A survey of z > 5.7 quasars in the Sloan Digital Sky Survey. II - Discovery of three additional quasars at z > 6

Xiaohui Fan, Michael A. Strauss, Donald P. Schneider, Robert H. Becker, Richard L. White, Zolt́an Haiman, Michael Gregg, Laura Pentericci, Eva K. Grebel, Vijay K. Narayanan, Yeong Shang Loh, Gordon T. Richards, James E. Gunn, Robert H. Lupton, Gillian R. Knapp, Željko Ivezić, W. N. Brandt, Matthew Collinge, Lei Hao, Daniel HarbeckFrancisco Prada, Joop Schaye, Iskra Strateva, Nadia Zakamska, Scott Anderson, Jon Brinkmann, Neta A. Bahcall, Don Q. Lamb, Sadanori Okamura, Alex Szalay, Donald G. York

Research output: Contribution to journalReview articlepeer-review


We present the discovery of three new quasars at z > 6 in ∼ 1300 deg2 of Sloan Digital Sky Survey imaging data, J114816.64+525150.3 (z = 6.43), J104845.05+463718.3 (z = 6.23), and J163033.90+401209.6 (z = 6.05). The first two objects have weak Lyα emission lines; their redshifts are determined from the positions of the Lyman break. They are only accurate to ∼0.05 and could be affected by the presence of broad absorption line systems. The last object has a Lyα strength more typical of lower redshift quasars. Based on a sample of six quasars at z > 5.7 that cover 2870 deg2 presented in this paper and in Paper I, we estimate the comoving density of luminous quasars at z ∼ 6 and M1450 < -26.8 to be (8 ± 3) × 10-10 Mpc-3 (for H 0 = 50 km s-1 Mpc-1, Ω = 1). Hubble Space Telescope imaging of two z > 5.7 quasars and high-resolution, ground-based images (seeing ∼0″.4) of three additional z > 5.7 quasars show that none of them is gravitationally lensed. The luminosity distribution of the high-redshift quasar sample suggests the bright-end slope of the quasar luminosity function at z ∼ 6 is shallower than ψ ∝ L-3.5 (2 σ), consistent with the absence of strongly lensed objects.

Original languageEnglish (US)
Pages (from-to)1649-1659
Number of pages11
JournalAstronomical Journal
Issue number4 1768
StatePublished - Apr 2003


  • Gravitational lensing
  • Quasars: absorption lines
  • Quasars: emission lines quasars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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