1. Eight billion years of galaxy evolution Eric Bell Borch, Zheng, Wolf, Papovich, Le Floc’h, & COMBO-17, MIPS, and GEMS teams Venice 28.03.06

2. Eric BellVenice 28.03.06 Demographics of the evolving galaxy population Where is the mass?

3. Eric BellVenice 28.03.06 Some demographics A bimodal galaxy population A bimodal galaxy population Red sequence Red sequence Non-star-forming Non-star-forming ~ color of ancient stars ~ color of ancient stars Blue cloud Blue cloud Star-forming Star-forming -18 -20 -22 Absolute magnitude in i-band Blanton et al. 2003; ApJ, 594, 186

4. Eric BellVenice 28.03.06 Evolution I Labbé et al. 2006 (M 2200 – V) rest -2 -2 -2 0 0 0 2 4 2 4 2 4 -22-20-18 MVMVMVMV Always a blue cloud Emergence of the red sequence -Some massive galaxies at all times… z ~ 1 z ~ 1.8 z ~ 2.6

5. Eric BellVenice 28.03.06 Evolution II Evolution II Bell et al. 2004

6. Eric BellVenice 28.03.06 Mass function: color split Borch et al. 2006 Local MFs Weak evolution in blue guys (~ disks) Strong evolution in red guys at L<2L* at least (~ spheroids) Blue cloud Red sequence Bundy et al. 2006

7. Eric BellVenice 28.03.06 Evolution IV Always a pronounced blue cloud Always a pronounced blue cloud Color redder with time Color redder with time Red sequence builds up with time Red sequence builds up with time Color of ancient stars at every epoch Color of ancient stars at every epoch Build-up of x3 or so since z~1 (Bell et al. 2004; Chen et al. 2003; Willmer, Faber et al. 2006; Blanton 2006; Bundy et al. 2006) Build-up of x3 or so since z~1 (Bell et al. 2004; Chen et al. 2003; Willmer, Faber et al. 2006; Blanton 2006; Bundy et al. 2006) In agreement with at least some models (Cole et al. 00; Somerville et al. in prep) In agreement with at least some models (Cole et al. 00; Somerville et al. in prep) Chen et al. 03 Borch et al. 2006 Blue cloud Red sequence Bundy et al. 2006

8. Eric BellVenice 28.03.06 Where’s the mass? A red sequence A red sequence Dominated by spheroids at z<1 Dominated by spheroids at z<1 Color evolves ~ passively Color evolves ~ passively  stellar mass density increases by x2 or more  stellar mass density increases by x2 or more Most mass is in spheroids at redshifts below ~0.7 Most mass is in spheroids at redshifts below ~0.7 A blue cloud A blue cloud Dominated by disks Dominated by disks Color reddens towards present day Color reddens towards present day Stellar mass function more or less constant since z~1 Stellar mass function more or less constant since z~1

9. Eric BellVenice 28.03.06 Demographics of the evolving galaxy population Where is the star formation?

10. Eric BellVenice 28.03.06 Cosmic SFR UV / IR / radio / emission lines UV / IR / radio / emission lines Luminosity function extrapolation a challenge Luminosity function extrapolation a challenge Reasonable agreement Reasonable agreement Hopkins 2004

11. Eric BellVenice 28.03.06 Which galaxies form stars? Red E/S0s are non-star-forming Red E/S0s are non-star-forming Most SF is in spiral galaxies Most SF is in spiral galaxies Rest-frame V-band absolute magnitude Rest-frame U-V E/S0Sa—Sd Irr/compact Clearly interacting Bell et al. 2005 Melbourne, Koo & Le Floc’h 2005 10 Log L IR 12 -4 log Φ -3

12. Eric BellVenice 28.03.06 Spitzer: new insights Spitzer 24μm data from the MIPS instrument team for the CDFS Spitzer 24μm data from the MIPS instrument team for the CDFS 83μJy limit corresponding to 3M  yr -1 at z~0.7 (Kroupa IMF ~ 0.5x Salpeter) 83μJy limit corresponding to 3M  yr -1 at z~0.7 (Kroupa IMF ~ 0.5x Salpeter) Spitzer image COMBO-17 and GEMS coverage Rieke et al. 2004; data described in Papovich et al. 2004

