The galaxy luminosity function and its evolution with Chandra

Aims. We have compiled one of the largest normal-galaxy samples ever to probe X-ray luminosity function evolution separately for early and late-type systems. Methods. We selected 207 normal galaxies up to redshift z similar to 1.4, with data from four major Chandra X-ray surveys, namely the Chandra deep fields (north, south and extended) and XBootes, and a combination of X-ray and optical criteria. We used template spectral energy-distribution fitting to obtain separate early- and late-type sub-samples, made up of 101 and 106 systems, respectively. For the full sample, as well as the two sub-samples, we obtained luminosity functions using both a non-parametric and a parametric, maximum-likelihood method. Results. For the full sample, the non-parametric method strongly suggests luminosity evolution with redshift. The maximum-likelihood estimate shows that this evolution follows similar to(1 + z)(k)(total), k(total) = 2.2 +/- 0.3. For the late-type sub-sample, we obtained k(late) = 2.4(-2.0)(+1.0). We detected no significant evolution in the early- type sub-sample. The distributions of early and late-type systems with redshift show that late types dominate at z >= 0.5 and hence drive the observed evolution for the total sample. Conclusions. Our results support previous results in X-ray and other wavebands, which suggests luminosity evolution with k = 2-3.