sigma-Tx and mass-Tx relations for galaxy clusters

We analyze the relation between the velocity dispersion of member galaxies of galaxy clusters and the X- ray temperature of the intracluster medium. We find that the scatter in the sigma_v versus T_x relation cannot be explained by observational errors; there is poor/no evidence for a relation steeper than T_x^0.5; there is evidence that beta_spec=0.8 (i.e. less than 1); strongly substructured clusters seem prefer to lie on the relation at larger values of sigma_v and T_x