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A. D. Lewis, J. T. Stocke, E. Ellingson (University of Colorado), E. J. Gaidos (Caltech Jet Propulsion Laboratory)
The Einstein Extended Medium Sensitivity Survey (EMSS) remains a critical cosmological constraint on the most massive clusters in the universe, though the detection of evolution in the cluster X-ray luminosity function (XLF) remains controversial. We have re-analyzed the EMSS cluster sample to establish if (1) the sample is incomplete, and (2) the previous determinations of XLF evolution require revision. We have performed a detailed analysis of all available ROSAT images of the EMSS clusters at z \geq 0.14 (those used in the XLF determination), confirming their existence, position, extent, and parameterizing their surface brightness (SB) distribution. We make an improved correction to the detected flux based on SB profiles, as well as a more precise K-correction using new X-ray temperature measurements.
In addition, the IPC X-ray images have been re-analyzed using a multi-aperture source detection algorithm. A catalog of 772 new source candidates detected within the central regions of the EMSS fields has been compiled. We have performed a detailed investigation of both random and non-random sub-samples of the new sources (the latter being specifically selected to discover clusters of galaxies), including statistical analysis, X-ray database search, and new optical imaging. We find that while the majority of these sources are not clusters, our optical imaging study did discover both low-redshift groups as well as distant clusters of galaxies, suggesting that ~2% of the new sources are actual distant clusters.
We present the changes to the EMSS sample, including misidentifications, flux corrections, new or improved redshift determinations, and the new clusters discovered in our IPC re-analysis. We also present estimates of the effects on the evolution of the cluster XLF. Our results indicate that the original EMSS was mildly incomplete, and that the previously reported negative evolution is now removed.
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