A survey of z > 5.7 quasars in the sloan digital sky survey. III. Discovery of five additional quasars

Xiaohui Fan, Joseph F. Hennawi, Gordon T. Richards, Michael A. Strauss, Donald P. Schneider, Jennifer L. Donley, Jason E. Young, James Annis, Huan Lin, Hubert Lampeitl, Robert H. Lupton, James E. Gunn, Gillan R. Knapp, W. N. Brandt, Scott Anderson, Neta A. Bahcall, Jon Brinkmann, Robert J. Brunner, Masataka Fukugita, Alexander S. SzalayGyula P. Szokoly, Donald G. York

Research output: Contribution to journalReview articlepeer-review

280 Scopus citations


We present the discovery of five new quasars at z > 5.7, selected from the multicolor imaging data of the Sloan Digital Sky Survey (SDSS). Three of them, at redshifts 5.93, 6.07, and 6.22, were selected from ∼1700 deg 2 of new SDSS Main Survey imaging in the northern Galactic cap. An additional quasar, at redshift 5.85, was discovered by co-adding the data obtained in the Fall Equatorial Stripe in the SDSS Southern Survey Region. The fifth object, at redshift 5.80, is selected from a nonstandard SDSS scan in the southern Galactic cap outside the Main Survey area. The spectrum of SDSS J162331.81+311200.5 (z = 6.22) shows a complete Gunn-Peterson trough at z abs > 5.95, similar to the troughs detected in the other three z ≳ 6.2 quasars known. We present a composite spectrum of the z > 5.7 quasars discovered in the SDSS to date. The average emission-line and continuum properties of z ∼ 6 quasars exhibit no significant evolution compared with those at low redshift. Using a complete sample of nine z > 5.7 quasars, we find that the density of quasars with M 1450 < -26.7 at z ∼ 6 is (6 ± 2) × 10 -10 Mpc -3 (H 0 = 65 km s -1 Mpc -1, Ω = 0.35, and Γ = 0.65), consistent with our previous estimates. The luminosity distribution of the sample is fitted with a power-law luminosity function ψ(L) ∝ L -3.2±0.7, somewhat steeper than but consistent with our previous estimates.

Original languageEnglish (US)
Pages (from-to)515-522
Number of pages8
JournalAstronomical Journal
Issue number2 1784
StatePublished - Aug 2004


  • Emission lines
  • Quasars
  • Quasars: absorption lines
  • Quasars: general

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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