Galaxy Formation: Simple or Not?

1. The Cosmic Dark Age Telescope: 6.5 m Infrared Optimized Next Generation Space Telescope to Launch in 2013 (+ …. Years) Galaxy Formation: Simple or Not?

2. Background Material • Cosmological Players • Cosmic Time Scale and the Dark Ages • Matter-Radiation Coupling/Radiation Drag • Galaxy Mean Density as Fundamental Constraint • Redshift – Age of the Universe Relation • Basic Framework of Perturbation Growth

5. Temperatures in the Dark Ages • Spin Temperature of H I • Kinetic Temperature of Atoms • Radiation Field Temperature • For a few million years MWB photons absorbed by H and the 3 Temps are equal (gas can’t cool) • Ten million years after decoupling, radiation field is too dilute and gas can rapidly cool • Kinetic and Spin temperatures equal; lower than radiation field (absorption state) • 100 million years later atomic collisions diluted and spin temperature lowered until in equilibrium with background radiation • When sources appear, spin temperatures warmer again than backgound (emission) Key thing to Observe

6. SKA: Not Yet under construction

8. This Means • Purely baryonic fluctuations are smoothed out by radiation drag All fluctuations up to mass 1012 solar masses are damped out by radiation • There can not be larger baryonic fluctuations because those would produce anisotropies in the CMB than are larger than observed • Dark Matter Seeds seem required for galaxies to exist

9. Galaxy Mean Density • Typical massive galaxy has mean over density of 105 • Background density scales as (1+z)3 • Therefore co-moving galaxy density = background at z = 50 • Galaxies can not form earlier else their observed mean densities at z=0 would be higher

10. Age-Redshift Values • Precision Age of Universe = 13.7 Gyr • At z = 100 Universe is 13.5 Myr old • At z = 20 Universe is 142 Myr old • At z = 10 Universe is 375 Myr old • At z = 5 Universe is 930 Myr old • At z = 3 Universe is 1.7 Gyr old • At z = 1 Universe is 4.8 Gyr old

11. CMB Anisotropies are well measured now

14. Fluctuations grow faster in the radiation dominated era  Dark Matter Seeds greatly facilitate galaxy formation!

15. Reality Check • Matter Dominated era: z a a(t)2/3 ; z = 1100  2.7 x 10-5 fluctuations present at decoupling (consistent with WMAP) • Radiation Dominated era: z a a(t) ; assume fluctuations in dark matter can start growing at t=10-15 seconds (z = 1028) ; then fluctuations in dark matter number density of 10-33 amplify to 10-5 at recombination  implies dark matter halos of 1066 particles mixed in with 1068 protons.

16. Problems With Simple Model of Monolithic Collapse of Baryons

19. Dynamical Timescales • Monolithic Collapse can not occur on faster time scale • For large galaxy, timescale is 2 x 108 years • Z = 10-20 (obs. Problems) • 500 solar mass per year • Huge ionization sources We find very few galaxies Composed of purely old stars

20. But • 1011 solar mass Jeans type objects don’t exist at recombination • This demands merger of subunits to maker larger units  “bottom up” galaxy formation • This takes time and re-ionization/reheating becomes a serious problem • CMB polarization signal suggests re-ionization epoch ends by around z =8 and galaxy collapse might start unimpeded then • Means that a monolithic collapse could reveal itself at z = 6.5 First candidate object discovered/announced on April 22, 2009

21. Current Wisdom: Bottom UP

22. NASA’s Over Simplification

23. Hubble Data Confirms High Densities of Bulding Blocks

24. Dark Matter Makes Galaxy Formation Possible • Purely baryonic fluctuations damp out • Dark Matter is not subject to radiation pressure in the Early Universe • Dark Matter therefore has several hundred more e-folding times to concentrate itself compared to the baryons • Expect merging of dark matter building blocks into large halos which then capture baryonic material.

25. Dark and Baryonic Matter

26. Dark Matter Network

27. Now

28. The Detailed Properties of Galaxies • Are not so easily reconcilable with the simple dark matter halo + baryons picture • Annoying result: BMF = 0.13 +/- way too small • Also, why no purely DM galaxies  maybe there are (Cortese etal 2008)

30. Galaxy Components

31. Wavelength and Structure

33. Interactions

34. The Assembly Process May Still be occurring M31 Pine Mountain Project to map debris in the Local Group XUV Extensions around Galaxies

36. XUV Disks • Remarkable New Discovery with GALEX mission • 30% of all disk galaxies show this XUV phenomenon • SF should not be occurring at these radii Very Large UV Disks have Implications for distant Galaxy observations

37. Narrow Band Imaging Hydrogen gas falling into halo at z = 3; Ionized gas glows in the filter that is ON source Lyman-Alpha Imaging

38. The Cosmic Blob • Discovered April 2009 in Narrow Band Survey • Presumed to be Lyman-Alpha at z = 6.5 • First of its kind discovered

39. Implications of Himiko • Dimensions are similar to size of galactic halo • Mass of ionized gas is very large • Good candidate for re-ionization events • May be first example of monolithic halo formation (size and mass are about right) • This is a new kind of object (unless its really H-alpha)

40. Summary • We have no understanding of what determines bulge versus disk dominance • Constancy of BMF very weird; No Dark Haloes weirder • Nature of DM now very important • We are actively searching for sources of re-ionization • We do understand a lot about galaxy modification via their interacting environment –still ongoing • No idea still, when, in redshift space/time the first bound objects with baryons in them really formed • If Himiko is real this is a major challenge to Bottom Up scenario.