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The Soft X-Ray Emission in a Large Sample of Galaxy Clusters with ROSAT PSPCThe study of soft X-ray emission of 38 X-ray selected galaxy clusters observed by ROSAT PSPC indicates that the soft excess phenomenon may be a common occurrence in galaxy clusters. Excess soft X-ray radiation, above the contribution from the hot intra-cluster medium, is evident in a large fraction of sources, and is clearly detected with large statistical significance in the deepest observations. The investigation relies on new, high resolution 21 cm HI observations. The sample selection also features analysis of infrared images, to further ensure reliability of results with respect to the characteristics of Galactic absorption. The possibility of background or calibration effects as cause of the excess emission is likewise investigated; a detailed analysis of the distribution of the excess emission with respect to detector position and Galactic HI column density shows that the excess emission is a genuine celestial phenomenon. We find evidence for a preferential distribution of the soft excess emission at distances larger than approx. 150-200 kpc from the centers of clusters; this behavior may be naturally explained in the context of a non-thermal Inverse-Compton scenario. Alternatively, we propose that the phenomenon maybe caused by thermal emission of very large-scale 'warm' filaments seen in recent hydrodynamic simulations. This new interpretation relieves the very demanding requirements of either the traditional intra-cluster 'warm' gas and the non-thermal scenarios. We also investigate the possibility of the soft excess originating from unresolved, X-ray faint cluster galaxies.
Document ID
20020067785
Acquisition Source
Marshall Space Flight Center
Document Type
Preprint (Draft being sent to journal)
Authors
Bonamente, Massimiliano
(Alabama Univ. AL United States)
Lieu, Richard
(Alabama Univ. AL United States)
Joy, Marshall K.
(NASA Marshall Space Flight Center Huntsville, AL United States)
Nevalainen, Jukka H.
(Alabama Univ. AL United States)
Six, N. Frank
Date Acquired
August 20, 2013
Publication Date
January 1, 2002
Subject Category
Space Radiation
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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