Abstract
We studied the properties of the intracluster medium (ICM) of galaxy clusters to outer regions observed with Suzaku. The observed temperature dropped by about ~30% from the central region to the virial radius of the clusters. The derived entropy profile agreed with the expectation from simulations within <em>r<sub>500</sub></em>, while the entropy profile in<em> r &gt; r<sub>500</sub></em> indicated a flatter slope than the simulations. This would suggest that the cluster outskirts were out of hydrostatic equilibrium. As for the metallicity, we studied the metal abundances from O to Fe up to ~0.5 times the virial radius of galaxy groups and clusters. Comparing the results with supernova nucleosynthesis models, the number ratio of type II to Ia supernovae is estimated to be ~3.5. We also calculated not only Fe, but also O and Mg mass-to-light ratios (MLRs) with K-band luminosity. The MLRs in the clusters had a similar feature.
Highlights
Clusters of galaxies, the largest virialized systems in the universe, are filled with the intracluster medium (ICM), which consists of X-ray emitting hot plasma with a typical temperature of a few times 107 K
The mass profile of a cluster, which is a useful parameter for constraining cosmology, is determined through X-ray measurements of the temperature and density structure of the ICM under the assumption of hydrostatic equilibrium of the ICM
In the framework scenario of a hierarchical formation of structures based on the cold dark matter (CDM) paradigm, clusters are thought to grow into larger systems through mass accretion flows along large-scale filamentary structures
Summary
The largest virialized systems in the universe, are filled with the intracluster medium (ICM), which consists of X-ray emitting hot plasma with a typical temperature of a few times 107 K. Recent observations with Chandra and XMM-Newton allowed detailed studies of the metals in the ICM These observations, showed abundance profiles of O, Mg, Si and Fe only for the central regions of very bright clusters or groups of galaxies dominated by cD galaxies in a reliable manner (e.g., [7, 9, 20, 35]). Rasmussen et al [26, 27] report the Si and Fe profiles of 15 groups of galaxies observed with Chandra They suggest that the Si to Fe ratios in the groups tend to increase with radius, and the IMLRs within r500 show a positive correlation with the total group mass (temperature). The solar abundance table is given by Anders & Grevesse [2], and errors are within the 90 % confidence region for a single parameter of interest
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