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Session 37 - X-ray Clusters: Implications for Cosmology.
Display session, Tuesday, June 09
Atlas Ballroom,
Spectroscopic observations of AGN are very useful for determining the structure and evolution of intervening gaseous material in the universe to high redshifts. Optical spectroscopy of AGN over the past 20 years has produced many interesting results concerning the evolution of the warm gas in Ly \alpha clouds. Another major component of gaseous material in the universe is the hot gas (kT = 1-10 keV) in clusters of galaxies. Due to the high gas temperatures, the strongest absorption lines in clusters arise from H-like and He-like Fe K \alpha (6.7-6.9 keV), with expected equivalent widths of \sim 10eV. Past X-ray telescopes have not had the combined effective area and spectral resolution to detect such absorption lines. In the next decade, several X-ray telescopes will be launched with the required characteristics to detect these absorption lines (AXAF, Astro-E, Spectrum X-Gamma, and Constellation). We will show that the distribution of equivalent widths derived from a collection of AGN observations is a very sensitive measure of cluster evolution out to z \sim 2. We will also make predictions for the distribution of equivalent widths in AGN samples based on several different cosmological scenarios.
