Astronomy & Astrophysics

A&A 480, 663-670 (2008)
DOI: 10.1051/0004-6361:20078193

The galaxy luminosity function and its evolution with Chandra

P. Tzanavaris and I. Georgantopoulos

Institute of Astronomy & Astrophysics, National Observatory of Athens, I. Metaxa & V. Pavlou, Penteli 152 36, Greece
e-mail: pana@astro.noa.gr

(Received 29 June 2007 / Accepted 1 September 2007)

Abstract
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 $z\sim 1.4$ , 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 $\sim (1+z)^{k_{\rm total}}$ , $k_{\rm total}=2.2$ $\pm$ 0.3. For the late-type sub-sample, we obtained $k_{\rm late}=2.4^_$ . 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 $z\ga 0.5$ 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.

Key words: surveys -- galaxies: luminosity function, mass function -- X-rays: galaxies -- X-rays: binaries