1998/07/31 by S. Schindler, P. Belloni, Schindler, S. +11
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9807335
15 pages, including 9 figures, accepted for publication in A&A
arxiv created 1998/07/31 · openalex publication_date 1998/07/31 · arxiv updated 2009/12/01 · openalex created_date 2019/07/30 · openalex updated_date 2026/07/28
Recent X-ray observations of the rich galaxy cluster CL 0939+4713 at z = 0.41\nwith the ROSAT/HRI as well as with the ASCA/GIS and ASCA/SIS are presented and\nanalysed. With the high resolution imaging data we confirm and extend the\nearlier impression that the cluster has a lot of substructure. Two maxima of\nthe cluster emission are obvious in the images, each of them shows even some\ninternal structure. For the total luminosity of the cluster in the ROSAT band\nwe obtain L = 6.4-0.3+0.7 1044 erg/s. We perform spectral fits for the\ntwo ASCA instruments and for the ROSAT/PSPC simultaneously. The most reliable\nnumbers for the temperature and metallicity for the intracluster gas are T =\n7.6+2.8-1.6 keV and m = 0.22+0.24-0.22 Msol, respectively. We find\na relatively small total mass, a small gas mass ratio and a small iron mass to\nlight ratio. These numbers together with relatively low luminosity for such an\noptically rich cluster and the pronounced substructure confirm that CL\n0939+4713 is a young cluster still far away from a virialised state.\n In the same ROSAT/HRI image the X-ray emission of a background quasar (z\n\≈ 2) can clearly be identified. With a luminosity of L \≈ 1.4\n1045 erg/s it belongs to the X-ray brightest quasars. A striking difference\nbetween the ROSAT/PSPC and the ROSAT/HRI observations (taken almost five years\napart) is the fainting of one X-ray source RXJ0943.0+4701 by at least a factor\nof ten. We try to identify this source from deep optical data. Our best\ncandidate is a blue compact object, possibly an AGN.\n