Astronomy & Astrophysics

Free access article

A&A 417, 839-846 (2004)
DOI: 10.1051/0004-6361:20031767

The VIRMOS deep imaging survey

I. Overview, survey strategy, and CFH12K observations

O. Le Fèvre¹, Y. Mellier^{2, 3}, H. J. McCracken^{1, 4}, S. Foucaud¹, S. Gwyn¹, M. Radovich^{2, 5}, M. Dantel-Fort³, E. Bertin^{2, 3}, C. Moreau¹, J.-C. Cuillandre⁶, M. Pierre⁷, V. Le Brun¹, A. Mazure¹ and L. Tresse¹

¹ Laboratoire d'Astrophysique de Marseille, UMR 6110, CNRS-Université de Provence, Traverse du Siphon-Les trois Lucs, 13012 Marseille, France
² Institut d'Astrophysique de Paris, UMR 7095, 98bis Bvd Arago, 75014 Paris, France
³ Observatoire de Paris, LERMA, UMR 8112, 61 Av. de l'Observatoire, 75014 Paris, France
⁴ Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
⁵ Osservatorio di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
⁶ Canada-France Telescope Corporation, 65-1238 Mamalahoa Hwy, Kamuela, Hawaii 96743, USA
⁷ Service d'Astrophysique, CE Saclay, L'Orme des Meurisiers, 91191 Gif-sur-Yvette Cedex, France

(Received 12 June 2003 / Accepted 19 December 2003 )

Abstract
This paper describes the CFH12K-VIRMOS survey: a deep ${\it BVRI}$ imaging survey in four fields totalling more than $17\deg^2$ , conducted with the $40\times30$ arcmin ² field CFH-12K camera. The survey is intended to be a multi-purpose survey used for a variety of science goals, including surveys of very high redshift galaxies and weak lensing studies. Four high galactic latitude fields, each $2\times2$ deg ², have been selected along the celestial equator: 0226-04, 1003+01, 1400+05, and 2217+00. The 16 deg ² of the "wide" survey are covered with exposure times of 2 hr, 1.5 hr, 1 hr, 1 hr, respectively while the $1.3\times1$ deg ² area of the "deep" survey at the center of the 0226-04 field is covered with exposure times of 7 h, 4.5 h, 3 h, 3 h, in ${\it BVRI}$ respectively. An additional area ~2 deg ² has been imaged in the 0226-04 field corresponding to the area surveyed by the XMM-LSS program (Pierre et al. 2003). The data is pipeline processed at the Terapix facility at the Institut d'Astrophysique de Paris to produce large mosaic images. The catalogs produced contain the positions, shapes, total and aperture magnitudes for 2.175 million objects measured in the four areas. The limiting magnitudes, measured as a $5\sigma$ measurement in a 3 arcsec diameter aperture is $I_{\rm AB}=24.8$ in the "Wide" areas, and $I_{\rm AB}=25.3$ in the deep area. Careful quality control has been applied on the data to ensure internal consistency and assess the photometric and astrometric accuracy as described in a joint paper (McCracken et al. 2003). These catalogs are used to select targets for the VIRMOS-VLT Deep Survey, a large spectroscopic survey of the distant universe (Le Fèvre et al. 2003). First results from the CFH12K-VIRMOS survey have been published on weak lensing (e.g. van Waerbeke & Mellier 2003). Catalogs and images are available through the VIRMOS database environment under Oracle (http://www.oamp.fr/cencos). They are open for general use since July 1st, 2003.

Key words: cosmology: observations -- galaxies: evolution -- cosmology: gravitational lensing -- cosmology: large-scale structure of universe

Offprint request: O. Le Fèvre, olivier.lefevre@oamp.fr