[61.05] On the Lack of a Soft X-Ray Excess from Galaxy Clusters

AAS 203rd Meeting, January 2004
Session 61 Galaxy Clusters and Large Scale Structure II
Oral, Tuesday, January 6, 2004, 10:00-11:30am, Centennial III

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[61.05] On the Lack of a Soft X-Ray Excess from Galaxy Clusters

E. J. Lloyd-Davies, J. N. Bregman (University of Michigan)

A soft X-ray excess has been claimed to exist in and around a number of galaxy clusters and this emission has been attributed to the warm-hot intergalactic medium that may constitute most of the baryons in the local universe. We have examined a study of the XMM-Newton observations by Kaastra et al. (2003) and find that their X-ray excess (or deficit) depends upon Galactic latitude and appears to be related to the surface brightness of the 1/4 keV emission, generally attributed to the Local hot bubble and the halo of the Milky Way. We suggest that the presence of the soft X-ray excess is due to incorrect subtraction of the soft X-ray background. A re-analysis of the observations, using backgrounds matched to the 1/4 keV X-ray background and hydrogen column in the vicinity of the clusters, supports this hypothesis.

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