Evolution of HighRedshift Quasars

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Evolution of High-Redshift Quasars

• Xiaohui Fan
• University of Arizona
• Leiden, Aug 2005
• CollaboratorsStrauss,Schneider,Richards,Gunn,Beck
  er,White,Rix,Pentericci,Walter,
  Carilli,Cox,Bertoldi,Omont,Brandt,
  Vestergaard,Eisenstein, Cool, Jiang,
  Diamond-Stanic, et al.

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High-redshift Quasars and the End of Cosmic Dark
Ages
Resolved CO emission from z6.42 quasar

• Existence of SBHs at the end of reionization
• BH accretion history in the Universe?

• Relation of BH growth and galaxy evolution?

• Probing the end of reionization?

Evolution of Quasar Density
Detection of Gunn-Peterson Trough
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SDSS Overview

• Primary Telescope 2.5m wide-field (2.5 deg)
• Imaging Survey (wide-field 54 CCD imager)
• Main Survey 10000 deg2
• Five bands, 3000 10000 Å
• rlim 22.5, zlim 20.5
• Spectroscopic Survey
• 106 galaxies (rlt17.8)
• 105 quasars ( 0 lt z lt 6.5), mostly color-selected
• Interesting stars, radio/x-ray sources etc.
• DR3 46,000 quasars
• DR4 include about 60,000 quasars

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The Highest Redshift Quasars Today

• zgt4 gt1000 known
• zgt5 gt60
• zgt6 9
• SDSS i-dropout Survey
• By sping 2005 6600 deg2 at zABlt20
• Nineteen luminous quasars at zgt5.7
• Many L and T brown dwarfs
• 30 at z6 expected in the whole survey

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Outline

• Evolution of luminosity function
• High-z quasar clustering and environment
• Evolution of quasar spectra and metallicity
• High-z quasar BH mass
• Dust and star formation in high-z quasar host
  galaxies

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46,420 Quasars from the SDSS Data Release Three
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Ly? forest
3
Ly?
2
CIV
redshift
CIII
MgII
FeII
1
FeII
H?
OIII
0
wavelength
4000 A
9000 A
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SDSS DR3 Sample46,000 quasars over 5000 deg2
Richards et al. 2005
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Evolution of quasar densities
Density of quasars
SFR of galaxies
Bouwens et al.
Exponential decline of quasar density at
high redshift, different from normal galaxies

Richards et al. 2005, Fan e al. 2005
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Quasar Density at z6

• From SDSS i-dropout survey
• Density declines by a factor of 40 from between
  z2.5 and z6
• Cosmological implication
• MBH109-10 Msun
• Mhalo 1012-13 Msun
• rare, 5-6 sigma peaks at z6 (density of 1 per
  Gpc3)
• Assembly of massive dark matter halo environment?
• Assembly of supermassive BHs?

Fan et al. 2004
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Simulating z6 Quasars

• The largest halo in Millennium simulation (500
  Mpc cube) at z6.2
• Virial mass 5x1012 M_sun
• Stellar mass 5x1010 M_sun
• SFR 300 M_sun/year
• Resembles properties of SDSS quasars
• Even the largest N-body simulation not big enough
  to produce one SDSS z6 quasar
• Today 1.5 x 1015 M_sun cluster
• Much massive halos existed at z6, but..
• How to assemble such mass BHs and their host
  galaxies in less than 1Gyr??
• Initial assembly from seed BH at zgtgt10
• Little or no feedback to stop BH/galaxy growth

Dark matter
galaxy
z6.2
z0
Springel et al. 2005
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Early Growth of Supermassive Black Holes
Formation timescale (assuming Eddington)
Vestergaard 2004
Dietrich and Hamann 2004
Lack of spectral evolution in high-redshift
quasars ? quasar BH estimate valid at high-z BH
mass estimate using emission line width to
approximate gravitational velocity, accurate to a
factor of 3 5 locally

• Billion solar mass BH at z6 indicates very
  early
• growth of BHs in the Universe

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Evolution of X-ray AGN LF-- downsizing
Hasinger et al. 2005

• At high-luminosity X-ray and optical traces the
  same population
• How does optically-selected quasar population
  evolve at low-luminosity?

