A survey of z ∼ 6 quasars in the sloan digital sky survey deep stripe. II. Discovery of six quasars at z AB>21

Linhua Jiang, Xiaohui Fan, Fuyan Bian, James Annis, Kuenley Chiu, Sebastian Jester, Huan Lin, Roberth Lupton, Gordon T. Richards, Michael A. Strauss, Viktor Malanushenko, Elena Malanushenko, Donald P. Schneider

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156 Scopus citations


We present the discovery of six new quasars at z ∼ 6 selected from the Sloan Digital Sky Survey (SDSS) southern survey, a deep imaging survey obtained by repeatedly scanning a stripe along the celestial equator. The six quasars are about 2 mag fainter than the luminous z 6 quasars found in the SDSS main survey and 1 mag fainter than the quasars reported in Paper I. Four of them comprise a complete flux-limited sample at 21 < z AB < 21.8 over an effective area of 195 deg 2. The other two quasars are fainter than z AB = 22 and are not part of the complete sample. The quasar luminosity function at z 6 is well described as a single power law Φ(L 1450) L β 1450 over the luminosity range -28 < M 1450 < -25. The best-fitting slope β varies from -2.6 to -3.1, depending on the quasar samples used, with a statistical error of 0.3-0.4. About 40% of the quasars discovered in the SDSS southern survey have very narrow Lyα emission lines, which may indicate small black hole masses and high Eddington luminosity ratios, and therefore short black hole growth timescales for these faint quasars at early epochs.

Original languageEnglish (US)
Pages (from-to)305-311
Number of pages7
JournalAstronomical Journal
Issue number1
StatePublished - 2009

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Cosmology: observations
  • Quasars: emission lines
  • Quasars: general


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