Clustering of low-redshift (z ≤ 2.2) quasars from the sloan digital sky survey

Nicholas P. Ross, Yue Shen, Michael Strauss, Daniel E. Vanden Berk, Andrew J. Connolly, Gordon T. Richards, Donald P. Schneider, David H. Weinberg, Patrick B. Hall, Neta A. Bahcall, Robert J. Brunner

Research output: Contribution to journalConference articlepeer-review


We present measurements of the Quasar Two-Point Correlation Function, ΞQ, over the redshift range 0.3 ≤ z ≤ 2.2 based upon a homogeneous sample of 38,208 quasars with spectroscopic redshifts from the Data Release 5 Quasar Catalogue. Over this redshift range, we find that the redshift-space correlation function, Ξ(s), is well-fit by a single power-law, with s0 = 5.95 ±0.45 h-1 Mpc and γs = 1.16-0.16+0.11 when fit over 1.0 ≤ s ≤ 25.0 h-1 Mpc. Dividing the sample into redshift slices, we find no evidence for evolution of quasar clustering, with the correlation length staying roughly constant at s0 ∼ 6 - 7 h-1 Mpc at z ≲ 2.2. Comparing our clustering measurements to those reported for X-ray selected AGN at z ∼ 0.5 -1, we find reasonable agreement in some cases but significantly lower correlation lengths in others. Assuming a standard ACDM cosmology, we find the linear bias evolves from b ∼ 1.4 at z = 0.5 to b ∼ 3 at z = 2.2, with b(z = 1.27) = 2.06 ± 0.03 for the full sample. We compare our data to analytical models and infer that quasars inhabit dark matter haloes of constant mass Mhalo ∼ 1 -2×10 12h-1M from redshifts z ∼ 2.5 (the peak of quasar activity) to z ∼ 0. The measured evolution of the clustering amplitude is in reasonable agreement with recent theoretical models, although measurements to fainter limits will be needed to distinguish different scenarios for quasar feeding and black hole growth.

Original languageEnglish (US)
Pages (from-to)186-190
Number of pages5
JournalAIP Conference Proceedings
StatePublished - 2008
EventClassification and Discovery in Large Astronomical Surveys - Ringberg Castle, Germany
Duration: Oct 14 2008Oct 17 2008


  • Clustering
  • Cosmology: Observations
  • Large-scale structure of universe, general
  • Quasars: General
  • Surveys

ASJC Scopus subject areas

  • General Physics and Astronomy


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