AAS Meeting #194 - Chicago, Illinois, May/June 1999
Session 19. Galaxy Clusters and Large Scale Structure
Oral, Monday, May 31, 1999, 10:00-11:30am, International Ballroom North

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[19.02] How does a Cluster's Dynamical State affect ICM Temperature Measurements?

B. F. Mathiesen, A. E. Evrard (U. of Michigan)

A relationship between intracluster medium (ICM) mass and temperature with small scatter (about 15%) has been found in both simulations and X-ray observations. This relationship already shows potential as a method for determining cluster masses, and may become quite precise if the relationship between a cluster's temperature structure and dynamical state can be understood. Using a preexisting ensemble of hydrodynamic cluster simulations, we select a sample of typical merger events and resimulate them with finely spaced outputs. Assuming a Raymond-Smith model for the particle emission, we create spatially resolved spectral images for each output and use them to create temperature maps of quality comparable to those available from the Chandra mission. The data demonstrate that even in relaxed clusters, cooler gas in the outskirts creates an excess of soft X-rays, typically biasing spectral fits to temperatures lower than the corresponding mass-weighted temperature. We also track the evolution of each cluster along the mass-temperature relation as it goes through major and minor accretion events, and measure the degree of scatter attributable to the process of absorption and equilibration. Finally, we discuss ways in which the underlying mass-weighted temperature structure of a cluster may be determined, given a spectral image of sufficient quality.

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