductionist views that the public favored. Non-scientific publications were arguing that planets in our Solar System were created to serve the Earth, even though it was acknowledged that they do not orbit the Earth. Like scientists, the public was aligning planetary taxonomy with theories they held most important to understand the cosmos, but unlike the scientists their theories were not reductionist. Apparently, pedagogical neglect during the Great Depression of Planetary Science coupled with a lack of theory advancement (and thus no recognized need for a utilitarian taxonomy) produced a generation of astronomers who thought that the folk concept had always been the only concept. In recent years, astronomers have fallen into historical presentism, teaching that the folk concept was actually developed during the Copernican Revolution (despite what the literature clearly shows), that the reductionist concept never existed, and that it has been normative to have a "planet" concept that is not scientifically useful. However, since 1955 there has been movement in the planetary science literature toward a concept that is broader than the folk one and is aligned again with the historic insight and purposes initiated by Galileo. Failure to understand this history has contributed to the recent controversy over the definition of a planet.
Determining the total line-of-sight extinction to actively accreting young stellar objects (YSOs) can be difficult, especially during outburst or flaring events. The diffuse interstellar bands (DIBs) have been shown in previous studies to correlate well with column densities of interstellar material, and therefore extinction measurements, for early-type stars. We employ the correlations found in the literature and new measurements of equivalent width in the 5780 A and 6614 A DIBs features of a sample of outbursting YSOs to infer their E(B-V) values. We compare the resulting extinction values to previous estimates for these sources, and discuss the prospects for the use of DIBs in understanding the environments of YSOs.
On Titan, methane (CH4) and ethane (C2H6) are the dominant species found in the lakes and seas. In this study, we have combined laboratory work and modeling to refine the methane-ethane binary phase diagram at low temperatures and probe how the molecules interact at these conditions. We used visual inspection for the liquidus and Raman spectroscopy for the solidus. Through these methods, we determined a eutectic point of 71.15 0.5 K at a composition of 0.644 0.018 methane-0.356 0.018 ethane mole fraction from the liquidus data. Using the solidus data, we found a eutectic isotherm temperature of 72.2 K with a standard deviation of 0.4 K. In addition to mapping the binary system, we looked at the solid-solid transitions of pure ethane and found that, when cooling, the transition of solid I-III occurred at 89.45 0.2 K. The warming sequence showed transitions of solid III-II occurring at 89.85 0.2 K and solid II-I at 89.65 0.2 K. Ideal predictions were compared with molecular dynamics simulations to reveal that the methane-ethane system behaves almost ideally, and the largest deviations occur as the mixing ratio approaches the eutectic composition.
Thanks to the Cassini-Huygens mission, Titan, the pale orange dot of Pioneer and Voyager encounters, has been revealed to be a dynamic, hydrologically shaped, organic-rich ocean world offering unparalleled opportunities to explore prebiotic chemistry. And while Cassini-Huygens revolutionized our understanding of each of the three "layers" of Titanthe atmosphere, the surface, and the interiorwe are only beginning to hypothesize how these realms interact. In this paper, we summarize the current state of Titan knowledge and discuss how future exploration of Titan would address some of the next decade's most compelling planetary science questions. We also demonstrate why exploring Titan, both with and beyond the Dragonfly New Frontiers mission, is a necessary and complementary component of an Ocean Worlds Program that seeks to understand whether habitable environments exist elsewhere in our solar system.
We study a phenomenological class of models where dark matter converts to dark radiation in the low redshift epoch. This class of models, dubbed DMDR, characterizes the evolution of comoving dark-matter density with two extra parameters, and may be able to help alleviate the observed discrepancies between early and late-time probes of the Universe. We investigate how the conversion affects key cosmological observables such as the cosmic microwave background (CMB) temperature and matter power spectra. Combining 3x2pt data from Year 1 of the Dark Energy Survey, Planck-2018 CMB temperature and polarization data, supernovae (SN) Type Ia data from Pantheon, and baryon acoustic oscillation (BAO) data from BOSS DR12, MGS and 6dFGS, we place new constraints on the amount of dark matter that has converted to dark radiation and the rate of this conversion. The fraction of the dark matter that has converted since the beginning of the Universe in units of the current amount of dark matter, , is constrained at 68% confidence level to be <0.32 for DES-Y1 3x2pt data, <0.030 for CMB +SN +BAO data, and <0.037 for the combined dataset. The probability that the DES and CMB+SN+BAO datasets are concordant increases from 4% for the CDM model to 8% (less tension) for DMDR. The tension in S8=8{m/0.3 } between DES-Y1 3x2pt and CMB +SN +BAO is slightly reduced from 2.3 to 1.9 . We find no reduction in the Hubble tension when the combined data is compared to distance-ladder measurements in the DMDR model. The maximum-posterior goodness-of-fit statistics of DMDR and CDM model are comparable, indicating no preference for the DMDR cosmology over CDM .
No abstract found.
This paper details speckle observations of binary stars taken at the Lowell Discovery Telescope, the WIYN telescope, and the Gemini telescopes between 2016 January and 2019 September. The observations taken at Gemini and Lowell were done with the Differential Speckle Survey Instrument (DSSI), and those done at WIYN were taken with the successor instrument to DSSI at that site, the NN-EXPLORE Exoplanet Star and Speckle Imager (NESSI). In total, we present 378 observations of 178 systems, and we show that the uncertainty in the measurement precision for the combined data set is 2 mas in separation, 1-2 in position angle depending on the separation, and 0.1 mag in magnitude difference. Together with data already in the literature, these new results permit 25 visual orbits and one spectroscopic-visual orbit to be calculated for the first time. In the case of the spectroscopic-visual analysis, which is done on the ternary star HD 173093, we calculate masses with a precision of better than 1% for all three stars in that system. Twenty-one of the visual orbits calculated have a K dwarf as the primary star; we add these to the known orbits of K-dwarf primary stars and discuss the basic orbital properties of these stars at this stage. Although incomplete, the data that exist so far indicate that binaries with K-dwarf primaries tend not to have low-eccentricity orbits at separations of one to a few tens of astronomical units, that is, on solar system scales.
Application of the radial velocity (RV) technique in the near-infrared is valuable because of the diminished impact of stellar activity at longer wavelengths, making it particularly advantageous for the study of late-type stars but also for solar-type objects. In this paper, we present the IGRINS RV open-source python pipeline for computing infrared RV measurements from reduced spectra taken with IGRINS, an R / 45,000 spectrograph with simultaneous coverage of the H band (1.49-1.80 m) and K band (1.96-2.46 m). Using a modified forward-modeling technique, we construct high-resolution telluric templates from A0 standard observations on a nightly basis to provide a source of common-path wavelength calibration while mitigating the need to mask or correct for telluric absorption. Telluric standard observations are also used to model the variations in instrumental resolution across the detector, including a yearlong period when the K band was defocused. Without any additional instrument hardware, such as a gas cell or laser frequency comb, we are able to achieve precisions of 26.8 m s-1 in the K band and 31.1 m s-1 in the H band for narrow-line hosts. These precisions are empirically determined by a monitoring campaign of two RV standard stars, as well as the successful retrieval of planet-induced RV signals for both HD 189733 and Boo A; furthermore, our results affirm the presence of the Rossiter-McLaughlin effect for HD 189733. The IGRINS RV pipeline extends another important science capability to IGRINS, with publicly available software designed for widespread use. * https://github.com/shihyuntang/igrins_rv
We extend results first announced by Franz et al., that identified vA 351 = H346 in the Hyades as a multiple star system containing a white dwarf. With Hubble Space Telescope Fine Guidance Sensor fringe tracking and scanning, and more recent speckle observations, all spanning 20.7 years, we establish a parallax, relative orbit, and mass fraction for two components, with a period, $P=2.70\,\mathrm{yr}$ and total mass 2.1 ${{ \mathcal M }}_{\odot }$ . With ground-based radial velocities from the McDonald Observatory Otto Struve 2.1 m Telescope Sandiford Spectrograph, and Center for Astrophysics Digital Speedometers, spanning 37 years, we find that component B consists of BC, two M dwarf stars orbiting with a very short period ( ${P}_{\mathrm{BC}}=0.749$ days), having a mass ratio ${{ \mathcal M }}_{{\rm{C}}}$ / ${{ \mathcal M }}_{{\rm{B}}}$ = 0.95. We confirm that the total mass of the system can only be reconciled with the distance and component photometry by including a fainter, higher-mass component. The quadruple system consists of three M dwarfs (A, B, C) and one white dwarf (D). We determine individual M dwarf masses ${{ \mathcal M }}_{{\rm{A}}}$ = 0.53 0.10 ${{ \mathcal M }}_{\odot }$ , ${{ \mathcal M }}_{{\rm{B}}}$ = 0.43 0.04 ${{ \mathcal M }}_{\odot }$ , and ${{ \mathcal M }}_{{\rm{C}}}$ = 0.41 0.04 ${{ \mathcal M }}_{\odot }$ . The white dwarf mass, 0.54 0.04 ${{ \mathcal M }}_{\odot }$ , comes from cooling models, an assumed Hyades age of 670 Myr, and consistency with all previous and derived astrometric, photometric, and radial velocity results. Velocities from H and He I emission lines confirm the BC period derived from absorption lines, with similar (He I) and higher (H) velocity amplitudes. We ascribe the larger H amplitude to emission from a region each component shadows from the other, depending on the line of sight. * We dedicate this paper to John Stauffer, who died on 2021 January 29, in honor of his many contributions to the field.
We report on our extensive photometry and imaging of comet 46P/Wirtanen during its 2018/19 apparition and use these data to constrain the modeling of Wirtanen's activity. Narrowband photometry was obtained in 9 epochs from 2018 October through 2019 March as well as 10 epochs during the 1991, 1997, and 2008 apparitions. The ensemble photometry reveals a typical composition and a secular decrease in activity since 1991. Production rates were roughly symmetric around perihelion for the carbon-bearing species (CN, C3, and C2), but steeper for OH and NH outbound. Our imaging program emphasized CN, whose coma morphology and lightcurve yielded rotation periods reported in a companion paper (Farnham et al. 2021). Here, we compare the gas and dust morphology on the 18 nights for which observations of additional species were obtained. The carbon-bearing species exhibited similar morphology that varied with rotation. OH and NH had broad, hemispheric brightness enhancements in the tailward direction that did not change significantly with rotation, which we attribute to their originating from a substantial icy grain component. We constructed a Monte Carlo model that replicates the shape, motion, and brightness distribution of the CN coma throughout the apparition with a single, self-consistent solution in principal axis rotation. Our model yields a pole having (R.A., decl.) = 319, -5 (pole obliquity of 70) and two large sources (radii of 50 and 40) centered at near-equatorial latitudes and separated in longitude by 160. Applications of the model to explain observed behaviors are discussed.
We describe the Dark Energy Survey (DES) photometric data set assembled from the first three years of science operations to support DES Year 3 cosmologic analyses, and provide usage notes aimed at the broad astrophysics community. Y3 GOLD improves on previous releases from DES, Y1 GOLD, and Data Release 1 (DES DR1), presenting an expanded and curated data set that incorporates algorithmic developments in image detrending and processing, photometric calibration, and object classification. Y3 GOLD comprises nearly 5000 deg2 of grizY imaging in the south Galactic cap, including nearly 390 million objects, with depth reaching a signal-to-noise ratio 10 for extended objects up to iAB 23.0, and top-of-the-atmosphere photometric uniformity <3 mmag. Compared to DR1, photometric residuals with respect to Gaia are reduced by 50%, and per-object chromatic corrections are introduced. Y3 GOLD augments DES DR1 with simultaneous fits to multi-epoch photometry for more robust galactic color measurements and corresponding photometric redshift estimates. Y3 GOLD features improved morphological star-galaxy classification with efficiency >98% and purity >99% for galaxies with 19 < iAB < 22.5. Additionally, it includes per-object quality information, and accompanying maps of the footprint coverage, masked regions, imaging depth, survey conditions, and astrophysical foregrounds that are used to select the cosmologic analysis samples.
One of the most striking and curious features of the small Kuiper Belt Object (KBO), Arrokoth, explored by New Horizons is the bright, annular neck it exhibits at the junction between its two lobes. Here we summarize past reported findings regarding the properties of this feature and then report new results regarding its dimensions, reflectivity and color, shape profile, and lack of identifiable craters. We conclude by enumerating possible origin scenarios for this unusual feature. New results include a new estimated measurement of the observed neck area of 8 1.5 km2, a total neck surface area of 32 km2, a 12.5:1 ratio of circumference to height, a normal reflectance histogram of the observed neck, and the fact that no significant (i.e., >2) neck color units were identified, meaning the neck's color is generally spatially uniform at the 1.5 km pixel-1 scale of the best color images. Although several origin hypotheses for the bright material in the neck are briefly discussed, none can be conclusively demonstrated to be the actual origin mechanism at this time; some future tests are identified.
This release contains some modest improvements in image combination performance. For the best performance, install the bottleneck. With bottleneck installed, median_combine is 2x faster. Changes in this version: Image combination is faster for average and sum combine, and improves for all operations if the bottleneck package is installed. Pixel-wise weighting can be done for sum and average combine. When filtering an ImageFileCollection by keyword value, and not explicitly using a regex search pattern (regex_match=True), escape all special characters in the keyword value for a successful search. Return mask and uncertainty from combine even if input images have no mask or uncertainty. Thanks to all of the people who contributed code, opened issues, and/or provided advice: Timothy P. Ellsworth-Bowers (@tbowers7) and Pey Lian Lim (@pllim) wrote code for this release. Yoonsoo Back (@ysBach) and Simon Conseil (@saimn) provided extensive input on image combination. Issues opened by Yash Gondhalekar (@Yash-10), Michael Kelley (@mkelley), Jane Rigby (@janerigby), and Aayushi Verma (@awesomecosmos) were closed in this release. Rieke Bohemann and Tim-Oliver Husser (@thusser) provided extensive details about issues with median combination which have been addressed in this release.
Recent cosmic shear studies have reported discrepancies of up to 1 on the parameter ${S_{8}=\sigma _{8}\sqrt{{\Omega _{\rm m}}/0.3}}$ between the analysis of shear power spectra and two-point correlation functions, derived from the same shear catalogues. It is not a priori clear whether the measured discrepancies are consistent with statistical fluctuations. In this paper, we investigate this issue in the context of the forthcoming analyses from the third year data of the Dark Energy Survey (DES Y3). We analyse DES Y3 mock catalogues from Gaussian simulations with a fast and accurate importance sampling pipeline. We show that the methodology for determining matching scale cuts in harmonic and real space is the key factor that contributes to the scatter between constraints derived from the two statistics. We compare the published scales cuts of the KiDS, Subaru-HSC, and DES surveys, and find that the correlation coefficients of posterior means range from over 80 per cent for our proposed cuts, down to 10 per cent for cuts used in the literature. We then study the interaction between scale cuts and systematic uncertainties arising from multiple sources: non-linear power spectrum, baryonic feedback, intrinsic alignments, uncertainties in the point spread function, and redshift distributions. We find that, given DES Y3 characteristics and proposed cuts, these uncertainties affect the two statistics similarly; the differential biases are below a third of the statistical uncertainty, with the largest biases arising from intrinsic alignment and baryonic feedback. While this work is aimed at DES Y3, the tools developed can be applied to Stage-IV surveys where statistical errors will be much smaller.
Beyond CDM, physics or systematic errors may cause subsets of a cosmological data set to appear inconsistent when analysed assuming CDM. We present an application of internal consistency tests to measurements from the Dark Energy Survey Year 1 (DES Y1) joint probes analysis. Our analysis relies on computing the posterior predictive distribution (PPD) for these data under the assumption of CDM. We find that the DES Y1 data have an acceptable goodness of fit to CDM, with a probability of finding a worse fit by random chance of p = 0.046. Using numerical PPD tests, supplemented by graphical checks, we show that most of the data vector appears completely consistent with expectations, although we observe a small tension between large- and small-scale measurements. A small part (roughly 1.5 per cent) of the data vector shows an unusually large departure from expectations; excluding this part of the data has negligible impact on cosmological constraints, but does significantly improve the p-value to 0.10. The methodology developed here will be applied to test the consistency of DES Year 3 joint probes data sets.
