Docstoc

alexander

Document Sample
alexander Powered By Docstoc
					The Obscured Growth Phase of Black
 Holes in Distant Massive Galaxies



      David M Alexander (Durham)
          What I’m not Going to Talk About:
Robust Identification of z~2-2.5 Compton-thick Quasars


                                         Optical AGN




                                              IR AGN




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
                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.
Today’s most massive galaxies hint of a violent past




                                         Heavens et al. (2004)


                               Formation must have been
    M87                       distant, rapid, and luminous
     Also need to grow a massive black hole




                                         Probe black-hole growth
                                            with AGN activity




    All massive galaxies appear to host a massive black hole
=> all galaxies have undergone luminous AGN activity in the past
                          Black Hole-Stellar Growth

                                                        Cannot “age” a black
Action: AGN activity




                        MBH = 0.15 % Mbulge             hole, as you can age
                                                       stars but the tightness
                                                         of the black-hole-
                                                            spheroid mass
                                                        relationship suggests
                                                        they may have grown
                                                             concordantly



                                                        Challenging tests for
                              Tremaine et al. (2002)    structure-formation
                                                               models


                       Action: Star formation
  Submillimeter/Millimeter: efficient selection of the
most bolometrically luminous far-IR galaxies in Universe
      850 micron SCUBA image
                                           (Blain & Longair 1996)




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




    Hughes et al. (1998)                           Lots of
                                                    them!
                                                    Before SCUBA2,
                                                  submm will miss hot
                           Smail et al. (2002)   ultraluminous sources
                            Galactic Properties…
    Chapman et al. (2003, 2005)                                 Strongly clustered
              Distant: typically     Swinbank et al. (2004)
              z~2-3




                                           Massive (Ha)

                                                              Blain et al. (2004)



Neri et al. (2003)




                                   Gas rich (CO)

Progenitors of todays
  massive galaxies?
    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)
    AGN properties? Has been challenging…
                          An optically bright AGN              (Ivison et al. 2002)
    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
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)
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%
       2Ms Chandra                 AGNs (bias corrected)
     (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
       Rapid black-hole growth phase, initiated
                  by major mergers?




                           BH mass Accretion S.Form
  Chapman et al. (2003)




 Fuel Supply



       Eddington-limited
            growth

Archibald et al. (2002)
                                                      Di Matteo et al. (2005)



   Eddington-limited growth during peak star formation?
   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!)
However:
 (1) are Eddington-limited black-hole masses appropriate?
          want to be able to “weigh” the black holes

 (2) has the intrinsic AGN luminosity been underestimated
                    (extinction corrections)?

        (3) are the host-galaxy masses accurate?
        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)
     Chapman et al. (2005)




 Can “weigh” their black holes using the virial black-hole mass
    estimator: MBH=G-1 RBLR V2BLR (e.g., Kaspi et al. 2000)
        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
  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
             Host-Galaxy Masses?
  Borys et al. (2005)



                                              Greve et al. (2005)




Stellar masses: some contaminated        CO dynamical masses:
       by an AGN in near-IR          avg ~1011 solar masses within
  (revised average ~2x1011 solar    ~2 kpc radius (i.e., bulge scale)
    masses with these removed)
        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?
SMGs Lie Suggestively Below Local Relationship




 Consistent with Chakrabarti et al. (2007,2008)
    simulations of SMGs; see talk tomorrow
And statistically below the apparent z~2 relationship
  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
Major-Merger Induced Growth of Massive Galaxies?
  The Dave Sanders et al. evolutionary picture

  SCUBA galaxies                                                 Normal QSOs

                                Obscured QSOs/IR lum QSOs




                                                                      Page et al. (2004)
                                                                      Normal quasars: not
                                                                      undergoing extreme
                                                                      star formation



                                            Page et al. (2004)
                                             Submm quasars


      Alexander et al. (2005)


                            Black Holes getting bigger
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
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)
         Black-hole Host galaxy properties

                                                   Avg Quasars
         Avg SMGs    Quasars




 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?
                      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)x108 Msolar 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?

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:9
posted:12/24/2011
language:
pages:29