Open AccessCross‐correlation of the unresolved X‐ray background with faint galaxies
Author(s) -
Newsam A. M.,
McHardy I. M.,
Jones L. R.,
Mason K. O.
Publication year - 1999
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.1999.02939.x
Subject(s) - physics , astrophysics , astronomy , qsos , galaxy , luminous infrared galaxy , peculiar galaxy , elliptical galaxy , galaxy cluster , radio galaxy , population , galaxy group , quasar , demography , sociology
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.