rachel somerville (STScI/JHU)

1. the role of feedback in galaxy formation models rachel somerville (STScI/JHU)

2. feedback 1 information about reactions to a product, a person's performance of a task, etc., used as a basis for improvement. 2 the modification or control of a process or system by its results or effects, e.g., in a biochemical pathway or behavioral response.

3. types of feedback • thermal: add heat to gas • kinetic: move gas around • radiative: destroy molecular clouds, ionize neutral gas here, i will discuss only thermal & kinetic feedback from Type II SNae and accreting black holes

4. feedback invoked to solve • overcooling/overmassive galaxy problem • massive galaxy quenching problem • overabundance of low-mass galaxies (slope of MF/LF); satellite problem • ‘global’ and ‘local’ angular momentum problems • cooling flow problem/entropy floors in galaxy clusters • strong correlation of black hole mass and galaxy properties

5. empirical mapping between halo mass & stellar mass special scale Mh~1012 Msun Milky Way (Klypin, Zhao & rss 2003) stellar masses of cluster galaxies (Lin & Mohr 2004) fraction of halo baryons in stars also matches galaxy clustering as fcn of stellar mass Moster, rss et al. 2009

6. z=5.7 (t=1.0 Gyr) • shock heating & atomic cooling • photoionization squelching • merging • star formation (quiescent & burst) • SN heating & SN-driven winds • chemical evolution • stellar populations & dust z=1.4 (t=4.7 Gyr) z=0 (t=13.6 Gyr) e.g. White & Frenk 1991 Kauffmann et al. 1993 Somerville & Primack 1999 Cole et al. 1994; 2000 Wechsler et al. 2002 Springel et al. 2006

7. outflow rate ~ few times SFR vW ~200-800 km/s (e.g. Martin 1999, 2005)

8. implementing supernova feedback in hydro simulations • thermal energy from Type II SNae dumped into gas; cooling/hydro forces often switched off for some time after injection (e.g. Thacker & Couchman 2000) • large-scale winds sometimes put in by hand (e.g. “constant velocity” or “momentum driven” winds (Springel & Hernquist 2003; Oppenheimer & Dave’ 2006)

9. supernova feedback in SAMs... dmrh/dt = (Vc) dm*/dt (Vc) = eSN (V0/Vc)a typically a = 2 (“energy driven”) gas may be ejected from halo (e.g., if Vc>Vthresh) gas may re-enter halo on e.g. mass doubling timescale e.g. Kauffmann, White & Guiderdoni 1993; rss & Primack 1999

10. observational signatures: X-ray bright, UV/IR excess, broad emission lines, high-ionization narrow lines radiatively efficient rare and short-lived high accretion rates (0.1-1 LEdd), fueled by cold gas via thin accretion disk triggered/fed by mergers or secular (bar) instabilities? may drive winds that can shut off further accretion onto the BH and sweep the cold gas out of the galaxy AGN feedback: ‘quasar mode’

11. Hydrodynamic simulations of galaxy mergers including black hole growth and feedback • self-regulated BH growth, reproducing MBH- relation (di Matteo et al. 2004) • AGN-driven wind removes nearly all cold gas at the end of the merger, leading to lower SFR and redder colors in the spheroidal remnant (Springel et al. 2004) • characteristic AGN ‘lightcurve’ (Hopkins et al. 2006) di Matteo, Springel & Hernquist 2005

12. momentum-driven winds:galactic outflows from hydrodynamic simulations of galaxy mergers (Springel, di Matteo & Hernquist; Hopkins et al.) rss et al. 2008

13. self-regulated BH growth • condition for halting accretion: sufficient injection of momentum within a dynamical time near the sphere of influence of the BH • deeper potential well requires a more massive BH to shut off accretion Hopkins et al. 2007 astro-ph/0701351 observed “black hole fundamental plane”

14. consequences of self-regulated BH growth • gas rich progenitors dissipate energy and produce more compact remnants (Dekel & Cox 2005; Cox et al. 2006; Robertson et al. 2006) • deeper potential well requires a more massive BH to shut off accretion • higher gas fraction --> more compact remnant --> more massive BH (‘BH fundamental plane’) gas fraction Hopkins et al. 2007a,b, 2008

