Lecture 3: The Highest Redshift Quasars: Early Black Hole Evolution and the End of Reionization Xiaohui Fan AGN Summer School, USTC May 25, 2007 Background: 46,420 Quasars from the SDSS Data Release Three

Quest to the Highest Redshift Quasars SDSS Radio CCD IR survey

The Highest Redshift Quasars Today z>4: >1000 known z>6: 15 SDSS i-dropout Survey: –Completed in June 2006: 7700 deg 2, z AB < luminous quasars at 5.7<z<6.4 Other on-going z~6 quasar surveys: –AGES (Cool et al.): Spitzer selected, one quasar at z=5.8 –FIRST-Bootes (Becker et al.): radio selected, one quasar at z=6.1 –QUEST, CFHT: i-dropout surveys similar to SDSS –Future IR-based survey: UKIDSS, VISTA, allows detection up to z~8-9. SDSS 2 : faint quasars in the deep SDSS stripe (Jiang, XF et al.), ~ additional z~6 quasars in next three years (six z~6 quasar in pilot obs)

What have changed in quasar properties since z~6? Luminous, “normal” looking quasars existed at z>6, half Gyr after the first star-formation –Timescale for formation of the first billion-M sun BH? –Timescale for the establishment of AGN structure: do quasar spectra at z~6 really look the same as at z~0? –Timescale for the establishment of M-sigma relation?

Outline Quasar luminosity function and BH mass function –Evolution in accretion properties? Quasar SEDs at high-redshift –First signs of cosmic evolution? Star-formation and dust in quasar host galaxies –Evolution of M-sigma relation? Probing Reionization with high-redshift quasars Summary

46,420 Quasars from the SDSS Data Release Three wavelength 4000 A9000 A redshift Ly  CIV CIII MgII HH OIII FeII Ly  forest

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 –M BH ~ M sun –M halo ~ M sun –rare, 5-6 sigma peaks at z~6 (density of 1 per Gpc 3) Assembly of supermassive BHs? Assembly of dark matter halo? Fan et al. 2006

Simulating z~6 Quasars The largest halo in Millennium simulation (500 Mpc cube) at z=6.2 –Virial mass 5x10 12 M_sun –Stellar mass 5x10 10 M_sun –Resembles properties of SDSS quasars –Such massive halos existed at z~6, but.. z=6.2 z=0 Dark mattergalaxy Springel et al. 2005

Constraining Early BH Growth Timescale –At z~6, the Universe is about 20 t edd old (radiative efficiency of 0.1) –Enough time to grow 10 9 M sun BH? Semi-analytic model of early BH growth (Volonteri & Rees 2006) –Traces halo merger and BH accretion/merger history –Negative feedbacks slowing down BH growth: Rocket effect from BH mergers (BH kicked out from shallow potential wells) Spin up of BHs –Increased radiative efficiency and Eddington timescale –Extremely difficult for standard thin-disk, Eddington-limited growth from stellar seed BHs… but still allowed Predictions on BH properties –Only BHs with ideal growth conditions (negative feedback not important) can grow to billion M sun at z~6 –Low BH fraction in halos at the high luminosity (mass) end Steep quasar luminosity function?

Evolution of Quasar LF Shape High-z quasar LF different from low-z –Bright-end slope of QLF is a strong function of redshift –Transition at z~2.5 (where quasar density peaks in the universe) – Different formation mechanism at low and high-z? – Faint quasar surveys needed! Richards, et al.; Fan et al. 2006

Quasar Luminosity Function at z~6 Based on: –SDSS Wide: 7700 deg 2, 17 quasars, z AB <20 –SDSS Deep: ~150 deg 2, 6 quasars, 20<z AB <21 –AGES: 1 quasar in 5 deg 2 at z AB <21.5 Steeppening of LF: –  L <-3.1 –Comparing to  L -2.4 at z~4 At z~7-8, quasar growth will severely limited by timescale: intermediate mass seeds and/or super-Eddington accretions may be needed Jiang, XF et al. in prep

McLure et al. SDSS DR 1 Fan et al. >1000 quasars at z>3 CIV  Upper Limit? BH mass determination at high-z Virial BH mass estimate using optical spectra: –Emission line width to approximate gravitational velocity –Bolometric luminosity vs. BLR size scaling relation –Accurate to a factor of locally Applying virial method to high-z (Vestergaard et al.) –Lack of spectral evolution in high- redshift quasars  quasar BH estimate valid at high-z –Using H  MgII and CIV for different redshift ranges BH mass at high-z: – M sun existed at z~6 –Upper envelop of BH mass at several M sun ? Negative feedback?

BH mass distribution MassL BOL L BOL /L Edd SDSS: DR3 Vestergaard, XF et al. in prep.

