The evolution of the cluster optical galaxy luminosity function between z = 0.4 and 0.9 in the DAFT/FADA survey^⋆

¹ UPMC Université Paris 06, UMR 7095, Institut d’Astrophysique de Paris, 98bis Bd Arago, 75014 Paris, France
e-mail: martinet@iap.fr
² Astrophysics and Cosmology Research Unit, University of KwaZulu-Natal, 4041 Durban, South Africa
³ LAM, OAMP, Université Aix-Marseille & CNRS, Pôle de l’Étoile, Site de Château Gombert, 38 rue Frédéric Joliot-Curie, 13388 Marseille 13 Cedex, France
⁴ INAF/Osservatorio Astronomico di Trieste, via Tiepolo 11, 34143 Trieste, Italy
⁵ Dept of Physics and Astronomy & centre for Interdisciplinary Exploration and Research in Astrophysics (CIERA), Northwestern University, Evanston, IL 60208-2900, USA
⁶ Department of Physics and Astronomy, Ohio University, 251B Clippinger Lab, Athens, OH 45701, USA
⁷ 23 rue d’Yerres, 91230 Montgeron, France
⁸ Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
⁹ Gemini Observatory, Casilla 603, La Serena, Chile
¹⁰ Argelander-Institut für Astronomie, Universitët Bonn, Auf dem Hügel 71, 53121 Bonn, Germany

Received: 12 March 2014
Accepted: 17 December 2014

Abstract

Context. There is some disagreement about the abundance of faint galaxies in high-redshift clusters, with contradictory results in the literature arising from studies of the optical galaxy luminosity function (GLF) for small cluster samples.

Aims. We compute GLFs for one of the largest medium-to-high-redshift (0.4 ≤ z < 0.9) cluster samples to date in order to probe the abundance of faint galaxies in clusters. We also study how the GLF depends on cluster redshift, mass, and substructure and compare the GLFs of clusters with those of the field. We separately investigate the GLFs of blue and red-sequence (RS) galaxies to understand the evolution of different cluster populations.

Methods. We calculated the GLFs for 31 clusters taken from the DAFT/FADA survey in the B,V,R, and I rest-frame bands. We used photometric redshifts computed from BVRIZJ images to constrain galaxy cluster membership. We carried out a detailed estimate of the completeness of our data. We distinguished the red-sequence and blue galaxies using a V − I versus I colour−magnitude diagram. We studied the evolution of these two populations with redshift. We fitted Schechter functions to our stacked GLFs to determine average cluster characteristics.

Results. We find that the shapes of our GLFs are similar for the B,V,R, and I bands with a drop at the red GLF faint ends that is more pronounced at high redshift: α_red ~ −0.5 at 0.40 ≤ z < 0.65 and α_red > 0.1 at 0.65 ≤ z < 0.90. The blue GLFs have a steeper faint end (α_blue ~ −1.6) than the red GLFs, which appears to be independent of redshift. For the full cluster sample, blue and red GLFs meet at M_V = −20, M_R = −20.5, and M_I = −20.3. A study of how galaxy types evolve with redshift shows that late-type galaxies appear to become early types between z ~ 0.9 and today. Finally, the faint ends of the red GLFs of more massive clusters appear to be richer than less massive clusters, which is more typical of the lower redshift behaviour.

Conclusions. Our results indicate that these clusters form at redshifts higher than z = 0.9 from galaxy structures that already have an established red sequence. Late-type galaxies then appear to evolve into early types, enriching the red sequence between this redshift and today. This effect is consistent with the evolution of the faint-end slope of the red sequence and the galaxy type evolution that we find. Finally, faint galaxies accreted from the field environment at all redshifts might have replaced the blue late-type galaxies that converted into early types, explaining the lack of evolution in the faint-end slopes of the blue GLFs.