We present a Bayesian method to cross-match 5,827,988 high proper-motion Gaia sources ( > 40 mas yr1) to various photometric surveys: Two Micron All Sky Survey, AllWISE data release from the Wide-field Infrared Explorer (WISE) mission, Galaxy Evolution Explorer, Radial Velocity Experiment, Sloan Digital Sky Survey, and Panoramic Survey Telescope and Rapid Response System (Pan-STARRS). To efficiently associate these objects across catalogs, we develop a technique that compares the multidimensional distribution of all sources in the vicinity of each Gaia star to a reference distribution of random field stars obtained by extracting all sources in a region on the sky displaced 2. This offset preserves the local field stellar density and magnitude distribution, allowing us to characterize the frequency of chance alignments. The resulting catalog with Bayesian probabilities >95 has a marginally higher match rate than current internal Gaia data release 2 (DR2) matches for most catalogs. However, a significant improvement is found with Pan-STARRS, where 99.8 of the sample within the Pan-STARRS footprint is recovered, as compared to a low 20.8 in Gaia DR2. Using these results, we train a Gaussian process regressor to calibrate two photometric metallicity relationships. For dwarfs of 3500 < Teff < 5280 K, we use metallicity values of 4378 stars from the Apache Point Observatory Galactic Evolution Experiment and Hejazi et al. to calibrate the relationship, producing results with a 1 precision of 0.12 dex and few systematic errors. We then indirectly infer the metallicity of 4018 stars with 2850 < Teff < 3500 K, which are wide companions of primaries whose metallicities are estimated with our first regressor, to produce a relationship with a 1 precision of 0.21 dex and significant systematic errors. Additional work is needed to better remove unresolved binaries from this second sample to reduce these systematic errors.
All LIDAR instruments are not the same, and advancement of LIDAR technology requires an ongoing interest and demand from the community to foster further development of the required components. The purpose of this white paper is to make the decadal survey panel aware of the need for further technical development, and the potential payoff of LIDARs.
On April 13, 2029 a once-per-thousand-year natural "experiment" occurs: the 340m asteroid Apophis will be subjected to Earth's tidal torques as it passes INSIDE the orbits of geosynchronous satellites. By measuring its physical response, including possible seismic vibrations, the interior structure of potentially hazardous asteroids may be deduced.
The five classical Uranian moons are possible ocean worlds that exhibit bizarre geologic landforms, hinting at recent surface-interior communication. However, Uranus' classical moons, as well as its ring moons and irregular satellites, remain poorly understood. We assert that a Flagship-class orbiter is needed to explore the Uranian satellites.
Atmosphere-regolith water vapor exchange processes are an important aspect of the Martian water cycle. Hygroscopic salts in the regolith furthers its role because salts lead to temperature- and humidity-dependent exchange processes. Here, we identify knowledge gaps in these processes and recommend strategies to resolve the Martian water cycle.
As the organic-rich endmember of the Ocean World spectrum and host of the most Earth-like atmosphere-surface interactions, the exploration of Titan is essential to a successful Ocean Worlds program and the study of terrestrial bodies, atmospheres, and exoplanets. Dragonfly will revolutionize our understanding but global questions will remain.
Laboratory studies are crucial to interpret observations and mission data, are key incubators for mission and instrument development, and are needed to assess habitability and search for life beyond Earth. Here we present an overview of the planetary science areas where laboratory studies are critically needed and make recommendations accordingly.
New Horizons revealed that icy worlds over 6 billion kilometers from the Sun are still incredibly diverse, active bodies, with cryovolcanics, a tectonic past, significant atmospheric structure, and a large, convecting nitrogen-ice glacier. The first reconnaissance with New Horizons answered many questions, but it generated many new ones.
Vera C. Rubin Observatory will be a key facility for small body planetary astronomy over the next decade. It will carry out the Legacy Survey of Space and Time (LSST), discovering and characterizing large numbers (10-100 times more than currently known) of small solar system bodies. We summarize science highlights and make brief recommendations.
Mars Polar Science is an integrated, compelling system that serves as a nearby analogue to numerous other planets, supports human exploration, and habitability. Mars possesses the closest and most easily accessible layered ice deposits outside of Earth, and accessing those layers to read the climate record would be a triumph for planetary science.
As one of two planetary objects (other than Earth) that have solid surfaces, thick atmospheres, and astrobiological significance, Titan, like Mars, merits ongoing study with multiple spacecraft. We propose that a Titan orbiter dedicated to geophysics, geology, and atmospheric science be added to the New Frontiers menu for the coming decade.
The in-situ observation and data collection at the dwarf planet Haumea would provide for invaluable insight into the history of the Kuiper Belt and the Solar System I as well as the on-going processes that lead to high spin rates, rings, and satellite systems. In this white paper, we will make a case for an exploration mission to the Haumea system.
The LightBeam spacecraft is a mission concept for a facility providing milliarcsecond-class imaging of solar system objects, from NEOs to the main belt to Jupiter Trojans. LightBeam achieves this via innovative in-space manufacturing techniques which enable a long-baseline optical interferometer to be flown in a cost-effective smallsat package.
We present the science drivers and a mission concept for a polar lander that would enable a future reading of the past few million years of the Martian climate record.
We analyze the 3D morphology and kinematics of 13 open clusters (OCs) located within 500 pc of the Sun, using Gaia EDR 3 and kinematic data from the literature. Members of OCs are identified using the unsupervised machine-learning method StarGO, using five parameters (X, Y, Z, ${\mu }_{\alpha }\cos \delta ,{\mu }_{\delta }$ ). The OC sample covers an age range of 25 Myr to 2.65 Gyr. We correct the asymmetric distance distribution that is due to parallax error using Bayesian inversion. The uncertainty in the corrected distance for a cluster at 500 pc is 3.0-6.3 pc, depending on the intrinsic spatial distribution of its members. We determine the 3D morphology of the OCs in our sample and fit the spatial distribution of stars within the tidal radius in each cluster with an ellipsoid model. The shapes of the OCs are well described with oblate spheroids (NGC 2547, NGC 2516, NGC 2451A, NGC 2451B, and NGC 2232), prolate spheroids (IC 2602, IC 4665, NGC 2422, Blanco 1, and Coma Berenices), or triaxial ellipsoids (IC 2391, NGC 6633, and NGC 6774). The semimajor axis of the fitted ellipsoid is parallel to the Galactic plane for most clusters. Elongated filament-like substructures are detected in three young clusters (NGC 2232, NGC 2547, and NGC 2451B), while tidal-tail-like substructures (tidal tails) are found in older clusters (NGC 2516, NGC 6633, NGC 6774, Blanco 1, and Coma Berenices). Most clusters may be supervirial and expanding. N-body models of rapid gas expulsion with a star formation efficiency of 1/3 are consistent with clusters more massive than 250 M, while clusters less massive than 250 M tend to agree with adiabatic gas expulsion models. Only five OCs (NGC 2422, NGC 6633, NGC 6774, Blanco 1, and Coma Berenices) show clear signs of mass segregation.
Most asteroids are somewhat elongated and have non-zero lightcurve amplitudes. Such asteroids can be detected in large-scale sky surveys even if their mean magnitudes are fainter than the stated sensitivity limits. We explore the detection of elongated asteroids under a set of idealized but useful approximations. We find that objects up to 1 mag fainter than a survey's sensitivity limit are likely to be detected, and that the effect is most pronounced for asteroids with lightcurve amplitudes 0.1-0.4 mag. This imposes a bias on the derived size and shape distributions of the population that must be properly accounted for.
We observed the occultation of the star Gaia DR2 4056440205544338944 by (28978) Ixion. The event was observed from two Lowell Observatory sites, using the 4.3 m Lowell Discovery Telescope (LDT), near Happy Jack, AZ, USA, and a 0.32 m telescope co-mounted with the Titan Monitoring telescope on Lowell's Mars Hill campus in Flagstaff, AZ. The LDT chord, at 44.86 s, was roughly 30% longer than the longest predicted possible chord. Under the assumption of a spherical body, Ixion's fitted diameter D = 709.6 0.2 km. The LDT light-curve profile was used to place an upper limit on the surface pressure P < 2 bar on any possible atmosphere of Ixion. At the distance of Ixion, the occulted star had a fitted projected diameter of 19.25 0.3 km assuming uniform disk illumination, giving a stellar angular diameter of 0.675 0.010 mas. Using the Gaia EDR3 parallax of 0.565 mas, the stellar radius is ${130}_{-17}^{+20}\,{R}_{\odot }$ <!-- --> . The measured size is consistent with prior spectral classification of this star as a reddened mid-M giant. This is one of only a modest number of M5 III stars to have a directly measured diameter, and is more distant than most.
We have compared spectroscopic data of Sputnik Planitia on Pluto, as acquired by New Horizons' Linear Etalon Imaging Spectral Array (LEISA) instrument, to the geomorphology as mapped by White et al. (2017) using visible and panchromatic imaging acquired by the LOng-Range Reconnaissance Imager (LORRI) and the Multi-spectral Visible Imaging Camera (MVIC). We have focused on 13 of the geologic units identified by White et al. (2017), which include the plains and mountain units contained within the Sputnik basin. We divided the map of Sputnik Planitia into 15 provinces, each containing one or more geologic units, and we use LEISA to calculate the average spectra of the units inside the 15 provinces. Hapke-based modeling was then applied to the average spectra of the units to infer their surface composition, and to determine if the composition resulting from the modeling of LEISA spectra reflects the geomorphologic analyses of LORRI data, and if areas classified as being the same geologically, but which are geographically separated, share a similar composition. We investigated the spatial distribution of the most abundant ices on Pluto's surface - CH4, N2, CO, H2O, and a non-ice component presumed to be a macromolecular carbon-rich material, termed a tholin, that imparts a positive spectral slope in the visible spectral region and a negative spectral slope longward of ~1.1 m. Because the exact nature of the non-ice component is still debated and because the negative spectral slope of the available tholins in the near infrared does not perfectly match the Pluto data, for spectral modeling purposes we reference it generically as the negative spectral slope endmember (NSS endmember). We created maps of variations in the integrated band depth (from LEISA data) and areal mass fraction (from the modeling) of the components. The analysis of correlations between the occurrences of the endmembers in the geologic units led to the observation of an anomalous suppression of the strong CH4 absorption bands in units with compositions that are dominated by H2O ice and the NSS endmember. Exploring the mutual variation of the CH4 and N2 integrated band depths with the abundance of crystalline H2O and NSS endmember revealed that the NSS endmember is primarily responsible for the suppression of CH4 absorptions in mountainous units located along the western edge of Sputnik Planitia. Our spectroscopic analyses have provided additional insight into the geological processes that have shaped Sputnik Planitia. A general increase in volatile abundance from the north to the south of Sputnik Planitia is observed. Such an increase first observed and interpreted by Protopapa et al., 2017 and later confirmed by climate modeling (Bertrand et al., 2018) is expressed geomorphologically in the form of preferential deposition of N2 ice in the upland and mountainous regions bordering the plains of southern Sputnik Planitia. Relatively high amounts of pure CH4 are seen at the southern Tenzing Montes, which are a natural site for CH4 deposition owing to their great elevation and the lower insolation they are presently receiving. The NSS endmember correlates the existence of tholins within certain units, mostly those coating the low-latitude mountain ranges that are co-latitudinal with the tholin-covered Cthulhu Macula. The spectral analysis has also revealed compositional differences between the handful of occurrences of northern non-cellular plains and the surrounding cellular plains, all of which are located within the portion of Sputnik Planitia that is presently experiencing net sublimation of volatiles, and which do not therefore exhibit a surface layer of bright, freshly-deposited N2 ice. The compositional differences between the cellular and non-cellular plains here hint at the effectiveness of convection in entraining and trapping tholins within the body of the cellular plains, while preventing the spread of such tholins to abutting non-cellular plains.
An analysis of the Large Magellanic Cloud (LMC) WC4 star BAT99-9 (HD 32125, FD 4, Brey 7, WS 3) shows that the star still contains photospheric nitrogen. Three N emission features (N V 1238, 1242, N IV 1719, and N IV 3479-3485) are unambiguously identified in the spectrum. CMFGEN models of the star yield an N/C ratio of 0.004 0.002 (by number) and a C/He ratio of $0.15_{-0.05}^{+0.10}$ . Due to the similarity of BAT99-9 to other WC4 stars, and the good fit achieved by CMFGEN to both the classic WC4 spectrum and the N lines, we argue that the N lines are intrinsic to BAT99-9. An examination of a limited set of rotating models for single-star evolution at LMC and Galactic metallicities shows that a model with a Galactic metallicity (z = 0.014) and a progenitor mass of around 50 M can have an N/C ratio similar to, or larger than, what we observe for a significant fraction of its lifetime. However, the LMC models (z = 0.006) are inconsistent with the observations. Both the single and binary BPASS models predict that many WC stars can have an N/C ratio similar to, or larger than, what we observe for a significant fraction of their lifetime. While the binary models cover a wider range of luminosities and provide a somewhat better match to BAT99-9, it is not currently possible to rule out BAT99-9 being formed through single-star evolution, given the uncertainties in mass-loss rates, and the treatment of convection and mixing processes.
We obtained thorough photometric observations of two binary near-Earth asteroids (66391) Moshup = 1999 KW4 and (88710) 2001 SL9 taken from 2000 to 2019. We modeled the data and derived physical and dynamical properties of the binary systems. For (66391) 1999 KW4, we derived its mutual orbit's pole, semimajor axis and eccentricity that are in agreement with radar-derived values (Ostro et al., 2006. Science, 314, 1276-1280). However, we found that the data are inconsistent with a constant orbital period and we obtained unique solution with a quadratic drift of the mean anomaly of the satellite of -0.65 0.16 deg./yr2 (all quoted uncertainties correspond to 3). This means that the semimajor axis of the mutual orbit of the components of this binary system, determined a = 2.548 0.015 km by Ostro et al. (2006), increases in time with a mean rate of 1.2 0.3 cm/yr. For (88710) 2001 SL9, we determined that the mutual orbit has a pole within 10 of (L, B) = (302, -73) (ecliptic coordinates), and is close to circular (eccentricity < 0.07). The data for this system are also inconsistent with a constant orbital period and we obtained two solutions for the quadratic drift of the mean anomaly: 2.8 0.2 and 5.2 0.2 deg./yr2, implying that the semimajor axis of the mutual orbit of the components (estimated a ~ 1.6 km) decreases in time with a mean rate of -2.8 0.2 or -5.1 0.2 cm/yr for the two solutions, respectively. The expanding orbit of (66391) 1999 KW4 may be explained by mutual tides interplaying with binary YORP (BYORP) effect (McMahon and Scheeres, 2010a. Icarus 209, 494-509). However, a modeling of the BYORP drift using radar-derived shapes of the binary components predicted a much higher value of the orbital drift than the observed one. It suggests that either the radar-derived shape model of the secondary is inadequate for computing the BYORP effect, or the present theory of BYORP overestimates it. It is possible that the BYORP coefficient has instead an opposite sign than predicted; in that case, the system may be moving into an equilibrium between the BYORP and the tides. In the case of (88710) 2001 SL9, the BYORP effect is the only known physical mechanism that can cause the inward drift of its mutual orbit. Together with the binary (175706) 1996 FG3 which has a mean anomaly drift consistent with zero, implying a stable equilibrium between the BYORP effect and mutual body tides (Scheirich et al., 2015. Icarus 245, 56-63), we now have three distinct cases of well observed binary asteroid systems with their long-term dynamical models inferred. They indicate a presence of all the three states of the mutual orbit evolution - equilibrium, expanding and contracting - in the population of near-Earth binary asteroids.
Generate star spot evolution and light curves following the models of Mackay et al. (2004), Llama et al. (2012), and Aigrain et al. (2015). This software is an open-source version, with some slight modifications, of what was introduced and used by Aigrain et al. (2015). View on GitHub: https://github.com/zclaytor/butterpy View on PyPI: https://pypi.org/project/butterpy/
A definitive orbit is derived for asteroid (317) Roxane's satellite Olympias [S/2009 (317)1] by combining the 2009 discovery images from Gemini North (Merline et al. 2009) with images from Keck and the VLT obtained in 2012, as well as images from its 2016-2017 apparition from the Starfire Optical Range. The orbit is retrograde with respect to the ecliptic but in the same sense as Roxane's spin. Olympias has a period of P=11.94400.0005 days, a semi-major axis of a=2453 km, and an orbital pole at RA=97, Dec=-71, or ecliptic coordinates =245, =-85, close to the south ecliptic pole. This satellite orbital pole is only 3 from Roxane's orbital pole (but in a retrograde sense) and restricts all observations of Olympias from Earth to within 4 of the satellite's orbital plane. By fitting the brightness ratios between Roxane (rotational period of 8.169610.00005 h) and Olympias as a Fourier series, we find a rotational period for Olympias of 8.25870.0001 h, making this an asynchronous wide binary. From the brightness ratios, and with the average infrared modeling diameter found in the literature of 19.160.39 km (error of the mean), we estimate triaxial ellipsoid radii of 14.58.57.2 km for Roxane and 3.62.52.0 km for Olympias. We can then apportion the mass between the two objects and find a density for both (assumed to be the same) of 2.160.18 g/cm3. There are only a few E-type binaries known and this is the first direct determination of E-type density from a binary. We suggest that the system was formed by the Escaping Ejecta Binary (EEB) mechanism of Durda et al. (2004a), probably forming closer together, and then undergoing the complex evolution steps described by Jacobson et al. (2014) involving synchronization, BYORP orbit expansion, loss of tidal lock, and then YORP spinup. Roxane and Olympias may be the only known EEB system to date. From the same 2016-2017 apparition the orbit of Linus around asteroid (22) Kalliope is derived from the SOR. This well-observed bright satellite is found to have a circular orbit with a period of P=3.59560.0004 days, in good agreement with the latest elements of Vachier et al. (2012) of P=3.59570.0001 days, and a semi-major axis of a=10996 km, somewhat greater than their a=108211 km for a slightly eccentric orbit (e=0.0070.010). With a diameter for Kalliope of 1616 km (Hanus et al. 2017), we derive a density for Kalliope of 3.720.25 g/cm3 from our one apparition study, the same as Hanus et al. (2017) but greater than the 3.240.16 of Vachier et al. (2012).
