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 _ { 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 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 } \propto T _ { X } ^ { 3 / 2 } .
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 intra-cluster 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 .