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Evolution of High-Redshift Quasars Xiaohui Fan University of Arizona Castel Gandolfo, Oct 2005 Collaborators:Strauss,Schneider,Richards, Hennawi,Gunn,Becker,White,Rix,Pentericci, Walter, Carilli,Cox,Bertoldi,Omont,Brandt, Vestergaard,Eisenstein, Cool, Jiang, DiamondStanic, et al. The Highest Redshift Quasars Today • • • • z>4: >1000 known z>5: >60 z>6: 9 SDSS i-dropout Survey: – By Spring 2005: 6600 deg2 at zAB<20 – Nineteen luminous quasars at z>5.7 • Complete sample for bright quasars at z~6: – ~8000 deg, ~25 quasars by 2006 • Next: work on faint sample at z~6 Outline • • • • • Evolution of luminosity function BH masses at high-z High-z quasar clustering and environment Evolution of quasar spectra and metallicity Dust and star formation in high-z quasar host galaxies 46,420 Quasars from the SDSS Data Release Three 5 Ly forest 3 Ly 2 redshift CIV CIII MgII FeII 1 FeII OIII H 0 4000 A wavelength 9000 A 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, mostly luminosity dependent Richards et al. 2005, Fan e al. 2005 Quasar Density at z~6 • From SDSS i-dropout survey – Density declines by a factor of ~40 from between z~2.5 and z~6 • Cosmological implication – MBH~109-10 Msun – Mhalo ~ 1012-13 Msun – rare, 5-6 sigma peaks at z~6 (density of 1 per Gpc3) • Assembly of massive dark matter halo environment? • Assembly of supermassive BHs? Fan et al. 2004 Simulating z~6 Quasars Dark matter galaxy • The largest halo in Millennium simulation (500 Mpc cube) at z=6.2 – – – – – z=6.2 – – z=0 • Springel et al. 2005 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 z~6 quasar… Today: 1.5 x 1015 M_sun cluster Much massive halos existed at z~6, but.. How to assemble such mass BHs and their host galaxies in less than 1Gyr?? – The universe was ~20 tedd old – Initial assembly from seed BH at z>>10 – Little or no feedback to stop BH/galaxy growth 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 z~6 indicates very early growth of BHs in the Universe 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? Evolution of the Shape of Quasar LF Richards et al. 2005 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 z~3 (where quasar density peaks in the universe) – Different formation mechanism at low and high-z? 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 z~2.5 – Few hundred faint quasars at z>3 – 10 – 20 at z~6 Evolution of faint quasars in SDSS Deep Survey • Sample reaches AGN luminosity at z~3 • Strong evolution in LF shape • Simple luminosity evolution clearly not a good description • “break” luminosity evolves: -- downsizing • faint end slope also evolve: -- steeper at high-z? Jiang et al. in prep. Downsizing of optical quasars High-z QLF from SDSS Deep Stripe Survey • 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 z>6 z ~ 4.5 (high-z) (low-z) Fan et al. 2005 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 highredshift • Another hint of quasars at z>3 being somewhat different from low-z quasars? Wyithe and Loeb 2004 Fan et al. in preparation Environment of a z=6.3 quasar • Deep VLT i-z-J imaging • 19 i-dropout candidates in 38 sq. arcmin at z<25.6 • >6 times higher than in GOODS etc. (also Stiavelle et al. 2005) quasar izJ composite (z_lim =26) Pentericci et al. 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 Chemical Enrichment at z>>6? • • • • 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? Barth et al. 2003 Fan et al. 2001 Early enrichment of quasars Top-heavy IMF Normal IMF PopIII • Metallicity in BLR of z~6 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 underproduce N/C – “normal” stars existed at very high-z in quasar environment. Venkatesan et al. 2004 z~6 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… Mid-IR SEDs of z~6 Quasars Min. from dust sublimation • Overall shape shows little evolution • But obj-obj variation significant – z=6.42 quasar: stronger dust emission with higher T? BH mass distribution CIV Upper Limit? L~M Fan et al. >1000 quasars at z>3 McLure et al. SDSS DR 1 How fast can the most massive high-z BH grow? Will it be stopped by negative feedback? BH Accretion Rate z>3 z<3 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 z>2: MF shape similar and flat at high-mass end, but the shape different at low-z Vestergaard et al. Probing the Host Galaxy Assembly Dust torus Spitzer ALMA Cool Dust in host galaxy Sub-mm and Radio Observation of High-z Quasars • Probing dust and star formation in the most massive high-z systems • Advantage: – No host galaxy contamination – Negative K-correction for both continuum and line luminosity at high-z – Give direction measurement to • Star formation rate • Gas morphology • Gas kinematics Sub-mm and Radio Observation of High-z Quasars • Using IRAM and SCUBA: ~30% of radio-quiet quasars at z>4 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 Arp 220 500 – 2000 Msun/year Quasars are likely sites of intensive star formation • FIR luminosity not correlated with UV luminosity of quasar Bertoldi et al. 2003 PSS J2322+1944 (z=4.12) • CO Einstein ring – Modeled by starforming disk with 2kpc radius – CO line-width 280km/s – BH Mass ~10^9 solar – Star formation rate 900 solar mass/year • 15 detections of CO at z>2 (5/6 known CO sources at z>4 are quasars) Carilli et al. 2003 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 High-resolution CO Observation of z=6.42 Quasar • 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 < M-sigma prediction • BH formed before complete galaxy assembly? Channel Maps caution: selection effect when using luminous quasars 60 km/s VLA CO 3—2 map 1 kpc Walter et al. 2004 High-z vs. Low-z Quasars • LF evolution: – Strong evolution in total density – Downsizing of characteristic luminosity – At z>3: • 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? Question • Should one be surprised about the existence of luminous, high-mass, high metallicity quasars at the end of reionization?