The 4.3-m Lowell Discovery Telescope located in Happy Jack, Arizona provides a diverse instrument suite and a demonstrated ability to target faint, fast-moving NEOs. We will give recent examples of high priority NEOs observed with the LDT to serve as informative analogs to the 2021 PDC asteroid. These examples are connected to the following projects: (1) An ongoing astrometric program that extends the orbital arc of potentially hazardous asteroids and virtual impactors by achieving detections down to apparent magnitudes of V~25. (2) The Mission Accessible Near-Earth Object Survey (MANOS) collects comprehensive physical characterization data to constrain the compositional, rotational, morphological, and orbital characteristics of the lowest v objects in near-Earth space (e.g. [1-2]). (3) Rotational and orbital characterization of Earth's second known mini-moon, 2020 CD3, when it was at an apparent magnitude of V~23 [3]. (4) High precision rotational lightcurves of NASA DART (Double Asteroid Redirect Test) mission target 65803 Didymos have served as the primary input to mission-critical models that have determined the non-gravitational orbital evolution of Didymos' satellite Dimorphos. These examples of science and planetary defense use cases at the LDT have benefited from several unique features of the facility. The Cassegrain focus of LDT is populated by an instrument cube that allows for five instruments to be simultaneously mounted, with switching between instruments taking less than a minute. This versatility allows for the efficient collection of complex data products within a single night, e.g. visible spectra + near-infrared spectra + photometry + astrometry. The accessibility of the full instrument suite on any given night has allowed for flexible scheduling in which rapid response observations can be conducted on very short notice. This flexible schedule coupled with dedicated LDT access for Lowell scientists and partner institutions enables cadence monitoring programs that can be difficult to perform at other facilities. Astrometric, photometric, and spectroscopic tracking of the 2021 PDC asteroid from its discovery in April 2021 through October 2021 would be an ideal use case for the LDT. As a whole these features of LDT make it one of the most capable NEO characterization tools in the world.
The degree of linear polarization of sunlight scattered by an asteroid contains valuable information for rapid characterization of the surface properties of Near-Earth objects. In the case of atmosphereless bodies the state of linear polarization varies as a function of the phase angle () and is described using the so-called Pr parameter (see left panel of Fig. 1). The properties of the phase-polarization curve (see right panel of Fig. 1) of an asteroid are mostly defined by its albedo (pV). Numerous calibrations between polarization and pV have been proposed for main-belt asteroids [1, 2]. However, main-belt asteroids rarely exceed phase angle > 30 while nearEarth object can be observed at phase angle as large as 100. These observation at higher phase angle to the NEOs allows for deeper characterization of the observed object, but there is currently a lack of observations of NEOs in polarimetry to accurately calibrate the albedo-polarization relationship at high phase angles. In this presentation I will discuss the current state of NEO observations in polarimetry and how polarimetry could be used to obtain reliable information on the geometric albedo of NEOs. With a proper calibration of the polarization-albedo relation, one could reduce the uncertainty on a newly discovered object by a factor of 10 with one single polarimetric observation obtained at a phase angle > 40. As an example, according to the current state of the albedo-polarization calibration at large phase angle and considering an H = 22.3 mag NEO (similar to 2021 PDC). Without any albedo information size estimation would be from 35 meters to 700 meters. However, one measurements of Pr at a phase angle of 40 would allow to obtain reliable information about the diameter of the object as follow: D < 80 meters if Pr < 1% 80 < D < 120 meters is 1 < Pr < 4% D > 120 meters if Pr > 4% while the typical uncertainties on Pr are generally lower than 0.1%. I will also discuss the specific case of 2021 PDC and what a few observations in polarimetry obtained with the FORS2 polarimeter on the Very Large Telescope could provide. FORS2 on the VLT is currently the only instrument capable of obtained reliable polarimetric observations on the V=21.5 mag objects.
The near-Earth objects (NEOs) include asteroids and comets that are in orbit close to the Earth. In some cases, they can even cross the Earth's orbit. The NEOs are one interesting population of small bodies for several reasons. There are objects that constitute a potential impact hazard. Because of the close approach to the Earth, they are more accessible to spacecraft, to detailed observations from ground-based facilities, and also allow us to study asteroids two to three orders of magnitude smaller than those observable on the main belt asteroids. The NEO Rapid Observation, Characterization and Key Simulations (NEOROCKS) project is funded (2020-2022) through the H2020 European Commission programme to improve knowledge on NEOs by connecting expertise in performing small body astronomical observations and the related modelling needed to derive their dynamical and physical properties. The IAC, and in particular members of the Solar System Group, participates in the NEOROCKS project and is currently leading one specific task to do observations of NEOs in support of the Arecibo Planetary Radar. These supporting observations include times-series photometry (lightcurves), visible to near-infrared spectroscopy, and astrometry (orbit determination). To do that we are using the telescopes from Roque de Los Muchachos and Teide Observatories, located at La Palma and Tenerife islands, respectively (Spain). Considering the current situation of the Arecibo telescope, in this work we focus in the obtention and analysis of lightcurve data for those targets that were observed in the past by the Arecibo telescope and have good signal-to-noise (SNR) radar data. Our photometry is intented to support and complement radar data and to help deriving physical properties like rotational period and shape. We have observed 8 asteroids to obtain their lightcurve. Figure 1 shows one example of lightcurve from the asteroid (52768) 1998 OR2, that we are observing in studing with Arecibo team. These are preliminary results.
Binary near-Earth asteroid (65803) Didymos is the target of NASA's Double Asteroid Redirection Test (DART) space mission and ESA's Hera mission. The DART mission is a planetary defense experiment with a planned launch in July 2021. The mission consists of a spacecraft that would impact Dimorphos, the satellite of Didymos, in October 2022 and change its orbital period around Didymos by > 73 seconds. The change would be measured by ground-based photometric and radar observations over several months after the impact. The Hera mission will characterize Didymos and its satellite starting in 2026. We estimated the pre-impact orbit of Dimorphos using the times of occultations and eclipses observed in lightcurves from 2003, 2015, 2017, and 2019 using a weighted least-squares approach. The data is consistent with three separate solutions corresponding to different values of Binary YORP, a radiative effect that could cause a drift in mean motion. The three nominal solutions are separated by about 50 in orbital phase during the planned DART mission impact in October 2022 and their formal 3-sigma uncertainties are about 30 for each. Data from the ongoing 2021 observation campaign (Thomas et al., this conference) will be used to refine the estimates further. Observations in December 2020 to March 2021 are expected to eliminate two of the three solutions and reduce the formal 3-sigma uncertainty in the orbital phase during the DART mission to be < 10.
The binary near-Earth asteroid (65803) Didymos is the target for the Asteroid Impact and Deflection Assessment (AIDA) mission, which is a concept with two primary spacecraft: NASA's DART (Double Asteroid Redirection Test) impactor and ESA's Hera orbiter (Cheng et al. 2018; Michel et al. 2018). DART is NASA's first planetary defense mission and will be the first demonstration of asteroid deflection by a kinetic impactor. The DART spacecraft is designed to impact Dimorphos, the secondary in the Didymos system, and modify its orbit through momentum transfer. DART will launch in mid-2021 and is scheduled to impact in fall 2022. The DART spacecraft will carry ASI's LICIACube (Light Italian Cubesat for Imaging of Asteroids, Dotto et al. 2021) to observe the DART impact event and the resulting impact ejecta. A key scientific goal of the DART and Hera missions is to measure and characterize the deflection caused by the DART impact. The impact will change the satellite orbit period, which will be measured by ground-based facilities in the post-impact period. In order to correctly interpret the data from the impact epoch, we need to understand the baseline, unperturbed dynamics of the system. The DART/Hera Observations Working Group is tasked with characterizing the Didymos-Dimorphos system properties with sufficient accuracy to measure the change in the binary orbital period to within 7.3 seconds. This measurement is a small, but observable fraction of the current orbital period of the satellite (Porb=11.92 hours). The observed period change is a critical input to the calculation of the momentum transfer enhancement parameter, "Beta" (). We are obtaining lightcurve observations during the current apparition (December 2020 to March 2021) to further characterize the system. Combining these observations with past data will provide us with the opportunity to establish the state of the system before impact to a high level of precision. We have two goals for our 2020-2021 Didymos observing effort: (1) Measure the amount of Binary YORP (BYORP) torque occurring in the system and (2) Establish whether or not the secondary is in synchronous rotation. An international group of observers affiliated with DART and Hera obtained time at 11 different facilities over the time period from December 2020 to March 2021. We will discuss our state of knowledge from previous observations (through 2019) and selected results from our 2020-2021 observations.
Asteroid regolith grain size is diagnostic of several poorly understood geophysical processes and has direct planetary defense applications. For example, it is well known that a rubble pile size barrier exists around asteroid diameters of 200-300m [1]. Small bodies with diameters below this size can rotate quickly with periods less than 2.2 hours, however, large objects generally do not rotate that quickly. This rotation rate barrier is attributed to a transition from large, gravity dominated objects to small, strength dominated ones [2]. Yet, it is unclear how this transition affects surface properties. Thermal (e.g. [3]) and in-situ (e.g. [4]) data suggest that object diameter influences surface grain size -- large bodies have fine surface grains and small bodies have coarse grains. However, rotation rate [5] and size-independent processes like thermal fracturing [6] and tidal interactions with planets [7] may be equally important in affecting surface properties. For planetary defense risk assessment, quantifying the nature of the regolith and near-subsurface material of potential impactors can inform early predictions of the momentum transfer from a kinetic impactor [8]. We will present an overview of Hapke radiative transfer and thermal modeling tools that we have adopted to constrain near-Earth asteroid surface regolith grain sizes. These can be used for hazard assessment of close-approaching near-Earth asteroids and for better understanding the surface characteristics of objects above and below the size barrier. In this work, we focus on the application of these tools with respect to characterizing surface properties of near-Earth asteroid 2021 PDC. Specifically, we will apply our modeling and data analysis tools to synthetic observations of 2021 PDC from the 4.3-m Lowell Discovery Telescope and NASA's Infrared Telescope Facility. We have adopted a probabilistic implementation of Hapke radiative transfer modeling [9] on unresolved asteroids to constrain surface regolith grain size. By collecting high signal-to-noise (S/N > 50) photometry of objects going through opposition, we can fit the data with our Hapke photometric model to constrain regolith grain size. Using multi-epoch thermal measurements that are collected at opposition and across a wide range of solar phase angles, we can estimate thermal inertia and, from it, the surface grain size following methods by [10] and [11]. A reasonable estimate for the rotation period is needed for this approach, but shape and spin properties are treated as unknown free-parameters when fitting to the observations. Detailed knowledge of the lightcurve period and amplitude can be used to constrain the range of these free parameters. We will compare the thermal-derived grain size estimates to those constrained by our implementation of the Hapke photometric model to better understand the surface properties of the body across multiple wavelengths. For example, a bare-rock thermal inertia value and coarse Hapke grain size may suggest an intact monolith, as opposed to a rubble pile comprised of various-sized boulders and fine surface grains.
Measurements of large-scale structure are interpreted using theoretical predictions for the matter distribution, including potential impacts of baryonic physics. We constrain the feedback strength of baryons jointly with cosmology using weak lensing and galaxy clustering observables (3 2pt) of Dark Energy Survey (DES) Year 1 data in combination with external information from baryon acoustic oscillations (BAO) and Planck cosmic microwave background polarization. Our baryon modelling is informed by a set of hydrodynamical simulations that span a variety of baryon scenarios; we span this space via a Principal Component (PC) analysis of the summary statistics extracted from these simulations. We show that at the level of DES Y1 constraining power, one PC is sufficient to describe the variation of baryonic effects in the observables, and the first PC amplitude (Q1) generally reflects the strength of baryon feedback. With the upper limit of Q1 prior being bound by the Illustris feedback scenarios, we reach $\sim 20{{\ \rm per\ cent}}$ improvement in the constraint of $S_8=\sigma _8(\Omega _{\rm m}/0.3)^{0.5}=0.788^{+0.018}_{-0.021}$ compared to the original DES 3 2pt analysis. This gain is driven by the inclusion of small-scale cosmic shear information down to 2.5 arcmin, which was excluded in previous DES analyses that did not model baryonic physics. We obtain $S_8=0.781^{+0.014}_{-0.015}$ for the combined DES Y1+Planck EE+BAO analysis with a non-informative Q1 prior. In terms of the baryon constraints, we measure $Q_1=1.14^{+2.20}_{-2.80}$ for DES Y1 only and $Q_1=1.42^{+1.63}_{-1.48}$ for DESY1+Planck EE+BAO, allowing us to exclude one of the most extreme AGN feedback hydrodynamical scenario at more than 2.
We demonstrate that highly accurate joint redshift-stellar mass probability distribution functions (PDFs) can be obtained using the Random Forest (RF) machine learning (ML) algorithm, even with few photometric bands available. As an example, we use the Dark Energy Survey (DES), combined with the COSMOS2015 catalogue for redshifts and stellar masses. We build two ML models: one containing deep photometry in the griz bands, and the second reflecting the photometric scatter present in the main DES survey, with carefully constructed representative training data in each case. We validate our joint PDFs for 10 699 test galaxies by utilizing the copula probability integral transform and the Kendall distribution function, and their univariate counterparts to validate the marginals. Benchmarked against a basic set-up of the template-fitting code BAGPIPES, our ML-based method outperforms template fitting on all of our predefined performance metrics. In addition to accuracy, the RF is extremely fast, able to compute joint PDFs for a million galaxies in just under 6 min with consumer computer hardware. Such speed enables PDFs to be derived in real time within analysis codes, solving potential storage issues. As part of this work we have developed GALPRO1, a highly intuitive and efficient PYTHON package to rapidly generate multivariate PDFs on-the-fly. GALPRO is documented and available for researchers to use in their cosmology and galaxy evolution studies.
The June 2, 2018 impact of asteroid 2018 LA over Botswana is only the second asteroid detected in space prior to impacting over land. Here, we report on the successful recovery of meteorites. Additional astrometric data refine the approach orbit and define the spin period and shape of the asteroid. Video observations of the fireball constrain the asteroid's position in its orbit and were used to triangulate the location of the fireball's main flare over the Central Kalahari Game Reserve. Twenty three meteorites were recovered. A consortium study of eight of these classifies Motopi Pan as an HED polymict breccia derived from howardite, cumulate and basaltic eucrite, and diogenite lithologies. Before impact, 2018 LA was a solid rock of ~156 cm diameter with high bulk density ~2.85 g cm3, a relatively low albedo pV ~ 0.25, no significant opposition effect on the asteroid brightness, and an impact kinetic energy of ~0.2 kt. The orbit of 2018 LA is consistent with an origin at Vesta (or its Vestoids) and delivery into an Earth impacting orbit via the 6 resonance. The impact that ejected 2018 LA in an orbit toward Earth occurred 22.8 3.8 Ma ago. Zircons record a concordant U Pb age of 4563 11 Ma and a consistent 207Pb/206Pb age of 4563 6 Ma. A much younger Pb Pb phosphate resetting age of 4234 41 Ma was found. From this impact chronology, we discuss what is the possible source crater of Motopi Pan and the age of Vesta's Veneneia impact basin.
