Quasar Clustering: Evidence for an Increase with Redshift and Implications for the Nature of Active Galactic Nuclei

The evolution of quasar clustering is investigated with a new sample of 388quasars with 0.30.0 are excluded at a 0.3% probability level,to be compared with epsilon=0.8 found for galaxies. The observed clusteringproperties appear qualitatively consistent with a scenario of Omega=1 CDM inwhich a) the difference between the quasar and the galaxy clustering can beexplained as a difference in the effective bias and redshift distributions, andb) the quasars, with a lifetime of t~10^8 yr, sparsely sample halos of massgreater than M_min~10^12-10^13 h^-1 M_sun. We discuss also the possibility thatthe observed change in the quasar clustering is due to an increase in thefraction of early-type galaxies as quasar hosts at high z.Comment: 8 pages including 2 eps figures, LaTeX (AAS v4.0), ApJ in pres