Temperature map of the Virgo cluster of galaxies observed with ASCA.
SHIBATA R., MATSUSHITA K., YAMASAKI N.Y., OHASHI T., ISHIDA M., KIKUCHI K., BOHRINGER H. and MATSUMOTO H.
Abstract (from CDS):
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 deg2. 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 (HR) 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 autocorrelation function for the HR 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 northwest region indicates an unusually large βspec value of 2-4. The upper limit for extended nonthermal emission in the Virgo Cluster is obtained to be LX∼9x1041 ergs.s–1 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.