13. Eric BellVenice 28.03.06 IR luminosity from 24μm flux Rest-frame 12-15μm correlates strongly with total IR luminosity in the local Universe, with < x2 scatter Rest-frame 12-15μm correlates strongly with total IR luminosity in the local Universe, with < x2 scatter Will be able to test IR flux estimates with Spitzer 70,160μm, Apex 350μm and 870μm and Herschel PACS and SPIRE Will be able to test IR flux estimates with Spitzer 70,160μm, Apex 350μm and 870μm and Herschel PACS and SPIRE Chary & Elbaz 2001; Papovich & Bell 2002; See also Dale et al. 2005 Log 10 L IR /L  Log 10 ν L ν,15μm /L  <0.3 dex scatter

14. Eric BellVenice 28.03.06 Evolution of IR LF IR LF very strongly evolving Almost all SF is in blue disks Total Blue / disk Local Red Le Floc’h et al. 2005 Bell et al. 2005

15. Eric BellVenice 28.03.06 Split by color Can compare integrated SFR with observed mass growth: IR- derived Can compare integrated SFR with observed mass growth: IR- derived Blue disks form stars Blue disks form stars Stars end up in red spheroid- dominated galaxies Stars end up in red spheroid- dominated galaxies Bell et al., in prep., Le Floc’h et al. 2005

16. Eric BellVenice 28.03.06 The evolution of the mass function… Can estimate evolution of the mass function with time Can estimate evolution of the mass function with time t t+dt For each mass bin: Work out average dM*/dt - stacking  average SFR - stacking  average SFR Multiply by Δt to work out ΔM*

17. Eric BellVenice 28.03.06 Results Hypothesis 1: SF in red  red Hypothesis 1: SF in red  red SF in blue  blue SF in blue  blue log space density log stellar mass All galaxies Red galaxies Blue galaxies z = 0.9 0.7 0.5 0.3 0.0 Obs. MF Pred. MF

18. Eric BellVenice 28.03.06 Results Hypothesis 1: All SF  red Hypothesis 1: All SF  red log space density log stellar mass All galaxies Red galaxies Blue galaxies z = 0.9 0.7 0.5 0.3 0.0 Obs. MF Pred. MF

19. Eric BellVenice 28.03.06 The role of mergers Merger rates Merger rates Morphologically- messed up things Morphologically- messed up things Close galaxy pairs Close galaxy pairs Neither are perfect Neither are perfect Patton et al. 2002 Bundy et al. 2004 Le Fevre et al. 2000 Conselice et al. 2003 Somerville et al. in prep. * Bell et al. 06

20. Eric BellVenice 28.03.06 The role of mergers Merger rates Merger rates Morphologically- messed up things Morphologically- messed up things Close galaxy pairs Close galaxy pairs Neither are perfect Neither are perfect Current estimates suggest ~1/3 merger per L* galaxy Current estimates suggest ~1/3 merger per L* galaxy Patton et al. 2002 Bundy et al. 2004 Le Fevre et al. 2000 Conselice et al. 2003 Somerville et al. in prep. * Bell et al. 06

21. Eric BellVenice 28.03.06 Conclusions Galaxies come in 2 flavours Galaxies come in 2 flavours Blue Blue Star-forming (often very intense) Star-forming (often very intense) Disk-dominated Disk-dominated Food for the red sequence Food for the red sequence Red Red Largely non-star-forming Largely non-star-forming Bulge-dominated Bulge-dominated Constant growth of red population through global suppression of SF in blue guys Constant growth of red population through global suppression of SF in blue guys Physical mechanisms of suppression Physical mechanisms of suppression Environment Environment Gas consumption Gas consumption Mergers Mergers ~1/3 merger per L* galaxy ~1/3 merger per L* galaxy

22. Eric BellVenice 28.03.06 SFR vs. SFH Borch et al. 2006

23. Eric BellVenice 28.03.06 Always a pronounced blue cloud Always a pronounced blue cloud Color redder with time Color redder with time Red sequence builds up with time Red sequence builds up with time Color of ancient stars at every epoch Color of ancient stars at every epoch Evolution III Faber, Willmer, Wolf et al. 2005 Passive evolution See also Bell et al. 2004