Coevolution of black holes and galaxies at high redshift

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Coevolution of black holes and galaxies at high
redshift
David M Alexander (Durham)
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Some key issues in observational cosmology
The growth of black holes
The black-hole-host connection
Mbh/Msph10-3
The role of environment?
Black Hole
Action AGN activity
Accretion Disk
Action Star formation
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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
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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)

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Particularly when allied with infrared
identification of the most heavily obscured AGNs
(1) Below detection limit stacked X-ray data of
IR-bright z2 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)
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Growth of black holes
Note the definition of high redshift here is
only z1-4 - the identification of large
numbers of typical zgt6 AGNs is challenging only
1 of zgt6 AGN probably per deep X-ray field and
none reliably identified to date (see Gilli and
Brandt talks)
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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
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Downsizing in active black-hole masses?
z1 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)
z0 Heckman et al. (2004)
In general this appears to be true - massive
black holes (108 solar masses) were growing more
rapidly at z1 than in the present day, where
smaller black holes (lt107 solar masses) were most
active (Heckman et al. 2004 Goulding et al.
2010) However, current observational constraints
do not yet allow robust conclusions
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Constraints at higher redshifts?
Limited constraints for highly selected sample
Model result (Soltan type approach)
z2 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 z2
constraints to Alexander et al. (2008) above
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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 MBHG-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 z2 and perhaps higher at z2-6
factor 4 based on Merloni et al.
(2010)Evolution perhaps only significant at
highest masses (gt3x108 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)
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Similar result for rapidly evolving z2 SMGs
Estimated MBH using virial mass estimator for the
few z2 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 average
MBH-MGALratio for various z2 populations But
require constraints of more typical z2-6 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)
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Tentative evidence for feedback inducing blow out?
4-8 kpc extent of broad OIII gas
Collapsed IFU spectrum of z2.07 SMG
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 z2
radio-loud AGNs
Di Matteo et al. (2005) simulation
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What role does environment play?
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z3.09 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 z3.09
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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
6.110.3 (enhanced at the 95 confidence level)
for AGNs with LX gt 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)
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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 z2.3
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
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And AGN fraction declines to lower redshifts
z3.09 protocluster AGN fraction

• Significant drop (1-2 orders of magnitude) in
  AGN fraction for similarly overdense regions at
  zlt1
• AGN activity has been switched off in galaxy
  clusters/protoclusters since z3 to zlt1
• Need to trace this out from z2-8 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
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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 z3.09 protocluster AGNs are luminous
enough to power the 10-100 kpc extended Ly?
emission
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Summary

• AGN cosmic downsizing possibly due to increase
  in active black hole with redshift
• typical active black holes at z1 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 z2 - 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 z2 feedback inducing blow
  out
• Environmental dependencies on black-hole growth
  AGN fraction increases in z2-3 protoclusters
  than compared to field - probably due to more
  massive active black holes
• AGN fraction significantly decreases compared to
  field at zlt1 - possibly due to gas depletion or
  heating
• AGN activity in z3 protocluster luminous enough
  to power 10-100 kpc Ly? halos - early evidence
  for ICM heating?