Prospects for SODART observations of nearby clusters ofgalaxies

Abstract

Using the current best understanding of the SODART mirror system, the Braggpanel and of the LEPC/HEPC responses [1] we have studied the feasibility andprospects for SODART studies of nearby clusters of galaxies. From simulatedHEPC data of the cluster Abell 2256, we demonstrate that SODART observationsof the hot intergalactic gas in nearby clusters offer an opportunity for efficientmapping of the hot gas temperature structure all the way to the virial radius.The temperature map is a good diagnostic of the dynamical state of a cluster,and for relaxed clusters the temperature profile derived from HEPC data allows astraight forward determination of the cluster mass profile with a formal accuracycomparable to the effects of systematics.As a case study for assessing the feasibility of Bragg panel observations ofclusters we have simulated observations of the Perseus cluster core with the LiFand RAP crystals. Using the LiF crystals, it is possible to scan each of the Fe-K lines from the hot gas in a few 30 ks exposures enabling possible detectionof turbulence and/or bulk flow of the hot gas. Substantially longer exposuresare required with the RAP crystals for studying lines originating in cool gas,but the line strengths are heavily dependent on the temperature of the cool gas.Hence, for the Perseus cluster, and perhaps a handful of other clusters, the uniquecapabilities of the Bragg panel for spectro-imaging of extended sources providedirect insight into the plasma processes in the gas.