The discovery of a high-redshift quasar without emission lines from Sloan Digital Sky Survey commissioning data

Xiaohui Fan, Michael A. Strauss, James E. Gunn, Robert H. Lupton, C. L. Carilli, M. P. Rupen, Gary D. Schmidt, Leonidas A. Moustakas, Marc Davis, James Annis, Neta A. Bahcall, J. Brinkmann, Robert J. Brunner, István Csabai, Mamoru Doi, Masataka Fukugita, Timothy M. Heckman, G. S. Hennessy, Robert B. Hindsley, Željko IvezićG. R. Knapp, D. Q. Lamb, Jeffrey A. Munn, A. George Pauls, Jeffrey R. Pier, Constance M. Rockosi, Donald P. Schneider, Alexander S. Szalay, Douglas L. Tucker, Donald G. York

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


We report observations of a luminous unresolved object at redshift z = 4.62, with a featureless optical spectrum redward of the Lyα forest region, discovered from Sloan Digital Sky Survey commissioning data. The redshift is determined by the onset of the Lyα forest at λ ∼ 6800 Å and a Lyman limit system at λ = 5120 Å. A strong Lya absorption system with weak metal absorption lines at z = 4.58 is also identified in the spectrum. The object has a continuum absolute magnitude of -26.6 at 1450 Å in the rest frame (h0 = 0.5, q0 = 0.5) and therefore cannot be an ordinary galaxy. It shows no radio emission (the 3 σ upper limit of its flux at 6 cm is 60 μJy), indicating a radio-to-optical flux ratio at least as small as that of the radio-weakest BL Lacertae objects known. It is also not linearly polarized to a 3 σ upper limit of 4% in the observed I band. Therefore, it is either the most distant BL Lac object known to date, with very weak radio emission, or a new type of unbeamed quasar, whose broad emission line region is very weak or absent.

Original languageEnglish (US)
Pages (from-to)L57-L60
JournalAstrophysical Journal
Issue number2 PART 2
StatePublished - Dec 1 1999

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Quasars: individual (SDSS 1533-00)
  • Radio continuum: galaxies
  • X-rays: galaxies


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