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W. H. Baumgartner, D. Horner, K. C. Gendreau (NASA/GSFC), C. A. Scharf (STScI), S. Molnar, R. F. Mushotzky (NASA/GSFC)
We present a database of X-ray redshifts for over 200 galaxy clusters observed with the ASCA satellite. Optical determinations of cluster redshifts suffer from the effects of shot noise, and from fore and background contamination from other clusters and field galaxies. X-ray measurements are not affected by these problems, and are a better redshift indicator because the X-ray gas is a more accurate tracer of the cluster potential. The temperature of this gas is typically 1 -- 10 keV and is well suited to the ASCA bandpass of 0.2 -- 10 keV. We fit a single temperature plasma model to all the available cluster data in the ASCA public archives and obtain X-ray redshifts. We compare the results to a compilation of optical data extracted from the literature and conclude that the X-ray redshifts are in excellent agreement; above 3 keV the x-ray and optical redshifts are the same with a standard deviation of delta z=0.02.
The author(s) of this abstract have provided an email address for comments about the abstract: wayne@milkyway.gsfc.nasa.gov