Quasar clustering from SDSS DR5: Dependences on physical properties

Yue Shen, Michael A. Strauss, Nicholas P. Ross, Patrick B. Hall, Yen Ting Lin, Gordon T. Richards, Donald P. Schneider, David H. Weinberg, Andrew J. Connolly, Xiaohui Fan, Joseph F. Hennawi, Francesco Shankar, Daniel E. Vanden Berk, Neta A. Bahcall, Robert J. Brunner

Research output: Contribution to journalArticlepeer-review

190 Scopus citations


Using a homogenous sample of 38,208 quasars with a sky coverage of 4000 deg2 drawn from the Sloan Digital Sky Survey Data Release Five quasar catalog, we study the dependence of quasar clustering on luminosity, virial black hole (BH) mass, quasar color, and radio loudness. At z < 2.5, quasar clustering depends weakly on luminosity and virial BH mass, with typical uncertainty levels 10% for the measured correlation lengths. These weak dependences are consistent with models in which substantial scatter between quasar luminosity, virial BH mass, and the host dark matter halo mass has diluted any clustering difference, where halo mass is assumed to be the relevant quantity that best correlates with clustering strength. However, the most luminous and most massive quasars are more strongly clustered (at the 2σ level) than the remainder of the sample, which we attribute to the rapid increase of the bias factor at the high-mass end of host halos. We do not observe a strong dependence of clustering strength on quasar colors within our sample. On the other hand, radio-loud quasars are more strongly clustered than are radio-quiet quasars matched in redshift and optical luminosity (or virial BH mass), consistent with local observations of radio galaxies and radio-loud type 2 active galactic nuclei. Thus, radio-loud quasars reside in more massive and denser environments in the biased halo clustering picture. Using the Sheth etal. (2001) formula for the linear halo bias, the estimated host halo mass for radio-loud quasars is 1013 h -1 M , compared to 2 × 1012 h -1 M for radio-quiet quasar hosts at z 1.5.

Original languageEnglish (US)
Pages (from-to)1656-1673
Number of pages18
JournalAstrophysical Journal
Issue number2
StatePublished - 2009

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Black hole physics
  • Cosmology: observations
  • Galaxies: active
  • Large-scale structure of universe
  • Quasars: general
  • Surveys


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