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[70.03] Oxygen Abundances in the ISM using X-ray Absorption Measurements towards Galaxy Clusters

W.H. Baumgartner (UMD, NASA/GSFC)

We present measurements of the oxygen abundance of the Galaxy by observing the K-shell X-ray photoionization edge towards galaxy clusters with the EPIC camera on XMM. This effect is most easily observed towards objects with galactic hydrogen columns (n_H) of a few times 1.0 x 10²¹ cm^-2. We observe 10 clusters near the galactic plane at several galactic longitudes and find oxygen abundances consistent with recent solar photospheric values. Since X-ray observations are sensitive to the total amount of oxygen present (gas + dust), these results combined with recent gas phase oxygen measurements in the local ISM indicate a high gas to dust ratio and that dust depletion onto grains is less prevalent than previously thought.

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Bulletin of the American Astronomical Society, 35#5
© 2003. The American Astronomical Soceity.