The VVDS-SWIRE-GALEX-CFHTLS surveys: physical properties of galaxies at z below 1.2 from photometric data ^*

¹ Institut d'Astrophysique de Paris, CNRS, Université Pierre & Marie Curie, UMR 7095, 98 bis Boulevard Arago, 75014 Paris, France e-mail: jwalcher@rssd.esa.int
² Laboratoire d'Astrophysique de Marseille (UMR6110), CNRS-Université de Provence, 38 rue Frederic Joliot-Curie, 13388 Marseille Cedex 13, France
³ INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, 40127, Bologna, Italy
⁴ Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 14 avenue Edouard Belin, 31400 Toulouse, France
⁵ IASF-INAF, via Bassini 15, 20133, Milano, Italy
⁶ Canada France Hawaii Telescope corporation, Mamalahoa Hwy, Kamuela, HI-96743, USA
⁷ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762, Porto, Portugal
⁸ Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands
⁹ IRA-INAF, via Gobetti 101, 40129, Bologna, Italy
¹⁰ INAF-Osservatorio Astronomico di Roma, via di Frascati 33, 00040, Monte Porzio Catone, Italy
¹¹ School of Physics & Astronomy, University of Nottingham, University Park, Nottingham, NG72RD, UK
¹² Astrophysical Institute Potsdam, An der Sternwarte 16, 14482, Potsdam, Germany
¹³ INAF-Osservatorio Astronomico di Brera, via Brera 28, 20021, Milan, Italy
¹⁴ Institute for Astronomy, 2680 Woodlawn Dr., University of Hawaii, Honolulu, Hawaii, 96822, USA
¹⁵ Observatoire de Paris, LERMA, 61 Avenue de l'Observatoire, 75014, Paris, France
¹⁶ Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127, Bologna, Italy
¹⁷ Centre de Physique Théorique, UMR 6207 CNRS-Université de Provence, 13288 Marseille, France
¹⁸ Max-Planck-Institut fur Extraterrestrische Physik, Giessenbachstrasse, 85748 Garching b. Muenchen, Germany
¹⁹ Universitats-Sternwarte, Scheinerstrasse 1, 81679 Muenchen, Germany
²⁰ Integral Science Data Centre, ch. d'Écogia 16, 1290, Versoix, Switzerland
²¹ Geneva Observatory, ch. des Maillettes 51, 1290, Sauverny, Switzerland
²² The Andrzej Soltan Institute for Nuclear Studies, ul. Hoza 69, 00-681 Warszawa, Poland
²³ INAF-Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131, Napoli, Italy
²⁴ University of California, San Diego 9500 Gilman Dr. La Jolla, CA 92093-0424, USA
²⁵ California Institute of Technology, MC 405-47, 1200 East California Boulevard, Pasadena, CA 91125, USA

Received: 29 July 2008
Accepted: 11 September 2008

Abstract

Measuring the build-up of stellar mass is one of the main objectives of studies of galaxy evolution. Traditionally, the mass in stars and the star formation rates have been measured by different indicators, such as photometric colours, emission lines, and the UV and IR emission. We intend to show that it is possible to derive the physical parameters of galaxies from their broad-band spectral energy distribution out to a redshift of 1.2. This method has the potential to yield the physical parameters of all galaxies in a single field in a homogeneous way, thus overcoming problems with the sample size that particularly plague methods relying on spectroscopy. We use an extensive dataset, assembled in the context of the VVDS survey, which reaches from the UV to the IR and covers a sample of 84 073 galaxies over an area of 0.89 deg². We also use a library of 100 000 model galaxies with a wide variety of star formation histories (in particular including late bursts of star formation). We find that we can determine the physical parameters stellar mass, age, and star formation rate with good confidence. We validate the star formation rate determination in particular by comparing it to a sample of spectroscopically observed galaxies with an emission-line measurement. While the attenuation in the galaxies shows more scatter, the mean over the sample is unbiased. Metallicity, however, cannot be measured from rest-frame optical photometry alone. As a first application we use our sample to build the number density function of galaxies as a function of stellar mass, specific star formation rate, and redshift. We are then able to study whether the stellar mass function at a later time can be predicted from the stellar mass function and star formation rate distribution at an earlier time. We find that, between redshifts of 1.02 and 0.47, the predicted growth in stellar mass from star formation agrees with the observed one. However, the predicted stellar mass density for massive galaxies is lower than observed, while the mass density of intermediate mass galaxies is overpredicted. This apparent discrepancy can be explained by major and minor mergers. Indeed, when comparing with a direct measurement of the major merger rate from the VVDS survey, we find that major mergers can account for about half of the mass build-up at the massive end. Minor mergers are very likely to contribute the missing fraction.