Clustering Analyses of 300,000 Photometrically Classified Quasars. I. Luminosity and Redshift Evolution in Quasar Bias
Abstract
Using ~300,000 photometrically classified quasars, by far the largest quasar sample ever used for such analyses, we study the redshift and luminosity evolution of quasar clustering on scales of ~50 h-1 kpc to ~20 h-1 Mpc from redshifts of z¯~0.75-2.28. We parameterize our clustering amplitudes using realistic dark matter models and find that a ΛCDM power spectrum provides a superb fit to our data with a redshift-averaged quasar bias of bz¯=1.40Q=2.41+/-0.08 (P<χ2=0.847) for σ8=0.9. This represents a better fit than the best-fit power-law model [ω=(0.0493+/-0.0064)θ-0.928+/-0.055 P<χ2=0.482]. We find bQ increases with redshift. This evolution is significant at >99.6% using our data set alone, increasing to >99.9999% if stellar contamination is not explicitly parameterized. We measure the quasar classification efficiency across our full sample as a=95.6+/-4.41.9%, a star-quasar separation comparable to the star-galaxy separation in many photometric studies of galaxy clustering. We derive the mean mass of the dark matter halos hosting quasars as MDMH=(5.2+/-0.6)×1012 h-1 Msolar. At z¯~1.9 we find a 1.5 σ deviation from luminosity-independent quasar clustering; this suggests that increasing our sample size by a factor of ~1.8 could begin to constrain any luminosity dependence in quasar bias at z~2. Our results agree with recent studies of quasar environments at z<0.4, which detected little luminosity dependence to quasar clustering on proper scales >~50 h-1 kpc. At z<1.6, our analysis suggests that bQ is constant with luminosity to within ΔbQ~0.6, and that, for g<21, angular quasar autocorrelation measurements are unlikely to have sufficient statistical power at z<~1.6 to detect any luminosity dependence in quasars' clustering.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2007
- DOI:
- 10.1086/511519
- arXiv:
- arXiv:astro-ph/0612190
- Bibcode:
- 2007ApJ...658...85M
- Keywords:
-
- Cosmology: Observations;
- Cosmology: Large-Scale Structure of Universe;
- Galaxies: Quasars: General;
- Surveys;
- Astrophysics
- E-Print:
- 13 pages, 9 figures, 2 tables