Halo occupation distribution modelling of green valley galaxies

Abstract

We present a clustering analysis of near-ultraviolet (NUV)-optical colour selected luminosity bin samples of green valley galaxies. These galaxy samples are constructed by matching the Sloan Digital Sky Survey Data Release 7 with the latest Galaxy Evolution Explorer source catalogue which provides NUV photometry. We present cross-correlation function measurements and determine the halo occupation distribution of green valley galaxies using a new multiple tracer analysis technique. We extend the halo occupation formalism, which describes the relation between galaxies and halo mass in terms of the probability P(N, Mh) that a halo of given mass Mh contains N galaxies, to model the cross-correlation function between a galaxy sample of interest and multiple tracer populations simultaneously. This method can be applied to commonly used luminosity threshold samples as well as to colour and luminosity bin selected galaxy samples, and improves the accuracy of clustering analyses for sparse galaxy populations. We confirm the previously observed trend that red galaxies reside in more massive haloes and are more likely to be satellite galaxies than average galaxies of similar luminosity. While the change in central galaxy host mass as a function of colour is only weakly constrained, the satellite fraction and characteristic halo masses of green satellite galaxies are found to be intermediate between those of blue and red satellite galaxies. © 2012 The Authors.