High-Redshift Superclustering of Quasi-stellar Object Absorption-Line Systems on 100 [ITAL]h[/ITAL][TSUP]−1[/TSUP] Mpc Scales

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Abstract
We have analyzed the clustering of C IV absorption-line systems in an extensive new catalog of heavy-element quasi-stellar object (QSO) absorbers. The catalog permits exploration of clustering over a large range in both scale (from about 1 to over 300 h-1 Mpc) and redshift (z from 1.2 to 4.5). We find significant evidence (5.0 σ; Q = 2.9 × 10-7) that C IV absorbers are clustered on comoving scales of 100 h-1 Mpc (q0 = 0.5) and less—similar to the size of voids and walls found in galaxy redshift surveys of the local universe (z < 0.2)—with a mean correlation function ξaa = 0.42 ± 0.10 over these scales. We find, on these scales, that the mean correlation function at low (zlow = 1.7), medium (zmed = 2.4), and high redshift (zhigh = 3.0) is ξaa = 0.40 ± 0.17, 0.32 ± 0.14, and 0.72 ± 0.25, respectively. Thus, the superclustering is present even at high redshift; furthermore, it does not appear that the superclustering scale, in comoving coordinates, has changed significantly since then. We find seven QSOs with rich groups of absorbers (potential superclusters) that account for a significant portion of the clustering signal, with two at redshift z ~ 2.8. We find that the superclustering is just as evident if we take q0 = 0.1 instead of 0.5; however, the inferred scale of clustering is then 240 h-1 Mpc, which is larger than the largest scales of clustering known at present. This discrepancy may be indicative of a larger value of q0 and hence Ω0. The evolution of the correlation function on 50 h-1 Mpc scales is consistent with that expected in cosmologies with density parameter ranging from Ω0 = 0.1 to 1. Finally, we find no evidence for clustering on scales greater than 100 h-1 Mpc (q0 = 0.5) or 240 h-1 Mpc (q0 = 0.1).
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