Large-Scale Structure at Z approximately 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 15-35 h^-1^ proper Mpc scale (H_0_ = 100 km s^-1^ Mpc^- 1^) as determined by the two-point C IV -C IV absorber correlation function, and we reject the null hypothesis that C IV systems are distributed randomly on such scales at the ~3.5 σ level. The structure likely reflects the distance between two groups of absorbers subtending ~13 x 5 x 21 h^-3^ and ~7 x 1 x 15 h^-3^ Mpc^3^ at z ~ 2.3 and z ~ 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 too small to detect such structure if it exists. We present also the Lyα forest lines found during the course of the survey.