Volume 544, August 2012
|Number of page(s)||9|
|Section||Cosmology (including clusters of galaxies)|
|Published online||07 August 2012|
1 Astronomical Department, Padova University, vicolo dell’Osservatorio 3, 35122 Padova, Italy
2 INAF – Astronomical Observatory of Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
3 School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD, UK
4 Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
5 Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94309, USA
6 Sterrenkundig Observatorium Vakgroep Fysica en Sterrenkunde Universeit Gent, Krijgslaan 281, S9 9000 Gent, Belgium
7 Observatoire de Genève, Laboratoire d’Astrophysique, École Polytechnique Fédérale de Lausanne (EPFL), 1290 Sauverny, Switzerland
8 GEPI, Observatoire de Paris, CNRS UMR 8111, Université Paris Diderot, 92125 Meudon Cedex, France
9 Royal Observatory, Blackheath Avenue, Greenwich, SE10 8XJ, UK
10 Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721, USA
Received: 12 April 2012
Accepted: 5 July 2012
We present new spectroscopic observations in a field containing the highest redshift cluster of the ESO Distant Cluster Survey (EDisCS). We measure galaxy redshifts and determine the velocity dispersions of the galaxy structures located in this field. Together with the main cluster Cl 1103.7−1245 (z = 0.9580; σclus = 522 ± 111 km s-1) we find a secondary structure at z = 0.9830, Cl 1103.7−1245c. We then characterize the galaxy properties in both systems, and find that they contain very different galaxy populations. The cluster Cl 1103.7−1245 hosts a mixture of passive elliptical galaxies and star-forming spirals and irregulars. In the secondary structure Cl 1103.7−1245c all galaxies are lower-mass star-forming irregulars and peculiars. In addition, we compare the galaxy populations in the Cl 1103.7−1245 z = 0.9580 cluster with those in lower redshift EDisCS clusters with similar velocity dispersions. We find that the properties of the galaxies in Cl 1103.7−1245 follow the evolutionary trends found at lower redshifts: the number of cluster members increases with time in line with the expected growth in cluster mass, and the fraction of passive early-type galaxies increases with time while star-forming late types become less dominant. Finally, we find that the mean stellar masses are similar in all clusters, suggesting that massive cluster galaxies were already present at z ~ 1.
Key words: galaxies: clusters: general / galaxies: evolution / galaxies: distances and redshifts
Based on observations collected at the European Southern Observatory (ESO) Chile, as part of programme 080.A-0180(A), as well as on programme 166.A-0.162 (the ESO Distant Cluster Survey).
Full Table 1 is only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (184.108.40.206) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/544/A104
© ESO, 2012
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