THE ORIGIN OF QUASAR CORRELATIONS

We suggest that the origin of the observed quasar correlation function, which is intermediate in strength between that of galaxies and of rich clusters, is the preferential location of quasars in small groups of galaxies. The quasars then trace the same large-scale structure of the parent galaxy groups. According to this picture, optically selected quasars are located in small groups of approximately 10L* galaxies on average, and have the same correlations as expected for the small groups. Radio-selected quasars are, according to the same picture, located in richer groups of approximately 30L* galaxies on average, having the stronger correlations expected for these richer groups. These results are consistent with observations of quasar environment and with the universal richness-dependent cluster correlation function. The results also imply that groups and clusters of galaxies, as well as the large-scale structure they trace, exist at the high redshifts observed in quasar correlations.