Galaxy Clustering around Nearby Luminous Quasars

Abstract

We examine the clustering of galaxies around a sample of 20 luminous low redshift ( z <~ 0.30) quasars observed with the Wide Field Camera-2 on the Hubble Space Telescope (HST). The HST resolution makes possible galaxy identification brighter than V = 24.5 and as close as 1" or 2" to the quasar. We find a significant enhancement of galaxies within a projected separation of <~ 100 h^-1^ kpc of the quasars. If we model the QSO/galaxy correlation function as a power law with a slope given by the galaxy/galaxy correlation function, we find that the ratio of the QSO/galaxy to galaxy/galaxy correlation functions is 3.8 +/- 0.8. The galaxy counts within r < 15 h^-1^ kpc of the quasars are too high for the density profile to have an appreciable core radius (~>100 h^-1^ kpc). Our results reinforce the idea that low redshift quasars are located preferentially in groups of 10-20 galaxies rather than in rich clusters. We see no significant difference in the clustering amplitudes derived from radio-loud and radio-quiet subsamples.