The Two-Point Correlation Function at Redshift 1/3

Abstract

We present the results of a study of the two-point correlation function for a sample of field galaxies taken from the CNOCI cluster survey. The sample consists of 144 galaxies within a contiguous region of space subtending 225 square arcminutes. The objects have r-band magnitudes 17.0 < r < 21.7 and redshifts 0.21 < z < 0.53. The median redshift of the sample is 0.36. The real space correlation function is found to be consistent with a power law ξ(r) = (r/r_0)^-1.7 with r_0 = 2.1 +0.6/-0.3 (Ω_0=1), or r_0 = 2.5 +0.7/-0.4 (Ω_0=0.2). Uncertainties are estimated using the bias-corrected bootstrap resampling method, with 300 resamplings. This low correlation length implies strong evolution since z~0.36 has occurred in either the correlation function or the luminosity function; if the observed correlation function is modeled as ξ(r,z) = ξ(r,0) * (1+z)^-(3+ε) with ξ(r,0) = (r/5.1 h^-1Mpc)^-1.7, then ε= 0.8 +1.0/-1.3. Comparison of the redshift space and real space correlation function indicates that the one-dimensional pairwise peculiar velocity dispersion σat z~0.36 is weakly inconsistent with 770 km s^-1, the value predicted by the Cosmic Virial Theorem if Ω_0=1. The observed correlation function is, however, consistent with σ=400 km s^-1, the value expected if Ω_0=0.2.