The mass distribution in galaxy clusters from their internal dynamics

We analyse the relation between the masses of cluster- and group-sized halos, extracted from LambdaCDM cosmological N-body and hydrodynamic simulations, and their velocity dispersions, at different redshifts from z=2 to z=0. The main aim of this analysis is to understand how the implementation of baryonic physics in simulations affects such relation, i.e. to what extent the use of the velocity dispersion as a proxy for cluster mass determination is hampered by the imperfect knowledge of the baryonic physics. In our analysis we use several sets of simulations with different physics implemented: one dark matter (DM hereafter) -- only simulation, one simulation with non-radiative gas, and two radiative simulations, one of which with feedback from Active Galactic Nuclei. Velocity dispersions are determined using three different tracers, DM particles, subhalos, and galaxies. We confirm that DM particles trace a relation that is fully consistent with the theoretical expectations based on the virial theorem, stating that the velocity dispersion is proportional to M^alpha with