Galaxy clustering in the CFHTLS-Wide: the changing relationship between galaxies and haloes since z  ~  1.2^⋆,⋆⋆

¹ Astronomical Institute, Graduate School of Science, Tohoku University, Sendai 980-8578, Japan
e-mail: jean.coupon@gmail.com
² Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, Taipei 10617, Taiwan
³ Excellence Cluster Universe, Technische Universität München, Boltzmannstr. 2, 85748 Garching, Germany
⁴ Universitäts-Sternwarte München, Scheinerstr. 1, 81679 München, Germany
⁵ Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98bis boulevard Arago, 75014 Paris, France
⁶ Laboratoire d’Astrophysique de Marseille (UMR 6110), CNRS-Université de Provence, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
⁷ Canada-France-Hawaii Telescope, 65–1238 Mamalahoa Highway, Kamuela, HI 9674, USA
⁸ INAF – Osservatorio Astronomico di Torino, 10025 Pino Torinese, Italy
⁹ SUPA, Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK

Received: 4 July 2011
Accepted: 28 February 2012

Abstract

It has become increasingly apparent that studying how dark matter haloes are populated by galaxies can provide new insights into galaxy formation and evolution. In this paper, we present a detailed investigation of the changing relationship between galaxies and the dark matter haloes they inhabit from z ~ 1.2 to the present day. We do this by comparing precise galaxy clustering measurements over 133 deg² of the “Wide” component of the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS) with predictions of an analytic halo occupation distribution (HOD) model where the number of galaxies in each halo depends only on the halo mass. Starting from a parent catalogue of  ~3 × 10⁶ galaxies at i′_AB<22.5 we use accurate photometric redshifts calibrated using  ~10⁴ spectroscopic redshifts to create a series of type-selected volume-limited samples covering 0.2 < z < 1.2. Our principal result, based on clustering measurements in these samples, is a robust determination of the luminosity-to-halo mass ratio and its dependence on redshift and galaxy type. For the full sample, this reaches a peak at low redshifts of M_h^peak = 4.5×10¹¹ h^-1 M_⊙ and moves towards higher halo masses at higher redshifts. For redder galaxies the peak is at higher halo masses and does not evolve significantly over the entire redshift range of our survey. We also consider the evolution of bias, average halo mass and the fraction of satellites as a function of redshift and luminosity. Our observed growth of a factor of  ~2 in satellite fraction between z ~ 1 and z ~ 0 is testament to the limited role that galaxy merging plays in galaxy evolution for  ~10¹² h^-1 M_⊙ mass haloes at z < 1. Qualitatively, our observations are consistent with a picture in which red galaxies in massive haloes have already accumulated most of their stellar mass by z ~ 1 and subsequently undergo little evolution until the present day. The observed movement of the peak location for the full galaxy population is consistent with the bulk of star-formation activity migrating from higher mass haloes at high redshifts to lower mass haloes at lower redshifts.