The projected stellar rotational velocity ( $v\sin i$ ) is critical for our understanding of processes related to the evolution of angular momentum in pre-main-sequence stars. We present $v\sin i$ measurements of high-resolution infrared and optical spectroscopy for 70 pre-main-sequence stars in the Taurus-Auriga star-forming region, in addition to effective temperatures measured from line-depth ratios, as well as stellar rotation periods determined from optical photometry. From the literature, we identified the stars in our sample that show evidence of residing in circumstellar disks or multiple systems. The comparison of infrared $v\sin i$ measurements calculated using two techniques shows a residual scatter of 1.8 km s-1, defining a typical error floor for the $v\sin i$ of pre-main-sequence stars from infrared spectra. A comparison of the $v\sin i$ distributions of stars with and without companions shows that binaries/multiples typically have a higher measured $v\sin i$ , which may be caused by contamination by companion lines, shorter disk lifetimes in binary systems, or tidal interactions in hierarchical triples. A comparison of optical and infrared $v\sin i$ values shows no significant difference regardless of whether the star has a disk or not, indicating that CO contamination from the disk does not impact $v\sin i$ measurements above the typical 1.8 km s-1 error floor of our measurements. Finally, we observe a lack of a correlation between the $v\sin i$ , presence of a disk, and H-R diagram position, which indicates a complex interplay between stellar rotation and evolution of pre-main-sequence stars.
We present the first spectroscopic measurements of the ATLAS and Aliqa Uma streams from the Southern Stellar Stream Spectroscopic Survey (S5), in combination with the photometric data from the Dark Energy Survey and astrometric data from Gaia. From the coherence of spectroscopic members in radial velocity and proper motion, we find that these two systems are extremely likely to be one stream with discontinuity in morphology and density on the sky (the "kink" feature). We refer to this entire stream as the ATLAS-Aliqa Uma stream, or the AAU stream. We perform a comprehensive exploration of the effect of baryonic substructures and find that only an encounter with the Sagittarius dwarf 0.5 Gyr ago can create a feature similar to the observed "kink." In addition, we also identify two gaps in the ATLAS component associated with the broadening in the stream width (the "broadening" feature). These gaps have likely been created by small mass perturbers, such as dark matter halos, as the AAU stream is the most distant cold stream known with severe variations in both the stream surface density and the stream track on the sky. With the stream track, stream distance, and kinematic information, we determine the orbit of the AAU stream and find that it has been affected by the Large Magellanic Cloud, resulting in a misalignment between the proper motion and stream track. Together with the Orphan-Chenab Stream, AAU is the second stream pair that has been found to be a single stream separated into two segments by external perturbation.
We present a search for RR Lyrae stars using the full six-year data set from the Dark Energy Survey covering 5000 deg2 of the southern sky. Using a multistage multivariate classification and light-curve template-fitting scheme, we identify RR Lyrae candidates with a median of 35 observations per candidate. We detect 6971 RR Lyrae candidates out to 335 kpc, and we estimate that our sample is >70% complete at 150 kpc. We find excellent agreement with other wide-area RR Lyrae catalogs and RR Lyrae studies targeting the Magellanic Clouds and other Milky Way satellite galaxies. We fit the smooth stellar halo density profile using a broken-power-law model with fixed halo flattening (q = 0.7), and we find strong evidence for a break at ${R}_{0}={32.1}_{-0.9}^{+1.1}\,\mathrm{kpc}$ with an inner slope of ${n}_{1}=-{2.54}_{-0.09}^{+0.09}$ and an outer slope of ${n}_{2}=-{5.42}_{-0.14}^{+0.13}$ . We use our catalog to perform a search for Milky Way satellite galaxies with large sizes and low luminosities. Using a set of simulated satellite galaxies, we find that our RR Lyrae-based search is more sensitive than those using resolved stellar populations in the regime of large (rh 500 pc), low-surface-brightness dwarf galaxies. A blind search for large, diffuse satellites yields three candidate substructures. The first can be confidently associated with the dwarf galaxy Eridanus II. The second has a distance and proper motion similar to the ultrafaint dwarf galaxy Tucana II but is separated by 5 deg. The third is close in projection to the globular cluster NGC 1851 but is 10 kpc more distant and appears to differ in proper motion.
We present the first joint analysis of cluster abundances and auto or cross-correlations of three cosmic tracer fields: galaxy density, weak gravitational lensing shear, and cluster density split by optical richness. From a joint analysis (4 2 pt +N ) of cluster abundances, three cluster cross-correlations, and the auto correlations of the galaxy density measured from the first year data of the Dark Energy Survey, we obtain m=0.30 5-0.038+0.055 and 8=0.78 3-0.054+0.064. This result is consistent with constraints from the DES-Y1 galaxy clustering and weak lensing two-point correlation functions for the flat CDM model. Consequently, we combine cluster abundances and all two-point correlations from across all three cosmic tracer fields (6 2 pt +N ) and find improved constraints on cosmological parameters as well as on the cluster observable-mass scaling relation. This analysis is an important advance in both optical cluster cosmology and multiprobe analyses of upcoming wide imaging surveys.
We present observations of main-belt comet (MBC) 259P/Garradd from 4 months prior to its 2017 perihelion passage to 5 months after perihelion using the Gemini North and South telescopes. The object was confirmed to be active during this period, placing it among seven MBCs confirmed to have recurrent activity. We find an average net pre-perihelion dust production rate for 259P in 2017 of ${\dot{M}}_{d}=(4.6\pm 0.2)$ kg s-1 (assuming grain densities of = 2500 kg m-3 and a mean effective particle size of ${\bar{a}}_{d}=2$ mm) and a best-fit start date of detectable activity of 2017 April 22 1, when the object was at a heliocentric distance of rh = 1.96 0.03 au and a true anomaly of = 3139 04. We estimate the effective active fraction of 259P's surface area to be from fact 7 10-3 to fact 6 10-2 (corresponding to effective active areas of Aact 8 103 m2 to Aact 7 104 m2) at the start of its 2017 active period. A comparison of estimated total dust masses measured for 259P in 2008 and 2017 shows no evidence of changes in activity strength between the two active apparitions. The heliocentric distance of 259P's activity onset point is much smaller than those of other MBCs, suggesting that its ice reservoirs may be located at greater depths than on MBCs farther from the Sun, increasing the time needed for a solar-irradiation-driven thermal wave to reach subsurface ice. We suggest that deeper ice on 259P could be a result of more rapid ice depletion caused by the object's closer proximity to the Sun compared to other MBCs.
Turbulence has the potential for creating gas density enhancements that initiate cloud and star formation (SF), and it can be generated locally by SF. To study the connection between turbulence and SF, we looked for relationships between SF traced by FUV images, and gas turbulence traced by kinetic energy density (KED) and velocity dispersion (vdisp) in the LITTLE THINGS sample of nearby dIrr galaxies. We performed 2D cross-correlations between FUV and KED images, measured cross-correlations in annuli to produce correlation coefficients as a function of radius, and determined the cumulative distribution function of the cross-correlation value. We also plotted on a pixel-by-pixel basis the locally excess KED, vdisp, and H I mass surface density, HI, as determined from the respective values with the radial profiles subtracted, versus the excess SF rate density SFR, for all regions with positive excess SFR. We found that SFR and KED are poorly correlated. The excess KED associated with SF implies a 0.5% efficiency for supernova energy to pump local H I turbulence on the scale of the resolution here, which is a factor of 2 too small for all of the turbulence on a galactic scale. The excess vdisp in SF regions is also small, only 0.37 km s-1. The local excess in HI corresponding to an excess in SFR is consistent with a H I consumption time of 1.6 Gyr in the inner parts of the galaxies. The similarity between this timescale and the consumption time for CO implies that CO-dark molecular gas has comparable mass to H I in the inner disks.
We present the fourth catalog of serendipitously discovered compact extragalactic emission-line sourcesH Dots. A total of 454 newly discovered objects are included in the current survey list. These objects have been detected in searches of moderately deep narrowband images acquired for the ALFALFA H project. The catalog of H Dots presented in the current paper was derived from searches carried out using ALFALFA H images obtained with the KPNO 2.1 m telescope. This results in a substantially deeper sample of Dots compared to our previous lists, which were all discovered in images taken with the WIYN 0.9 m telescope. The median R-band magnitude of the current catalog is 21.59, more than 1.6 mag fainter than the median for the 0.9 m sample (a factor of 4.4 fainter). Likewise, the median emission-line flux of the detected sources is a factor of 4.3 fainter. The line flux completeness limit of the current sample is ~3 10-16 erg s-1 cm-2. We present accurate coordinates, apparent magnitudes, and narrowband line fluxes for each object in the sample. Unlike our previous lists of H Dots, the current sample does not include follow-up spectroscopy.
The apparent clustering in longitude of perihelion and ascending node of extreme trans-Neptunian objects (ETNOs) has been attributed to the gravitational effects of an unseen 5-10 Earth-mass planet in the outer solar system. To investigate how selection bias may contribute to this clustering, we consider 14 ETNOs discovered by the Dark Energy Survey, the Outer Solar System Origins Survey, and the survey of Sheppard and Trujillo. Using each survey's published pointing history, depth, and TNO tracking selections, we calculate the joint probability that these objects are consistent with an underlying parent population with uniform distributions in and . We find that the mean scaled longitude of perihelion and orbital poles of the detected ETNOs are consistent with a uniform population at a level between 17% and 94% and thus conclude that this sample provides no evidence for angular clustering.
We present a new (2+1)D galaxy cluster finder based on photometric redshifts called Wavelet Z Photometric (WaZP) applied to DES first year (Y1A1) data. The results are compared to clusters detected by the South Pole Telescope (SPT) survey and the redMaPPer cluster finder, the latter based on the same photometric data. WaZP searches for clusters in wavelet-based density maps of galaxies selected in photometric redshift space without any assumption on the cluster galaxy populations. The comparison to other cluster samples was performed with a matching algorithm based on angular proximity and redshift difference of the clusters. It led to the development of a new approach to match two optical cluster samples, following an iterative approach to minimize incorrect associations. The WaZP cluster finder applied to DES Y1A1 galaxy survey (1511.13 deg2 up to mi = 23 mag) led to the detection of 60 547 galaxy clusters with redshifts 0.05 < z < 0.9 and richness Ngals 5. Considering the overlapping regions and redshift ranges between the DES Y1A1 and SPT cluster surveys, all SZ based SPT clusters are recovered by the WaZP sample. The comparison between WaZP and redMaPPer cluster samples showed an excellent overall agreement for clusters with richness Ngals ( for redMaPPer) greater than 25 (20), with 95 per cent recovery on both directions. Based on the cluster cross-match, we explore the relative fragmentation of the two cluster samples and investigate the possible signatures of unmatched clusters.
We extend results first announced by Franz et al. (1998), that identified vA351 = H346 in the Hyades as a multiple star system containing a white dwarf. With Hubble Space Telescope Fine Guidance Sensor fringe tracking and scanning, and more recent speckle observations, all spanning 20.7 years, we establish a parallax, relative orbit, and mass fraction for two components, with a period, P = 2.70y and total mass 2.1M. With ground-based radial velocities, we find that component B consists of BC, two M dwarf stars orbiting with a very short period (PBC = 0.749 days), having a mass ratio MC/MB=0.95. We confirm that the total mass of the system can only be reconciled with the distance and component photometry by including a fainter, higher mass component. The quadruple system consists of three M dwarfs (A,B,C) and one white dwarf (D); MA=0.57M, MB=0.48M, and MC=0.45M. The WD mass, 0.53M, comes from cooling models, an assumed Hyades age of 670My, and consistency with all previous and derived astrometric, photometric, and RV results. Velocities from H and He I emission lines confirm the BC period derived from absorption lines, with similar (HeI) and higher (H) velocity amplitudes. We ascribe the larger H amplitude to emission from a region each component shadows from the other, depending on the line of sight.
Epsilon Eri is a young solar-like star with a ~3 yr X-ray activity cycle, detected by us for the first time in a dedicated XMM-Newton long-term monitoring campaign. The magnetic structures on the Sun are intimately linked to the 11-yr activity cycle and they were spatially and temporally resolved throughout the solar cycle. However, for other stars these structures can not be spatially resolved with present-day X-ray instruments. We have, thus, developed a new technique which allows us to reproduce the stellar X-ray variability in terms of time-variations in the coverage of the corona with the same kind of magnetic structures observed on the Sun: active regions (ARs), cores of active regions (COs) and flares (FLs). This poster presents this new method and the results we obtained for the case of Epsilon Eri. Our approach is to simulate a grid of emission measure distributions (EMDs) derived from the analysis of regions observed in the solar corona to artificially reproduce a solar-like corona with the physical characteristics of Epsilon Eri. The three magnetic structures are allowed to contribute to the total coronal EMD with varying area coverage fraction. Thus, from a comparison between these pseudo-solar EMDs and the observations of Epsilon Eri, we are able to associate to each state of the X-ray activity cycle of Epsilon Eri the percentage of ARs, COs and FLs on the corona of the star. The observed amplitude of the X-ray luminosity in the cycle of Epsilon Eri is much smaller than on the Sun. Our analysis provides a physical explanation for this: the simulated EMDs indicate that in all phases of the X-ray cycle a large portion of the corona of Epsilon Eri is covered by active structures. Therefore, there is little space for adding further magnetic structures in the cycle maximum. In the future, this method will be applied to other stars providing an important contribution to better understand the solar-stellar corona connection.
Applications of the radial velocity (RV) technique to the near infrared (NIR) are valuable for their diminished susceptibility to the impact of stellar activity and their suitability for studying late-type stars. In this paper, we present the \texttt{IGRINS RV} open source \texttt{python} pipeline for computing infrared RV measurements from reduced spectra taken with IGRINS, a R$\equiv \lambda/\Delta \lambda \sim$45,000 spectrograph with simultaneous coverage of the H band (1.49--1.80 $\mu$m) and K band (1.96--2.46 $\mu$m). Using a modified forward modeling technique, we construct high resolution telluric templates from A0 standard observations on a nightly basis to provide a source of common-path wavelength calibration while mitigating the need to mask or correct for telluric absorption. A0 standard observations are also used to model the variations in instrumental resolution across the detector, including a yearlong period when the K band was defocused. Without any additional instrument hardware, such as a gas cell or laser frequency comb, we are able to achieve precisions of 26.8 \ms in the K band and 31.1 \ms in the H band for narrow-line hosts. These precisions are validated by a monitoring campaign of two RV standard stars as well as the successful retrieval of planet-induced RV signals for both HD\,189733 and $\tau$\,Boo\,A; furthermore, our results affirm the presence of the Rossiter-McLaughlin effect for HD\,189733. The \texttt{IGRINS RV} pipeline extends another important science capability to IGRINS, with publicly available software designed for widespread use.
Variability of Classical T Tauri Systems occurs over a range of timescales. A common source of this variability is caused by accretion shocks, which can hamper the detectability of young planets within these systems, further motivating the characterization of accretion signatures. We present analysis of small-amplitude photometric variability in the K2 lightcurve of CI Tau occurring on timescales of 1 d. Our findings reveal that the amplitude of this stochastic variability exhibits the same periodic signatures as detected in the large-amplitude variability, indicating that the physical mechanism modulating these brightness features is the same.
We present the first results from the POKEMON (Pervasive Overview of Kompanions of Every M-dwarf in Our Neighborhood) survey, the largest speckle survey of stellar multiplicity ever produced for the objects that comprise over 70% of the stars in our galaxy: the M-dwarfs. We have conducted a volume-limited survey through M9 that inspected, at diffraction-limited resolution, every M-dwarf out to 15pc, with additional brighter targets to 25pc. POKEMON utilized the Differential Speckle Survey Instrument (DSSI) at the 4.3m Lowell Discovery Telescope, along with the NN-Explore Exoplanet Stellar Speckle Imager (NESSI) on the 3.5-m WIYN telescope. We report the discovery of 30+ new companions to these nearby M-dwarfs. Given the priority these targets have for exoplanet studies with TESS, and in the future JWST - and the degree to which initially undetected multiplicity has skewed Kepler results - a comprehensive survey of our nearby low-mass neighbors provides a homogeneous, complete catalog of fundamental utility. Prior knowledge of secondary objects - or robust non-detections, as captured by this survey - immediately clarify the nature of exoplanet transit detections from these current and upcoming missions.
We present an analysis of TESS and Kepler light curves for 4,947 K+K wide binaries from the SUPERWIDE Catalog. We use these systems to examine the usefulness of the "Lobster" diagram, a plot which allows for the identification of over-luminous components in wide binaries using Gaia data alone. These over-luminous components are believed to be unresolved binaries, making the wide binaries a triple (or even quadruple) system. To confirm this, we search through the high cadence light curves from TESS, Kepler and K2 and the data products produced from the MIT Quick Lookup Pipeline for signals from eclipses and from rotational modulation in spotted fast-rotating stars. We identify 64 eclipsing systems and 115 systems showing signs of fast rotation. We highlight the systems containing eclipsing binaries, fast rotators (P<5 days) and rotators (P>5 days) on the "Lobster" diagram. Eclipsing binaries are overwhelmingly found to be in areas that show a component is over-luminous. Fast rotators are also more likely to be found in these areas while stars showing rotation with periods > 5 days are more likely to be found where true wide binaries are believed to be located.
