1. The Active to Passive Transition Alvio Renzini, Ringberg Schloss, May 21, 2010 ● Star Formation ceases in many galaxies, first in the most massive ones, later in less massive ones. ● Where, when and how is it happening? ● A Fresh Vision, some answers, and new questions.

2. A different, fully empirical approach to Galaxy Evolution, and the origin of the Schechter Mass Function ● SFR(M,t) ≃ 250 (M/10 11 M ⊙ )(t/3.5Gyr) -2.2 ● Mass function of SF galaxies is (almost) independent of redshift ● Mass (Nature) quenching and environment (Nurture) quenching are independent of each other: they are “separable” From Peng, Lilly, Kovač, Bolzonella, Pozzetti, Renzini, Zamorani & the zCOSMOS Team: ArXiv:1003.4747 Based on 3 remarkable simplicities:

3. Starbursts or just High SFR at z~2? SFR from radio stacks SMGs may be the real, major-merger driven, starburst galaxies SFR ∝ ~M 0.9+/-0.1 with very small dispersion!!! No starbursting galaxies! just galaxies with high SFR, continuously fed by cold-stream accretion! (What's that?) Daddi et al. 2007

4. SFRs of sBzKs in COSMOS from stacked 1.4 Ghz flux From Radio (VLA) From UV (uncorrected) =2.1 1.6 Elbaz '07 Noeske '07 Brinchmann '04 Daddi '09 = 270M 11 (t/3.4x10 9 yr) -2.5

5. The cosmic evolution of the specific SFR=SFR/Mass Gonzalez et al (2009)

6. The SFR-Mass relation for local SDSS galaxies is independent of envirnonment Low density (D1) High density (D4) From H

7. The SFR of star-forming galaxies depends on the stellar mass of galaxies but does not depend on environment

8. SFR independent of environment also among zCOSMOS galaxies up to z~1

9. At z~2 the high SFR makes galaxies to grow quasi-exponentially dM/dt=SFR(M,t) = 250 (M/10 11 M ⊙ )(t/3.5Gyr) -2.2 They grow ~exponentially before (z>2)

10. In spite of making stars at very high rate, their mass function is almost unevolving Galaxies must turn passive (SFR ~ 0), Something must quench them, either internal or extermal: mass and/or environment M* Ilbert et al. 2009

11. The red line separates the quenched from the active star- forming galaxies The zCOSMOS 20K sample

12. Empirical definition of mass quenching and environment quenching efficiency m (m,m 0,)=[f red (m,)-f red (m 0,)]/f blue (m 0,) (, 0,m)=[f red (, m)-f red ( 0,m)]/f blue ( 0,m) Both vary between ~0 and ~1

13. The “Environment Quenching” Is Independent of mass among local SDSS galaxies!!! (m)

14. The “Mass Quenching” Is independent of environment for local SDSS galaxies!!! m()m()

15. The quenched fraction among local SDSS galaxies as a function of mass and environment

16. Mass and Environment quenching are separable also for the 20K sample of zCOSMOS Galaxies with z up to ~1. It is then assumed that separability remains valid at all redshifts.

17. A continuity equation for the flow of galaxies ● The mass of SF galaxies grows as: ● dM/dt = SFR(M,t) = 250 (M/10 11 M ⊙ )(t/3.5Gyr) -2.2 and are quenched according to the rate:

19. The Mass function for blue, red and all galaxies, from the SDSS

20. The evolution of the mass function from the empirical model z=5 z=0

21. Fraction of Passive Galaxies according to quenching mechanism

22. The Concordance Cosmology Stage

23. At the beginning of the era of Precision Cosmology Somebody said: “Now that the stage has been set up, what we need is a good play” I think this phenomenological model tells what the plot is and ought to be. For the real play one needs to introduce the real physical processes at work, and force them to follow the plot … Not an easy job with this turbulent company of actors....

24. ● Cold Streams ● IMF ● AGN Feedback ● Winds ● Star Formation ● Clump Physics ● Strangulation ● Ram pressure ● SN Feedback ● Disk instability ● Chemistry ● Mergers ● Starbursts The Characters of the Play

25. The End

26. Summary Two key observational inputs: Separability of mass and environment in SDSS and zCOSMOS Constancy of the mass-function M* and  of star-forming galaxies since z = 2 Three supporting observational facts for star-forming galaxies: sSFR is roughly independent of mass sSFR is independent of environment sSFR declines strongly with epoch since z ~ 2 Two simplifying assumptions: blue/red (= active/passive) dichotomy with instantaneous quenching transitions between the two major mergers are assumed to result (amongst others) in quenching, minor mergers are ignored Three other observationally-derived inputs: growth of structure with time, N(  ) merging rate in different environments and epochs faint end slope of star-forming mass-function Model successfully reproduces several key features of today's galaxy population: establishes Schechter function of star-forming galaxies and produces double Schechter functions of passive galaxies reproduces detailed SDSS relationships between M*, ,  * etc for different components and in different environments accurately reproduces f red(m) in different environments qualitatively explains several overall trends of passive galaxies with mass (i.e. age,  /Fe etc)