Schedule Mar 18, 2011
OVII Emission in Stacked Cluster Spectra
Jeremy Sanders (Univ. Cambridge)

High resolution X-ray spectroscopy allows accurate determinations of the temperature distribution of the intracluster medium (ICM) in the cores of galaxy clusters. For the first time we detect O VII emission, emitted from material around 0.35 keV (~4MK), in a stacked 1.2 Ms spectrum of objects with central temperatures below 1 keV. The ratio of the O VII to Fe XVII emission is 1/4 to 1/8 of the amount expected if the material is cooling radiatively. Another interesting finding is that the average nitrogen to oxygen abundance ratio is 4 times the Solar value, which has implications for understanding intermediate mass stars in these objects.

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