The mass-temperature relation of 22 nearby clusters

We present a new investigation of the mass-temperature (M-tot-T-x) relation of 22 nearby clusters based on the analysis of their ROSAT X-ray surface b rightness profiles (S-x[r]) and their ASCA emission-weighted temperatures. Two methods of the cluster mass estimations are employed and their results are compared: (1) the conventional beta -model for gas distribution along w ith the isothermal and hydrostatic equilibrium assumptions, and (2) the NFW profile for dark matter distribution whose characteristic density and leng th are determined by the observed S-x(r). These two models yield essentiall y the same goodness of fits far S-x(r) and the similar M-tot-T-x relations, with the latter demonstrating a significant departure from the simple grav itational scaling of M-tot proportional to T-x(3/2). It is also shown that the best-fit M-tot-T-x relations could be reconciled with the theoretical e xpectation if the low-temperature clusters (T-x < 3.5 keV) are excluded fro m the list, which lends support to the scenario that the intracluster mediu m is preheated in the early phase of cluster formation. Together with the e ntropy-temperature distribution, the existence of a similarity break at T-x = 3-4 keV in the dynamical scaling relations for galaxy clusters has been confirmed.