Evolution of Quasar Population 0 z 6.3

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Evolution of Quasar Population0 lt z lt 6.3

• Xiaohui Fan
• Institute For Advanced Study

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Introduction

• Evolution of quasars provides
• Constraints on quasar model
• Information on large scale structure
• Picture of UV ionizing background
• Difficulty in studying quasar evolution
• Lack of large, uniform sample
• Complicated selection effect
• Interpreting the data whats the relation
  between quasar and galaxy evolution

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New Era in Quasar Astronomy

• New observations
• Emergence of large, uniform quasar surveys
  including tens of thousands of quasars
• First detection of quasars and galaxies at zgt5
  explosion in the number of quasars at zgt4

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New Era in Quasar Astronomy

• New Observations
• Study of galaxy evolution at zgt2 enables the
  comparison of high-z populations
• Discovery of supermassive BHs in normal galaxies
  relation between galaxy and BH properties
• New Models
• Semi-analytic models that include BH and AGN
  activity in galaxy evolution picture, and the
  realization of the connection between BH activity
  and merger
• New Question
• Characterize quasar evolution with new samples
• Relation between Quasar and Galaxy Evolution

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Outline

• SDSS Quasar Survey
• Evolution of Quasar Luminosity Function
• Comparing to galaxy evolution
• Large Scale Distribution of Quasars
• Clustering and bias of quasars
• Search for the First Quasars
• What do z6 quasars tell us about cosmology
• Multiwavelength Observation of High-z Quasars
• Summary
• Collaboration Anderson, Richards, Schneider,
  Strauss, Vanden Berk All SDSS collaborators

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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, 3000-10000A
• r_lim 23, z_lim 21
• Deep Survey 300 deg2, r_lim 25
• Spectroscopic Survey
• 106 galaxies (rlt17.8)
• 105 quasars ( 0 lt z lt 6)
• Interesting stars, radio/x-ray sources etc.

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Survey Status

• Survey Started Apr 2000
• Currently
• 2000 deg2 imaging
• More than 150,000 spectra
• Early Data Release
• June 2001
• 560 deg2 of imaging and spectroscopy
• Final Data Release 2005 - 2006

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SDSS Filter System

• Five filters cover entire optical wavelength
• u (3560), g(4680), r(6180), i(7490), z(8870)
• u under Balmer jump ? separating quasars and hot
  stars
• z extends beyond 1 micron ? red sources,
  quasars, BDS
• z2.8 quasars and A/F stars have similar color
  in all bands

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SDSS Quasar Selection Pipeline
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SDSS Quasar Survey

• Color Selection of Quasars
• Candidates defined as outliers in SDSS color
  space
• Not strongly biased against red quasars
• Morphological Cut
• Includes extended sources at low-z
• Not biased against AGNs
• Automatic Targeting Optical Counterparts of radio
  (FIRST) and X-ray (RASS) sources

Z3.5
Z4
Z3
Z3.5
Z2
Z4.5
Z5
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SDSS Quasar Survey

• Low-z quasars (zlt3)
• i_lim lt 19.1 ?100,000 quasars
• Efficiency 65 completeness 90
• High-z quasars (zgt3)
• i_lim lt 20.5
• 10000 quasars at z gt 3 500 1000 at z gt 4
• z band allows detection of quasars up to z6.5
• Progress gt 10,000 quasars discovered from early
  SDSS data at 0 lt z lt 6.3

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Evolution of Quasar LF

• Sample
• 4000 quasars from SDSS main sample covering 300
  deg2
• 110 quasars at zgt3.6 covering 500 deg2
  (follow-up spectroscopy done separately)
• 25 quasars at z gt 4.5 covering 1000 deg2
• Correction of Selection Effect
• Selection probability calculated from simulation
  of quasar colors, as function of z, M and SED
  shape
• Sample biased against red quasars (alpha gt 2.5)
• Sample slightly biased against weak EM lines

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Evolution of Quasar LF

• Color Selection Insensitive to certain redshift
  range
• z0.7
• z2.8 stellar locus crosses quasar locus
• z3.5
• z4.6

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Evolution of Quasar LF from SDSS Sample
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Evolution of Quasar LF from SDSS Sample
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Evolution of Quasar Luminosity Density (Madau
Plot for Quasars)
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Evolution of Quasar Luminosity Density as a
Function of Cosmic Age
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Quasar Evolution at High-z
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Shape of Quasar LF at High-z

• LF fit by a single power law in luminosity range
  probed
• At z4 quasar luminosity function much FLATTER
  than LF at z2
• Shape of quasar LF evolves with redshift as well
• Even less UV ionizing photon at high-z from
  quasar than previously calculated?