Evolution of Eddington Ratio Luminous quasars at all redshifts have L bol /L edd ~ Luminosity dependence (expected) –L bol /L edd ~ 1 at several L * Redshift dependence: –At constant luminosity: L bol /L edd increase by ~3 from z=1 to z=5 –At z>4, all quasars basically shining at Eddington Next step: –Full MF –Extend to low-L To what extent is quasar evolution driven by accretion rate changes? Vestergaard, XF et al. in prep.

Outline Quasar luminosity function and BH mass function –Evolution in accretion properties? Quasar SEDs at high-redshift –First signs of cosmic evolution? Star-formation and dust in quasar host galaxies –Evolution of M-sigma relation? Probing Reionization with high-redshift quasars Summary

NV OI SiIV Ly a Ly a forest Rapid chemical enrichment in quasar vicinity Quasar env has supersolar metallicity : no metallicity evolution Does this lack of evolution in rest-frame UV also apply to other wavelength? The Lack of Evolution in Quasar Emission Line Properties Fan et al.2004

High Metallicity at high-z 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? Barth et al Nagao et al. 2006

Quasar Metallicity at z~6 Jiang, XF et al near-IR spectroscopy: Gemini + Keck

Early enrichment of quasars Venkatesan et al Metallicity in BLR of z~6 quasars: 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. Top-heavy IMF Normal IMF PopIII

Quasar spectral energy distribution Spitzer  Dust torus  Cool Dust in host galaxy hot dust BLR disk

Evolution of Quasar SEDs: X-ray to radio To the first order, average SEDs of z~6 quasar consistent with low-z template However, detailed analysis might be indicating first signs of SED evolution: –Dust properties (Spitzer and extinction) –Fraction of radio-loud quasars Jiang, XF et al. 2006a

Hot dust in z~6 Quasars Lack of evolution in UV, emission line and X-ray  disk and emission line regions form in very short time scale But how about dust? Timescale problem: running out of time for AGB dust Spitzer observations of z~6 quasars: probing hot dust in dust torus (T~1000K) Two unusual SEDs among 13 objects observed. dust Jiang, XF et al. 2006a No hot dust??

Where did the hot dust go? typical J  m24  m5.6  m4.8  m3.5  m Host dust contribution luminosity J0005 (z=5.85): SED consistent with disk continuum only No similar objects known at low-z formation of the first dust ? Larger sample… ~80 objects in Spitzer Cycle 4 Jiang, XF 2006a

Supernova Dust in z~6 quasar? (Maiolino et al. 2004) SDSS J1048 (z=6.2) –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 < 1Gr –No time for dust from evolved low – intermediate mass stars… Dust extinction produced by SN dust fits the data

Evolution of Radio-loudness Match all SDSS quasars to FIRST and NVSS catalog: –For the whole flux- limited sample, radio- loud fraction doesn’t strongly depend on luminosity or redshift –However, this seems to be an artifact of marginal distribution… Jiang, XF et al. 2006b

Radio-loud fraction is a strong function of luminosity and redshift Luminosity dependence: RLF ~ L 0.5 At z~1: RLF changes from 17% (M=-27) to 2% (M=-22) Redshift dependence: RLF ~ (1+z) -1.7 For M=-27: RLF changes from 17% (z=1) to 2% (z=5) Log(1+z) MiJiang, XF et al. 2006b log(radio-loud fraction)

Lineless quasars: radio quiet BL Lac or quasars with no BLR? No emission line, radio-quiet quasars at z>4 –~1% of high-z quasars –No obvious low-z counterparts –No BL Lac signature –A separate population of quasars? Fan et al Ly  distribution Diamond-Stanic et al Lineless Quasars: EW(Ly  )<10 Log EW (Ly  )

Outline Quasar luminosity function and BH mass function –Evolution in accretion properties? Quasar SEDs at high-redshift –First signs of cosmic evolution? Star-formation and dust in quasar host galaxies –Evolution of M-sigma relation? Probing Reionization with high-redshift quasars Summary

Co-formation of BH/Galaxy at high-z Host galaxies of z~6 quasars should have ULIRG properties –Star formation rate? –Mass of host galaxies? –FIR/radio observations: Direct probes of star formation Future: Hershel/ALMA Li et al. astro-ph/

Probing the Host Galaxy Assembly Spitzer ALMA  Dust torus  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 AGN contamination –Negative K-correction for both continuum and line luminosity at high-z –Give measurements to Star formation rate Gas morphology Gas kinematics

Sub-mm Observations 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 ~ 10 8 M sun Among z~6 quasars: 5(+2)/19 detected in submm If dust heating came from starburst  star formation rate of 500 – 2000 M sun /year Support for star formation origin of FIR luminosity: z~6 quasars follow starburst galaxy FIR/radio relation No correlation between FIR and UV Heating source still open question Arp 220 Bertoldi et al.

