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What do we need to know about galaxy formation?
rachel somerville University of Michigan
Hubble Science Legacy Workshop April 2002


what's next?
test the CDM paradigm constrain the nature of the dark matter and dark energy gain better understanding of "gastrophysics"
n

cooling ­ star formation ­ feedback ­ dust ­ chemical enrichment ­ role of BH/AGN ­ magnetic fields...


MW (-20) SMC (-16) Sculptor (-10)


HST (V

606)

diffraction limited 10m at V


galaxy observations with NHST
kinematics and stellar populations of dwarf galaxies (z<1) high resolution (sub-kpc) imaging and kinematics of more luminous intermediate to high redshift galaxies (1

trouble for CDM? problems on small scales
too much substructure on dwarf galaxy scales? dark matter halos too "cuspy" in center? angular momentum distribution J(r) incompatible with exponential disks?


the substructure "crisis"

Moore et al. 1999 Klypin et al. 1999

Font et al. 2001


Gnedin 2000


resolved by photoionization?
see also Bullock, Kravtsov & Weinberg 2000; Benson et al. 2002

rss 2002 rss 2002


The faint-end slope of the luminosity function: is there an environmental dependence? CDM prediction: in dense environments, more dwarf halos collapse before re-ionization Юdwarf-to-giant ratio larger in over-dense regions

Tully, rss, Trentham & Verheijen 2002


search for barren dark halos
dwarf groups with very high mass-tolight ratios (Tully, rss, Trentham & Verheijen 2002) direct detection via lensing (Metcalf & Madau 2001)?


what do we expect to see at z=3?
predictions from semi-analytic models


cusps and angular momentum
are CDM halo mass profiles consistent with galaxy kinematics?
n n

need complete samples to understand statistics need to understand how baryons modify profiles

is the angular momentum profile of halos predicted by CDM consistent with the structure of galactic disks and spheroids?
n n

segregation: JDM Ю Jbar (magnitude and direction) transfer
w bars/spiral arms, viscosity w feedback (SN/AGN)?


galaxy mass profiles
high resolution kinematics from sub-kpc to 100 kpc scales can constrain properties of DM halos + modification by baryons

stellar radial velocities

mass

radius (kpc)
stellar/gas kinematics satellites & lensing


Angular momentum conserved

Angular momentum transferred

CDM models for the Milky Way

Klypin,,Zhao & rss 2002 Klypin Zhao & rss 2002


cusps destroyed by primordial rotating bars?

density radius (units of bar radius) Weinberg & Katz, preprint


star formation
what determines how efficiently a galaxy can turn cold gas into stars? how does this efficiency scale with redshift/galaxy properties? what is the physical basis of empirical scaling laws (e.g. Kennicutt) is the IMF universal in space and time? why does it have the observed shape?


star formation in galaxies
study Kennicutt-type relations at z>2 with ALMA + new Hubble?

Kennicutt 1998


spatially resolved star formation histories from fossil evidence

Ellis et al. 2001


feedback
what does the energy from massive stars and SN do to the ISM/IGM/ICM? how does this impact future generations of stars?
n n n

positive/negative? thermal/kinetic/pressure? turbulence/outflows?

what about AGN?


heavy elements and dust
how efficiently are metals expelled from DM halos?
n n

efficient early enrichment of IGM thermal signatures

what determines the degree of optical/UV extinction a galaxy experiences?
n n n

mass of dust? dust geometry, density, composition? age of stellar population?


The Bolometric Madau Diagram

dust

luminosity

starlight

wavelength

redshift

rss in prep


what determines galaxy "type"?
which of the many observational "sequences" are truly fundamental?
n

B/T, V/, color, spectral type...

when was the Hubble sequence as we know it established?
n n

role of mergers spheroid formation


scaling relations
what is the physical origin of scaling relations like the Tully-Fisher relation and the fundamental plane? why do they have so little scatter?


the merger rate as a function of epoch
a direct test of the hierarchical assembly of galaxies

Brinchmann & Ellis 2000

Le Fevre et al. 2000


measure the merger rate as function of environment, redshift galaxy type, mass, luminosity to z=5

Ferguson et al. 2001


Wish list: super-Sloan
high resolution kinematics and multiband imaging for complete sample of galaxies, reaching well below L* (z=0-5) multiphase information: neutral, ionized, and molecular gas metallicity indicators dust content (FIR/UV) coordinate with IGM and lensing data