Cross-correlation of the unresolved X‐ray background with faint galaxies |
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| Authors: | A M Newsam I M McHardy L R Jones K O Mason |
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| Institution: | Department of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ; Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead CH41 1LD; School of Physics and Space Research, University of Birmingham, Edgbaston, Birmingham B15 2TT; Mullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking RH5 6NT |
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| Abstract: | At the faint end of the deepest X-ray surveys, a population of X-ray luminous galaxies is seen. In this paper, we present the results of a cross-correlation between the residual, unresolved X-ray photons in a very deep X-ray survey and the positions of faint galaxies, in order to examine the importance of these objects at even fainter flux levels. We measure a significant correlation on all angular scales up to ∼1 arcmin. This signal could account for a significant fraction of the unresolved X‐ray background, approximately 35 per cent if the clustering is similar to optically selected galaxies. However, the angular form of the correlation is seen to be qualitatively similar to that expected for clusters of galaxies and the X-ray emission could be associated with hot gas in clusters or with QSOs within galaxy clusters rather than emission from individual faint galaxies. The relative contribution from each of these possibilities cannot be determined with the current data. |
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| Keywords: | galaxies: active galaxies: clusters: general diffuse radiation X-rays: galaxies X-rays: general |
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