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
What Im not Going to Talk About Robust
Identification of z2-2.5 Compton-thick Quasars
Compton-thick quasars (LXgt1044 erg/s) at z2 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 z2 Starbursts and Quasars
Weighing the Black Holes of z2 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
Todays most massive galaxies hint of a violent
past
Heavens et al. (2004)
Formation must have been distant, rapid, and
luminous
M87
5
Also need to grow a massive black hole
All massive galaxies appear to host a massive
black hole gt 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
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
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
Galactic Properties
Chapman et al. (2003, 2005)
Distant typically z2-3
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 gt3L galaxies (duty
cycle corrected)
11
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 lt30 at mid-IR
Pope et al. (2008)
13
SMGs are distant (z2), 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 f850gt4mJy) indicating long
(almost continuous) black-hole growth during
intense star-formation episodes
14
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
(opticalnear-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
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 MBHG-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 fEdd0.2-0.5 (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, hgt0.1 and h0.2 (BL SMGs/obscured
  ULIRGs)
• This implies MBH(0.6-1)x108 solars for typical
  SMGs
• M,dyn(CO)1011 solars for r2kpc (within bulge
  Greve et al. 2005)
• M,stellar2x1011 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 z2
relationship
24
Conclusion black-holes in typical SCUBA galaxies
appear to be comparatively small (0.6-1)x108
Msolar, for 0.1-0.2EddThe black-hole growth
appears to lag that of the host galaxy in massive
star-forming galaxies, in apparent contradiction
with that found for z2 quasars/radio
galaxies Appears to necessitate the need for an
AGN dominated phase that predominantly grows the
black hole
25
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 i20
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 (IDd from optical-mid-IR
  spectra and X-rays) at z2-2.5 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)x108 Msolar for
  0.1-0.2Edd)
• Given their host-galaxy masses (gt1011 Msolar),
  the black hole growth appears to lag the stellar
  growth, contrary to that found in z2 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?