1. HWR Princeton, 2005 Observing the Assembly of Galaxies Hans-Walter Rix Max-Planck-Institute for Astronomy Heidelberg

2. HWR Princeton, 2005 Overview I. The Build-Up of the Stellar Mass in Galaxies II. The Formation and Evolution of Massive Galaxies Thursday May 5, 2:00PM III. The Evolution of (Internal) Galaxy Structure Wednesday May 11, 2:00PM IV. Archeo-Cosmology in the Local Group Friday, May 13, 2:00PM

3. HWR Princeton, 2005 I. The Build-Up of Stellar Mass 1.Casting the problem into specific questions 2.Diagnostic Tools 3.A brief survey of surveys 4.Estimating the star-formation rate = f(z) 5.Estimating the stellar mass density = f(z) 6.Results

4. HWR Princeton, 2005 1. Re-phrasing “the build-up of stellar mass” What is and ? What epoch encloses the formation of most stars? How to best measure and ? How much important are mergers in triggering SF and in setting the present-day mass function? What are the expectations from models?

5. HWR Princeton, 2005 2. Diagnostic tools for star-formation rates and stellar masses Star formation rate estimates are based on UV luminosity produced by hot, massive, short-lived stars –Observe the UV –Observe H  –Observe absorbed UV flux, re- radiated by dust in thermal IR ! L IR (re-radiated) >> L UV (escaped) ! –M tot estimate is based on stars >10Mo, which are small fraction of M tot Kroupa 2002

6. HWR Princeton, 2005 Starlight and Re-processed Starlight Devriend et al 2000 Single-age, dust-free stellar population

7. HWR Princeton, 2005 ground SED of an ageing stellar population of solar metalicity with dust Spitzer Herschel (2007) Redshift

8. HWR Princeton, 2005 f(24  m) vs L bol Papovich and Bell 2003 Given that Spitzer can only observe well at 24  m, what are the bolometric corrections?

9. HWR Princeton, 2005 Mass measurements in cosmologically distant galaxies Dynamics: –OK to z~1, but quite expensive. –Very limited spatial resolution conceptually problematic –Currently not feasible for most galaxies z>1.5 Clustering: –Measures halo mass, not stellar mass M * = L x (M/L) * with M/L from SEDs

10. HWR Princeton, 2005 Stellar Masses from Spectral Energy Distributions Optical/near-IR spectra of galaxies are a nearly 1D sequence Near-degeneracy of age, metallicity and dust Source of despair or opportunity? t stars = [Gyrs] Bell and de Jong 2001 B K

11. HWR Princeton, 2005 Mapping one or few integrated galaxy colors to –age –dust extinction –metallicity is poor! Mapping (optical -- across 4000A break) color to M/L should be robust!

12. HWR Princeton, 2005 M/L from Colors? Compare to  dyn ! Van der Wel, Franx, can Dokkum and Rix, 2004 at z~1

13. HWR Princeton, 2005 Look-back Galaxy Surveys: Desiderata Select SFR surveys by SFR, and mass surveys by stellar mass –SFR: assure most of the intense star-burst are not missing due to dust –Stellar mass: select galaxies obs > (1+z) 4000A break Number of galaxies as a function of –Epoch  redshift (few %) –Luminosity/stellar mass –Color/stellar age  1,000 – 10,000 galaxies Measure galaxy sizes/internal structure ~0.3” resolution Either N field >> 1 or  field > 2xcorrelation length ~10’

14. HWR Princeton, 2005 A Survey Survey NameN field Field size HST imaging # of bands DepthN redshift HDFs/UDF32.5’+7 R=29 700 GOODS212’+10i=27.5400 3000 (5%) FIRES25’+10 K AB =26 600 (5%) COMBO-17 GEMS 330’+22R=24 30,000 (1%) MUNICS330’-7K=19.5 20.000 (5%) GDDS/LCIRS230’-7H=21.5500 (2000) SUBARURest- UV Steidel et alRest- UV

15. HWR Princeton, 2005

16. HWR Princeton, 2005 COMBO-17 Wolf, Meisenheimer, Rix et al. 01/03 Heidelberg, Oxford,Potsdam,Edinburgh 3 fields @ 30’x30’ 17 filters to m r ~23.6 ~10.000 redshifts (1.5%)+ SEDs per field Wavelength [nm] MBMB Z

17. HWR Princeton, 2005 Comparison of COMBO-17 with VIMOS Spectra (data from Le Fevre et al 2004)

18. HWR Princeton, 2005 A quick Tour through Redshift Space GEMS(CDFS) Abell 901 S11 (random)

19. HWR Princeton, 2005

20. HWR Princeton, 2005 Stellar Masses from the COMBO-17 Survey Borch, Rix, Meisenheimer et al 2005 Stellar masses to z~1 can be estimated for 10.000s of galaxies Flux limit (R-band) is VERY different from mass limits. 0.65<z<0.75

21. HWR Princeton, 2005 FIRES: F aint I nfra -R ed -E xtragalactic -S urvey ultra-deep VLT survey *HDF-south 100 hours in JHK FWHM=0.45” *MS1054: 5xlarger area 25 hours in JHK per pointing Franx, Rix, Rudnick, Labbe, van Dokkum, Foerster-Schreiber, Trujillo, Moorwood, et al. 2001-2005 Selecting and studying galaxies z>2 in their rest-frame optical bands

22. HWR Princeton, 2005 Not a Ly-break!! Just a red SED

23. HWR Princeton, 2005 What kind of galaxies are found in such a search? Galaxies without many (really) young stars won’t be found by their Ly-break or their sub-mm dust emission. Ditto for galaxies with significant dust extinction that are not powerful enough for a sub-mm detection. Remember: both UV searches (dust) and sub-mm searches (fainter galaxies) have ~10 corrections to get total SFR

