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Session 37 - X-ray Clusters: Implications for Cosmology.
Display session, Tuesday, June 09
Atlas Ballroom,
The High Energy Transmission Grating (HETG) onboard AXAF will provide the first opportunity since the Einstein Focal Plane Crystal Spectrometer (FPCS) to obtain high resolution X-ray spectra from the cores of galaxy clusters. The cores of these objects are known to contain large quantities of cool gas and should be rich sources of X-ray line emission. With an energy resolution of E/\Delta E \sim 1000, the HETG will be capable of resolving individual X-ray emission lines in the cluster spectrum. Measurement of individual line fluxes will provide several independent and simultaneous determinations of the amount of cooling material in these objects, currently thought to be as high as 100--1000 M_ødot yr^-1. The detection of lines produced by material at several different densities and temperatures would verify that the gas in cluster cores is inhomogeneous as implied by broad-band X-ray surface brightness profiles. X-ray line profiles can provide information on opacity in the core and line widths will allow us to place limits on the turbulence in the gas which is likely to dominate over broadening due to inflow velocity or thermal broadening. Finally, accumulated cold material in cluster cores should produce a number of effects (X-ray line flux reduction, absorption edges, etc.) which are potentially observable with AXAF's high energy resolution. Using detailed, realistic simulations, we demonstrate some of the potential insights which AXAF HETG observations of cluster cooling cores will provide.
