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[35.04] The unresolved X-ray background: results from XMM-Newton and Chandra

M.A. Worsley, A.C. Fabian (IoA, Cambridge, UK), X. Barcons, S. Mateos (CSIC-UC, Santander, Spain), G. Hasinger, H. Brunner (MPE, Garching, Germany)

Most of the soft, and a growing fraction of the harder X-ray background has been resolved into emission from point sources; yet the resolved fraction above ~\thinspace\rm{keV} has only been poorly constrained. We use the deep XMM-Newton 700\thinspace\rm{ks} observation of the Lockman Hole, and a photometric approach, to estimate the total flux attributable to resolved sources in a number of different energy bands. We find the resolved fraction to be nearly ~00% in the soft bands at or below 2\thinspace\rm{keV}, but this decreases rapidly above ~\thinspace\rm{keV} to ~0-70%. The available photometry from the Chandra Deep Fields North and South is able to confirm this trend; with indications of an unresolved source population emerging at hard energies. The unresolved background component has the spectral signature of a population of highly obscured AGN. Finally, we report on the progress we have made in trying to identify and analyse the missing sources.

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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.