New spectroscopic redshifts from the CDFS and a test of the cosmological relevance of the GOODS-South field^*

¹ GEPI, Observatoire de Paris-Meudon, 92195 Meudon, France e-mail: Chazhiyat.Ravikumar@obspm.fr
² Institut d'Astrophysique du CNRS, 98bis Boulevard Arago, 75014 Paris, France
³ Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching bei München, Germany
⁴ Inter University Center for Astronomy & Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007, India
⁵ Laboratoire d'Astrophysique de Marseille, Observatoire Astronomique de Marseille-Provence, 2 place Le Verrier, 13248 Marseille, France
⁶ Dipartimento di Astronomia, Vicolo Osservatorio 2, 35122 Padova, Italy
⁷ ESO, Karl-Schwarzschild Strase 2, 85748 Garching bei München, Germany
⁸ INAF, Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, 50125 Florence, Italy
⁹ LERMA, Observatoire de Paris, 61 Av. de l'Observatoire, 75014 Paris, France
¹⁰ National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719, USA
¹¹ CEA Saclay/DSM/DAPNIA/Service d'Astrophysique, Orme des Merisiers, 91191 Gif-sur-Yvette Cedex, France
¹² MPIA, Königstuhl 17, 69117 Heidelberg, Germany
¹³ Centre de Recherche Astronomique de Lyon, 9 avenue Charles Andr, 69561 Saint-Genis-Laval Cedex, France
¹⁴ National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing 100012, PR China
¹⁵ INAF – Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy

Received: 4 April 2006
Accepted: 28 November 2006

Abstract

Context.This paper prepares a series of papers analysing the Intermediate MAss Galaxy Evolution Sequence (IMAGES) up to a redshift of one. Intermediate mass galaxies () are selected from the Chandra Deep Field South (CDFS) for which we identify a serious lack of spectroscopically determined redshifts.

Aims.Our primary aim in this study is therefore to obtain a sample of intermediate-mass galaxies with known spectroscopic redshift to be used for further analysis of their 3D-kinematics. We also intend to test whether this important cosmological field may be significantly affected by cosmic variance.

Methods.The spectroscopic observations were carried out using VIMOS on the ESO VLT. The data reduction was done using a set of semi-automatic IRAF procedures developed by our team.

Results.We have spectroscopically identified 691 objects including 580 galaxies, 7 QSOs, and 104 stars. The overall completeness achieved is about 76% for objects with in the CDFS after excluding instrumental failures. This study provides 531 new redshifts in the CDFS. It confirms the presence of several large-scale structures in the CDFS, which are found to be more prominent than in other redshift surveys. To test the impact of these structures in the GOODS-South field, we constructed a representative redshift catalog of 640 galaxies with and . We then compared the evolution of rest-frame U, B, V, and K galaxy luminosity densities to the one derived from the Canada France Redshift Survey (CFRS). The GOODS South field shows a significant excess of luminosity densities in the –0.75 range, which increases with the wavelength, reaching up to 0.5 dex at 2.1 μm. Stellar mass and specific star formation evolutions might be significantly affected by the presence of the peculiar large-scale structures at and at , which contain a significant excess of evolved, massive galaxies when compared to other fields.

Conclusions.This leads to a clear warning about the results based on the CDFS/GOODS South fields, especially those related to the evolution of red luminosity densities, i.e. stellar mass density and specific star formation rate. Photometric redshift techniques, when applied to that field, are producing quantities that are apparently less affected by cosmic variance (0.25 dex at 2.1 μm), however, at the cost of any ease in disentangling the evolutionary and cosmic variance effects.