Volume 406, Number 3, August II 2003
|Page(s)||789 - 795|
|Section||Cosmology (including clusters of galaxies)|
|Published online||17 November 2003|
The origin of X-ray emission of two distant () cluster candidates with XMM-Newton
CEA/Saclay DSM/DAPNIA/SAp, L'Orme des Merisiers, 91191 Gif-sur-Yvette, France
2 Observatoire de la Côte d'Azur, CERGA, BP 4229, 06304 Nice Cedex 4, France
3 ESO, Karl-Schwarzschild-Straße 2, 85748 Garching, Germany
4 Astronomical Observatory, Juliane Maries Vej 30, 2100 Copenhagen, Denmark
5 INAF – Osservatorio Astronomico di Bologna via Ranzani 1, 40127 Bologna, Italy
6 Laboratoire d'Astrophysique de Marseille, Traverse du Siphon – BP 8, 13376 Marseille Cedex 12, France
7 INAF – Osservatorio Astronomico di Trieste via G.B. Tiepolo 11, 34131 Trieste, Italy
Corresponding author: D. M. Neumann, email@example.com
Accepted: 14 April 2003
We present here a study of data of two distant galaxy cluster candidates. One of these was discovered serendipitously in near infrared data, CL J0533-2411, the other one corresponds to the cluster EIS J0533-2412 part of the EIS cluster survey. The estimated redshift of is . is a rich system (), with a spectroscopically confirmed redshift of . Both galaxy concentrations show firm X-ray detections, located within of their optical center. However, we cannot resolve the sources with . If the X-ray emission originates from the X-ray emitting intra-cluster medium (ICM) it would be extremely concentrated which is rather unlikely (core radii below kpc and kpc, respectively). We argue that the X-ray sources are more likely AGN members of the galaxy concentrations. We set an upper limit for the bolometric luminosity of a hot ICM in the range ~ erg/s for , depending on the exact redshift. For the limit is erg/s. We interpret our result in the following way: (and possibly ) are proto-clusters and show matter overdensities before collapse, which explains the low significance of extended X-ray emission.
Key words: cosmology: observations / cosmology: large-scale structure of Universe / galaxies: clusters: individual: , / X-rays: galaxies: clusters / galaxies: active
© ESO, 2003
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