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Coevolution of black holes and galaxies at high redshift

Coevolution of black holes and galaxies at high redshift. David M Alexander (Durham). Some key issues in observational cosmology. The growth of black holes. The black-hole-host connection. M bh /M sph ~10 -3. The role of environment?. Black Hole. Action: AGN activity. Accretion Disk.

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Coevolution of black holes and galaxies at high redshift

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  1. Coevolution of black holes and galaxies at high redshift David M Alexander (Durham)

  2. Some key issues in observational cosmology The growth of black holes The black-hole-host connection Mbh/Msph~10-3 The role of environment? Black Hole Action: AGN activity Accretion Disk Action: Star formation

  3. Difficulty in Constructing a Complete AGN Census SDSS optical quasar selection identifies a small fraction (~1-10%) of all AGNs Central engine Obscuring “torus” X-rays: penetrate high column densities • Most AGNs are hidden at optical wavelengths by dust and gas • Host-galaxy dilution for lower-lum AGNs X-ray surveys provide a more complete census of AGN activity

  4. High (quasar) luminosities Just CDF-N sources Moderate (Seyfert) luminosities Low luminosities X-ray Surveys: great steps towards a complete census of AGN activity Murray et al. (2005) 5 ks Chandra Bootes 2 Ms Chandra deep fields Brandt et al. (2001), Alexander et al. (2003); Giacconi et al. (2002); Luo et al. (2008) • Detection of even low-luminosity AGN out to high redshift • Need deeper spectroscopy (~70% complete) although photozs now getting to good quality (e.g., Luo et al. 2010)

  5. Particularly when allied with infrared identification of the most heavily obscured AGNs (1) Below detection limit: stacked X-ray data of IR-bright z~2 galaxies - hidden AGNs Daddi et al. (2007); see also Fiore et al. (2008, 2009), Donley et al. (2008), and others (2) Spectroscopic identification of individual X-ray undetected luminous AGNs Optical spectroscopy IR spectra and SEDs Alexander et al. (2008) Steidel et al. (2002); Alexander et al. (2008)

  6. Growth of black holes Note: the definition of high redshift here is “only” z~1-4 - the identification of large numbers of typical z>6 AGNs is challenging: only ~1 of z>6 AGN probably per deep X-ray field and none reliably identified to date (see Gilli and Brandt talks)

  7. Key result from X-ray surveys: AGN “cosmic downsizing” Ueda et al. (2003) Hasinger et al. (2005) Fiore et al. (2003) Also Cowie et al. (2003); Barger et al. (2005); La Franca et al. (2005); Aird et al. (2010) amongst others Luminosity-dependent density evolution: high-luminosity AGNs (i.e., quasars) peaked at higher redshifts than typical AGNs

  8. Downsizing in “active” black-hole masses? z~1: Babic et al. (2007) Growing more rapidly now Grew more rapidly in past Grew more rapidly in past Growing more rapidly now See also Ballo et al. (2007); Alonso-Herrero et al. (2008) z~0: Heckman et al. (2004) In general this appears to be true - massive black holes (~108 solar masses) were growing more rapidly at z~1 than in the present day, where smaller black holes (<107 solar masses) were most active (Heckman et al. 2004; Goulding et al. 2010) However, current observational constraints do not yet allow robust conclusions

  9. Constraints at higher redshifts? Limited constraints for highly selected sample Model result (Soltan type approach) z~2 ULIRGs vs SDSS Marconi et al. (2004) Alexander et al. (2008) Higher-redshift constraints are key since many models predict rapid black-hole growth at high redshift But these are challenging due to lack of spec-zs of a complete sample and black-hole-host galaxy mass relationship uncertainties: Brusa et al. (2009) similar z~2 constraints to Alexander et al. (2008) above

  10. Tracing the black-hole-host mass relationship Black-hole masses estimated with virial technique (see Vestergaard talk) Host-galaxy masses estimated from a variety of techniques: Host vel disp (em and abs lines), CO line widths, absolute magnitudes, stellar masses, and SED fitting Virial black-hole mass estimator: MBH=G-1 RBLR V2BLR Merloni et al. (2010) result in COSMOS Challenging to measure *both* black hole and host mass without significant uncertainties (see Wang talk) But general concensus is for modest evolution in MBH-MGAL ratio with redshift - with relationship ~2-4x higher at z~2 and perhaps higher at z~2-6: factor ~4 based on Merloni et al. (2010)Evolution perhaps only significant at highest masses (>3x108 solar masses): see Di Matteo talk (also Merloni et al. 2010) See also McLure et al. (2006); Peng et al. (2006a,b); Shields et al. (2006); Woo et al. (2006, 2008); Salviandar et al. (2007); Treu et al. (2007); Jahke et al. (2009); De Carli et al. (2010)