Submm and CO observation of z=6.42 quasar: probing the earliest ISM Strong submm source: –Dust T: 50K –Dust mass: 7x10 8 M sun Strong CO source (multiple transitions) –T kin ~ 100K –Gas mass: 2x10 10 M sun –n H2 ~ 10 5 Gas/dust, Temp, density typical of local SB Bertoldi et al.

[CII] detection of z=6.42 quasar Mailino et al [CII] 158  m line: –Brightest ISM line –Direct probe of SF region J1148 (z=6.42) –Both [CII] and L FIR consistent with the brightest local ULIRGs –SFR~ 10 3 M sum

High-resolution CO Observation of z=6.42 Quasar Spatial Distribution –Radius ~ 2 kpc –Two peaks separated by 1.7 kpc –CO brightness similar to typical ULIRG SF core. Velocity Distribution –CO line width of 280 km/s –Dynamical mass within central 2 kpc: ~ M_sun –Total bulge mass ~ M_sun < M-sigma prediction BH formed before complete galaxy assembly? Walter et al kpc VLA CO 3—2 map  60 km/s  Channel Maps

M-  relation at high-z Host mass from CO –15 CO detections at z>2 –Line width all ~ km/s –Taking at face value: Strong evolution of M-   BH forms early Similar results from HST studies of lensed quasar host (Peng et al.) Caveats: –Are luminous quasars biased? –Are CO observations biased? –Need detailed simulations of dust and gas properties of high-z quasar host galaxies Shields et al. 2006

Summary: High-z vs. Low-z Quasars LF and BH mass evolution: –Flattening of luminosity/mass functions –Billion solar mass BH existed at z~6 –Average Eddington ratio might be increasing at high-z –Are high-z and low-z quasars accreting differently? Spectral evolution: –Little or no evolution in continuum/emission line properties –Strong evolution in radio, Dust and X-ray properties might be evolving as well. –Approaching the epoch of AGN structure formation? BH/galaxy co-evolution –ISM of high-z quasar hosts similar to that of local ULIRGs –narrow CO line width –Large BH in small hosts at high-z? Wish list: 1.Larger sample and fainter quasars to break degeneracy 2.Better models/observations in dust/gas

Next: ALMA!

Outline Quasar luminosity function and BH mass function –Evolution in accretion properties? Quasar SEDs at high-redshift –First signs of cosmic evolution? Star-formation and dust in quasar host galaxies –Evolution of M-sigma relation? Probing Reionization with high-redshift quasars Summary

From Avi Loeb reionization Two Key Constraints: 1.WMAP 3-yr: z reion =11+/-3 2. IGM transmission: z reion > 6

The end of dark ages: Movie

Searching for Gunn-Peterson Trough Gunn and Peterson (1965) –“It is observed that the continuum of the source continues to the blue of Ly-α ( in quasar 3C9, z=2.01)” –“only about one part of 5x10 6 of the total mass at that time could have been in the form of intergalactic neutral hydrogen ” Absence of G-P trough  the universe is still highly ionized First detection of complete G-P trough: SDSS J1030 (z=6.28, Becker et al. 2001) G-P optical depth  evolution of ionizing background and neutral fraction of the IGM

Three stages Pre-overlap Overlap Post-overlap From Haiman & Loeb

Keck/ESI 30min exposure  Gunn-Peterson Trough in z=6.28 Quasar Keck/ESI 10 hour exposure  White et al. 2003

End of Reionization Epoch: Open Questions What’s the Status of IGM at z~6? –Measurements of Gunn-Peterson optical depth –Evolution of UV background –Constraints on IGM neutral fraction Was the Universe mostly neutral by z~6-8? –Distribution of dark gaps –Evolution of Lyman alpha emitters What is the source of reionization?

Evolution of Lyman Absorptions at z=5-6  z = 0.15

Evolution of Gunn-Peterson Optical Depth (1+z) 4.5

Accelerated Evolution at z>5.7 Optical depth evolution accelerated –z<5.7:  ~ (1+z) 4.5 –z>5.7:  ~ (1+z) >11 –> Order of magnitude increase in neutral fraction of the IGM  End of Reionization Dispersion of optical depth also increased –Some line of sight have dark troughs as early as z~5.7 –But detectable flux in ~50% case at z>6 –End of reionization is not uniform, but with large scatter (1+z) 4.5 (1+z) 11 Fan et al. 2006

Ionization State of the IGM G-P optical depth at z~6: –Small neutral fraction needed for complete G-P trough –By itself not indication that the object is beyond the reionization epoch The evolution of G-P optical depth: –Tracking the evolution of UV background and neutral fraction of the IGM (McDonald & Mirada-Escude 2000) –Assuming photoionization:  ~  2 /   : IGM overdensity  : photoionizing rate

