The Obscured Growth Phase of Black Holes in Distant Massive Galaxies

1. The Obscured Growth Phase of Black Holes in Distant Massive Galaxies David M Alexander (Durham)

2. IR AGN Optical AGN What I’m not Going to Talk About: Robust Identification of z~2-2.5 Compton-thick Quasars Compton-thick quasars (LX>1044 erg/s) at z~2 are as numerous as unobscured quasars: extending Daddi et al. (2007) to confirming individual C-thick AGNs

3. What I will Talk About: Black-hole-Galaxy Growth in z~2 Starbursts and Quasars “Weighing the Black Holes of z~2 Submillimeter Galaxies and Exploring their Evolutionary Status”D.M. Alexander et al. AJ, submitted “Is there an Evolutionary Link between Quasars and Submillimeter Galaxies?”K. Coppin et al. in prep.

4. Today’s most massive galaxies hint of a violent past Heavens et al. (2004) Formation must have been distant, rapid, and luminous M87

5. Probe black-hole growth with AGN activity Also need to grow a massive black hole All massive galaxies appear to host a massive black hole => all galaxies have undergone luminous AGN activity in the past

6. Black Hole-Stellar Growth Cannot “age” a black hole, as you can age stars but the tightness of the black-hole-spheroid mass relationship suggests they may have grown concordantly MBH = 0.15 % Mbulge Action: AGN activity Challenging tests for structure-formation models Tremaine et al. (2002) Action: Star formation

7. (Blain & Longair 1996) Submillimeter/Millimeter: efficient selection of the most bolometrically luminous far-IR galaxies in Universe 850 micron SCUBA image Lots of them! Before SCUBA2, submm will miss hot ultraluminous sources Coppin et al. (2006)

8. (Blain & Longair 1996) Smail et al. (2002) Submillimeter/Millimeter: efficient selection of the most bolometrically luminous far-IR galaxies in Universe 850 micron SCUBA image Lots of them! Before SCUBA2, submm will miss hot ultraluminous sources Hughes et al. (1998)

9. Swinbank et al. (2004) Massive (Ha) Neri et al. (2003) Strongly clustered Gas rich (CO) Blain et al. (2004) Galactic Properties… Chapman et al. (2003, 2005) Distant: typically z~2-3 Progenitors of todays massive galaxies?

10. All massive galaxies possibly went through a “SCUBA phase” ~3x108 yr activity cycle (based on gas consumption) and then passive evolution Faber-Jackson Est. halo velocity dispersion Swinbank et al. (2006) Space density consistent with >3L* galaxies (duty cycle corrected)

11. (Ivison et al. 2002) AGN properties? Has been challenging… An optically bright AGN Pope et al. (2008) (Ivison et al. 1998) A mid-IR bright AGN A radio-bright AGN Alexander et al. (2005) Alexander et al. (2005) Most moderately luminous Most are heavily obscured A few mid-IR/optical/radio bright AGN but most of the AGN are X-ray faint: heavily obscured and only moderately luminous

12. Bolometric Luminosity typically Dominated by Star Formation Alexander et al. (2005) AGN contribution ~10% at FIR and <30% at mid-IR Pope et al. (2008)

13. SMGs are distant (z~2), massive (~1011 solar masses), and gas rich (~30% gas mass fraction) galaxies… potentially all massive galaxies were SMGs at some time in the past AGN activity is often present but intense star formation appears to dominate the energetics (i.e., similar to ULIRGs) 17/20 SMGs with redshifts Are X-ray detected: ~28-50% AGNs (bias corrected) 2Ms Chandra (CDF-N/GOODS-N) field However a large fraction of SMGs host AGNs (~28-50% of SMGs with f850>4mJy) …indicating long (almost continuous) black-hole growth during intense star-formation episodes

14. Fuel Supply Archibald et al. (2002) Eddington-limited growth S.Form Accretion BH mass Rapid black-hole growth phase, initiated by major mergers? Chapman et al. (2003) Di Matteo et al. (2005) Eddington-limited growth during peak star formation?

15. Black-hole-host galaxy relationship in SMGs? Stellar masses estimated using Spitzer IRAC (+optical+near-IR) Borys et al. (2005) If assumed Eddington-limited accretion then the black-hole growth substantially lags the stellar growth (by a factor ~50!)