We propose to use JWST and NIRCam to carry out a search for the faintest trans-Neptunian objects (TNOs) ever detected. We will detect 30 objects as small as 7 km at distances up to 45 AU, placing strong constraints on the small size distribution, and thereby testing competing models for the formation and collisional evolution of trans-Neptunian objects. We will also probe deep into the size regime of Centaurs and Jupiter Family Comets, empirically measuring the size distribution of similarly-sized TNOs where Centaurs and JFCs are sourced. The result of this program will be a huge advance in our understanding of the dynamical and chemical evolution currently occurring in the distant Solar System. This experiment can only be carried out with JWST.
We propose to observe the leading and trailing hemispheres of the Uranian moons Ariel, Umbriel, Titania, and Oberon using NIRSpec IFU (G395M, 2.87 - 5.27 microns) to determine whether NH3-rich species, organics, and carbonates are present and measure CO2 ice and H2O ice features on these moons. These observations will provide an ideal opportunity to investigate the spectral evidence for past ocean world activity on these moons, assess the organic constituents on their surfaces, and measure carbon and hydrogen isotopes to assess the formation conditions in the Uranian subnebula. These science goals are highly challenging to investigate with ground-based facilities because of strong overprinting telluric bands over the 2.9 to 3.5 microns wavelength range. Furthermore, Earth's atmosphere is opaque between 4.2 and 4.5 microns, making detection and measurement of the 4.27-micron CO2 ice band on the Uranian moons and other planetary surfaces impossible to do using ground-based facilities. JWST is therefore the only existing facility that can make these observations. We require 9.96 hours of science time, and 20.72 hours of total charged time, to make the eight observations required to complete this project's science objectives. These observations will generate an important dataset that will inform the spectroscopic priorities of future spacecraft mission concepts that aim to explore Uranus and its moons.
The Lucy spacecraft - to be launched at approximately the same time as JWST - will perform the first ever in situ exploration of the Jupiter Trojan asteroids. Trojans are the largest population of solar system bodies currently unvisited by spacecraft, and revealing their composition and formation history is the key to untangling disparate hypothesis for the early dynamical evolution of the entire solar system. Understanding these enigmatic bodies requires not just the high spatial resolution imagery and spectroscopy that will be afforded by Lucy, but also the superb near- and mid-infrared spectroscopy of which JWST is uniquely capable. The high signal-to-noise, high spectral resolution, and extended wavelength coverage beyond the capabilities of Lucy will allow JWST to sensitively probe the organic, carbonate, and silicate components of the surfaces of the Trojans. Meanwhile, the Lucy spectra and images will place these observations into their geological and historical context, greatly extending the scientific utility of both the JWST observations and the Lucy visit. Together these observations will paint a rich picture of this population, allowing us to trace connections with other bodies studied remotely and in situ across the solar system.
We studied the weak-lined T Tauri star Hubble 4, a known long-period binary, and its star-spot phenomena. We used optical radial velocity (RV) data taken over a span of 14 yr (2004-2010, 2017-2019) at the McDonald Observatory 2.7 m Harlan J. Smith Telescope and single epoch imaging from the Hubble Space Telescope (HST)/Wide Field Camera 3 instrument. The observed and apparent RV variations show contributions, respectively, from the binary motion as well as from a large spot group on one of the stars, presumed to be the primary. Fitting and removing the orbital signal from the RVs, we found the lower bound on the lifetime of a previously identified large spot group on the surface of the star to be at least 5.1 yr. An 5 yr lower limit is a long, but not unprecedented, duration for a single spot group. The later epoch data indicate significant spot evolution has occurred, placing an upper bound on the spot group lifetime at 12 yr. We find that pre-main-sequence evolutionary models for the age of Taurus (2 Myr), combined with component mass estimates from the literature, permit us to reproduce the HST relative photometry and the binary-induced contribution to the apparent RV variations. The long-lived star spot we find on Hubble 4 has significant implications for dynamo models in young stars, as it adds evidence for long lifetimes of magnetic field topologies. There are also significant implications for young star exoplanet searches, as long-lived coherent RV signals may be spot induced and not the result of planetary motion. * This paper includes data taken at The McDonald Observatory of The University of Texas at Austin.
The Near-Infrared High Throughput Spectrograph (NIHTS) is in operation on the 4.3 m Lowell Discovery Telescope (LDT) in Happy Jack, AZ. NIHTS is a low-resolution spectrograph (R 200) that operates from 0.86 to 2.45 microns. NIHTS is fed by a custom dichroic mirror which reflects near-infrared wavelengths to the spectrograph and transmits the visible to enable simultaneous imaging with the Large Monolithic Imager (LMI), an independent visible wavelength camera. The combination of premier tracking and acquisition capabilities of the LDT, a several arcminutes field of view on LMI, and high spectral throughput on NIHTS enables novel studies of a number of astrophysical and planetary objects including Kuiper Belt Objects, asteroids, comets, low mass stars, and exoplanet hosts stars. We present a summary of NIHTS operations, commissioning, data reduction procedures with two approaches for the correction of telluric absorption features, and an overview of select science cases that will be pursued by Lowell Observatory, Northern Arizona University, and LDT partners.
We present a catalog of 4195 optically confirmed Sunyaev-Zeldovich (SZ) selected galaxy clusters detected with signal-to-noise ratio >4 in 13,211 deg2 of sky surveyed by the Atacama Cosmology Telescope (ACT). Cluster candidates were selected by applying a multifrequency matched filter to 98 and 150 GHz maps constructed from ACT observations obtained from 2008 to 2018 and confirmed using deep, wide-area optical surveys. The clusters span the redshift range 0.04 < z < 1.91 (median z = 0.52). The catalog contains 222 z > 1 clusters, and a total of 868 systems are new discoveries. Assuming an SZ signal versus mass-scaling relation calibrated from X-ray observations, the sample has a 90% completeness mass limit of M 500c > 3.8 1014 M , evaluated at z = 0.5, for clusters detected at signal-to-noise ratio >5 in maps filtered at an angular scale of 2.4. The survey has a large overlap with deep optical weak-lensing surveys that are being used to calibrate the SZ signal mass-scaling relation, such as the Dark Energy Survey (4566 deg2), the Hyper Suprime-Cam Subaru Strategic Program (469 deg2), and the Kilo Degree Survey (825 deg2). We highlight some noteworthy objects in the sample, including potentially projected systems, clusters with strong lensing features, clusters with active central galaxies or star formation, and systems of multiple clusters that may be physically associated. The cluster catalog will be a useful resource for future cosmological analyses and studying the evolution of the intracluster medium and galaxies in massive clusters over the past 10 Gyr.
We perform a comprehensive study of Milky Way (MW) satellite galaxies to constrain the fundamental properties of dark matter (DM). This analysis fully incorporates inhomogeneities in the spatial distribution and detectability of MW satellites and marginalizes over uncertainties in the mapping between galaxies and DM halos, the properties of the MW system, and the disruption of subhalos by the MW disk. Our results are consistent with the cold, collisionless DM paradigm and yield the strongest cosmological constraints to date on particle models of warm, interacting, and fuzzy dark matter. At 95% confidence, we report limits on (i) the mass of thermal relic warm DM, mWDM>6.5 keV (free-streaming length, fs10 h-1 kpc ), (ii) the velocity-independent DM-proton scattering cross section, 0<8.8 10-29 cm2 for a 100 MeV DM particle mass [DM-proton coupling, cp(0.3 GeV )-2], and (iii) the mass of fuzzy DM, m>2.9 10-21 eV (de Broglie wavelength, dB0.5 kpc ). These constraints are complementary to other observational and laboratory constraints on DM properties.
The V-type asteroids are of major scientific interest as they may sample multiple differentiated planetesimals. Determination of their physical properties is crucial for understanding the diversity and multiplicity of planetesimals. Previous studies have suggested distinct polarimetric behaviours for the V-type asteroids. Similarly to phase-polarization curves, asteroid phase-magnitude curves (hereinafter called "phase curves") are also diagnostic of surface and regolith properties, and can be used to unveil a variety of distinct behaviours. We present well determined phase curves for ~20 V-type asteroids for the first time. Their phase curve parameters are consistent with those for moderate and high albedo asteroids. The computed median G12 parameter for the V-type asteroids is G12 = 0.14. We do not find substantial evidence for any clustering into distinct phase curve parameters groups. Only one asteroid (2763) Jeans shows exceptionally high G2 value. The derived median G12 may be used in single parameters fitting of V-type asteroids.
The last sets of Panoramic Camera (Pancam) visible/near-infrared (432-1009 nm) multispectral observations made under varying viewing and illumination geometries by the Mars Exploration Rovers Spirit and Opportunity were examined using radiative transfer models to study the surface scattering and microphysical nature of rock and soil units at both sites. Nearly 12,000 individual measurements were collected for this study of soil, dust, and rock units over phase angles of ~0 to ~150. Images were acquired on sols 1944-1946 (June 2009) at Troy, the final resting place of Spirit on the western side of Home Plate in Gusev crater, and by Opportunity at three locations on the western rim of Endeavour crater in Meridiani Planum between sols 2785 (November 2011) and 3867 (December 2014). Sky models were developed from observations of atmospheric opacity, which enabled corrections for diffuse skylight when combined with surface facet orientations determined from stereo images. Model results were improved by removing data affected by scattered light evident in some high phase angle images (resulting from minor dust contamination on the camera windows). At Troy, relatively dust-free "gray" rock units exhibited narrow, forward scattering behaviors akin to previous analyses of similar gray rock units at Gusev crater. Soils and "red" rocks coated with greater amounts of dust were more backscattering. Red rocks exhibited higher single scattering albedo (w), macroscopic roughness (), and opposition effect width (h) parameters, indicative of rough, low-porosity surfaces perhaps with more uniform grain size distributions. At Meridiani Planum, rubbly soils near Sao Gabriel crater and Cape Tribulation exhibited w values typical of previous soil analyses. However, the large drift "dust" deposits found in depressions on the northern tip of Cape York near Turkey Haven demonstrated elevated w values with a downturn toward 1009 nm, consistent with minor hydration of these materials. The dust deposits were modeled with the lowest values and highest h values of all soil units analyzed during the Opportunity mission, indicative of a smooth surface with homogeneous grain size distribution and/or lower porosity than other units. The dust unit scattering function was dissimilar to those for atmospheric and airfall-deposited dusts, however, suggesting that the originally deposited materials had been modified, perhaps by hydration and ongoing aeolian effects. Analyses of phase curve ratios among the units studied here and from laboratory data of analog soils suggested that surface scattering is a major control on the peak phase angle position of the "arch" in phase curve ratios, alongside the effects of particle-scale roughness.
Analyses of Type Ia supernovae (SNe Ia) have found puzzling correlations between their standardized luminosities and host galaxy properties: SNe Ia in high-mass, passive hosts appear brighter than those in lower mass, star-forming hosts. We examine the host galaxies of SNe Ia in the Dark Energy Survey 3-yr spectroscopically confirmed cosmological sample, obtaining photometry in a series of 'local' apertures centred on the SN, and for the global host galaxy. We study the differences in these host galaxy properties, such as stellar mass and rest-frame U - R colours, and their correlations with SN Ia parameters including Hubble residuals. We find all Hubble residual steps to be >3 in significance, both for splitting at the traditional environmental property sample median and for the step of maximum significance. For stellar mass, we find a maximal local step of 0.098 0.018 mag; 0.03 mag greater than the largest global stellar mass step in our sample (0.070 0.017 mag). When splitting at the sample median, differences between local and global U - R steps are small, both 0.08 mag, but are more significant than the global stellar mass step (0.057 0.017 mag). We split the data into sub-samples based on SN Ia light-curve parameters: stretch (x1) and colour (c), finding that redder objects (c > 0) have larger Hubble residual steps, for both stellar mass and U - R, for both local and global measurements, of 0.14 mag. Additionally, the bluer (star-forming) local environments host a more homogeneous SN Ia sample, with local U - R rms scatter as low as 0.084 0.017 mag for blue (c < 0) SNe Ia in locally blue U - R environments.
On UT 29 June 2015, the occultation by Pluto of a bright star (r = 11.9) was observed from the Stratospheric Observatory for Infrared Astronomy (SOFIA) and several ground-based stations in New Zealand and Australia. Pre-event astrometry allowed for an in-flight update to the SOFIA team with the result that SOFIA was deep within the central flash zone (~22 km from center). Analysis of the combined data leads to the result that Pluto's middle atmosphere is essentially unchanged from 2011 and 2013 (Person et al. 2013; Bosh et al. 2015); there has been no significant expansion or contraction of the atmosphere. Additionally, our multi-wavelength observations allow us to conclude that a haze component in the atmosphere is required to reproduce the light curves obtained. This haze scenario has implications for understanding the photochemistry of Pluto's atmosphere.
Pluto's surface is geologically complex because of volatile ices that are mobile on seasonal and longer time scales. Here we analyzed New Horizons LEISA spectral data to globally map the nitrogen ice, including nitrogen with methane diluted in it. Our goal was to learn about the seasonal processes influencing ice redistribution, to calculate the globally averaged energy balance, and to place a lower limit on Pluto's N2 inventory. We present the average latitudinal distribution of nitrogen and investigate the relationship between its distribution and topography on Pluto by using maps that include the shifted bands of methane in solid solution with nitrogen (which are much stronger than the 2.15- m nitrogen band) to more completely map the distribution of the nitrogen ice. We find that the global average bolometric albedo is 0 . 83 0 . 11 , similar to that inferred for Triton, and that a significant fraction of Pluto's N2 is stored in Sputnik Planitia. We also used the encounter-hemisphere distribution of nitrogen ice to infer the latitudinal distribution of nitrogen over the rest of Pluto, allowing us to calculate the global energy balance. Under the assumption that Pluto's nitrogen-dominated 11.5 bar atmosphere is in vapor pressure equilibrium with the nitrogen ice, the ice temperature is 36 . 93 0 . 10 K, as measured by New Horizons' REX instrument. Combined with our global energy balance calculation, this implies that the average bolometric emissivity of Pluto's nitrogen ice is probably in the range 0.47-0.72. This is consistent with the low emissivities estimated for Triton based on Voyager results, and may have implications for Pluto's atmospheric seasonal variations, as discussed below. The global pattern of volatile transport at the time of the encounter was from north to south, and the transition between condensation and sublimation within Sputnik Planitia is correlated with changes in the grain size and CH4 concentration derived from the spectral maps. The low emissivity of Pluto's N2 ice suggests that Pluto's atmosphere may undergo an extended period of constant pressure even as Pluto recedes from the Sun in its orbit.
A prominent fossa trough (Uncama Fossa) and adjacent 28-km diameter impact crater (Hardie) in Pluto's Viking Terra, as seen in the high-resolution images from the New Horizons spacecraft, show morphological evidence of in-filling with a material of uniform texture and red-brown color. A linear fissure parallel to the trough may be the source of a fountaining event yielding a cryoclastic deposit having the same composition and color properties as is found in the trough and crater. Spectral maps of this region with the New Horizons LEISA instrument reveal the spectral signature of H2O ice in these structures and in distributed patches in the adjacent terrain in Viking Terra. A detailed statistical analysis of the spectral maps shows that the colored H2O ice filling material also carries the 2.2-m signature of an ammoniated component that may be an ammonia hydrate (NH3nH2O) or an ammoniated salt. This paper advances the view that the crater and fossa trough have been flooded by a cryolava debouched from Pluto's interior along fault lines in the trough and in the floor of the impact crater. The now frozen cryolava consisted of liquid H2O infused with the red-brown pigment presumed to be a tholin, and one or more ammoniated compounds. Although the abundances of the pigment and ammoniated compounds entrained in, or possibly covering, the H2O ice are unknown, the strong spectral bands of the H2O ice are clearly visible. In consideration of the factors in Pluto's space environment that are known to destroy ammonia and ammonia-water mixtures, the age of the exposure is of order 109 years. Ammoniated salts may be more robust, and laboratory investigations of these compounds are needed.
