1995/11/02 by A. Sołtan, Andrzej M. Soltan, Guenther Hasinger +11
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics (astro-ph) #Astrophysics and Cosmic Phenomena #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #astro-ph
paper · pdf · doi:10.48550/arxiv.astro-ph/9511009
18 pages, uuencoded gzipped postscript (due to technical reason one figure is not included into ps file), accepted for publication in the A&Ap
arxiv created 1995/11/02 · openalex publication_date 1995/11/02 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Large-scale fluctuations of the X-ray background are investigated using the\nROSAT All-Sky Survey. The autocorrelation function of the extragalactic\nbackground at 1 keV is determined at separations 0.1 - 40 deg. We detect a\nsignificant signal for separations < 6 deg, which is larger than previous upper\nlimits. We analyse the cross-correlation between the angular positions of Abell\nclusters of galaxies and the intensity of the X-ray background. The\ncross-correlation extends to several degrees for clusters of distance class\n.leq. 4. We conclude that Abell clusters are associated with extended, low\nsurface brightness X-ray haloes. The mean luminosity of the diffuse sources in\nthe 0.5-2.0 keV band is equal to approx 2.5 * 1043 h-2 erg s-1 and\ntheir characteristic radius a = 10 h-1 Mpc (H0 = 100 h km s-1 Mpc-1).\nIt is shown that the higher density of normal galaxies and AGNs around clusters\ncannot be responsible for the increased X-ray emission. This is because it\nwould produce a signal in the autocorrelation function measurable by the Ginga\nLAC experiment. Apparent extended emission could be produced either by a number\nof discrete sources associated with groups of galaxies concentrated around rich\nclusters or by a hot diffuse gas. It is shown that sources associated with\nAbell clusters account for approx. 30 % of the X-ray background fluctuations on\nscales above 1 deg.\n