The VVDS-VLA deep field

IV. Radio-optical properties

¹ INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy e-mail: sandro.bardelli@oabo.inaf.it
² IRA-INAF, via Gobetti 101, 40129, Bologna, Italy
³ Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy
⁴ Laboratoire d'Astrophysique de Marseille, (UMR 6110) CNRS-Université de Provence, 38 rue Frederic Joliot-Curie, 13388 Marseille Cedex 13, France
⁵ Astrophysical Institute Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
⁶ IASF-INAF, via Bassini 15, 20133 Milano, Italy
⁷ INAF-Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
⁸ Max Planck Institut fur Astrophysik, 85741 Garching, Germany
⁹ Institut d'Astrophysique de Paris, UMR 7095, 98bis Bd Arago, 75014 Paris, France
¹⁰ Laboratoire d'Astrophysique de Toulouse/Tarbes (UMR 5572) CNRS, 14 Av. E. Belin, 31400 Toulouse, France
¹¹ School of Physics & Astronomy, University of Nottingham, University Park, Nottingham NG72RD, UK
¹² INAF-Osservatorio Astronomico di Brera, via Brera 28, Milan, Italy
¹³ Institute for Astronomy, 2680 Woodlawn Dr., University of Hawaii, Honolulu, Hawaii, 96822, USA
¹⁴ Observatoire de Paris, LERMA, 61 avenue de l'Observatoire, 75014 Paris, France
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 Universitá di Milano-Bicocca, Dipartimento di Fisica, Piazza delle Scienze 3, 20126 Milano, Italy

Received: 11 July 2008
Accepted: 5 November 2008

Abstract

Aims. The availability of wide angle and deep surveys, both in the optical and the radio band, allows us to explore the evolution of radio sources with optical counterparts up to redshift in an unbiased way using large numbers of radio sources and well defined control samples of radio-quiet objects.

Methods. We use the 1.4 GHz VIMOS-VLA Deep Survey, the optical VIMOS-VLT Deep Survey and the CFHT Legacy Survey to compare the properties of radio-loud galaxies with respect to the whole population of optical galaxies. The availability of multiband photometry and high quality photometric redshifts allows us to derive rest-frame colors and radio luminosity functions to a limit of a B rest-frame magnitude of M_B=-20. We derive spectrophotometric types, following the classification of Zucca et al. (2006, A&A, 455, 879), in order to have a priori knowledge of the optical evolution of different galaxy classes.

Results. Galaxy properties and luminosity functions are estimated up to for radio-loud and radio-quiet early and late type galaxies. Radio-loud late type galaxies show significantly redder colors than radio-quiet objects of the same class and this is related to the presence of more dust in stronger star forming galaxies. We estimate the optical luminosity functions, stellar masses and star formation rate distributions for radio sources and compare them with those derived for a well defined control sample, finding that the probability of a galaxy to be a radio emitter significantly increases at high values of these parameters. Radio-loud early type galaxies exhibit luminosity evolution in their bivariate radio-optical luminosity function, due to evolution in the radio-optical ratio. The lack of evolution of the mass function of radio-loud early type galaxies means that no new AGN are formed at redshift . In contrast, radio-loud late type objects exhibit a strong evolution, both in luminosity and density, of the radio luminosity function for . This evolution is a direct effect of the strong optical evolution of this class and no significant change with redshift in the radio-optical ratio is required. With the knowledge of the radio-optical ratio and the optical and radio luminosity functions for late type galaxies, we show that it is possible to estimate the star formation history of the Universe up to redshift , using optical galaxies as tracers of the global radio emission.