2001ApJ...553...78X

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 brightness profiles (S_Xr) and their ASCA emission-weighted temperatures. Two methods of the cluster mass estimations are employed and their results are compared: (1) the conventional β-model for gas distribution along with the isothermal and hydrostatic equilibrium assumptions, and (2) the NFW profile for dark matter distribution whose characteristic density and length are determined by the observed S_X(r). These two models yield essentially the same goodness of fits for S_X(r) and the similar M_tot-T_X relations, with the latter demonstrating a significant departure from the simple gravitational scaling of M_tot∝T^3/2_X. It is also shown that the best-fit M_tot-T_X relations could be reconciled with the theoretical expectation if the low-temperature clusters (T_X<3.5 keV) are excluded from the list, which lends support to the scenario that the intracluster medium is preheated in the early phase of cluster formation. Together with the entropy-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.