  11. Similar result for rapidly evolving z~2 SMGs Estimated MBH using virial mass estimator for the few z~2 SMGs with broad lines Estimated MGAL for the majority which are host-galaxy dominated SAM results, including feedback Alexander et al. (2008); Hainline et al. (2010) Not significant difference in averageMBH-MGALratio for various z~2 populations But require constraints of more typical z~2-6 AGNs - want to test if there is a black-hole mass dependence: need better spectroscopy, imaging, and larger-area deep X-ray surveys Lamastra et al. (2010)

  12. Tentative evidence for feedback inducing blow out? Collapsed IFU spectrum of z~2.07 SMG ~4-8 kpc extent of broad [OIII gas] Broad (800 km/s) high-velocity (200-500 km/s) [OIII] gas Alexander et al. (2010); see Nesvadba et al. (2006,2007,2008) for results on rarer z~2 radio-loud AGNs Di Matteo et al. (2005) simulation

  13. What role does environment play?

  14. z=3.09 SSA22 protocluster A key laboratory of black-hole growth mechanisms: a distant protocluster? 400ks Chandra exposure of SSA22 Predicted to become a massive Coma-like cluster by the present day The galaxy density is ~6x higher than the field already at z~3.09

  15. LX > 3 × 1043 ergs s−1 Enhanced black-hole growth compared to the field • The AGN activity per galaxy is larger in the protocluster compared to the field by a factor of 6.1+10.3 (enhanced at the 95% confidence level) for AGNs with LX > 3 × 1043 ergs s−1. • Fraction of LAEs hosting AGNs appears to be positively correlated with the local LAE density (96% confidence level). Lehmer et al. (2009a) LBGs LAEs Lehmer et al. (2009b)

  16. More massive black holes active at earlier times? Host galaxies appear more massive in protocluster • If the AGN fraction is larger in the protocluster simply due to the presence of more massive SMBHs, then an average protocluster AGN would be more luminous than an average field AGN by the same factor • For this to be the case, the SMBHs would have to be ≈3−10 times more massive in the protocluster than the field: likely 108-109 solar masses rather than 107-108 solar masses Good agreement with that found for a z=2.3 protocluster (Digby-North et al. 2010) Lehmer et al. (2009a) Implication: the characteristic X-ray luminosity and “active” black-hole mass appears to be a function of environment as well as redshift

  17. And AGN fraction declines to lower redshifts z~3.09 protocluster AGN fraction • Significant drop (1-2 orders of magnitude) in AGN fraction for similarly overdense regions at z<1 • AGN activity has been “switched off” in galaxy clusters/protoclusters since z~3 to z<1 • Need to trace this out from z~2-8 with X-ray observations of more protoclusters/overdense regions AGN fraction in massive galaxy clusters Martini et al. (2009) Require more constraints for more protoclusters, particularly at high redshift Need deep X-ray observations of other overdense regionsNeed wider area X-ray surveys to cover full range of environments

  18. Geach et al. (2009) Has heating of the ICM tentatively started? Ly images of some protocluster AGNs Potential heating mechanisms AGN power NASA press conference movie Star-formation power ~17% of extended Ly emitters host luminous AGN in the z~3.09 protocluster; AGNs are luminous enough to power the 10-100 kpc extended Ly emission

  19. Summary • AGN cosmic downsizing possibly due to increase in active black hole with redshift • typical active black holes at z~1 are ~108 solar masses; more work required to obtain reliable results at higher redshifts • Evolution in black-hole-host mass relationship quite modest out to z~2 - may be stronger out to higher redshift but current samples are limited • possible black-hole mass dependence - need constraints for typical black holes • possible evidence for z~2 feedback inducing blow out • Environmental dependencies on black-hole growth: AGN fraction increases in z~2-3 protoclusters than compared to field - probably due to more massive “active” black holes • AGN fraction significantly decreases compared to field at z<1 - possibly due to gas depletion or heating • AGN activity in z~3 protocluster luminous enough to power 10-100 kpc Ly halos - early evidence for ICM heating?

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