In 2015 the New Horizons spacecraft reached the Pluto system and returned unprecedentedly detailed measurements of its surface properties. These measurements have already been integrated into global reflectance, topography and narrow-band multispectral surface maps. However, analysis of the hyperspectral data from the Ralph/LEISA infrared spectrometer, which lets us analyse the surface composition, has until now been confined to the high-resolution encounter hemisphere of Pluto. We use an innovative technique - intensity-based registration - to co-register this high-resolution data with lower-resolution measurements taken during the spacecraft's approach, and present the first global qualitative composition maps for CH<!--l. 82 -->4, N<!--l. 82 -->2 and H<!--l. 82 -->2O ice, and a tholin-like red material. We compare these maps with the other maps produced for Pluto and study the global extent of the previously-described latitudinal distribution of the surface components, which is relatively longitudinally constant with the exception of Sputnik Planitia. We also correlate these compositional components with geological features and propose physical interpretations, which include: CH<!--l. 82 -->4-ice-rich dissected plateaus in high northern latitudes, CH<!--l. 82 -->4-rich eroded terrain with N<!--l. 82 -->2-rich infill in medium northern latitudes, CH<!--l. 82 -->4-rich bladed terrain in low northern latitudes, and a red material belt overlaying H<!--l. 82 -->2O ice in low southern latitudes.
In this paper we discuss in a thermodynamic, geologically empirical way the long-term nature of the stable majority ices that could be present in Kuiper Belt object (KBO) 2014 MU69 (also called Arrokoth; hereafter "MU69") after its 4.6 Gyr residence in the Edgeworth-Kuiper belt (EKB) as a cold classical object. We compare the upper bounds for the gas production rate (~1024 molecules/s) measured by the New Horizons (NH) spacecraft flyby on 01 Jan 2019 to estimates for the outgassing flux rates from a suite of common cometary and KBO ices at the average ~ 40 K sunlit surface temperature of MU69, but do not find the upper limit very constraining except for the most volatile of species (e.g. CO, N2, CH4). More constraining is the stability versus sublimation into vacuum requirement over Myr to Gyr, and from this we find only 3 common ices that are truly refractory: HCN, CH3OH, and H2O (in order of increasing stability), while NH3 and H2CO ices are marginally stable and may be removed by any positive temperature excursions in the EKB, as produced every 108-109 years by nearby supernovae and passing O/B stars. To date the NH team has reported the presence of abundant CH3OH and H2O on MU69's surface (Stern et al., 2019; Grundy et al., 2020). NH3 has been searched for, but not found. We predict that future absorption feature detections, if any are ever derived from higher signal-to-noise ratio spectra, will be due to an HCN or poly-H2CO based species. Consideration of the conditions present in the EKB region during the formation era of MU69 lead us to state that it is highly likely that it "formed in the dark", in an optically thick mid-plane, unable to see the nascent, variable, highly luminous Young Stellar Object (YSO)/TTauri Sun, and that KBOs contain HCN and CH3OH ice phases in addition to the H2O ice phases found in their short period (SP) comet descendants. Finally, when we apply our ice thermal stability analysis to bodies/populations related to MU69, we find that methanol ice is likely ubiquitous in the outer solar system; that if Pluto isn't a fully differentiated body, then it must have gained its hypervolatile ices from proto-planetary disk (PPD) sources in the first few Myr of the solar system's existence; and that hypervolatile rich, highly primordial comet C/2016 R2 was placed onto an Oort Cloud orbit on a similar few Myr timescale.
We investigate what can be learned about a population of distant Kuiper Belt Objects (KBOs) by studying the statistical properties of their light curves. Whereas others have successfully inferred the properties of individual, highly variable KBOs, we show that the fraction of KBOs with low amplitudes also provides fundamental information about a population. Each light curve is primarily the result of two factors: shape and orientation. We consider contact binaries and ellipsoidal shapes, with and without flattening. After developing the mathematical framework, we apply it to the existing body of KBO light curve data. Principal conclusions are as follows. (1) When using absolute magnitude H as a proxy for the sizes of KBOs, it is more accurate to use the maximum of the light curve (minimum H) rather than the mean. (2) Previous investigators have noted that smaller KBOs tend to have higher-amplitude light curves, and have interpreted this as evidence that they are systematically more irregular in shape than larger KBOs; we show that a population of flattened bodies with uniform proportions, independent of size, could also explain this result. (3) Our method of analysis indicates that prior assessments of the fraction of contact binaries in the Kuiper Belt may be artificially low. (4) The pole orientations of some KBOs can be inferred from observed changes in their light curves over time scales of decades; however, we show that these KBOs constitute a biased sample, whose pole orientations are not representative of the population overall. (5) Although surface topography, albedo patterns, limb darkening, and other surface properties can affect individual light curves, they do not have a strong influence on the statistics overall. (6) Photometry from the Outer Solar System Origins Survey (OSSOS) survey is incompatible with previous results and its statistical properties defy easy interpretation. We also discuss the promise of this approach for the analysis of future, much larger data sets such as the one anticipated from the upcoming Vera C. Rubin Observatory.
The Kuiper belt represents a vast treasure of scientific information. From evolved, planet-sized bodies to relatively primordial smaller bodies, the science that can be done with Kuiper belt data touches many aspects of solar system formation and evolution. These connections along with advancements in telescope and spacecraft technology have created the conditions for a golden age for Kuiper belt science, as exemplified by the breadth and depth of topics in this special issue.
We introduce a new software package for modelling the point spread function (PSF) of astronomical images, called PIFF (PSFs In the Full FOV), which we apply to the first three years (known as Y3) of the Dark Energy Survey (DES) data. We describe the relevant details about the algorithms used by PIFF to model the PSF, including how the PSF model varies across the field of view (FOV). Diagnostic results show that the systematic errors from the PSF modelling are very small over the range of scales that are important for the DES Y3 weak lensing analysis. In particular, the systematic errors from the PSF modelling are significantly smaller than the corresponding results from the DES year one (Y1) analysis. We also briefly describe some planned improvements to PIFF that we expect to further reduce the modelling errors in future analyses.
We explore the relation between diffuse intracluster light (central galaxy included) and the galaxy cluster (baryonic and dark) matter distribution using a sample of 528 clusters at 0.2 z 0.35 found in the Dark Energy Survey (DES) Year 1 data. The surface brightness of the diffuse light shows an increasing dependence on cluster total mass at larger radius, and appears to be self-similar with a universal radial dependence after scaling by cluster radius. We also compare the diffuse light radial profiles to the cluster (baryonic and dark) matter distribution measured through weak lensing and find them to be comparable. The IllustrisTNG galaxy formation simulation, TNG300, offers further insight into the connection between diffuse stellar mass and cluster matter distributions - the simulation radial profile of the diffuse stellar component does not have a similar slope with the total cluster matter content, although that of the cluster satellite galaxies does. Regardless of the radial trends, the amount of diffuse stellar mass has a low-scatter scaling relation with cluster's total mass in the simulation, out-performing the total stellar mass of cluster satellite galaxies. We conclude that there is no consistent evidence yet on whether or not diffuse light is a faithful radial tracer of the cluster matter distribution. Nevertheless, both observational and simulation results reveal that diffuse light is an excellent indicator of the cluster's total mass.
Recent work measuring the binary fraction of evolved red supergiants (RSGs) in the Magellanic Clouds points to a value between 15% and 30%, with the majority of the companions being unevolved B-type stars as dictated by stellar evolution. Here I extend this research to the Local Group galaxies M31 and M33 and investigate the RSG binary fraction as a function of metallicity. Recent near-IR photometric surveys of M31 and M33 have led to the identification of a complete sample of RSGs down to a limiting $\mathrm{log}L/{L}_{\odot }\geqslant 4.2$ . To determine the binary fraction of these M31 and M33 RSGs, I used a combination of newly obtained spectroscopy to identify single RSGs and RSG+OB binaries, as well as archival UV, visible, and near-IR photometry to probabilistically classify RSGs as either single or binary based on their colors. I then adjusted the observed RSG+OB binary fraction to account for observational biases. The resulting RSG binary fraction in M33 shows a strong dependence on galactocentric distance, with the inner regions having a much higher binary fraction ( ${41.2}_{-7.3}^{+12.0} \% $ ) than the outer regions ( ${15.9}_{-1.9}^{+12.4} \% $ ). Such a trend is not seen in M31; instead, the binary fraction in lightly reddened regions remains constant at ${33.5}_{-5.0}^{+8.6} \% $ . I conclude that the changing RSG binary fraction in M33 is due to a metallicity dependence, with higher-metallicity environments having higher RSG binary fractions. This dependence most likely stems not from changes in the physical properties of RSGs due to metallicity but from changes in the parent distribution of OB binaries.
We perform a joint analysis of the counts of redMaPPer clusters selected from the Dark Energy Survey (DES) year 1 data and multiwavelength follow-up data collected within the 2500 deg2 South Pole Telescope (SPT) Sunyaev-Zel'dovich (SZ) survey. The SPT follow-up data, calibrating the richness-mass relation of the optically selected redMaPPer catalog, enable the cosmological exploitation of the DES cluster abundance data. To explore possible systematics related to the modeling of projection effects, we consider two calibrations of the observational scatter on richness estimates: a simple Gaussian model which account only for the background contamination (BKG), and a model which further includes contamination and incompleteness due to projection effects (PRJ). Assuming either a CDM +m or w CDM +m cosmology, and for both scatter models, we derive cosmological constraints consistent with multiple cosmological probes of the low and high redshift Universe, and in particular with the SPT cluster abundance data. This result demonstrates that the DES Y1 and SPT cluster counts provide consistent cosmological constraints, if the same mass calibration data set is adopted. It thus supports the conclusion of the DES Y1 cluster cosmology analysis which interprets the tension observed with other cosmological probes in terms of systematics affecting the stacked weak lensing analysis of optically selected low-richness clusters. Finally, we analyze the first combined optically SZ selected cluster catalog obtained by including the SPT sample above the maximum redshift probed by the DES Y1 redMaPPer sample (z =0.65 ). Besides providing a mild improvement of the cosmological constraints, this data combination serves as a stricter test of our scatter models: the PRJ model, providing scaling relations consistent between the two abundance and multiwavelength follow-up data, is favored over the BKG model.
In 2019, the Research and Education Collaborative Occultation Network (RECON) obtained multiple-chord occultation measurements of two Centaur objects: 2014 YY49 on 2019 January 28 and 2013 NL24 on 2019 September 4. RECON is a citizen-science telescope network designed to observe high-uncertainty occultations by outer solar system objects. Adopting circular models for the object profiles, we derive a radius $r={16}_{-1}^{+2}$ km and a geometric albedo ${p}_{V}={0.13}_{-0.024}^{+0.015}$ for 2014 YY49 and a radius $r={66}_{-5}^{+5}$ km and a geometric albedo ${p}_{V}={0.045}_{-0.008}^{+0.006}$ for 2013 NL24. To the precision of these measurements, no atmosphere or rings are detected for either object. The two objects measured here are among the smallest distant objects measured with the stellar occultation technique. In addition to these geometric constraints, the occultation measurements provide astrometric constraints for these two Centaurs at a higher precision than has been feasible by direct imaging. To supplement the occultation results, we also present an analysis of color photometry from the Pan-STARRS surveys to constrain the rotational light curve amplitudes and spectral colors of these two Centaurs. We recommend that future work focus on photometry to more deliberately constrain the objects' colors and light curve amplitudes and on follow-on occultation efforts informed by this astrometry.
We present a deep imaging and spectroscopic search for emission from (3200) Phaethon, a large near-Earth asteroid that appears to be the parent of the strong Geminid meteoroid stream, using the 4.3 m Lowell Discovery Telescope. Observations were conducted on 2017 December 14-18 when Phaethon passed only 0.07 au from the Earth. We determine the 3 upper level of dust and CN production rates to be 0.007-0.2 kg s-1 and 2.3 1022 molecules s-1 through narrowband imaging. A search in broadband images taken through the SDSS r' filter shows no 100 m class fragments in Phaethon's vicinity. A deeper but star-contaminated search also shows no sign of fragments down to 15 m. Optical spectroscopy of Phaethon and comet C/2017 O1 (ASASSN) as a comparison confirms the absence of cometary emission lines from Phaethon and yields 3 upper levels of CN, C2, and C3 of 1024-1025 molecules s-1, 2 orders of magnitude higher than the CN constraint placed by narrowband imaging, due to the much narrower on-sky aperture of the spectrographic slit. We show that narrowband imaging could provide an efficient way to look for weak gas emission from near-extinct bodies near the Earth, though these observations require careful interpretation. Assuming Phaethon's behavior is unchanged, our analysis shows that the DESTINY+ mission, currently planning to explore Phaethon in 2026, may not be able to directly detect a gas coma.
Planetesimals are compact astrophysical objects roughly 1-1000 km in size, massive enough to be held together by gravity. They can grow by accreting material to become full-size planets. Planetesimals themselves are thought to form by complex physical processes from small grains in protoplanetary disks. The streaming instability (SI) model states that millimeter/centimeter-sized particles (pebbles) are aerodynamically collected into self-gravitating clouds that then directly collapse into planetesimals. Here we analyze ATHENA simulations of the SI to characterize the initial properties (e.g., rotation) of pebble clouds. Their gravitational collapse is followed with the PKDGRAV N-body code, which has been modified to realistically account for pebble collisions. We find that pebble clouds rapidly collapse into short-lived disk structures from which planetesimals form. The planetesimal properties depend on the cloud's scaled angular momentum, $l=L/({{MR}}_{{\rm{H}}}^{2}{\rm{\Omega }})$ , where L and M are the angular momentum and mass, RH is the Hill radius, and is the orbital frequency. Low-l pebble clouds produce tight (or contact) binaries and single planetesimals. Compact high-l clouds give birth to binary planetesimals with attributes that closely resemble the equally sized binaries found in the Kuiper Belt. Significantly, the SI-triggered gravitational collapse can explain the angular momentum distribution of known equally sized binariesa result pending verification from studies with improved resolution. About 10% of collapse simulations produce hierarchical systems with two or more large moons. These systems should be found in the Kuiper Belt when observations reach the threshold sensitivity.
We investigate potential gains in cosmological constraints from the combination of galaxy clustering and galaxy-galaxy lensing by optimizing the lens galaxy sample selection using information from Dark Energy Survey (DES) Year 3 data and assuming the DES Year 1 METACALIBRATION sample for the sources. We explore easily reproducible selections based on magnitude cuts in i -band as a function of (photometric) redshift, zphot, and benchmark the potential gains against those using the well-established REDMAGIC [E. Rozo et al., Mon. Not. R. Astron. Soc. 461, 1431 (2016), 10.1093/mnras/stw1281] sample. We focus on the balance between density and photometric redshift accuracy, while marginalizing over a realistic set of cosmological and systematic parameters. Our optimal selection, the MAGLIM sample, satisfies i <4 zphot+18 and has 30 % wider redshift distributions but 3.5 times more galaxies than REDMAGIC. Assuming a w CDM model (i.e. with a free parameter for the dark energy equation of state) and equivalent scale cuts to mitigate nonlinear effects, this leads to 40% increase in the figure of merit for the pair combinations of m, w , and 8, and gains of 16% in 8, 10% in m, and 12% in w . Similarly, in CDM , we find an improvement of 19% and 27% on 8 and m, respectively. We also explore flux-limited samples with a flat magnitude cut finding that the optimal selection, i <22.2 , has 7 times more galaxies and 20 % wider redshift distributions compared to MAGLIM, but slightly worse constraints. We show that our results are robust with respect to the assumed galaxy bias and photometric redshift uncertainties with only moderate further gains from increased number of tomographic bins or the inclusion of bin cross-correlations, except in the case of the flux-limited sample, for which these gains are more significant.
The stellar, gaseous and young stellar disks in the LITTLE THINGS sample of nearby dwarf irregular galaxies are fitted with functions to search for correlations between the parameters. We find that the H I radial profiles are generally flatter in the center and fall faster in the outer regions than the V-band profiles, while young stars are more centrally concentrated, especially if the H I is more centrally flat. This pattern suggests that the H I is turning into molecules in the center, and the molecular clouds are forming stars and FUV. A model that assumes the molecular surface density is proportional to the total gas surface density to a power of 1.5 or 2, in analogy with the Kennicutt-Schmidt relation, reproduces the relationship between the ratio of the visible to the H I scale length and the H I Sersic index. The molecular fraction is estimated as a function of radius for each galaxy by converting the FUV to a molecular surface density using conventional calibrations. The average molecular fraction inside 3RD is 23% 17%. However, the break in the stellar surface brightness profile has no unified tracer related to star formation.
