A parametric physical model for the intracluster medium and its use in joint SZ/X-ray analyses of galaxy clusters

We present a parametrized model of the intracluster medium that is suitable for jointly analysing pointed observations of the Sunyaev-Zel'dovich (SZ) effect and X-ray emission in galaxy clusters. The model is based on assumptions of hydrostatic equilibrium, the Navarro, Frenk and White model for the dark matter and a softened power-law profile for the gas entropy. We test this entropy-based model against high and low signal-to-noise ratio ratio mock observations of a relaxed and recently merged cluster from N-body/hydrodynamic simulations, using Bayesian hyperparameters to optimize the relative statistical weighting of the mock SZ and X-ray data. We find that it accurately reproduces both the global values of the cluster temperature, total mass and gas mass fraction (f_gas), and the radial dependencies of these quantities outside the core (r > 100 kpc). For reference, we also provide a comparison with results from the single isothermal β model. We confirm previous results that the single isothermal β model can result in significant biases in derived cluster properties.