24. HWR Princeton, 2005 SED fits for DRGs Near-IR selected UV selected Förster-Schreiber, Franx, Rix et al; FIRES

25. HWR Princeton, 2005 Improving Mass, SFR and A v Estimates at z~2.5 through IRAC (3.6  m-8  m) data Labbe, Franx, Rix et al 2005 Förster-Schreiber, Rix et al 2005; FIRES

26. HWR Princeton, 2005 Comparing dynamical (?) with SED masses Van Dokkum, Franx, Rix, et al. 2004

27. HWR Princeton, 2005 Results I: Cosmic Star-Formation Rate

28. HWR Princeton, 2005 SFR’s from thermal-IR flux 0<z<1 Zheng, Rix, Rieke, Bell et al 2004 Stacking galaxy classes (z,L) from COMBO-17 and measuring the 24  m flux

29. HWR Princeton, 2005 SFR’s from thermal-IR flux 0<z<1 Zheng, Rix, Rieke, Bell et al 2004 L IR /L UV = f(SFR) @ all z,L opt Local relation Through stacking, Spitzer’s (single source) confusion limit can be beat by >10 to <10  Jy IR flux dominates in all galaxies (to 3% of L*) to z~1.2; – large majority of UV photons absorbed. Mean L IR /L UV drops with galaxy luminosity  faint galaxies contribute hardly to SF integral “Correction” seems to be a function of (absolute) SFR only –Insensitive to stellar luminosity, redshift

30. HWR Princeton, 2005 State of Affairs: Star-fomration rate Borch, Rix, Meisenheimer et al 2005

31. HWR Princeton, 2005 Why the drop of the SFR since z~1? or In what type of galaxies did stars form back then?

32. HWR Princeton, 2005 Whence the UV flux at z~0.7? j 280 (z~0.7) ~ 4 x j 280nm (now)  Pick f(2800A) as a proxy for young stars (t<t dyn ) [not necessarily true in massive, old systems] Explore “morphology” of galaxies that give rise to these photons Subjective – use 6 eyes [Morphologies from GEMS, see Thursday] UV-to-optical flux (M 280nm – V) UV luminous “blue” Wolf, Bell, Rix et al 2004 0.65<z<0.75

33. HWR Princeton, 2005 At M V >-19 and z~0.75 –½ the flux comes from seemingly normal spirals –20% from visibly interacting systems only minority of UV flux from manifestly interacting systems at z~0.75  drop in (major) merger rate not cause of SFR drop z~0.75 Normal spirals Interacting/Peculiar UV-light contribution by Galaxy type at z~0.75

34. HWR Princeton, 2005 Results II: Evolution of the Stellar Mass Density with Redshift

35. HWR Princeton, 2005 The Evolution of the Stellar Mass Function over the Last 7 Gyrs Borch, Meisenheimer, Rix, Bell et al 2005, COMBO-17 Present-day stellar mass function COMBO-17 survey; 30,000 galaxies Mean stellar mass Build-Up

36. HWR Princeton, 2005 Where is the stellar mass at z=2-3.5? DRGs (“distant red galaxies”) vs Ly-Break Galaxies Distant red galaxies likely dominate the mass budget

37. HWR Princeton, 2005 : State of Affairs Borch, Meisenheimer, Rix et al 2005

38. HWR Princeton, 2005 …half the mass since z~1.5… Borch et al 2005

39. HWR Princeton, 2005 Putting it together Borch, Meisenheimer, Rix et al 2005

40. HWR Princeton, 2005 Summary Waning SFR not a consequence of waning major mergers –Waning cold gas supply SED-based stellar mass estimates now available for 1000’s of galaxies to z~3 –Need to observe at least to  rest >4000A –Available testing against dynamics OK “Distant red galaxies”, between Ly-break and sub-mm galaxies, may contain the bulk of stellar mass 2<z<3.5 –Found through near-IR surveys –Quite frequent objects with SFR x t SFR ~10 10-11 M can be traced from z~3.5 to 0 –enclosing ~90% of all stars formed Integral over SFR estimate agrees with to < 2 –Assuming diet-Salpeter IMF (e.g. Kroupa 2002) –Leaves not much room for overlooked SFR

41. HWR Princeton, 2005 Where do we go from here? Role of merging in the build-up of the galaxy mass function is observationally barely constrained Comprehensive linkeage of SED-based and dynamical masses Beat field-to-field variations at z>2 Relate stellar masses at different z to halo masses –Lensing, clustering

42. HWR Princeton, 2005

43. HWR Princeton, 2005

44. HWR Princeton, 2005

45. HWR Princeton, 2005

46. HWR Princeton, 2005

47. HWR Princeton, 2005

48. HWR Princeton, 2005

49. HWR Princeton, 2005

50. HWR Princeton, 2005

51. HWR Princeton, 2005 Förster-Schreiber, Franx, Rix et al 2005

52. HWR Princeton, 2005 Improving Mass, SFR and A v Estimates at z~2.5 through IRAC (3.6  m-8  m) data Labbe, Franx, Rix et al 2005 Förster-Schreiber, Rix et al 2005; FIRES

53. HWR Princeton, 2005 SED Fitting of FIRES Galaxies

54. HWR Princeton, 2005 Where is the stellar masses at z=2-3.5 DRGs (“distant red galaxies”) vs Ly-Break Galaxies Förster-Schreiber, Franx, Rix et al 2005

55. HWR Princeton, 2005