We identify red supergiants (RSGs) in our spiral neighbors M31 and M33 using near-IR (NIR) photometry complete to a luminosity limit of $\mathrm{log}L/{L}_{\odot }=4.0$ . Our archival survey data cover 5 deg2 of M31, and 3 deg2 for M33, and are likely spatially complete for these massive stars. Gaia is used to remove foreground stars, after which the RSGs can be separated from asymptotic giant branch (AGB) stars in the color-magnitude diagram. The photometry is used to derive effective temperatures and bolometric luminosities via MARCS stellar atmosphere models. The resulting H-R diagrams show superb agreement with the evolutionary tracks of the Geneva evolutionary group. Our census includes 6400 RSGs in M31 and 2850 RSGs in M33 within their Holmberg radii; by contrast, only a few hundred RSGs are known so far in the Milky Way. Our catalog serves as the basis for a study of the RSG binary frequency being published separately, as well as future studies relating to the evolution of massive stars. Here we use the matches between the NIR-selected RSGs and their optical counterparts to show that the apparent similarity in the reddening of OB stars in M31 and M33 is the result of Malmquist bias; the average extinction in M31 is likely higher than that of M33. As expected, the distribution of RSGs follows that of the spiral arms, while the much older AGB population is more uniformly spread across each galaxy's disk.
We present a catalog of 23,790 extended low-surface-brightness galaxies (LSBGs) identified in $\sim 5000\,{\deg }^{2}$ from the first three years of imaging data from the Dark Energy Survey (DES). Based on a single-component Sersic model fit, we define extended LSBGs as galaxies with g-band effective radii ${R}_{\mathrm{eff}}(g)\gt 2\buildrel{\prime\prime}\over{.} 5$ and mean surface brightness ${\bar{\mu }}_{\mathrm{eff}}(g)\gt 24.2\,\mathrm{mag}\,{\mathrm{arcsec}}^{-2}$ . We find that the distribution of LSBGs is strongly bimodal in (g - r) versus (g - i) color space. We divide our sample into red (g - i 0.60) and blue (g - i < 0.60) galaxies and study the properties of the two populations. Redder LSBGs are more clustered than their blue counterparts and are correlated with the distribution of nearby (z < 0.10) bright galaxies. Red LSBGs constitute 33% of our LSBG sample, and $\sim 30 \% $ of these are located within 1 of low-redshift galaxy groups and clusters (compared to 8% of the blue LSBGs). For nine of the most prominent galaxy groups and clusters, we calculate the physical properties of associated LSBGs assuming a redshift derived from the host system. In these systems, we identify 41 objects that can be classified as ultradiffuse galaxies, defined as LSBGs with projected physical effective radii ${R}_{\mathrm{eff}}\gt 1.5\,\mathrm{kpc}$ and central surface brightness ${\mu }_{0}(g)\gt 24.0\,\mathrm{mag}\,{\mathrm{arcsec}}^{-2}$ . The wide-area sample of LSBGs in DES can be used to test the role of environment on models of LSBG formation and evolution.
We obtained broad- and narrowband images of the hyperactive comet 46P/Wirtanen on 33 nights during its 2018/2019 apparition, when the comet made a historic close approach to the Earth. With our extensive coverage, we investigated the temporal behavior of the comet on both seasonal and rotational timescales. We used CN observations to explore the coma morphology, revealing that there are two primary active areas that produce spiral structures. The direction of rotation of these structures changes from pre- to postperihelion, indicating that the Earth crossed the comet's equatorial plane sometime around perihelion. We also used the CN images to create photometric light curves that consistently show two peaks in the activity, confirming the two source regions. We measured the nucleus's apparent rotation period at a number of epochs using both the morphology and the light curves. These results all show that the rotation period is continuously changing throughout our observation window, increasing from 8.98 hr in early November to 9.14 hr around perihelion and then decreasing again to 8.94 hr in February. Although the geometry changes rapidly around perihelion, the period changes cannot be primarily due to synodic effects. The repetition of structures in the coma, both within a night and from night to night, strongly suggests that the nucleus is in a near-simple rotation state. We also detected two outbursts, one on December 12 and the other on January 28. Using the apparent velocities of the ejecta in these events, 68 5 and 162 15 m s-1, respectively, we derived start times of 2018 December 12 at 00:13 UT 7 minutes and 2019 January 27 at 20:01 UT 30 minutes.
Using data from the Infrared Array Camera on the Spitzer Space Telescope, we present photometric observations of a sample of 100 trans-Neptunian objects (TNOs) beyond 2.2 m. These observations, collected with two broadband filters centered at 3.6 and 4.5 m, were done in order to study the surface composition of TNOs, which are too faint to obtain spectroscopic measurements. With this aim, we have developed a method for the identification of different materials that are found on the surfaces of TNOs. In our sample, we detected objects with colors that are consistent with the presence of small amounts of water, and we were able to distinguish between surfaces that are predominantly composed of complex organics and amorphous silicates. We found that 86% of our sample have characteristics that are consistent with a certain amount of water ice, and the most common composition (73% of the objects) is a mixture of water ice, amorphous silicates, and complex organics. Twenty-three percent of our sample may include other ices, such as carbon monoxide, carbon dioxide, methane, or methanol. Additionally, only small objects seem to have surfaces dominated by silicates. This method is a unique tool for the identification of complex organics and to obtain the surface composition of extremely faint objects. Furthermore, this method will be beneficial when using the James Webb Space Telescope for differentiating groups within the trans-Neptunian population.
We report the discovery by the ground-based Hungarian-made Automated Telescope Network (HATNet) survey of the transiting exoplanet HAT-P-68b, which has a mass of 0.724 0.043 MJ, and radius of 1.072 0.012 RJ. The planet is in a circular P = 2.2984 day orbit around a moderately bright V = 13.937 0.030 magnitude K-dwarf star of mass ${0.673}_{-0.014}^{+0.020}$ M, and radius 0.6726 0.0069 R. The planetary nature of this system is confirmed through follow-up transit photometry obtained with the Fred L. Whipple Observatory (FLWO) 1.2 m telescope, high-precision radial velocities measured using Keck I/High Resolution Echelle Spectrometer (HIRES), FLWO 1.5 m/Tillinghast Reflector Echelle Spectrograph (TRES), and Observatoire de Haute-Provence (OHP) 1.9 m/Sophie, and high-spatial-resolution speckle imaging from WIYN 3.5 m/DSSI. HAT-P-68 is at an ecliptic latitude of +3 and outside the field of view of both the NASA Transiting Exoplanet Survey Satellite primary mission and the K2 mission. The large transit depth of 0.036 mag (r band) makes HAT-P-68b a promising target for atmospheric characterization via transmission spectroscopy. * Based on observations obtained with the Hungarian-made Automated Telescope Network. Based in part on observations made with the Keck I telescope at Maunakea Observatory, Hawaii (Keck time awarded through NASA programs N133Hr and N169Hr). Based in part on observations obtained with the Tillinghast Reflector 1.5 m telescope and the 1.2 m telescope, both operated by the Smithsonian Astrophysical Observatory at the Fred Lawrence Whipple Observatory in Arizona. Based on radial velocities obtained with the Sophie spectrograph mounted on the 1.93 m telescope at Observatoire de Haute-Provence.
We present new results on the Eris/Dysnomia system including analysis of new images from the WFC3 instrument on the Hubble Space Telescope (HST). Seven HST orbits were awarded to program 15171 in January and February 2018, with the intervals between observations selected to sample Dysnomia over a full orbital period. Using relative astrometry of Eris and Dysnomia, we computed a best-fit Keplerian orbit for Dysnomia. Based on the Keplerian fit, we find an orbital period of 15.7858990.000050 days, which is in good agreement with recent work. We report a non-zero eccentricity of 0.0062 at the 6.2- level, despite an estimated eccentricity damping timescale of 17 Myr. Considering the volumes of both Eris and Dysnomia, the new system density was calculated to be 2.430.05 g cm-3, a decrease of ~4% from the previous value of 2.520.05 g cm-3. The new astrometric measurements were high enough precision to break the degeneracy of the orbit pole orientation, and indicate that Dysnomia orbits in a prograde manner. The obliquity of Dysnomia's orbit pole with respect to the plane of Eris' heliocentric orbit was calculated to be 78.290.65 and is in agreement with previous work; the next mutual events season will occur in 2239. The Keplerian orbit fit to all the data considered in this investigation can be excluded at the 6.3- level, but identifying the cause of the deviation was outside the scope of this work.
Cosmic voids gravitationally lens the cosmic microwave background (CMB) radiation, resulting in a distinct imprint on degree scales. We use the simulated CMB lensing convergence map from the Marenostrum Institut de Ciencias de l'Espai (MICE) N-body simulation to calibrate our detection strategy for a given void definition and galaxy tracer density. We then identify cosmic voids in Dark Energy Survey (DES) Year 1 data and stack the Planck 2015 lensing convergence map on their locations, probing the consistency of simulated and observed void lensing signals. When fixing the shape of the stacked convergence profile to that calibrated from simulations, we find imprints at the 3 significance level for various analysis choices. The best measurement strategies based on the MICE calibration process yield S/N 4 for DES Y1, and the best-fitting amplitude recovered from the data is consistent with expectations from MICE (A 1). Given these results as well as the agreement between them and N-body simulations, we conclude that the previously reported excess integrated Sachs-Wolfe (ISW) signal associated with cosmic voids in DES Y1 has no counterpart in the Planck CMB lensing map.
We analyze Dark Energy Survey (DES) data to constrain a cosmological model where a subset of parametersfocusing on mare split into versions associated with structure growth (e.g., mgrow) and expansion history (e.g., mgeo). Once the parameters have been specified for the CDM cosmological model, which includes general relativity as a theory of gravity, it uniquely predicts the evolution of both geometry (distances) and the growth of structure over cosmic time. Any inconsistency between measurements of geometry and growth could therefore indicate a breakdown of that model. Our growth-geometry split approach therefore serves both as a (largely) model-independent test for beyond- CDM physics, and as a means to characterize how DES observables provide cosmological information. We analyze the same multiprobe DES data as [Phys. Rev. Lett. 122, 171301 (2019), 10.1103/PhysRevLett.122.171301] : DES Year 1 (Y1) galaxy clustering and weak lensing, which are sensitive to both growth and geometry, as well as Y1 BAO and Y3 supernovae, which probe geometry. We additionally include external geometric information from BOSS DR12 BAO and a compressed Planck 2015 likelihood, and external growth information from BOSS DR12 RSD. We find no significant disagreement with mgrow=mgeo. When DES and external data are analyzed separately, degeneracies with neutrino mass and intrinsic alignments limit our ability to measure mgrow, but combining DES with external data allows us to constrain both growth and geometric quantities. We also consider a parametrization where we split both m and w , but find that even our most constraining data combination is unable to separately constrain mgrow and wgrow. Relative to CDM , splitting growth and geometry weakens bounds on 8 but does not alter constraints on h .
There are over 300 Indian reservations in the United States that are occupied by Native Americans (Indians). The reservations were developed to keep Native Americans off European settlements. The reservations were created to allow the Native Americans to maintain their cultural identity and govern themselves. Most reservation schools do not provide all the necessities that neighboring schools (border towns) offer to their students. Areas that are often overlooked are Science, Math, Technology, and Engineering. Due to the lack of resource and support, Native Americans are less likely to see themselves in professional STEM roles as adults. They are also less likely to pursue higher education or leave the Reservation. The Native American Astronomy Outreach Program was developed 24 years ago to offer support to the reservation teachers to encourage more STEM in the classroom daily. Since then, the program has grown with a greater purpose, to encourage students to pursue higher learning, see themselves as professionals in STEM, and to hopefully, one day have a Native American Astronomer. The Native American Astronomy Outreach Program not only supports STEM but we also include cultural connections with high priority. Keeping the language alive and striving to carry on the traditional teachings is of upmost importance to the program. The program is specifically designed to help students get excited about STEM, especially Astronomy.
The binary fraction of massive main-sequence OB stars is thought to be as high as 70% or greater. However, until recently, only around a dozen binary red supergiants (RSGs) had been identified, despite the fact that these stars are the evolved descendants of a large portion of OB stars. My research focuses on searching for these "missing" binary RSGs. As dictated by stellar evolution, binary RSGs will likely have B-type companions and such systems will have unique photometric signatures due to the shape of their spectral energy distributions. After observing candidate RSG+B star binaries spectroscopically in the Local Group galaxies of M31, M33 and the Magellanic Clouds, we've discovered over 250 new systems. I'll discuss how these results have allowed us to place constraints on the binary fraction of RSGs as a function of metallicity and the greater impacts this has on our understanding of massive star evolution, supernovae populations, and the creation of gravitational wave events.
NGC 3603-A1 is likely the most massive binary star ever "weighed" through its orbital mass. The system is hard to observe, as it is found in the dense core of NGC 3603, with other massive stars within an arcsecond. Analysis of VLT spectroscopy in 2008 found a mass of 116 31 M for the primary and 89 16 M for secondary (Schnurr et al. 2008, MNRAS 389, L38). As an extremely massive, double-lined eclipsing binary, this system provides unique insight into the accuracy of model-dependent methods of determining stellar masses for very high mass stars. We use previously unanalyzed archival spectra and imaging from HST to test the accuracy of the ground-based results and to increase the precision of these masses. From these spectroscopic data, we found a mass ratio of 0.72 0.03, which agrees with the VLT mass ratio of 0.75 0.3. We have also produced a light curve for A1 using HST photometry, which provides a more accurate measurement of the systems inclination. Ultimately we hope to refine the masses of A1 with new observations. SB's work was supported by through the National Science Foundation REU program grant to NAU (awards 1852478 and 1950901), while PM's efforts were supported in part through AST-1612874.
The outer disks of dwarf galaxies provide an extreme environment for studies of star formation because of their low gas densities and metallicities. Previous work has found evidence of young star clusters in the outer disks of dwarf galaxies, but it is unclear how these star clusters could have formed there since the gas density is too low to fragment into clouds via gravitational instability. We searched for young star clusters in the outer disks of dwarf galaxies with new deep images of three dwarf galaxies in four filters from the Local Irregulars That Trace Luminosity Extremes, The H I Nearby Galaxy Survey (LITTLE THINGS). We confirmed one young star cluster in the outer disk of DDO 43, which also appeared in H and far ultraviolet images. We found three additional young star cluster candidates, one in the outer disk of DDO 43 and two in the outer disk of DDO 187. We use photometry of the young star cluster and cluster candidates and a model catalog of cluster evolution to estimate the age and mass and measure diameters of the star clusters. We found that the confirmed young star cluster and the candidate cluster in DDO 43 have reasonable masses and diameters but the two cluster candidates in DDO 187 are very small. Our findings suggest that it is possible for stars to form in the outer disks of dwarf galaxies. This research has been supported by NSF awards 1852478 and 1950901 to Northern Arizona University for the 2020 REU program.
The Quad-camera Wavefront-sensing Six-channel Speckle Interferometer (QWSSI) is a new speckle imaging instrument operational on the 4.3-m Lowell Discovery Telescope. QWSSI is built to efficiently make use of collected photons and detector real estate. The instrument images on a single EMCCD at four wavelengths in the optical (577, 658, 808, and 880nm) with 40nm bandpasses. Longward of 1um, two imaging wavelengths in the near-infrared are collected at 1150 and 1570nm on two InGaAs cameras. All remaining non-imaging visible light is sent into a wavefront EMCCD. With simultaneous wavefront sensing, QWSSI characterizes atmospheric aberrations in the wavefront for each speckle frame. This results in additional data that can be utilized during post-processing, enabling advanced techniques such as Multi-Frame Blind Deconvolution. The design philosophy was optimized for an inexpensive, rapid build; virtually all parts were commercial-off-the-shelf, and custom parts were 3D printed. QWSSI's unique build and capabilities represent a new frontier in civilian high-resolution speckle imaging.
We announce the discovery of a new "transition" Wolf-Rayet (WR) star, BAT99-9. WR stars are classified into two different classes, based on their optical spectra: the nitrogen sequence WN-type (show strong emission lines of helium and nitrogen) and the carbon sequence WC-type (show strong emission lines of carbon). WR stars are the evolved He-burning descendants of the most massive O-type stars, with the products of their nuclear fusion brought to the surface. The Large Magellanic Cloud (LMC) WC BAT99-9 is unique as it still has nitrogen in its spectrum, which is unheard of in WC stars! There is a group of stars called WN/C stars, whose spectra are that of WN-type WR stars with the exception of a single carbon line, C IV 5812. It is unclear whether these stars have a higher abundance of carbon than the WNs, as the strength of this line is heavily influenced by other parameters. The model analysis is presented as part of an analysis of three other WC-type stars in the LMC. We found that the WCs' chemical abundances are in agreement with both binary and single-star evolutionary models. However, for BAT99-9, binary evolution models may better explain the timescales with nitrogen still being on the surface. This work is supported through the NASA Astrophysics Data Analysis Program80NSSC18K0729 as well as a grant from the Space Telescope Science Institute (GO-13781).
