[e-mail]

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• ???
• (????????)
• wuxb_at_bac.pku.edu.cn

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Content

• Introduction quasars in large sky surveys
• Photometric redshifts of quasars in SDSS
• How to find high-z quasars
• Discussion BATC LAMOST...

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1. Introduction

• ???(quasars)

• Originally discovered in radio survey (3C) in
  1950s first identified as star-like optical
  sources with emission lines in 1963 Maarten
  Schmidt (1963) realized the redshift of 3C 273
  (z0.158)
• First named simply as quasi-stellar radio
  sources, shorten to quasars by H.-Y. Chiu(???)
  (1964), accepted by ApJ in 1970
• More than 100,000 discovered the largest
  redshift is 6.4 (Fan(???), et al. 2003)

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????????????????? 1963?Maarten Schmidt????????????
?H??????????
Maarten Schmidt
???3C 273????????0.16
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Examples of quasars discovered with the largest
optical telescope (2.16m) in China (Wu, Bade
Beckmann 1999, AA, 347, 63)
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Spectra of three most distant quasars (Fan et al.
2003)
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• Large Optical Sky Quasar Surveys
• Palomar-Green (PG) Bright Quasar Survey (BQS)
  Blt16, 10000 deg2, 120 Quasars (7)
• Large Bright Quasar Survey (LBQS) Blt17.5, 103
  quasars
• 2dF 200 deg2, U-Vlt-0.3, 2.6 104 quasars
• Sloan Digital Sky Survey(SDSS) eventual 10000
  deg2, ugriz selection, 105 quasars
• Data Release 5 (2006) Spectroscopic area 5740
  deg2.
• 79,394 Quasars (redshift lt2.3)
• 11,217 Quasars (redshift gt2.3)

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Understanding the distribution and evolution of
quasars
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The first quasar and the cosmic reionization
Detection of A Complete Gunn-Peterson Trough
VLT observation
High-redshift quasars probe the end of
reionization epoch
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Physics Model for the Central Engine of Quasars

• Supermassive black hole
• Accretion disk
• Broad line region
• Dusty torus
• Narrow line region
• Jet

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2. Photometric redshifts of quasars in SDSS

• Sloan Digital Sky Survey I
• Photometry 3 x 108 objects
• Limiting magnitudes at the detection limit, S/N
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• Spectroscopy gt106 objects (106 galaxies 105
  quasars)
• Galaxies r lt17.77 Quasars i lt19.1
• Only photometric redshifts for fainter objects

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Spectroscopy The best way to determine the
redshift of quasars, though not always possible,
esp. for fainter quasars
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Photometric Systems of SDSS
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SDSS composite quasar spectrum (EDR 2200 quasars)
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Predicted magnitude and color of quasars

• Quasar spectrum f(?), SDSS transmission
  efficiency s(?) (u,g,r,i,z)

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Comparison with the data of 18678 quasars in SDSS
DR1
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Photometric redshift determinations

• Chi2 minimization
• Using 4 colors for zlt3.6 and 3 colors for zgt3.6
  (Ly? moves out of u band)

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Comparison of photo-z with spectroscopic-z for
18678 SDSS DR1 quasars
68 with ?zlt0.2
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Examples of wrong photometric redshifts
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Improvements on photo-z

• More composite quasar spectra
• Red quasars, BAL quasars, radio-loud/quiet
• More photometric data in other bands
• UV(GALEX), near-IR(JHK),
• VO application

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3. How to find high-z quasars

• Separate quasars from stars
• Using quasar colors to select hi-z quasar
  candidates
• Spectroscopic identifications, usually with huge
  ground-based telescopes

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Location difference of quasars stars in
color-color diagram
quasars
stars
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Predicted colors of quasars, galaxies and stars
in SDSS system, Wu, Zhang Zhou (2004)
Quasars with zgt3.5
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4. Discussion

• BATC Beijing-Arizona-Taipei-Connecticut Survey
• 60/90 Schmidt telescope
• 15 intermediate-band filters covering 3200-10000A
• FOV 1 degree limiting magnitude V21
• Surveyed area gt100 degree2

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BATC filter systems
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Theoretical color-z relations of quasars in BATC
system Wu, Zhang Zhou (2004)
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Theoretical colors of quasars and stars in BATC
system, Wu, Zhang Zhou (2004)
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Theoretical colors of quasars, galaxies and stars
in BATC system, Wu, Zhang Zhou (2004)
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Selection criteria for quasar candidates with
zgt3.5 (for BATC)
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Possible applications to LAMOST?