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Evolution of Quasar LF

• Quasar density peaks at z 2 3 and declines by
  a factor of 20 from 3 to 5.5
• The exponentially decline (10-0.5z) continues
  to zgt5
• Luminous high-z quasar evolves faster than normal
  galaxy population
• Current surveys do not probe the faint end of LF
  at high-z majority of high-z quasars have not
  been observed!
• Little constraint on faint end LF evolution
• Total amount of UV ionization still uncertain

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Clustering of Quasars

• What does quasar clustering tell us?
• Bias factor of quasars ? average DM halo mass
• Combining with quasar density ? quasar lifetime
  
• Density of quasar (obs) / density of halo
  (inferred from halo mass) ? fraction of quasar
  being active
• Difficulty
• Observation quasars are rare ? very
  sparse-sampled
• Theory L(quasar) is a function of mass,
  accretion rate, radiative efficiency, dust. ?
  difficult to compare with models

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Quasar Two-point Correlation Function at zlt2.5
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Quasar Two-point Correlation Function at zlt2.5
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FunctionQuasars vs. Galaxies
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Distribution of z4 Quasars in 500 deg2
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Preliminary Results at High-z
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Evolution of Quasar Clustering
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Evolution of Quasar Clustering

• At zlt2 r_0 7 Mpc/h
• Slow evolution with redshift
• Might be function of luminosity
• At z4
• Quasars strongly clustered (r_0 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 M_solar, and short
  life-time (107-108 years)

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Search for the First Quasars

• Color selection of i-drop out quasars
• SDSS z-filter sensitive to z6.5
• At zgt5.5, quasars have only i-z color
• Major contaminants are L and T type Brown Dwarfs

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Search for the First Quasars

• Separating z6 quasars and BDs
• Using IR photometry
• For quasar z-J 1
• For late-L to T z-J gt 2.5
• SDSS sensitive to z6.5

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SDSS Red Object Survey

• Search for i-drop objects
• ( i-z gt 2)
• Follow-up J and z band photometry
• Eliminate spurious detection
• Separate BD and high-z quasar
• gt 1000 sq. deg surveyed ( z lt 20)
• Four luminous quasars 5.8 lt z lt 6.3
• A dozen T dwarf and large number of L dwarf
• Establishing T dwarf spectral sequence
• Complete sample of BDs ? LF and MF

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Discovery of Two z5.8 Quasars

• Very Luminous (M_B -27.5 -28)
• J0836 radio loud (20cm 1mJy)
• Strong metal lines early metal production

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Limit on Re-ionization Redshift

• Lyman decrement 90
• No Gunn-Peterson Trough Universe highly ionized
  at z6
• Upper limit on Gunn-Peterson optical depth lt 0.4

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Discovery of Quasars at zgt6
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Cosmological Implications?

• M_BH 5 x 109 M_solar
• Assuming Eddington and no lensing
• Density of z5.8 quasars consistent with
  extrapolation from zlt5
• These luminous quasars must be in very massive
  halo and on the tail of mass func at high-z
• Strong constraints on quasar and large scale
  structure models
• Next FIND THE FAINT ONES!

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X-ray Observation of SDSS1044

• An X-ray study of zgt4.8 SDSS quasars with Chandra
  and XMM (P.I. N. Brandt)
• First target SDSS1044 (z5.8)
• 40ks on XMM, 32 counts detected

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X-ray Observation of SDSS1044

• SDSS1044 is X-ray weak
• 10 times weaker than normal z4 quasars with
  similar luminosity
• Indication of heavy absorption in the immediate
  environment
• IR observation shows that it is a CIV BAL quasar

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Sub-mm and Radio Obs of High-z Quasars

• A 250 GHz and 1.4GHz survey of 41 quasars at
  zgt3.6 (w/ Carilli, Rupen)
• 16/41 detected in 250GHz (rest-frame sub-mm)
  brighter than 1mJy
• Combination of cm and submm ? submm radiation
  from thermal dust with mass 108 M_solar
• Dust heating can be from AGN or from starburst ?
  star forming rate of 500 2000 M_solar/year
• Future FIR-submm observations could reveal the
  relation between quasar and starburst

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Color Space Outliers Others Than Normal Quasars

• Brown Dwarfs
• L dwarf (Teff 1400 2000K)
• T dwarf (Teff 800 1400 K), methane dominated
  IR spectrum, smallest free-floating object
• Compact Field EA and Emission Line Galaxy
• Weird BAL Quasars
• Cool White Dwarfs
• Subdwarfs
• Carbon Stars
• Mystery Objects New Class of Objects??

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Summary

• SDSS quasar survey
• 100,000 quasars at 0 lt z lt 6.5 in five years
• Currently, 10, 000 quasars, including 200 at zgt4
• Quasar Density Evolution
• Strong redshift evolution, different from galaxy
• Exponential decline at zgt3, until at least z6
• Quasars are strongly clustered
• High-z quasars in massive halos and are short
  lived
• Observations of z6 quasars
• Early metal production
• IGM highly ionized at z6

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Whats Next?

• Evolution of faint quasars
• High-z shape of LF nature of ionizing
  background
• Low-z AGN/galaxy connection
• Evolution of different types of quasars radio,
  X-ray, BAL, narrow-line etc.
• Evolution of quasar clustering
• Clustering at different luminosity, subclass ?
  relation to host galaxy mass
• High-order statistics, power spectrum at high-z
  from quasars
• Complete sample at zgt6
• SED of high-z quasars role of dust and absorption