Astronomers still do not know how the widest systems with separations larger than 10,000 au form. And yet, these systems have proved invaluable for calibrating metallicity relations and studying Galactic tides. One possible way to gain insight into their formation history is to examine the higher order multiplicity fraction, i.e. how many triples, quadruples, etc. To study this, we present a catalog of 99,203 wide binaries with probabilities greater than 95% of being gravitationally bound pairs. These binaries were identified through a Bayesian analysis of the high proper motion stars (> 40 mas/yr) in the Gaia DR2 catalog, along with supplemental stars from the SUPERBLINK high proper motion survey. Taking advantage of the linearity of the slope of the color-magnitude relationship of the K dwarf main sequence stars, we represent the relative over-luminosity of the components in K+K wide binaries in a plot we call the "Lobster" diagram. This diagram allows us to identify over-luminous components that most likely contain companions unresolved by Gaia DR2. Using this, we place a lower limit on the higher order multiplicity fraction of K+K wide binaries at 39.6%. To further prove that the "lobster" diagram highlights higher order multiples, we use the Lightkurve package in Python to identify eclipsing binary systems in TESS, K2 and Kepler and see where they fall on the diagram. Of the 12 eclipsing binaries identified, 11 were predicted to host an over-luminous component. In addition, we show that the presence of a spot modulation or unperiodic signal in a light curve suggests that system is more likely to show an over-luminous component. Finally, we present the first results of a speckle follow-up campaign examining the widest K+K systems (> 10,000 au) making use of the QWSSI speckle camera for the first time, a new instrument that we built at Lowell Observatory.
M dwarfs are known to possess strong and highly variable ultraviolet (UV) radiation that might play an important role in the habitability and atmospheric loss of their planets. The Star-Planet Activity Research CubeSat (SPARCS) is a dedicated space-based observatory that will photometrically monitor the flaring activity of a sample of M dwarfs of different ages simultaneously at near-UV and the far-UV wavelengths. Hence, the mission adopts a 9-cm reflective telescope to project a 40' field-of-view onto two back-illuminated delta-doped CCDs with high UV quantum efficiency. To achieve its science objective, the satellite is equipped with a dedicated science payload processor that manages detector thermal control as well as science observations, and performs near-real time image reduction and aperture photometry in order to automatically and actively control subsequent integration times and gains when flaring events are detected. We present the approach adopted for the SPARCS dynamic exposure control loop and its pre-flight tests and performance using synthetic M dwarf light curves and full-frame images in the two SPARCS passbands. Acknowledgements: Funding for SPARCS is provided by NASA's Astrophysics Research and Analysis program, NNH16ZDA001N.
We present stratospheric observations of the ~3-5.4 micron spectra of young planetary nebulae by the SOFIA instrument FLITECAM. The goals of this study were to characterize the NIR emission of Polycyclic Aromatic Hydrocarbons (PAHs) in planetary nebulae and study the evolution of PAH features within these objects. Using airborne 3-5.4 micron grism spectroscopy of three young, Carbon-rich planetary nebulae: IC 5117, PNG 093.9-00.1, and BD +30 3639, we investigated the spectral variation of the 3.3 micron PAH feature and its associated aliphatic features (3.4-3.6 microns), characterized the weak 5.25 PAH emission feature, and set limits on the theoretical contribution of the 4.4-4.8 micron deuterated-PAH features. All features, including atomic emission lines, were fit with a series of Gaussians to determine their flux. We further characterized the 3.3 micron PAH feature by measuring equivalent width and central wavelength, and by classifying the shape of the emission. We also determined the PAH/Aliphatic ratio for each target. The 3.3 micron PAH emission feature is observed in all three objects, as is PAH emission at 5.25 microns. PNG 093.9-00.1 exhibits NGC 7027-like aliphatic emission in the 3.4-3.6 micron region while aliphatic emission in IC 5117 and BD +30 3639 is weaker, and exhibits less structure.
Using near-IR photometry, we are identifying red supergiants (RSG) in the irregular barred galaxy NGC6822 to compare with stellar evolutionary models. This research is complementary to our previous work, in which we located RSGs in the starburst galaxy IC10. These stars are the coolest of the evolved massive stars and have K and M spectral types and temperatures below 4100 K. Typically, they can be up to a thousand times the radius of the Sun and are therefore highly luminous. To find them in NGC6822, we first used GAIA parallax and proper motion values to filter out foreground red dwarfs before transforming the J and K magnitudes to effective temperatures and luminosities. Then, we used these values to apply RSG temperature and luminosity constraints. Next, we will compare our results to previous spectroscopically confirmed RSGs. Finally, we will use the color magnitude diagram to eliminate lower-mass AGB stars contaminants. Stellar evolutionary theory provides us with the expected quantity of RSG populations. Here, we propose a new sample of RSG candidates in NGC6822 that can be utilized as an observational test of such theory. By comparing our results in IC10 and NGC6822 with the RSG content studies done by our collaborators in M31, M33, and the LMC, our results can be used in further studies to test the effectiveness of RSG population projection methods. Additionally, by locating a population of RSGs in NGC6822, future possibilities for studying these massive stars with direct spectroscopic follow-up are created.
We call attention to the very unusual spectrum of the LMC star 2MASS J05073893-6826061, which shows an unprecedented combination of odd properties, including intense UV and IR excesses, no Balmer transitions, weak C II emission, and a dense thicket of narrow, difficult to identify absorption lines. The spectrum of this V = 15.6 star has recently been reported by Margon et al. (ApJ, 898, 85, 2020), where it is referred to as object 233-1. The position of 233-1 on the H-R diagram implies that this star may be a very hot, H-poor post-AGB object, caught in a brief stage of evolution. Membership in the LMC seems certain. The object shows weak C II 7231, 7236 emission, with the doublet well resolved, appearing at the LMC velocity, and the Gaia proper motion and parallax data are also compatible with membership. There is no evidence for large amplitude photometric variability or surrounding nebulosity. The most remarkable spectral features are a series of dozens of narrow absorption lines, unresolved at our 1~A resolution, in the 3300-5000 A range. Identification of these features is problematic due to the sheer number of observed transitions, making chance coincidences with common atomic species and ionization states likely. Cross-correlation of atomic line lists with the spectrum does reveal strong evidence for the presence of O II, and less convincing although still substantial evidence for He I, He II, Si III, and N II. Although the late-type, low-mass [WC] stars do share the UV and IR excesses and C II 7231, 7236 emission seen in 233-1, as well as occasional narrow absorption lines, their spectra, dominated by dozens of very strong C II and He I emission lines, are quite different. The combination of the weak C II emission, lack of H, UV and IR excess, and numerous narrow absorption lines in 233-1 seems very unusual. We plan continued monitoring of the object. P.M. is grateful for the support of NSF grant AST-1612874 and the Mt. Cuba Astronomical Foundation.
We used existing data from the New Horizons Long-range Reconnaissance Imager (LORRI) to measure the optical-band (0.4 0.9 m) sky brightness within seven high-Galactic latitude fields. The average raw level measured while New Horizons was 42-45 au from the Sun is 33.2 0.5 nW m-2 sr-1. This is 10 as dark as the darkest sky accessible to the Hubble Space Telescope, highlighting the utility of New Horizons for detecting the cosmic optical background (COB). Isolating the COB contribution to the raw total required subtracting scattered light from bright stars and galaxies, faint stars below the photometric detection limit within the fields, and diffuse Milky Way light scattered by infrared cirrus. We removed newly identified residual zodiacal light from the IRIS 100 m all-sky maps to generate two different estimates for the diffuse Galactic light. Using these yielded a highly significant detection of the COB in the range 15.9 4.2 (1.8 stat., 3.7 sys.) nW m-2 sr-1 to 18.7 3.8 (1.8 stat., 3.3 sys.) nW m-2 sr-1 at the LORRI pivot wavelength of 0.608 m. Subtraction of the integrated light of galaxies fainter than the photometric detection limit from the total COB level left a diffuse flux component of unknown origin in the range 8.8 4.9 (1.8 stat., 4.5 sys.) nW m-2 sr-1 to 11.9 4.6 (1.8 stat., 4.2 sys.) nW m-2 sr-1. Explaining it with undetected galaxies requires the assumption that the galaxy count faint-end slope steepens markedly at V > 24 or that existing surveys are missing half the galaxies with V < 30.
Variability of Classical T Tauri stars (CTTS) occurs over a vast range of timescales. CTTS in particular are subject to variability caused by accretion shocks, which can occur stochastically, periodically, or quasi-periodically on timescales over a few days. The detectability of young planets within these systems is likely hampered by activity; therefore, it is essential that we understand the origin of young star variability over a range of timescales to help disentangle stellar activity from signatures of planetary origin. We present an analysis of the stochastic small-amplitude photometric variability in the K2 lightcurve of CI Tau occurring on timescales of 1 day. We find the amplitude of this variability exhibits the same periodic signatures as detected in the large-amplitude variability, indicating that the physical mechanism modulating these brightness features is the same. The periods detected are also in agreement with the rotation period of the star (6.6 days) and the orbital period of the planet (9.0 days) known to drive pulsed accretion onto the star.
We investigate the mineralogical makeup of L5 Martian Trojan asteroids via reflectance spectroscopy, paying special attention to (101429) 1998 VF31, the only L5 Trojan that does not belong to the Eureka family (Christou, 2013). We find that this asteroid most likely belongs to the Bus-Demeo S-complex, in agreement with Rivkin et al. (2007). We compare it with a variety of solar system bodies and obtain good spectral matches with Sq- or S-type asteroids, with spectra of the lunar surface and of Martian and lunar meteorites. Mixture fitting to spectral endmembers suggests a surface abundance of Mg-rich orthopyroxene and iron metal or, alternatively, a combination of plagioclase and metal with a small amount of Mg-poor orthopyroxene. The metallic component may be part of the intrinsic mineral makeup of the asteroid or an indication of extreme space weathering. In light of our findings, we discuss a number of origin scenarios for (101429). The asteroid could be genetically related to iron-rich primitive achondrite meteorites (Rivkin et al 2007), may have originated as impact ejecta from Mars - a scenario proposed recently for the Eureka family asteroids (Polishook et al., 2017) - or could represent a relic fragment of the Moon's original solid crust, a possibility raised by the asteroid's close spectral similarity to areas of the lunar surface. If, on the other hand, (101429) is a relatively recent addition to the Martian Trojan clouds (Christou et al., 2020), its origin is probably traced to high-inclination asteroid families in the Inner Main Belt. For the olivine-dominated Eureka family, we find that the two smaller asteroids in our sample are more spectrally similar to one another than to (5261) Eureka, the largest family member. Spectral profiles of these three asteroids are closely similar shortward of ~0.7 m but diverge at longer wavelengths. For the two smaller asteroids in particular, we find the spectra are virtually identical in the visible region and up to 0.8 m. We attribute spectral differences in the near-IR region to differences in either: degree of space weathering, olivine chemical composition and/or regolith grain size.
By controlling instrumental errors to below 10 cm s-1, the EXtreme PREcision Spectrograph (EXPRES) allows for a more insightful study of photospheric velocities that can mask weak Keplerian signals. Gaussian processes (GP) have become a standard tool for modeling correlated noise in radial velocity data sets. While GPs are constrained and motivated by physical properties of the star, in some cases they are still flexible enough to absorb unresolved Keplerian signals. We apply GP regression to EXPRES radial velocity measurements of the 3.5 Gyr old chromospherically active Sun-like star, HD 101501. We obtain tight constraints on the stellar rotation period and the evolution of spot distributions using 28 seasons of ground-based photometry, as well as recent Transiting Exoplanet Survey Satellite data. Light-curve inversion was carried out on both photometry data sets to reveal the spot distribution and spot evolution timescales on the star. We find that the >5 m s-1 rms radial velocity variations in HD 101501 are well modeled with a GP stellar activity model without planets, yielding a residual rms scatter of 45 cm s-1. We carry out simulations, injecting and recovering signals with the GP framework, to demonstrate that high-cadence observations are required to use GPs most efficiently to detect low-mass planets around active stars like HD 101501. Sparse sampling prevents GPs from learning the correlated noise structure and can allow it to absorb prospective Keplerian signals. We quantify the moderate to high-cadence monitoring that provides the necessary information to disentangle photospheric features using GPs and to detect planets around active stars.
We present the occurrence rates for rocky planets in the habitable zones (HZs) of main-sequence dwarf stars based on the Kepler DR25 planet candidate catalog and Gaia-based stellar properties. We provide the first analysis in terms of star-dependent instellation flux, which allows us to track HZ planets. We define as the HZ occurrence of planets with radii between 0.5 and 1.5 R orbiting stars with effective temperatures between 4800 and 6300 K. We find that for the conservative HZ is between ${0.37}_{-0.21}^{+0.48}$ (errors reflect 68% credible intervals) and ${0.60}_{-0.36}^{+0.90}$ planets per star, while the optimistic HZ occurrence is between ${0.58}_{-0.33}^{+0.73}$ and ${0.88}_{-0.51}^{+1.28}$ planets per star. These bounds reflect two extreme assumptions about the extrapolation of completeness beyond orbital periods where DR25 completeness data are available. The large uncertainties are due to the small number of detected small HZ planets. We find similar occurrence rates between using Poisson likelihood Bayesian analysis and using Approximate Bayesian Computation. Our results are corrected for catalog completeness and reliability. Both completeness and the planet occurrence rate are dependent on stellar effective temperature. We also present occurrence rates for various stellar populations and planet size ranges. We estimate with 95% confidence that, on average, the nearest HZ planet around G and K dwarfs is 6 pc away and there are 4 HZ rocky planets around G and K dwarfs within 10 pc of the Sun.
The Kepler mission and subsequent ground-based follow-up observations have revealed a number of exoplanet host stars with nearby stellar companions. This study presents speckle observations of 57 Kepler objects of interest (KOIs) that are also double stars, each observed over a 3-8 yr period, which has allowed us to track their relative motions with high precision. Measuring the position angle and separation of the companion with respect to the primary can help determine if the pair exhibits common proper motion, indicating it is likely to be a bound binary system. We report on the motions of 34 KOIs that have close stellar companions, three of which are triple stars, for a total of 37 companions studied. Eighteen of the 34 systems are confirmed exoplanet hosts, including one triple star, while four other systems have been subsequently judged to be false positives and twelve are yet to be confirmed as planet hosts. We find that 21 are most likely to be common proper motion pairs, 4 are line-of-sight companions, and 12 are of an uncertain disposition at present. The fraction of the confirmed exoplanet host systems that are common proper motion pairs is approximately 86% in this sample. In this subsample, the planets are exclusively found with periods of less than 110 days, so that in all cases the stellar companion is found at a much larger separation from the planet host star than the planet itself. A preliminary period-radius relation for the confirmed planets in our sample suggests no obvious differences at this stage with the full sample of known exoplanets.
We explore the persistence of the alignment of brightest cluster galaxies (BCGs) with their local environment. We find that a significant fraction of BCGs do not coincide with the centroid of the X-ray gas distribution and/or show peculiar velocities (they are not at rest with respect to the cluster mean). Despite this, we find that BCGs are generally aligned with the cluster mass distribution even when they have significant offsets from the X-ray centre and significant peculiar velocities. The large offsets are not consistent with simple theoretical models. To account for these observations BCGs must undergo mergers preferentially along their major axis, the main infall direction. Such BCGs may be oscillating within the cluster potential after having been displaced by mergers or collisions, or the dark matter halo itself may not yet be relaxed.
In this paper we investigate how implementing machine learning could improve the efficiency of the search for Trans-Neptunian Objects (TNOs) within Dark Energy Survey (DES) data when used alongside orbit fitting. The discovery of multiple TNOs that appear to show a similarity in their orbital parameters has led to the suggestion that one or more undetected planets, an as yet undiscovered "Planet 9", may be present in the outer solar system. DES is well placed to detect such a planet and has already been used to discover many other TNOs. Here, we perform tests on eight different supervised machine learning algorithms, using a data set consisting of simulated TNOs buried within real DES noise data. We found that the best performing classifier was the Random Forest which, when optimized, performed well at detecting the rare objects. We achieve an area under the receiver operating characteristic (ROC) curve, (AUC) = 0.996 0.001. After optimizing the decision threshold of the Random Forest, we achieve a recall of 0.96 while maintaining a precision of 0.80. Finally, by using the optimized classifier to pre-select objects, we are able to run the orbit-fitting stage of our detection pipeline five times faster.
209 publications and 3235 citations in 2021.
209 publications and 3235 citations total.
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