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J. Krick (U. Michigan), J.S. Arabadjis (MIT), J. N. Bregman (U. Michigan)
X-ray observations of extragalactic sources are corrected for Galactic absorption, often under the assumption that the Galactic column is a constant value that can be measured from 21 cm observations. However, the Galactic column can vary on small scales and this can have an important effect in the absorption correction of extended sources, such as clusters of galaxies. By not including variations in the HI column, systematic residuals appear in spectral fits to extended sources that are manifest as either excess absorption or excess emission. We discuss the degree to which that this can lead to a very soft emission component in galaxy clusters, as has been claimed.