The Vimos VLT deep survey: compact structures in the CDFS

¹ Laboratoire d'Astropysique de Marseille, UMR 6110 CNRS-Université de Provence, BP 8, 13376 Marseille Cedex 12, France e-mail: christophe.adami@oamp.fr
² INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
³ IASF - INAF, via Bassini 15, 20133 Milano, Italy
⁴ Laboratoire d'Astrophysique de l'Observatoire Midi-Pyrénées (UMR 5572), 14 avenue E. Belin, 31400 Toulouse, France
⁵ IRA - INAF, via Gobetti 101, 40129 Bologna, Italy
⁶ INAF - Osservatorio Astronomico di Capodimonte, via Moiariello 16, 80131 Napoli, Italy
⁷ Università di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy
⁸ Max Planck Institut fur Astrophysik, 85741, Garching, Germany
⁹ Institut d'Astrophysique de Paris, UMR 7095, 98 bis Bd Arago, 75014 Paris, France
¹⁰ European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching bei München, Germany
¹¹ INAF - Osservatorio Astronomico di Brera, via Brera 28, Milan, Italy
¹² Observatoire de Paris, LERMA, 61 avenue de l'Observatoire, 75014 Paris, France

Received: 6 April 2005
Accepted: 20 July 2005

Abstract

We used the Vimos VLT Deep Survey in combination with other spectroscopic, photometric, and X-ray surveys from the literature to detect several galaxy structures in the Chandra Deep Field South (CDFS). Both a friend-of-friend-based algorithm applied to the spectroscopic redshift catalog and an adaptative kernel galaxy density and color maps correlated with photometric redshift estimates were used. 
We mainly detected a chain-like structure at and two massive groups at and 1.098 showing signs of ongoing collapse. We also detected two galaxy walls at and at (extremely compact in redshift space). The first one contains the chain-like structure and the last one contains one of the two massive groups in its center. Finally, other galaxy structures that are probably loose low mass groups were detected. 
We compared the group galaxy population with simulations in order to assess the richness of these structures and studied their galaxy morphological contents. The higher redshift structures appear to probably have lower velocity dispersion than the nearby ones. The number of moderately massive structures we detected is consistent with what is expected for an LCDM model, but a larger sample is required to put significant cosmological constraints.