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A&A 458, 39-52 (2006)
DOI: 10.1051/0004-6361:20065161

The VIMOS VLT Deep Survey: the build-up of the colour-density relation

O. Cucciati1, 2, A. Iovino1, C. Marinoni1, 3, O. Ilbert4, 5, S. Bardelli6, P. Franzetti7, O. Le Fèvre5, A. Pollo5, G. Zamorani6, A. Cappi6, L. Guzzo1, H. J. McCracken8, 9, B. Meneux7, 1, R. Scaramella10, 11, M. Scodeggio7, L. Tresse5, E. Zucca6, D. Bottini7, B. Garilli7, V. Le Brun5, D. Maccagni7, J. P. Picat12, G. Vettolani10, A. Zanichelli10, C. Adami5, M. Arnaboldi13, S. Arnouts5, M. Bolzonella6, S. Charlot14, 8, P. Ciliegi6, T. Contini12, S. Foucaud7, I. Gavignaud12, 15, B. Marano4, A. Mazure5, R. Merighi6, S. Paltani16, 17, R. Pellò12, L. Pozzetti6, M. Radovich13, M. Bondi10, A. Bongiorno4, G. Busarello13, S. de la Torre5, L. Gregorini10, F. Lamareille12, G. Mathez12, Y. Mellier8, 9, P. Merluzzi13, V. Ripepi13, D. Rizzo12, S. Temporin1 and D. Vergani7

1  INAF - Osservatorio Astronomico di Brera, via Brera 28, Milan, Italy;
    e-mail: olga.cucciati@brera.inaf.it
2  Universitá di Milano-Bicocca, Dipartimento di Fisica, Piazza della Scienza 3, 20126 Milano, Italy
3  Centre de Physique Théorique, UMR 6207 CNRS-Université de Provence, 13288 Marseille, France
4  Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy
5  Laboratoire d'Astropysique de Marseille, UMR 6110 CNRS-Université de Provence, BP 8, 13376 Marseille Cedex 12, France
6  INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
7  IASF - INAF, via Bassini 15, 20133 Milano, Italy
8  Institut d'Astrophysique de Paris, UMR 7095, 98 bis Bvd Arago, 75014 Paris, France
9  Observatoire de Paris, LERMA, 61 Avenue de l'Observatoire, 75014 Paris, France
10  IRA - INAF, via Gobetti 101, 40129 Bologna, Italy
11  INAF - Osservatorio Astronomico di Roma, via di Frascati 33, 00040 Monte Porzio Catone, Italy
12  Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées (UMR 5572), 14 avenue E. Belin, 31400 Toulouse, France
13  INAF - Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
14  Max Planck Institut fur Astrophysik, 85741 Garching, Germany
15  European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
16  Integral Science Data Centre, ch. d'Écogia 16, 1290 Versoix, Switzerland
17  Geneva Observatory, ch. des Maillettes 51, 1290 Sauverny, Switzerland

(Received 8 March 2006 / Accepted 19 July 2006)

Abstract
We investigate the redshift and luminosity evolution of the galaxy colour-density relation using the data from the First Epoch VIMOS-VLT Deep Survey (VVDS). The size (6582 galaxies with good quality redshifts), depth ( $I_\leq 24$) and redshift sampling rate (20% on the mean) of the survey enable us to reconstruct the 3D galaxy environment on relatively local scales (R=5$\,h^$ Mpc) up to redshift $z \sim 1.5$. Particular attention has been devoted to calibrate a density reconstruction scheme, which factors out survey selection effects and reproduces in an unbiased way the underlying "real" galaxy environment. We find that the colour-density relation shows a dramatic change as a function of cosmic time. While at lower redshift we confirm the existence of a steep colour-density relation, with the fraction of the reddest(/bluest) galaxies of the same luminosity increasing(/decreasing) as a function of density, this trend progressively disappears in the highest redshift bins investigated. Our results suggest the existence of an epoch (more remote for brighter galaxies) characterized by the absence of the colour-density relation on the R=5$\,h^$ Mpc scales investigated. The rest frame u*-g' colour-magnitude diagram shows a bimodal pattern in both low and high density environments up to redshift $z \sim 1.5$. We find that the bimodal distribution is not universal but strongly depends upon environment: at lower redshifts the colour-magnitude diagrams in low and high density regions are significantly different while the progressive weakening of the colour-density relation causes the two bimodal distributions to nearly mirror each other in the highest redshift bin investigated. Both the colour-density and the colour-magnitude-density relations, on the R=5$\,h^$ Mpc scales, appear to be a transient, cumulative product of genetic and environmental factors that have been operating over at least a period of 9 Gyr. These findings support an evolutionary scenario in which star formation/gas depletion processes are accelerated in more luminous objects and in high density environments: star formation activity is progressively shifting with cosmic time towards lower luminosity galaxies (downsizing), and out of high density environments.


Key words: cosmology: observations -- large scale structure of Universe -- galaxies: distances and redshifts -- galaxies: evolution -- galaxies: statistics -- galaxies: fundamental parameters



© ESO 2006


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