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Probing the Evolution of Faint Quasar

• SDSS Southern Deep Spectroscopic Survey
• 270 deg along Fall Equator in the Southern
  Galactic Cap
• Down to 25 mag in SDSS bands with repeated
  imaging
• Spectroscopic follow-up using 300-fiber Hectospec
  spectrograph on 6.5-meter MMT
• Reaches AGN luminosity at z2.5
• Few hundred faint quasars at zgt3
• 10 20 at z6

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Evolution of faint quasars in SDSS Deep Survey
Jiang et al. in prep.
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Whats the Faint End Slope of QLF?

• Faint slope measurement
• Ranges from -1.o to -2.0
• lead to large uncertainties in
• in the total luminosity and
• mass density of quasar pop.

z0
Hao et al. 2004
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Evolution of the Shape of Quasar LF
Richards et al. 2005
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High-z QLF from SDSS Deep Stripe Survey
z 4.5

• High-z quasar LF different from low-z
• High-z LF much flatter
• Implies that more luminous quasars grow early in
  the Universe
• Similar to the early growth of massive galaxies??
• Quasars are not major contributors to
  reionization at zgt6

(high-z)
(low-z)
Fan et al. 2005
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Evolution of Quasar LF Shape
Richards, et al. Fan et al. 2005

• High-z quasar LF different from low-z
• Bright-end slope of QLF is a strong function of
  redshift
• Transition at z3 (where quasar density peaks in
  the universe)
• Different formation mechanism at low and high-z?

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Clustering of Quasars

• What does quasar clustering tell us?
• Correlation function of quasars vs. of dark
  matter
• Bias factor of quasars ? average DM halo mass
• Clustering probably provides the most effective
  probe to the statistical properties of quasar
  host galaxies at high-redshift
• Combining with quasar density ? quasar lifetime
  and duty cycle

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Large Scale Distributionof Quasars
SDSS
2dF
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Quasar Two-point Correlation Function from SDSS
at zlt2.5
Van den Berk et al. in preparation
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Clustering of Quasars

• What does quasar clustering tell us?
• Bias factor of quasars ? average DM halo mass
• Clustering provides the most effective probe to
  the statistical properties of quasar host DM
  properties at high-redshift
• Another hint of quasars at zgt3 being somewhat
  different from low-z quasars?

Fan et al. in preparation
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Environment of a z6.3 quasar

• Deep VLT i-z-J imaging
• 19 i-dropout candidates
• in 38 sq. arcmin at zlt25.6
• gt6 times higher than in
• GOODS etc.
• However, Willott et al. found no excess i-dropout
  around three zgt6 quasars (but with shallower
  images)

quasar
izJ composite (z_lim 26) Pentericci et al.
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I-dropout around z6.3 quasar
Stiavelli et al. 2005 HST Keck data
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The Lack of Evolution in Quasar Intrinsic
Spectral Properties

Ly a
NV
Ly a forest
OI
SiIV

• Rapid chemical enrichment in quasar vicinity
• Quasar env has supersolar metallicity -- metal
  lines, CO, dust etc.
• High-z quasars and their environments mature
  early on

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Chemical Enrichment at zgtgt6?

• Strong metal emission ? consistent with
  supersolar metallicity
• NV emission ? multiple generation of star
  formation from enriched pops
• Fe II emission ? type II SNe some could be Pop
  III?
• Question can we generalize the conclusion drawn
  from regions around central BHs to the whole
  early Universe?

Fan et al. 2001
Barth et al. 2003
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Early enrichment of quasars

• Metallicity in BLR of z6 quasars 1 -- 10 solar
• Nuclear synthesis model shows
• Normal IMF is sufficient (given high SFR)
• Type Ia is not critical in Fe production
• Mostly Pop III under-produce N/C
• normal stars existed at very high-z in quasar
  environment.

