Tracking the impact of environment on the galaxy stellar mass function up to z  ~  1 in the 10 k zCOSMOS sample ^⋆

¹ INAF – Osservatorio Astronomico di Bologna, via Ranzani 1 40127 Bologna, Italy
e-mail: micol.bolzonella@oabo.inaf.it
² ETH Zurich, Institute of Astronomy, Wolfgang-Pauli-Straße 27, 8093 Zurich, Switzerland
³ Laboratoire d’Astrophysique de Marseille, Université d’Aix-Marseille, CNRS, 38 rue Frédéric Joliot-Curie, 13388 Marseille Cedex 13, France
⁴ INAF – Osservatorio Astronomico di Brera, via Brera 28, 20121 Milano, Italy
⁵ INAF – IASF Milano, via Bassini 15, 20133 Milano, Italy
⁶ Laboratoire d’Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 avenue Édouard Belin, 31400 Toulouse, France
⁷ Institute for Astronomy, Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, Scotland, UK
⁸ INAF – Osservatorio Astronomico di Torino, 10025 Pino Torinese (TO), Italy
⁹ European Southern Observatory, Karl-Schwarzschild-Straße 2, 85748 Garching bei München, Germany
¹⁰ INAF – Osservatorio Astronomico di Padova, vicolo dell’Osservatorio 5, 35122 Padova, Italy
¹¹ Max-Planck-Institut für Extraterrestrische Physik, Giessen-bachstraße, 84571 Garching bei München, Germany
¹² Dipartimento di Astronomia, Università di Bologna, via Ranzani 1, 40127 Bologna, Italy
¹³ Instituto de Astrofisica de Andalucia, CSIC, Apdo. 3004, 18080 Granada, Spain
¹⁴ Instituto de Astrofisica de Canarias, vía Láctea s/n, 38205, La Laguna, Tenerife, Spain
¹⁵ Institute for the Physics and Mathematics of the Universe (IPMU), University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-shi, Chiba 277-8568, Japan
¹⁶ University of Massachusetts, Amherst, USA
¹⁷ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁸ LBNL & BCCP, University of California, Berkeley, CA 94720, USA
¹⁹ Centre de Physique Théorique, UMR 6207 CNRS, Université de Provence, Case 907, 13288 Marseille, France
²⁰ Institut d’Astrophysique de Paris, UMR 7095 CNRS, Université Pierre et Marie Curie, 98bis Boulevard Arago, 75014 Paris, France
²¹ Universitäts-Sternwarte, Scheinerstraße 1, 81679 München, Germany
²² Argelander-Institut für Astronomie, Auf dem Hügel 71, 53121 Bonn, Germany
²³ INAF - Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monteporzio Catone, Italy
²⁴ DSM/Irfu/Service d’Astrophysique, CEA Saclay, 91191 Gif-sur-Yvette, France
²⁵ California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125, USA
²⁶ INAF – Osservatorio Astronomico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
²⁷ Institute for Astronomy, 2680 Woodlawn Drive, University of Hawaii, Honolulu, HI 96822, USA
²⁸ National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA
²⁹ Max Planck Institut für Plasma Physics and Excellence Cluster Universe, Boltzmannstraße 2, 85748 Garching bei München, Germany
³⁰ Research Center for Space and Cosmic Evolution, Ehime University, Bunkyo-cho, Matsuyama 790-8577, Japan
³¹ Large Binocular Telescope Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721-0065, USA

Received: 30 June 2009
Accepted: 21 September 2010

Abstract

We study the impact of the environment on the evolution of galaxies in the zCOSMOS 10 k sample in the redshift range 0.1 ≤ z ≤ 1.0 over an area of  ~1.5 deg². The considered sample of secure spectroscopic redshifts contains about 8500 galaxies, with their stellar masses estimated by SED fitting of the multiwavelength optical to near-infrared (NIR) photometry. The evolution of the galaxy stellar mass function (GSMF) in high and low density regions provides a tool to study the mass assembly evolution in different environments; moreover, the contributions to the GSMF from different galaxy types, as defined by their SEDs and their morphologies, can be quantified. At redshift z ~ 1, the GSMF is only slightly dependent on environment, but at lower redshifts the shapes of the GSMFs in high- and low-density environments become extremely different, with high density regions exhibiting a marked bimodality, not reproducible by a single Schechter function. As a result of this analysis, we infer that galaxy evolution depends on both the stellar mass and the environment, the latter setting the probability of a galaxy to have a given mass: all the galaxy properties related to the stellar mass show a dependence on environment, reflecting the difference observed in the mass functions. The shapes of the GSMFs of early- and late-type galaxies are almost identical for the extremes of the density contrast we consider, ranging from isolated galaxies to rich group members. The evolution toward z = 0 of the transition mass ℳ_cross, i.e., the mass at which the early- and late-type GSMFs match each other, is more rapid in high density environments, because of a difference in the evolution of the normalisation of GSMFs compared to the total one in the considered environment. The same result is found by studying the relative contributions of different galaxy types, implying that there is a more rapid evolution in overdense regions, in particular for intermediate stellar masses. The rate of evolution is different for sets of galaxy types divided on the basis of their SEDs or their morphologies, tentatively suggesting that the migration from the blue cloud to the red sequence occurs on a shorter timescale than the transformation from disc-like morphologies to ellipticals. Our analysis suggests that environmental mechanisms of galaxy transformation start to be more effective at z < 1. The comparison of the observed GSMFs to the same quantities derived from a set of mock catalogues based on semi-analytical models shows disagreement, in both low and high density environments: in particular, blue galaxies in sparse environments are overproduced in the semi-analytical models at intermediate and high masses, because of a deficit of star formation suppression, while at z < 0.5 an excess of red galaxies is present in dense environments at intermediate and low masses, because of the overquenching of satellites.