HIGH-REDSHIFT SUPERCLUSTERING OF QUASI-STELLAR OBJECT ABSORPTION-LINE SYSTEMS ON 100 h~(-1) Mpc SCALES

摘要

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 x 10~(-7)) that C Ⅳ absorbers are clustered on comoving scales of 100 h~(-1) Mpc (q_0 = 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 < ξ_(aa) > = 0.42 ± 0.10 over these scales. We find, on these scales, that the mean correlation function at low ( < z > _(low) = 1.7), medium ( < z > _(med) = 2.4), and high redshift ( < z > _(high)= 3.0) is < ξ_(aa) > = 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 q_0 = 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 q_0 and hence Ω_0. The evolution of the correlation function on 50 h~(-1) Mpc scales is consistent with that expected in cosmologies with density parameter ranging from Ω_0 = 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).