The DEEP2 Galaxy Redshift Survey: Clustering of Quasars and Galaxies at<i>z</i>= 1
Abstract
We present the clustering of Deep Extragalactic Evolutionary Probe 2 (DEEP2) galaxies at 0.7 < z < 1.4 around quasars identified using both the Sloan Digital Sky Survey (SDSS) and DEEP2 surveys. We measure the two-point cross-correlation of a sample of 36 optically selected, spectroscopically identified quasars from the SDSS and 16 more found in the DEEP2 survey with the full DEEP2 galaxy sample over scales 0.1 h-1 Mpc < rp < 10 h-1 Mpc. The clustering amplitude is found to be similar to the autocorrelation function of DEEP2 galaxies, with a relative bias of b = 0.89 ± 0.24 between quasars and DEEP2 galaxies at z ~ 1. No significant dependence is found on scale, quasar luminosity, or redshift over the ranges we probe here. The clustering amplitude errors are comparable to those from significantly larger quasar samples, such as the 2dF (Two Degree Field) QSO Redshift Survey. This results from the statistical power of cross-correlation techniques, which exploit the fact that galaxies are much more numerous than quasars. We also measure the local environments of quasars using the third-nearest-neighbor surface density of surrounding DEEP2 galaxies. Quasars are found in regions of similar mean overdensity to blue DEEP2 galaxies; they differ in environment from the red DEEP2 galaxy population at 2 σ significance. Our results imply that quasars do not reside in particularly massive dark matter halos at these redshifts, with a mean dark matter halo mass of M200 ~ 3 × 1012 M☉ in a concordance ΛCDM cosmology.