Large-Scale Structure as Seen from QSO Absorption-Line Systems

We study clustering on very large scales -- from several tens to hundreds of comoving Mpc -- using an extensive catalog of heavy-element QSO absorption-line systems. We find significant evidence that C IV absorbers are clustered on comoving scales of 100 $h^{-1}$ Mpc ($q_0=0.5$) and less. The superclustering is present even at high redshift ($z\sim 3$); furthermore, it does not appear that the superclustering scale (comoving) has changed significantly since then. Our estimate of that scale increases to 240 $h^{-1}$ Mpc if $q_0=0.1$, which is larger than the largest scales of clustering seen at the present epoch. This may be indicative of a larger value of $q_0$, and hence $\Omega_0$. We identify 7 high-redshift supercluster candidates, with 2 at redshift $z\sim 2.8$. The evolution of the correlation function on 50 $h^{-1}$ Mpc scales is consistent with that expected in cosmologies with $\Omega_0=$ ranging from 0.1 to 1. Finally, we find no evidence for clustering on scales greater than 100 $h^{-1}$ Mpc ($q_0=0.5$) or 240 $h^{-1}$ Mpc ($q_0=0.1$).