The VIMOS VLT Deep Survey^*

The assembly history of the stellar mass in galaxies: from the young to the old universe

¹ INAF – Osservatorio Astronomico di Bologna - via Ranzani,1, 40127, Bologna, Italy e-mail: lucia.pozzetti@oabo.inaf.it
² Laboratoire d'Astrophysique de Toulouse/Tabres (UMR5572), CNRS, Université Paul Sabatier – Toulouse III, Observatoire Midi-Pyriénées, 14 av. E. Belin, 31400 Toulouse, France
³ Max Planck Institut fur Astrophysik, 85741 Garching, Germany
⁴ INAF – IASF – via Bassini 15, 20133, Milano, Italy
⁵ Laboratoire d'Astrophysique de Marseille, UMR 6110 CNRS-Université de Provence, BP8, 13376 Marseille Cedex 12, France
⁶ INAF – Osservatorio Astronomico di Brera, via Brera 28, Milan, Italy
⁷ Institute for Astronomy, 2680 Woodlawn Dr., University of Hawaii, Honolulu 96822, Hawaii
⁸ Institut d'Astrophysique de Paris, UMR 7095, 98 bis Bvd Arago, 75014 Paris, France
⁹ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
¹⁰ INAF – IRA – via Gobetti 101, 40129 Bologna, Italy
¹¹ INAF – Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
¹² School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG72RD, UK
¹³ Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
¹⁴ Observatoire de Paris, LERMA, 61 Avenue de l'Observatoire, 75014 Paris, France
¹⁵ Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy
¹⁶ Centre de Physique Théorique, UMR 6207 CNRS-Université de Provence, 13288 Marseille, France
¹⁷ Integral Science Data Centre, ch. d'Écogia 16, 1290 Versoix
¹⁸ Geneva Observatory, ch. des Maillettes 51, 1290 Sauverny, Switzerland
¹⁹ Astronomical Observatory of the Jagiellonian University, ul Orla 171, 30-244 Kraków, Poland
²⁰ INAF – Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
²¹ Universitá di Milano-Bicocca, Dipartimento di Fisica, Piazza delle Scienze 3, 20126 Milano, Italy
²² Università di Bologna, Dipartimento di Fisica, via Irnerio 46, 40126 Bologna, Italy

Received: 4 April 2007
Accepted: 16 August 2007

Abstract

We present a detailed analysis of the Galaxy Stellar Mass Function (GSMF) of galaxies up to as obtained from the VIMOS VLT Deep Survey (VVDS). Our survey offers the possibility to investigate the GSMF using two different samples: (1) an optical (I-selected ) main spectroscopic sample of about 6500 galaxies over 1750 arcmin² and (2) a near-IR (K-selected ) sample of about 10 200 galaxies, with photometric redshifts accurately calibrated on the VVDS spectroscopic sample, over 610 arcmin². We apply and compare two different methods to estimate the stellar mass from broad-band photometry based on different assumptions about the galaxy star-formation history. We find that the accuracy of the photometric stellar mass is satisfactory overall, and show that the addition of secondary bursts to a continuous star formation history produces systematically higher (up to 40%) stellar masses. We derive the cosmic evolution of the GSMF, the galaxy number density and the stellar mass density in different mass ranges. At low redshift () we find a substantial population of low-mass galaxies (<10) composed of faint blue galaxies (). In general the stellar mass function evolves slowly up to and more rapidly above this redshift, in particular for low mass systems. Conversely, a massive population is present up to and has extremely red colours (–0.8). We find a decline with redshift of the overall number density of galaxies for all masses (% for at ), and a mild mass-dependent average evolution (“mass-downsizing”). In particular our data are consistent with mild/negligible (%) evolution up to for massive galaxies (). For less massive systems the no-evolution scenario is excluded. Specifically, a large fraction () of massive galaxies have been assembled and converted most of their gas into stars at , ruling out “dry mergers” as the major mechanism of their assembly history below . This fraction decreases to at . Low-mass systems have decreased continuously in number density (by a factor of up to ) from the present age to , consistent with a prolonged mass assembly also at . The evolution of the stellar mass density is relatively slow with redshift, with a decrease of a factor of at and about at .