X-ray Diagnostics of Thermal Conditions of the Hot Plasmas in the Centaurus Cluster

Abstract

X-ray data of the Centaurus cluster, obtained with XMM-Newton for 45 ksec, were analyzed. Deprojected EPIC spectra from concentric thin shell regions were reproduced equally well by a single-phase plasma emission model, or by a two-phase model developed by ASCA, both incorporating cool (1.7–2.0 keV) and hot ( ∼ 4 keV) plasma temperatures. However, EPIC spectra with higher statistics, accumulated over 3-dimentional thick shell regions, were reproduced better by the two-phase model than by the singe-phase one. Therefore, hot and cool plasma phases are inferred to co-exist in the cluster core region within ∼ 70 kpc. The iron and silicon abundances of the plasma were reconfirmed to increase significantly towards the center, while that of oxygen was consistent with being radially constant. The implied non-solar abundance ratios explains away the previously reported excess X-ray absorption from the central region. Although an additional cool ( ∼ 0.7 keV) emission was detected within ∼ 20 kpc of the center, the RGS data gave tight upper limits on any emission with a tempeartures – 2 –