EDP Sciences
Free Access
Volume 417, Number 3, April III 2004
Page(s) 819 - 825
Section Cosmology (including clusters of galaxies)
DOI https://doi.org/10.1051/0004-6361:20034229
Published online 26 March 2004

A&A 417, 819-825 (2004)
DOI: 10.1051/0004-6361:20034229

Abundance constraints and direct redshift measurement of the diffuse X-ray emission from a distant cluster of galaxies

Yasuhiro Hashimoto1, X. Barcons2, H. Böhringer1, A. C. Fabian3, G. Hasinger1, V. Mainieri1 and H. Brunner1

1  Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, 85748 Garching, Germany
2  Instituto de Física de Cantabraia (CSIC-UC), 39005 Santander, Spain
3  Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK

(Received 26 August 2003 / Accepted 12 January 2004)

We report on the XMM-Newton (XMM) observation of RX J1053.7+5735, one of the most distant X-ray selected clusters of galaxies, which also shows an unusual double-lobed X-ray morphology, indicative of a possible equal-mass cluster merger. The cluster was discovered during the ROSAT deep pointings in the direction of the Lockman Hole. All XMM Lockman Hole observations (PV, AO-1 & AO-2 phases) with the European Photon Imaging Camera (EPIC) were combined for the analysis, totaling exposure times ~648 ks, 738 ks, and 758 ks for pn, MOS1, and MOS2, respectively. With this "deep" dataset, we could detect the Fe K line and obtain a strong constraint on cluster metallicity, which is difficult to achieve for clusters at  z > 1. The best-fit abundance is 0.46 +0.11-0.07 times the solar value. The Fe line emission also allows us to directly estimate the redshift of diffuse gas, with a value z = 1.14+0.01-0.01. This is one of the first clusters whose X-ray redshift is directly measured prior to the secure knowledge of cluster redshift by optical/NIR spectroscopy. We could also estimate the X-ray redshift separately for each of the two lobes in the double-lobed structure, and the result is consistent with the two lobes being part of one cluster system at the same redshift. Comparison with other metallicity measurements of nearby and distant clusters shows that there is little evolution in the ICM metallicity from  $z \sim 1$ to the present.

Key words: X-rays: galaxies: clusters -- cosmology: cosmological parameters -- galaxies: high-redshift

Offprint request: Yasuhiro Hashimoto, hashimot@mpe.mpg.de

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© ESO 2004

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