Highredshift Quasars in the SDSS

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High-redshift Quasars in the SDSS

• Xiaohui Fan
• Institute For Advanced Study

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High-redshift Quasar Projects

• I-dropout (zgt5.7) quasar survey
• APO 3.5m, Calar Alto, UKIRT, HET, Keck
• Fan, Strauss, Schneider, Becket, White, Knapp
• High-z luminosity function and clustering of SDSS
  main sample
• Strauss, Fan, Schneider, Stoughton, Richards
• Faint high-z quasars
• 2dF, HET, Megallan
• Chiu, Zheng, Fan, Schneider, Richards, Strauss
• X-ray follow-up
• Brandt, Vignali, Schneider, Fan, Strauss

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Numbers, Numbers.

• Zgt4 300 from SDSS
• Zgt5 19 from SDSS (12 from main sample)
• Zgt6 4 (3 new this year)
  

Total Discoveries
SDSS Discoveries
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Color-color Diagram of High-Redshift Quasars
from the Main Quasar Sample
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Evolution of Quasar Luminosity Function
SFR of Normal Gal
Exponential decline of quasar density at
high redshift, different from normal galaxies


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Evolution of Quasar Luminosity Function
SFR of Normal Gal
Exponential decline of quasar density at
high redshift, different from normal galaxies


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Clustering of Quasars

• What does quasar clustering tell us?
• Bias factor of quasars ? average DM halo mass
• A biased large scale power spectrum at high-z
• Combining with quasar density ? quasar lifetime
• Quasar clustering ? halo mass ? density of quasar
  halos
• Density of observed (active) quasars / density of
  quasar halos ? fraction of quasar being active,
  quasar duty cycle or lifetime

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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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Distribution of z4 Quasars in 500 deg2
Fan et al. in preparation
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Evolution of Quasar Clustering
Fan et al. in preparation
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Evolution of Quasar Clustering

• At zlt2 r0 7 Mpc/h
• Comparable to current day galaxies
• Slow evolution with redshift
• At z4
• Quasars strongly clustered (r0 20 Mpc/h)
• Stronger than the clustering of low-z quasars or
  high-z LBGs
• Luminous high-z quasars are in massive system and
  represent very rare peaks of the density field
• Quasar correlation consistent with a quasar halo
  mass of 1012 1013 Msun, and a short life-time
  of 107-8 years.

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Search for the First Quasars
Fan, Narayanan, Lupton, Strauss et al.

• Color selection of i-drop out quasars
• At zgt5.5, Lya enters z-band ? quasars have only
  red i-z measurement faint objects z-band
  only detections
• Technical Challenges
• Rare objects ? contaminant elimination
• Elimination of false z-band only detections ?
  improved cosmic ray rejection in PHOTO v.5.3
  (MAYBE_CR)
• Reliability of faint z photometry ? follow-up
  high S/N z photometry
• Major contaminants are L and T type Brown Dwarfs
  ? additional IR photometry

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Search for the First Quasars
Fan, Narayanan, Lutpon, Strauss et al.

• Separating z6 quasars and BDs
• Follow-up IR photometry
• For quasar z-J 1
• For late-L to T
• z-J gt 2

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SDSS Red Object Survey

• Survey area 3000 deg2 zABlt20 search for both
  brown dwarfs and high-z quasars
• Large number of L dwarfs and 20 T dwarfs
  discovered
• Establish L/T spectral and temperature sequence
• Complete sample of brown dwarfs LF and mass
  density
• Seven luminous quasars at zgt5.7
• Discovered at APO 3.5m
• High S/N, high resolution spectroscopy at
  Keck/VLT/HET
• Three new objects this season z6.05, 6.20 and
  6.40 (new redshift record for quasars)

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new

new
new
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Metals at z6.3

• Strong metal lines detected ? strength comparable
  to low-redshift quasars
• NV/CIV ratio metallicity
• NV/CIV 0.7 ? Supersolar metallicity for z6.28
  quasar (t0.8Gyr) ?
• Early production of heavy element and
  multi-generation of stat formation

Keck ESI/NIRSPEC
Keck ESI/ NIRSPEC
Fan, Narayanan, Lupton, Strauss et al.
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Quasar Density at z6

• Based on seven zgt5.7 quasars
• Density declines by a factor of 20 from z3
• Number density implies that quasars are unlikely
  to provide enough UV background if LF is similar
  to that at low-z
• Cosmological implication
• MBH109-10 Msun
• Mhalo 1013 Msun
• How to produce such massive BH in less than
  1Gyr??
• They are the highest peak of density field and on
  the tail of mass function, might provide
  sensitive test to structure formation and BH
  evolution
• Need to Find Faint Ones

Fan et al. 2001
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reionization
From Avi Loeb
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Increasing Lya absorption with redshift
zabs fobs/fcon -------------------------
-- 5.5 0.10 5.7
0.05 6.0 lt0.002 Zero flux over
300Å immediately blueward of Lya emission
in z6.28 quasar ? Detection of complete
Gunn-Peterson Trough tgtgt1 over large
region of IGM
Ly ßOVI
Becker, Fan, White et al.
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The Highest redshift quasar SDSS 11485150 at
z6.40
Z4.95 intervening system ????
- G-P Trough
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VLT/FOS2
Detection of A Complete Gunn-Peterson Trough
VLT observation
T-0.0010.003
Pentericci et al.
Pentericci, Fan, Rix et al. 2001
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Keck/ESI spectrum
G-P Trough
G-P Trough

• No flux in 300 Å region
• Flux decrement gt 300
• (Keck VLT)
• G-P troughs for Lyß, ?
• Have we reached the
• reionization epoch ???

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Implications of Complete Gunn-Peterson Trough

• G-P optical depth at z6
• Small neutral fraction needed for complete G-P
  trough
• By itself not indication that the object is
  beyond the reionization epoch
• For uniform IGM
• Optical depth increases with redshift even with
  const. ionizing background
• Measurement of optical depth can be used to
  constrain ionizing background

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Three stages
Pre-overlap
Overlap
Post-overlap
From Haiman Loeb
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Mass-averaged
postoverlap
Reionization epoch
Pre- overlap
Volume-averaged
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Mass-averaged
postoverlap
Reionization epoch
Pre- overlap
Volume-averageed
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X-ray Observation of the Highest-redshift
Quasars

• First exploration of X-ray universe at zgt5
• 16 SDSS quasars observed with Chandra/XMM
  (5-10ks, Brandt et al.)
• 12 detected (zgt4.5)
  
  
• 8 SDSS objects detected at zgt5 (out of nine
  total in literature)
• main conclusion opt/X flux ratio weakly
  dependent on redshift

Tentative evidence that
quasars at zgt4 X-ray fainter than at z2
? Presence of large amount of gas??
Average slope at z2
Average slope at z4.6
Average slope at z4.5

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Next Faint Quasars at zgt4

• Goal evolution of faint quasars at high-z
• Data Southern Survey images
• Facilities
• Southern survey plates
• 2dF/SDSS
• HET
• New multiobject spectrographs on 6-10m telescopes
• First results from 2dF/SDSS (Glazebrook, Zheng,
  Chiu et al.)