Venkatesan et al. 2004
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Lack of evolution in X-ray
X-ray - optical slope
X-ray photon index
Strateva et al. Shemmer et al.
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z6 Quasar SEDs from X-ray to radio
dust

• Lack of evolution in UV, emission line and X-ray
  ? disk and emission line regions form in very
  short time scale
• old quasars in a young universe
• But how about dust? Timescale problem running
  out of time for AGB dust Spitzer

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Mid-IR SEDs of z6 Quasars
Min. from dust sublimation

• Overall shape shows little evolution
• But obj-obj variation significant
• z6.42 quasar stronger dust emission with higher
  T?

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Supernova Dust in z6 quasar?(Maiolino et al.
2004)

• SDSS J1048 (z6.2)
• Highest-z Low-BAL
• Typical SED at near UV ? moderate dust
• But blue in far-UV
• SED suggesting unusual dust extinction

• Age of the universe lt 1Gr
• No time for dust from evolved low intermediate
  mass stars
• Dust extinction produced by SN dust fits the data
• Implications on energetics and extinctions of
  high-z galaxies

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No evolution? thats not always the case

• No emission line, radio-quiet quasars at zgt4
• lt1 of high-z quasars
• No BL Lac signature
• A separate population of quasars?

Fan et al. 2005
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Evolution of Quasar BH Mass Function

• Lack of spectral evolution
• Similar BLR structure
• BH mass scaling relation at low-z still valid at
  high-z
• Quasar mass function represents accretion
  history traced by luminous quasars
• Not surprisingly, closely follows evolution of
  luminosity function
• Flatter MF at high-z
• Probing evolution of accretion rate?
• At zgt2 MF shape similar and flat at high-mass
  end, but the shape different at low-z

Vestergaard et al.
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Probing the Host Galaxy Assembly
? Dust torus
Spitzer
ALMA

• Cool Dust in
• host galaxy

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Sub-mm and Radio Observationof High-z Quasars

• Probing dust and star formation in the most
  massive high-z systems
• Using IRAM and SCUBA 30 of radio-quiet quasars
  at zgt4 detected at 1mm (observed frame) at 1mJy
  level
• ? submm radiation in
• radio-quiet quasars
• come from thermal
• dust with mass 108 Msun
• If dust heating came from starburst
• ? star formation rate of
• 500 2000 Msun/year
• ?Quasars are likely sites
• of intensive star formation

Arp 220
Bertoldi et al. 2003
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• Submm, CO and CII detection
• in the highest-redshift quasar
• Dust mass 108 109Msun
• H2 mass 1010Msun
• Star formation rate 103/yr
• co-formation of SBH and
• young galaxies

Mailino et al. 2005
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High-resolution CO Observation of z6.42 Quasar
VLA CO 32 map

• Spatial Distribution
• Radius 2 kpc
• Two peaks separated by 1.7 kpc
• Velocity Distribution
• CO line width of 280 km/s
• Dynamical mass within central 2 kpc 1010 M_sun
• Total bulge mass 1011 M_sun
• lt M-sigma prediction
• BH formed before
• complete galaxy assembly?

1 kpc
Walter et al. 2004
Channel Maps
? 60 km/s ?
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High-z vs. Low-z Quasars

• LF evolution
• Strong evolution in total density
• Downsizing of characteristic luminosity
• At zgt3
• Declining density
• Flatter LF/MF
• Stronger clustering
• Are high-z and low-z quasars different?
• Spectral evolution
• Little or no evolution in continuum/emission line
  properties
• Dust properties might have changed
• High-metallicity requires presence of evolved
  stellar pop at high-z
• How does this constrain host evolution?
• BH/galaxy co-evolution
• Billion solar-mass BH at the end of reionization
• Strong star-formation associated with BH growth
• Has M-sigma relation established at high-z?

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Question for discussion

• Should one be surprised about the existence of
  luminous, high-mass, high metallicity quasars at
  the end of reionization?
• What do we learn from they about the co-evolution
  of early galaxies and BHs?