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Temperature Map of the Virgo Cluster of Galaxies Observed with ASCA

R. Shibata·K. Matsushita·N. Y. Yamasaki·T. Ohashi·M. Ishida·K. Kikuchi·H. Boehringer·H. Matsumoto
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Abstract

The temperature distribution of the intracluster medium (ICM) in the Virgo cluster of galaxies has been derived from extensive mapping observations with ASCA covering an area of 19 deg^2. In the spectral analysis, the inner region within a radius of ~60' from M87 is characterized by an ICM temperature of kT \~2.5 keV with little variation. On the other hand, the outer regions indicate significant variation of the temperature with an amplitude of about 1 keV. The temperature map was produced from the hardness ratio (H.R.) values with a resolution of about 5'. Besides the previously reported hot region with kT > 4 keV between M87 and M49, several hot regions with kT = 3-4 keV are detected in the cluster outskirts. The auto-correlation function for the H.R. variation shows that the temperature variation is correlated within a size of about 300 kpc, suggesting that gas blobs falling in the Virgo cluster have a typical size of groups of galaxies. A correlation with the velocity dispersion of member galaxies shows that only the north-west region indicates an unusually large beta_spec value of 2-4. The upper limit for extended non-thermal emission in the Virgo cluster is obtained to be L_X ~9 x 10^41 ergs/s in the 2 - 10 keV band. We discuss that these features consistently indicate that the Virgo cluster is in a relatively early stage of the cluster evolution.

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R. Shibata, K. Matsushita, N. Y. Yamasaki, T. Ohashi, M. Ishida, K. Kikuchi, H. Boehringer, H. Matsumoto. 2000-10-19. Temperature Map of the Virgo Cluster of Galaxies Observed with ASCA. https://doi.org/10.1086/319075

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