Evolution of the Highest Redshift Quasars

Xiaohui FanUniversity of Arizona

Collaborators: Becker, Bertoldi, Carilli, Cox,Diamond-Stanic, Hennawi, Ivezic, Jiang, Kelly,Richards, Schneider, Strauss, Vestergaard, Walter,Wang, White, SDSS collaboration

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-Msun 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?

• Study of quasar evolution needs:– Large survey to increase sample size– Deep survey to break redshift/luminosity degeneracy– Multiwavelength study to probe different scales of

AGN structure

Outline

• Update on high-redshift quasar searches• 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?

• Summary

The Highest Redshift Quasars Today• z>4: >1000 known • z>5: >60• z>6: 13 (12 SDSS

discoveries)• SDSS i-dropout Survey:

– Current Status:• >7000 deg2

• 23 luminous quasars at 5.7<z<6.4

– By this June:• Completion of a color-

selected flux-limited sample of luminous high-z quasars in the entire SDSS high-latitude area (~8000 deg2 )

The Highest Redshift Quasars Today

• 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.– SDSS2 : faint quasars in the deep SDSS

stripe (Jiang, XF et al.), ~10 - 30 additional z~6 quasars in next three years (three z~6 quasar in pilot obs)

46,420 Quasars from the SDSS Data Release Three

wavelength4000 A 9000 A

reds

hift

0

1

2

3

5

Lyα

CIV

CIIIMgII

HαOIII

FeII

FeII

Lyα 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– 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 ofsupermassive BHs?

Fan et al. 2004

Simulating z~6 Quasars• The largest halo in Millennium

simulation (500 Mpc cube) at z=6.2– Virial mass 5x1012 M_sun– Stellar mass 5x1010 M_sun– Resembles properties of SDSS quasars– Such 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– Low radiative efficiency or massive

seed BH– Little or no feedback to stop

BH/galaxy growth

z=6.2

z=0

Dark matter galaxy

Springel et al. 2005

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

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– Status after Year One:

• Large number of z>3 quasar to probe LF evolution• Three z~6 quasar to demonstrate target selection

McLure et al. SDSS DR 1

Fan et al. >1000 quasars at z>3

CIVUpper 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 3 - 5 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 Hβ MgII and CIV for different redshift ranges

• BH mass at high-z:– 109-10 Msun existed at z~6– Upper envelop of BH mass at several 1010

Msun? Negative feedback?

BH mass distribution

Mass LBOL LBOL/LEdd

SDSS: DR3 Vestergaard, XF et al. in prep.

Evolution of Eddington Ratio

• Luminous quasars at all redshifts haveLbol/Ledd ~0.01 - 1

• Luminosity dependence (expected)– Lbol/Ledd ~ 1 at several L*

• Redshift dependence:– At constant luminosity: Lbol/Ledd

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.

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?• Does this lack of evolution in rest-frame UV also apply to other

wavelength?

Barth et al. 2003Nagao et al. 2006

Quasar spectral energy distribution

Spitzer

Dust torus

Cool Dust in host galaxy

hot dustBLR

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– X-ray - optical flux ratio?– A population of lineless high-

z 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

J0005

8.0μm 24μm5.6μm4.8μm3.5μm

Hos

t dus

t con

tribu

tion

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…

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 ~ L0.5

• 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(

radi

o-lo

udfra

ctio

n)

X-ray properties: evolution?• Studies of αoxas function of luminosity

and redshift:– Strong degeneracy of L and z– mild evolution at high-z?

• High-z quasars are X-ray bright? (Kelly et al.)

• No strong evolution? (Steffen et al.)– Faint high-z quasars!

Redshift dependenceLum

inis

ty d

epen

denc

e

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. 2006

Ly α distribution

Diamond-Stanic et al. 2006

LinelessQuasars:EW(Lyα)<10

Log EW (Ly α)

Probing the Host Galaxy Assembly

Spitzer

ALMA

Dust torus

Cool Dust in host galaxy

Sub-mm and Radio Observationof 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 dustwith mass ~ 108 Msun

• Among z~6 quasars: 5(+2)/19 detected insubmm

• If dust heating came from starburst star formation rate of

500 – 2000 Msun/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: 7x108 Msun

• Strong CO source (multiple transitions)– Tkin ~ 100K– Gas mass: 2x1010 Msun

– nH2 ~ 105

• Gas/dust, Temp, density typical of local SB

Bertoldi et al.

[CII] detection of z=6.42 quasar

Mailino et al. 2005

• [CII] 158μm line:– Brightest ISM line– Direct probe of SF region

• J1148 (z=6.42)– Both [CII] and LFIR consistent

with the brightest local ULIRGs– SFR~ 103 Msum

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: ~ 1010 M_sun– Total bulge mass ~ 1011 M_sun < M-sigma prediction

• BH formed beforecomplete galaxy assembly?

Walter et al. 2004

1 kpc

VLA CO 3—2 map

60 km/s

Channel Maps

M-σ relation at high-z• Host mass from CO

– 15 CO detections at z>2– Line width all ~200 - 300 km/s– Taking at face value:

• Strong evolution of M-σ → 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 degeneracy2. Better models/observations in dust/gas

1148+52 z=6.42: Dust and Gas detection

Off channelsRms=60uJy

46.6149 GHzCO 3-2

• Dust formation: 1.4e9yr (AGB winds) > t_univ (8.7e8yr) => dust formed in high mass stars? => silicate grains?

• C, O production (3e7 M_sun): few e8 yr => Star formation started early (z = 10)?

L_FIR = 1.2e13 L_sun, M_dust =7e8M_sunM(H_2) = 2e10 M_sun

S_250 = 5.0 +/- 0.6 mJy

•M(dust) = 7e8 M_sun

•M(H_2) = 2e10 M_sun

•M_dyn (r=2.5kpc) = 5e10 M_sun

•M_BH = 3e9 M_sun => M_bulge = 1.5e12 M_sun

• Gas/dust = 30, typical of starburst

• Dynamical vs. gas mass => baryon dominated?

• Dynamical vs. ‘bulge’ mass => M – σ breaks-down at high z? [SMBH forms first?]

1148+52: Masses

1148+5251: radio-FIR SED

Star forming galaxy characteristics: radio-FIR SED, Gas/Dust, CO excitation and T_B => Coeval starburst/AGN? SFR = 1e3 M_sun/yr

Stellar spheroid formation in few e7 yrs = e-folding time for SMBH

=> Coeval formation of galaxy/SMBH at z = 6.4 ?

S_1.4= 55 +/- 12 uJy1048+46

Beelen et al.

T_D = 50 K

VLA imaging of CO3-2 at 0.4” and 0.15” resolution

Separation = 0.3” = 1.7 kpc

T_B = 20K Typical of starburst nuclei

Merging galaxies?

rms=50uJy at 47GHz

CO extended to NW by 1”(=5.5 kpc) tidal(?) feature

IRAM Plateau de Bure

• FWHM = 305 km/s• z = 6.419 +/- 0.001

ν2

(3-2)

(7-6)

(6-5)

• Tkin=100K, nH2=105cm-3

Typical of starburst nuclei (eg. NGC253, Arp220)

PSS J2322+1944 (z=4.12)

• CO Einstein ring– Modeled by star-

forming 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

PSS J2322+1944 (z=4.12)

• CO Einstein ring– Modeled by star-

forming 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