The VIMOS VLT Deep Survey^*

Tracing the galaxy stellar mass assembly history over the last 8 Gyr

¹ IASF – INAF, via Bassini 15, 20133, Milano, Italy e-mail: daniela@lambrate.inaf.it
² INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127, Bologna, Italy
³ INAF – Osservatorio Astronomico di Brera, via Brera 28, 20021, Milan, Italy
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, 98bis Bvd Arago, 75014 Paris, France
⁷ Laboratoire d'Astrophysique de Toulouse/Tarbes (UMR 5572), CNRS, Université Paul Sabatier – Toulouse III, Observatoire Midi-Pyrénées, 14 Av. E. Belin, 31400 Toulouse, France
⁸ IRA – INAF, via Gobetti, 101, 40129 Bologna, Italy
⁹ INAF – Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
¹⁰ School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG72RD, UK
¹¹ Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
¹² Institute for Astronomy, 2680 Woodlawn Dr., University of Hawaii, Honolulu, Hawaii, 96822, USA
¹³ Observatoire de Paris, LERMA, 61 avenue de l'Observatoire, 75014 Paris, France
¹⁴ Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy
¹⁵ Centre de Physique Théorique, UMR 6207 CNRS-Université de Provence, 13288 Marseille, France
¹⁶ Integral Science Data Centre, Ch. d'Écogia 16, 1290 Versoix, Switzerland
¹⁷ Geneva Observatory, Ch. des Maillettes 51, 1290 Sauverny, Switzerland
¹⁸ Astronomical Observatory of the Jagiellonian University, ul Orla 171, 30-244 Kraków, Poland
¹⁹ INAF – Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
²⁰ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
²¹ Università di Milano-Bicocca, Dipartimento di Fisica, Piazza delle Scienze 3, 20126 Milano, Italy
²² Laboratoire AIM, CEA/DSM – CNRS – Université Paris Diderot, IRFU/SAp, 91191 Gif-sur-Yvette, France

Received: 18 May 2007
Accepted: 27 March 2008

Abstract

Aims. Our aim is to investigate the history of mass assembly for galaxies of different stellar masses and types.

Methods. We selected a mass-limited sample of 4048 objects from the VIMOS VLT Deep Survey (VVDS) in the redshift interval . We then used an empirical criterion, based on the amplitude of the 4000 ÅBalmer break (D_n4000), to separate the galaxy population into spectroscopically early- and late-type systems. The equivalent width of the [OII]3727 line is used as proxy for the star formation activity. We also derived a type-dependent stellar mass function in three redshift bins.

Results. We discuss to what extent stellar mass drives galaxy evolution, showing for the first time the interplay between stellar ages and stellar masses over the past 8 Gyr. Low-mass galaxies have small D_n4000 and at increasing stellar mass, the galaxy distribution moves to higher D_n4000 values as observed in the local Universe. As cosmic time goes by, we witness an increasing abundance of massive spectroscopically early-type systems at the expense of the late-type systems. This spectral transformation of late-type systems into old massive galaxies at lower redshift is a process started at early epochs (z > 1.3) and continuing efficiently down to the local Universe. This is also confirmed by the evolution of our type-dependent stellar mass function. The underlying stellar ages of late-type galaxies apparently do not show evolution, most likely as a result of a continuous and efficient formation of new stars. All star formation activity indicators consistently point towards a star formation history peaked in the past for massive galaxies, with little or no residual star formation taking place in the most recent epochs. In contrast, most of the low-mass systems show just the opposite characteristics, with significant star formation present at all epochs. The activity and efficiency of forming stars are mechanisms that depend on galaxy stellar mass, and the stellar mass assembly becomes progressively less efficient in massive systems as time elapses. The concepts of star formation downsizing and mass assembly downsizing describe a single scenario that has a top-down evolutionary pattern in how the star formation is quenched, as well as how the stellar mass is grown. The role of (dry) merging events seems to be only marginal at z < 1.3, as our estimated efficiency in stellar mass assembly can possibly account for the progressive accumulation of observed passively evolving galaxies.