The Warm-Hot Intergalactic Medium in Cluster Vicinities(Chapter 2. Thermal Structure/Dynamics of Groups and Clusters of Galaxies, The Extreme Universe in the Suzaku Era)

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A large (30-50%) fraction of baryons is thought to reside in the warm-hot intergalactic medium (WHIM), the intergalactic medium with T = 10^<5-7> K and n_H = 10^<-6>-10^<-4> cm^<-3>. With currently available detectors, cluster vicinities are the most promising location to search for signals from the WHIM. We studied two cluster vicinities: the Coma cluster and A2218. In the Coma vicinity, we observed Ne IX absorption and emission lines. The line-of-sight scale of the plasma is calculated to be larger than the virial radius of the cluster. Although we did not detect signals from the WHIM in A2218 vicinity, we obtained upper limits for the O VII and O VIII line intensities that are significantly tighter than the previously reported ones around other clusters. Comparing numerical simulations and our results shows that our sensitivity reaches to the high density end of the WHIM.
理論物理学刊行会の論文
2007-12-19