Are large X-ray clusters in thermal equilibrium?

We simulate the formation of a large X-ray cluster using a fully three-dimensional hydrodynamical code coupled to a particle-mesh scheme that models the dark matter component. We focus on a possible decoupling between electron and ion temperatures. We then solve the energy transfer equations between electrons, ions, and neutral particles without assuming thermal equilibrium between the three gases (T_e ≠ T_i ≠ T_n). We self-consistently solve the chemical equations for a hydrogen-helium primordial plasma without assuming ionization-recombination equilibrium. We find that the electron temperature differs from the true dynamical temperature by 20% at the virial radius of our simulated cluster. This could lead to a marginal underestimation of the total mass in the outer regions of large X-ray clusters.