QUANTIFYING THE MORPHOLOGIES AND DYNAMICAL EVOLUTION OF GALAXY CLUSTERS. Ⅱ. APPLICATION TO A SAMPLE OF ROSAT CLUSTERS

摘要

We quantify the morphologies and dynamical states of 59 galaxy clusters using the power ratio technique of Buote & Tsai applied to ROSAT PSPC X-ray images. The clusters exhibit a particularly strong P_2/P_0-P_4/P_0 correlation in the 1 h_(80)~(-1) Mpc aperture which may be interpreted as an evolutionary track; the location of a cluster on the correlation line indicates the dynamical state of the cluster, and the distribution of clusters along this track measures the rate of formation and evolution of clusters in our sample. The power ratios anticorrelate with the cooling flow rate, indicating a reasonable dependence of the flow rate on cluster morphology. The relationship of the power ratios to the optical Bautz-Morgan (BM) type is more complex. This is because the power ratios are sensitive to unrelaxed regions of clusters within a specified scale, whereas BM types are sensitive to unrelaxed regions over many scales. We discuss further astrophysical applications exploiting the relationship between the power ratios and the evolutionary states of clusters.