Physical properties of galaxies and their evolution in the VIMOS VLT Deep Survey^*,**

I. The evolution of the mass-metallicity relation up to z ~ 0.9

¹ Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 Av. E. Belin, 31400 France
² INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
³ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
⁴ Laboratoire d'Astrophysique de Marseille, UMR 6110 CNRS-Université de Provence, BP 8, 13376 Marseille Cedex 12, France
⁵ Max Planck Institut für Astrophysik, 85741 Garching, Germany
⁶ Institut d'Astrophysique de Paris, UMR 7095, 98 bis Bvd Arago, 75014 Paris, France
⁷ IASF – INAF, via Bassini 15, 20133 Milano, Italy
⁸ Integral Science Data Centre, ch. d'Écogia 16, 1290 Versoix, Switzerland
⁹ Geneva Observatory, ch. des Maillettes 51, 1290 Sauverny, Switzerland
¹⁰ Max Planck Institut für Extraterrestrische Physik (MPE), Giessenbachstrasse 1, 85748 Garching bei München, Germany
¹¹ IRA – INAF, via Gobetti 101, 40129 Bologna, Italy
¹² INAF – Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
¹³ Canada France Hawaii Telescope corporation, Mamalahoa Hwy, Kamuela, HI-96743, USA
¹⁴ School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG72RD, UK
¹⁵ Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
¹⁶ INAF – Osservatorio Astronomico di Brera, via Brera 28, 20021 Milan, Italy
¹⁷ Institute for Astronomy, 2680 Woodlawn Dr., University of Hawaii, Honolulu, Hawaii 96822, USA
¹⁸ Observatoire de Paris, LERMA, 61 Avenue de l'Observatoire, 75014 Paris, France
¹⁹ Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy
²⁰ Centre de Physique Théorique, UMR 6207 CNRS-Université de Provence, 13288 Marseille, France
²¹ Universitätssternwarte München, Scheinerstrasse 1, 81679 München, Germany
²² The A. Soltan Institute for Nuclear Studies ul. Hoza 69, 00-681 Warszawa, Poland
²³ INAF – Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy

Received: 16 June 2008
Accepted: 30 November 2008

Abstract

Aims. We want to derive the mass-metallicity relation of star-forming galaxies up to z ~ 0.9, using data from the VIMOS VLT Deep Survey. The mass-metallicity relation is commonly understood as the relation between the stellar mass and the gas-phase oxygen abundance.

Methods. Automatic measurement of emission-line fluxes and equivalent widths have been performed on the full spectroscopic sample of the VIMOS VLT Deep Survey. This sample is divided into two sub-samples depending on the apparent magnitude selection: wide ( < 22.5) and deep ( < 24). These two samples span two different ranges of stellar masses. Emission-line galaxies have been separated into star-forming galaxies and active galactic nuclei using emission line ratios. For the star-forming galaxies the emission line ratios have also been used to estimate gas-phase oxygen abundance, using empirical calibrations renormalized in order to give consistent results at low and high redshifts. The stellar masses have been estimated by fitting the whole spectral energy distributions with a set of stellar population synthesis models.

Results. We assume at first order that the shape of the mass-metallicity relation remains constant with redshift. Then we find a stronger metallicity evolution in the wide sample as compared to the deep sample. We thus conclude that the mass-metallicity relation is flatter at higher redshift. At z ~ 0.77, galaxies at 10^9.4 solar masses have -0.18 dex lower metallicities than galaxies of similar masses in the local universe, while galaxies at 10^10.2 solar masses have -0.28 dex lower metallicities. By comparing the mass-metallicity and luminosity-metallicity relations, we also find an evolution in mass-to-light ratio: galaxies at higher redshifts being more active. The observed flattening of the mass-metallicity relation at high redshift is analyzed as evidence in favor of the open-closed model.