Numerical Convergence of Hydrodynamical SPH Simulations of Cooling Clusters

The results from hydrodynamical TREESPH simulations of galaxy clusters are used to investigate the dependence of the final cluster X-ray properties upon the numerical resolution and the assumed star formation models for the cooled gas. A comparison between runs with different star formation methods shows that the results of simulations, based on star formation methods in which gas conversion into stars is controlled by an efficiency parameter c_{star}, are sensitive to the simulation numerical resolution. In this respect star formation methods based instead on a local density threshold, are shown to give more stable results. Final X-ray luminosities are found to be numerically stable, with uncertainties of a factor 2.