Evolution of Ionization State UV Ionizing background: –Assuming photoionization and model of IGM density distribution –UV background declines by close to an order of magnitude from z~5 to 6.2 –Increased dispersion suggests a highly non- uniform UV background at z>5.8 From GP optical depth measurement, volume averaged neutral fraction increase by >~ order of magnitude from z~5.5 to 6.2 XF et al Neutral fraction UV background

Evolution of Proximity Zone Size Around Quasars Size of Proximity Zone region R p ~ (L Q t Q / f HI ) 1/3 Size of quasar proximity zone decreases by a factor of ~2.4 between z=5.8 and 6.4 (Fan et al. 2006) Consistent with neutral fraction increased by a factor of ~15 over this narrow redshift range But see eg Bolton and Haehnelt (2006) for complications in this intepretation Fan et al Haiman, Mesinger, Wyithe, Loeb et al. Proximity zone size (Mpc) redshift z em

Uncertainties in interpretation of proximity zone sizes Bolton & Haehnelt (2006), Maselli et al. (2006) –Observed size of proximity zone much smaller than true HII region size –Neutral fraction <~ a few percent –Consistent with G-P constraints Mesinger et al. (2004), Wyithe et al. (2005) –Neutral fraction ~10-30% Better models and simulated spectra needed… Maselli et al Bolton & Haehelt 2006

Dark Gap Distributions Dark gap statistics (Songaila & Cowie 2002) –Gaps: regions where all pixels have  >2.5 Gaps among z~6 quasars –Average length shows the most dramatic increase at z>5.8  IGM is dominated by long, dark gaps Consistent with overlap at z~6-8? –Dispersions Even at z>6, gap lengths are still finite Upper limit on neutral fraction –If IGM largely neutral, GP damping wing will wipe out all HII region transmissions –Existence of transmission at z>6 places an upper limit of average neutral fraction <30% –Independent upper limit on neutral fraction XF et al. 2006

Iye et al Kashikawa et al Ly  Galaxy LF at z>6 Neutral IGM has extended GP damping wing  attenuates Ly  emission line New Subaru results –Declining density at z~6-7 (2-3  result) –Reionization not completed by z~6.5 –Neutral fraction could be as high as a few tenths but strongly model-dependent –cf. Malhotra & Rhoads, Hu et al.: lack of evolution in Ly  galaxy density

GRBs as Probes of Reionization Detected to z=6.30 Advantages: –Bright –Flat K-correction due to time dilation at high-z –Small surrounding HII regions: could use damping wing of Gunn- Peterson trough to probe high neutral fraction Constraining neutral fraction –How to distinguish internal absorption from IGM damping wing?? –Using : f HI < 0.6 (2-sigma) by fitting both DLA and IGM profiles Damping wing? GRB Kawai et al. 2005

What ionized the Universe: AGNs, Star Formation or Else Exponential decline of quasar density at high redshift, different from normal galaxies Richards et al. 2005, Fan et al SFR of galaxies Density of quasars Bouwens et al.

Reionization by AGNs? Can quasars do it? –No too few quasars Can low-luminosity AGNs ionize the IGM by z~6? –Stacking X-ray image of LBGs in UDF… too few faint AGNs Can accretion to seed BHs ionize the IGM by z~15? –Dijkstra, Haiman & Loeb (2004) –Soft X-ray background overproduced if quasars produce ~10 photons/H atom –‘Preionization’ to f(HI)~50% by X-rays is still allowed (e.g. Ricotti et al.) XF et al Hopkins et al Contributions from AGN Observerd UV background

Reionization by stellar sources? Necessary for reionization 6<z<9 (Stiavelli et al 2003) Large uncertainties in reionization photon budget: –IGM clumpiness –UV radiation and escape efficiency –Large cosmic variance in deep field data –Galaxy luminosity function at high-z Bouwens & Illingworth

Probing Reionization History WMAP

Surveys of quasars at z~7 LBT: LBC-Red i-z-Y selection (1 deg 2 /night) UKIDSS: YJHK photometry

Y-band survey: highest-redshift qusars and coolest brown dwarfs Reionization history: 2 hour on LBT/Lucifer

Summary of IGM Measurements IGM evolution accelerated at z>6 –Neutral fraction increased by order of mag from z=5.5 to z>6 –f HI a few percent; IGM not neutral yet at z~6.5 IGM evolution is not uniform –~order of mag fluctuation in large scale UV background IGM is not mostly neutral at z~6 –Transmission spikes in GP trough z~6 marks the end of overlapping stage of an inhomogeneous reionization