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J. P. Henry (Institute for Astronomy, University of Hawaii)
We have determined the cluster X-ray temperature function from two flux-limited samples. The first sample is comprised of 25 clusters with average redshift 0.05. The second is comprised of 14 clusters with average redshift 0.38. We perform maximum likelihood fits of cluster evolution models to these data in order to constrain cosmological parameters. For an open model with zero cosmological constant we find that the density parameter is \Omega0 = 0.52 ±0.11, the rms mass density fluctuation averaged over 8 h-1 Mpc spheres is \sigma8 = 0.71 ±0.09, and the effective index of the mass density fluctuation spectrum on cluster scales is n = -(1.7 ±0.3) where all errors are symmetrized at 68% confidence. The corresponding results for the case where a cosmological constant produces a flat universe are: 0.45 ±0.11, 0.77 ±0.15, and -(1.7 ±0.3). These results agree with those determined from a variety of different independent methods, including supernovae, galaxy-galaxy correlations, fluctuations in the microwave background, and cluster peculiar velocities.
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