15. observational signatures: radio emission/jets, bubbles in X-ray images radiatively inefficient common in massive galaxies, especially in groups/clusters low accretion rates (low Eddington ratio, <10-3 Bondi accretion or ADAF?) fueled by ‘drizzles’ of gas from hot halo? jets may heat surrounding hot gas, offsetting or quenching cooling flow AGN feedback: ‘radio mode’

16. radio jets and hot bubbles Allen et al. 2006; see also Birzan et al. 2004 • bubbles seen in ~70% of “cooling flow” clusters (Dunn & Fabian 2006) • can estimate jet power • using PdV argument • total heating rate may be ~x10 higher (Binney & Omma 2007)

17. “radio mode” heatingenergy budget • assume radio mode powered by Bondi accretion from hot halo (Nulsen & Fabian 2000) • energy offsets cooling in “hot mode” halos • required heating rates consistent with observational constraints Allen et al. & Rafferty et al. groups & clusters; Best et al. study rss et al. 2008

18. hot vs. cold flows • halos with primarily “cold” vs. “hot” flows separated by a critical mass of few x 1012 Msun at low redshift (e.g. Birnboim & Dekel 2003; Keres et al. 2004; 2008); • typical to assume heating processes only effective when a quasi-static hot gas halo is present (i.e. in large mass halos) Dekel & Birnboim 2006

19. redshift dependence of dominant gas accretion mode more difficult to quench massive galaxies at high redshift (Dekel & Birnboim 2006) Ocvirk et al. 2007

20. model for the co-evolution of galaxies, black holes, and AGN • top-level halos start with a ~100 Msun seed BH • mergers trigger bursts of star formation and accretion onto BH; based on hydrodynamical merger simulations (Cox et al., Robertson et al.) • following a merger, BH accrete at Eddington until they reach ‘critical mass’, then enter ‘blowout’ (power-law decline) phase (Hopkins et al. lightcurves) • energy released by accretion drives a wind • BH merge when their galaxies merge; mass is conserved • ‘Bondi’ accretion mode fed by hot halo gas rss, Hopkins, Cox, Robertson & Hernquist 2008

21. z=0 importance of different FB modes is mass-dependent: • SN-driven winds remove baryons from small-mass halos • some process(es) prevent cooling in large-mass halos (radio jets, clumps, conduction, cosmic ray pressure?) rss, Hopkins, Cox, Robertson & Hernquist 2008

22. quenching of massive galaxies (note the slope is wrong for low mass galaxies. this is not due to AGN FB, & cannot be easily solved by ‘tweaking’) z=0 SSFR stellar mass rss, Hopkins, Cox, Robertson & Hernquist 2008

23. global sf history & stellar mass assembly history bursts rss et al. 2008 (updated version)

24. stellar mass function evolution solid: MORGANA dash: Munich Mill. dot-dash: rss08 Fontanot, de Lucia, Monaco, rss, Santini 2009, MNRAS (arXiv:0901.1130) “raw” model predictions with convolved errors

25. stellar mass assembly without mass errors with errors (0.25 dex) solid: MORGANA dash: Munich Mill. dot-dash: rss08 data: integrated composite MF in models, mass in low mass galaxies evolves little; mass in high mass galaxies evolves more Fontanot et al. 2009

27. SFR from different indicators/surveys differ by up to x10 models do pretty well for massive galaxies; low-mass galaxies are too low at all z evolution of the SF sequence data: red square: Drory et al. 2008 blue: Bell et al. 2007 cyan: Martin et al. 2007 green: Grazian et al. 2006 magenta: Noeske et al. 2007 red x: Chen et al. 2008 blue diamond: Dunne et al. 2008 Fontanot et al. 2009

28. stellar populations in low mass model galaxies are too old, downsizing is too weak partly, but not wholly, due to biases intrinsic to age estimates from Balmer lines (see Trager & rss 2008) archeological downsizing data: Gallazzi et al. 2007 Fontanot et al. 2009

29. low mass halos were less efficient at converting baryons into stars at high redshift in SAMs, galaxies move along z=0 SMHM relation -- no evolution SN FB more efficient at high z? evolution of stellar-to-halo mass relationship stellar mass Moster, rss et al. 2009 halo mass

30. multi-wavelength properties IR-sub-mm UV-optical rss, Gilmore & Primack; Gilmore, rss & Primack (in prep)

