A New Measure of the Clustering of QSO Heavy-Element Absorption-Line Systems

Abstract

We examine the line-of-sight clustering of QSO heavy-element absorption-line systems, using a new measure of clustering, called the reduced second moment measure, that directly measures the mean over-density of absorbers. While closely related to other second-order measures such as the correlation function or the power spectrum, this measure has a number of distinct statistical properties which make possible a continuous exploration of clustering as a function of scale. From a sample of 352 C IV absorbers with median redshift 2.2, drawn from the spectra of 274 QSOs, we find that the absorbers are strongly clustered on scales from 1 to 20 Mpc. Furthermore, there appears to be a sharp break at 20 Mpc, with significant clustering on scales up to 100 Mpc in excess of that which would be expected from a smooth transition to homogeneity. There is no evidence of clustering on scales greater than 100 Mpc. These results suggest that strong C IV absorbers along a line of sight are indicators of clusters and possibly superclusters, a relationship that is supported by recent observations of ``Lyman break'' galaxies.

13 pages (LaTex, uses aaspp4.sty and psfig.sty), with 3 encapsulated PostScript figures. To appear in The Astrophysical Journal. Extended new discussion of the statistical properties of the reduced second moment measure, and a new figure highlighting the excess clustering on comoving scales greater than 20 Mpc

References in corpus (6)

• A Large Structure of Galaxies At Redshift z~3 and its Cosmological Implications
• The Angular Clustering of Lyman-Break Galaxies at Redshift z=3
• Physical Properties of the Lyman Alpha Forest in a Cold Dark Matter Cosmology
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• The Form and Evolution of the Clustering of QSO Heavy-Element Absorption-Line Systems

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• Probing Reionization and Early Cosmic Enrichment with the MgII Forest
• The Bright Ages Survey. I. Imaging Data
• Ly-alpha forest: efficient unbiased estimation of second-order properties with missing data
• Estimating Third-Order Moments for an Absorber Catalog