Poster Abstracts

Name/Affiliation:  Catarina Alves de Oliveira (European Space Agency)

Title:  Herschel survey of brown dwarf disks in rho Ophiuchi

Abstract:
Recent observations of the rho Ophiuchi cluster (1 Myr) with the Herschel Space Observatory allow us to probe the spectral energy distribution (SED) of the brown dwarf population in the far-IR, where the disk emission peaks. We detected 12 Class II brown dwarfs with Herschel, which corresponds to one-third of all currently known brown dwarf members. We performed aperture photometry at 70, 100, and 160 micron, and constructed their SEDs,complemented with ancillary photometry at shorter wavelengths. We compared the observed SEDs to a grid of synthetic disks produced with the radiative transfer code MCFOST, and used the relative figure of merit estimated from the Bayesian inference of each disk parameter to analyse the structural properties. Comparison to models reveals that the disks are best described by an inner radius between 0.01 and 0.07AU, and a flared disk geometry with a flaring index between 1.05 and 1.2. Furthermore, we can exclude values of the disk scale-height lower than 10 AU (measured at a fiducial radius of 100 AU). We combined the Herschel data with recent ALMA observations of the brown dwarf GY92-204 (ISO-Oph-102), and by comparing its SED to the same grid of disk models, we derived an inner disk radius of 0.035AU, a scale height of 15AU with a flaring index of 1.15, an exponent for dust settling of -1.5, and a disk mass of 0.001Msun. This corresponds to a disk-to-central object mass ratio of ~1%. We conclude that the structural parameters constrained by the extended SED coverage (inner radius and flaring index) show a narrow distribution for the young brown dwarfs detected in rho Ophiuchi, suggesting that these objects share the same disk evolution and, perhaps, formation. [2013A&A...559A.126A]