31. efficiency of spheroid formation in mergers Hopkins et al. 2008 • usual assumption in SAMs: all mergers with mass ratio above some value (1:3-1:4) produce spheroidal remnants • simulations show: gas rich mergers are less efficient at producing starbursts and forming spheroids (& BH) • i.e. even major mergers between gas rich galaxies can produce disk-dominated remnants disk mass fraction gas fraction Springel & Hernquist 2005 Robertson et al. 2006 Hopkins, rss et al. 2009

32. mass functions by type standard spheroid formation recipe new spheroid formation recipe Hopkins, rss et al. MNRAS 2009 arXiv:0901.4111

33. the ‘bulgeless galaxy problem’ Weinzirl et al. 2008: H-band bulge-disk decompositions of 146 galaxies from the OSU Bright Spiral Galaxy Survey log (m*/msun)>10; B/T<0.75 new model old spheroid model Weinzirl et al. data stellar mass H-band

34. why does it work? gas fraction in merger progenitors radio mode quenching time since Big Bang

35. bulge mass vs. bh mass rss et al. 2008

36. BH were more massive relative to their spheroids in the past BH accretion history • ‘old’ model still peaks at • too high a redshift • ‘new’ spheroid model • does pretty well rss et al. in prep

37. gas cools to rotation supported disk mergers drive starburst and accretion onto SMBH; leave behind spheroidal remnant spheroid potential tells BH how much it can grow yes no hot halo? gas accretion mode depends on DM halo mass and redshift BH mass determines how much galaxy can grow stays quenched cooling continues

38. summary • current models rely on gas ejection by SN-driven winds to achieve small baryon fractions in low mass halos. however, current FB recipes do not reproduce SF histories of low-mass galaxies. • “radio mode” AGN feedback seems to be a promising mechanism for stopping cooling in massive halos -- but many details remain to be worked out. • AGN driven winds may be responsible for regulating BH growth and imprinting the BH mass-galaxy scaling relations. direct effect on galaxy properties is minor.

39. summary • observed mass assembly history and SFR history reproduced (w/in observational errors) for massive galaxies (M*>few 1010 Msun) • low mass galaxies form too early, are too passive at all redshifts (z<2), and have stellar pops that are too old at z~0 • may indicate that modelling of SN FB in current models needs to be modified • possible dearth of both very rapidly SF galaxies and quenched galaxies at z~2 • latest models still fail to reproduce enough bright SMGs

41. models predict distribution of stellar ages and metallicities in each galaxy convolve with ‘simple stellar population’ (SSP) models emission from stars Devriendt, Guiderdoni & Sadat 1999

42. modeling dust absorption and emission • full (3D) radiative transfer in post-processing (refs) • full radiative transfer applied within simplied geometries • analytic recipes for dust absorption, templates for dust emission

43. dust absorption two-component model: diffuse ‘cirrus’ dense ‘birthclouds’ optical depth of ‘cirrus’ dust proportional to column density of metals in disk HI ~ Zgas NH stars and dust assumed uniformly mixed in a ‘slab’ optical depth of ‘birthclouds’ proportional toHI stars within birthclouds enshrouded within a ‘screen’ of dust stars are freed from birthclouds on timescale ~107 yr Charlot & Fall 2000; de Lucia & Blaizot 2007; etc

44. dust emission energy emitted = energy absorbed empirical template emission spectra: Ldust determines shape of emission spectrum (ratio of warm/cold dust) Sanders & Mirabel ; Devriendt & Guiderdoni; Chary & Elbaz;

45. improved dust emission templates from spitzer irs Rieke et al. 2009

46. check of method for most statistical quantities (such as LF and counts), the analytic dust recipe gives similar results to full RT with GRASIL! Fontanot, rss et al. 2009 Fontanot, rss & Silva in prep

47. The Bolometric Luminosity History of the Universe luminosity density log wavelength redshift

48. the next set of slides are taken from work with UCSC graduate student Rudy Gilmore & Joel Primack: Gilmore, Madau, Primack, rss & Haardt 2009, MN in press “GeV gamma-ray attenuation and the high-redshift UV background” rss, Gilmore & Primack in prep “Panchromatic Galaxy Properties in Hierarchical Models” Gilmore, rss & Primack in prep “The Extragalactic Background Light and Implications for Gamma-ray Spectra”

49. luminosity density z=0

50. luminosity density evolution z=0 z=0.5 z=1.0 z=1.5 z=2.0 z=2.5