Superclustering of quasi-stellar object absorption clouds

Abstract

We examine the clustering of C IV absorption line systems along the lines of sight to the 55 quasars in the survey of Sargent, Boksenberg, and Steidel. We confirm their original result that there is strong clustering of these systems at separations less than 1000 km s^-1^. We show that the peculiar velocities of the clouds combine with the one-dimensional nature of the sampling to preclude any detailed comparison of the observed clustering strength on these scales with that found for nearby systems such as galaxies. We show that the sample also contains significant clustering on larger scales, 1000-10,000 km s^-1^. This probably reflects true spatial clustering of an amplitude exceeding that observed for any nearby systems, even rich clusters of galaxies. The signal is due mainly to high equivalent width absorbers and is dominated by a single very large "absorption supercluster" in the quasar 0237-233. It seems likely that this structure was produced by processes other than gravitational instability.