EDP Sciences
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Volume 408, Number 1, September II 2003
Page(s) 51 - 56
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20030963

A&A 408, 51-56 (2003)
DOI: 10.1051/0004-6361:20030963

Galaxy and hot gas distributions in the z = 0.52 galaxy cluster RBS 380 from CHANDRA and NTT observations

R. Gil-Merino1 and S. Schindler2

1  Institute für Physik, Universität Potsdam, Am Neuen Palais 10, 14469 Potsdam, Germany
2  Institut für Astrophysik, Universität Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria
    e-mail: Sabine.Schindler@uibk.ac.at

(Received 19 May 2003 / Accepted 17 June 2003)

We present CHANDRA X-ray and NTT optical observations of the distant z=0.52 galaxy cluster RBS 380 - the most distant cluster of the ROSAT Bright Source (RBS) catalogue. We find diffuse, non-spherically symmetric X-ray emission with a X-ray luminosity of $L_{\rm X}(0.3{-}10~{\rm keV})=1.6\times 10^{44}$ erg/s, which is lower than expected from the RBS. The reason is a bright AGN in the centre of the cluster contributing considerably to the X-ray flux. This AGN could not be resolved with ROSAT. In optical wavelength we identify several galaxies belonging to the cluster. The galaxy density is at least  2 times higher than expected for such a X-ray faint cluster, which is another confirmation of the weak correlation between X-ray luminosity and optical richness. The example of the source confusion in this cluster shows how important high-resolution X-ray imaging is for cosmological research.

Key words: galaxies: clusters: general -- intergalactic medium -- cosmology: observations -- cosmology: theory -- dark matter  -- X-rays: galaxies

Offprint request: R. Gil-Merino, rmerino@astro.physik.uni-potsdam.de

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