16. However: are Eddington-limited black-hole masses appropriate?want to be able to “weigh” the black holes has the intrinsic AGN luminosity been underestimated (extinction corrections)? are the host-galaxy masses accurate?

17. Chapman et al. (2005) Weighing the Black Holes in SMGs D.M. Alexander, AJ, submitted Not all SMGs are heavily obscured, some have broad Ha or Hb in the near-IR (Swinbank et al. 2004; Takata et al. 2006) Swinbank et al. (2004) Can “weigh” their black holes using the virial black-hole mass estimator: MBH=G-1 RBLR V2BLR (e.g., Kaspi et al. 2000)

18. Eddington Ratios and Black-Hole Masses Careful use of the virial black-hole mass estimator for the broad Ha and Hb emission line (Greene & Ho 2005) Spread of properties (MBH and dM/dt): For broad-line objects, median MBH~(1-3)x108 Msolar and fEdd~0.2-0.5 (depending on BLR geometry) – two types of broad-line SMGs: high luminosity and low luminosity

19. Are the Intrinsic AGN Luminosities Underestimated? Absorption corrections consistent with other studies and AGN properties consistent with ULIRGs (potential local analogs) Agreement between AGN mid-IR component and intrinsic X-ray luminosity: mid-IR appears to be isotropic indicator of AGN luminosity

20. Host-Galaxy Masses? Borys et al. (2005) Greve et al. (2005) Stellar masses: some contaminated by an AGN in near-IR (revised average ~2x1011 solar masses with these removed) CO dynamical masses: avg ~1011 solar masses within ~2 kpc radius (i.e., bulge scale)

21. Physical properties of SMGs used here: • Edd rate, h>0.1 and h~0.2 (BL SMGs/obscured ULIRGs) • This implies MBH~(0.6-1)x108 solars for typical SMGs • M*,dyn(CO)~1011 solars for r~2kpc (within bulge; Greve et al. 2005) • M*,stellar~2x1011 solars (Borys et al. 2005 with near-IR excess objects removed): whole gal but ultimate system mass?

22. SMGs Lie Suggestively Below Local Relationship Consistent with Chakrabarti et al. (2007,2008) simulations of SMGs; see talk tomorrow

23. And statistically below the apparent z~2 relationship

24. Conclusion: black-holes in typical SCUBA galaxies appear to be comparatively small [~(0.6-1)x108 Msolar, for ~0.1-0.2*Edd]The black-hole growth appears to lag that of the host galaxy in massive star-forming galaxies, in apparent contradiction with that found for z~2 quasars/radio galaxies Appears to necessitate the need for an AGN dominated phase that predominantly grows the black hole

25. Page et al. (2004) Normal quasars: not undergoing extreme star formation Page et al. (2004) Submm quasars Absorbed quasars Major-Merger Induced Growth of Massive Galaxies? The Dave Sanders et al. evolutionary picture Normal QSOs SCUBA galaxies Obscured QSOs/IR lum QSOs Alexander et al. (2005) Black Holes getting bigger

26. Testing the Evolutionary Link between Quasars and Submm Galaxies K. Coppin et al. in prep. IRAM CO observations Selected submm detected quasars in same redshift range as submm galaxies: some are rare monsters and some are more typical systems

27. Comparison between Quasars and SMGs Average gas masses and implied CO dynamical masses similar between SMGs and quasars (if quasars are assumed to be more face on: i~20 degrees)

28. Black-hole Host galaxy properties Avg Quasars Quasars Avg SMGs Are submm Quasars at a different evolutionary stage to SMGs? Low dyn masses consistent with other CO studies of Quasars (e.g., Walter+ 04) but does the CO trace the bulge in these systems?

29. Conclusions • Compton-thick quasars (ID’d from optical-mid-IR spectra and X-rays) at z~2-2.5 are as numerous as unobscured quasars • SMGs host concordant black hole-stellar growth: all massive galaxies were potentially SMGs at some time during the past • The black holes of SMGs are comparatively small (typically MBH=(0.6-1)x108Msolar for 0.1-0.2*Edd) • Given their host-galaxy masses (>1011 Msolar), the black hole growth appears to lag the stellar growth, contrary to that found in z~2 quasars • Are submm-detected quasars more evolved than SMGs? • the CO detected quasars have similar gas and dynamical masses as the SMGs but have black holes ~30x larger: not clear if the CO traces the bulge in these systems?