12:15-1:00 Group Discussion: Outstanding Questions, Chairs: Deidre Hunter and Bruce Elmegreen Traditionally a summary, but instead hoping for a discussion on some of the remaining burning questions & how to address them A little review -> everyone’s name will appear on the screen, but be patient Hot Components: Bulges, but still confused about bulge vs bar & decomposition How can the models be distinguished? What have you been impressed by at this meeting? Do we understand bulges perfectly? Bob: Are masses of clumps consistent with bulge growth? Stijn: Depends on how many and how long, but probably wouldn’t need too much time to get enough mass for the bulge Forming through mergers -> Phil Hopkins, but don’t know if the right shape comes out Bob: Think Rosie said most profound aspect of meeting: isolation/environment High z communicating w/ nearby -> truth should come from consistency Stijn: Careful about high z to nearby Joss: same sense as Bob -> lots of ways to get small bulges, but big bulges probably more difficult, like M31 -> never understood Lia: mergers give big bulges so very easily, trivial big bulges are not necessarily the formation for every big bulge Joss: is there another way besides mergers, though? Lia: depends on psuedo-bulge or peanut bulge or classical bulge Lia: haven’t seen published statistics on clumps forming bulges yet Bruce: feedback question Jerry: simulators can tell us if resulting merger from clumps is rotating -> Bruce: non-rotating Lia: not necessarily clear -> got disks rather than classical bulges Peter: some bulges do indeed spin (like Sombrero) Joss: any other way to make big bulges Bruce: can you make a bulge from ILR heating from spirals? Jerry: if heat in plane, ultimately will heat vertical direction Key question that needs to be addressed: Stijn: Enough mergers to account for present day ellipticals? Read somewhere perhaps no Jerry: Big question is how NOT to make bulges? Bob: some galaxies way off on their own (Kim-unspoken: What about bulge and Super massive black hole connections?) Thick disks: several models, so what can we do at high z and locally to distinguish possible models? Rosie: Answer is what you have written there: kinematics, metallicity, SFH, MW + other galaxies Bruce: deep stellar studies beyond Curt: how do thin & thick disks vary from galaxy to galaxy? Joss: Thomas Bensby’s talk- MW thick disk Rosie: need to be careful about how we define a thick disk in external galaxies as well as in MW - Sophia apples to apples or oranges or pears Bob: Is there universal agreement that Rix & Bovy are wrong? (Don’t quote!) Jon Bird: thin + thick of MW can be modeled by several different scale heights -> summation of continuum of populations/components But go from thick to thin -> rapid transition Ken: thick disks do seem to ubiquitous-> every disk has a thick disk but not every disk has a bulge Also thick disk farther out in some galaxies or thick disk in MW short in Key questions: how do thick disks change from one galaxy to another (mass) and also in radius Need a proper definition Rosie: need more data: metallicity, ages; more spectroscopy Sebastian: old metal-poor Cold Components: Exponential shapes - observations (see slides!) Exponential shapes - how to make them? (overwhelmed by the variety -> some way to distinguish or is everything going on & no way to disentangle) Curt: vote for everything, but need velocity dispersion & kinematics to learn more about exponentials Fillipo: at the end a bit confused about Type I, II, III -> use different methods, find different results, different types as a function of angle in galaxy Bruce: perhaps azimuthal averaging for surface brightness profiles isn’t enough anymore for asymmetries Rosie: Ken showed excellent Gaussian fits but others have fit w/ other types of profiles Jerry: certainly one galaxy was really clumpy, but still nice Gaussian fit Curt: apples & oranges thing -> various kinds of dwarfs Heikko: after Ken’s talk, looking at Sersic fits and large scatter Peter: Kim’s & Deidre’s FI profiles Chris: missing in discussion: if building outskirts of disks, what about molecular gas? Deidre: is molecular gas really needed? Bruce: last conference w/o ALMA data Bob: radio observations don’t look like exponential disks Bruce: but CO might be exponential Sukanya: HI disk in MW (Bob Benjamin) has break at stellar break (Sorry!): CO profile w/ same break Peter: Bob said truncation, but only in one particular angle DJ: CO is important, pressure issues, better off tracing dust, cold vs warm HI Rosie: when Annette Fergusen found very distant HII regions, did find a very small amount of CO, probably is molecular gas out there Stijn: even in absence of CO, flow region Deidre: so better off looking at FUV Bob: how do you get anything collapsing when Q = 10 Joss: microphysics- Q isn’t local property Bob: Bruce will say turbulence Joss: microphysics Bob: then why such beautiful spiral structure Joss: threshold Bruce: how do we get spirals in far outer disks? Jerry: probably not self-gravitating, driven by shear out there Lia: paper on that (missed it!) Ken: was involved in that analysis- underlying DM (different paper) Bob: triaxial halo Ivan: tidal interactions w/ subhalos Curt: kinematic wave takes a long time to wind up Sukanya: have looked at triaxial halos, but don’t get outer spirals w/o interactions Joss: disks are not necessarily entirely circular -> mildly elliptical Fillipo: mechanism knows about internal spiral arms; also warps; shearing Jerry: that’s continuity, doesn’t mean gravitating Big Questions & how to answer them: Joss: SF at very high Q environments Peter: *gas* profiles at high redshift compared to clumps at high redshift Bruce: Linda touched on this - mass representation in CO maps Bruce: Enormous number of questions, lots of things to think about One of favorite talks: series of questions Too many facts, but even more questions Very happy: 10 time zones or more to be here & thank you for hard work, let’s keep asking these questions