Large-Scale Structure at z~2.5

Abstract

We have made a statistically complete, unbiased survey of C IV systems toward a region of high QSO density near the South Galactic Pole using 25 lines of sight spanning $1.5<z<2.8$. Such a survey makes an excellent probe of large-scale structure at early epochs. We find evidence for structure on the $15-35h^{-1}$ proper Mpc scale ($H_0\equiv 100$ km $s^{-1}$ Mpc$-1$) as determined by the two point C IV - C IV absorber correlation function, and reject the null hypothesis that C IV systems are distributed randomly on such scales at the $\sim 3.5\sigma$ level. The structure likely reflects the distance between two groups of absorbers subtending $\sim 13\times 5\times 21h^{-3}$ and $\sim 7\times 1\times 15h^{-3}$ Mpc${}^3$ at $z\sim 2.3$ and $z\sim 2.5$ respectively. There is also a marginal trend for the association of high rest equivalent width C IV absorbers and QSOs at similar redshifts but along different lines of sight. The total number of C IV systems detected is consistent with that which would be expected based on a survey using many widely separated lines of sight. Using the same data, we also find 11 Mg II absorbers in a complete survey toward 24 lines of sight; there is no evidence for Mg II - Mg II or Mg II - QSO clustering, though the sample size is likely still small to detect such structure if it exists.

56 pages including 32 of figures, in gzip-ed uuencoded postscript format, 1 long table not included, aastex4 package. Accepted for publication in ApJ Supplements