---
abstract: 'We present a parameterized model of the intra-cluster 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 (NFW) 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 mock observations of a relaxed and recently-merged cluster from $N$-body/hydrodynamic simulations, using Bayesian hyper-parameters to optimise 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 ($f_\rmn{gas}$), as well as the radial dependencies of these quantities outside of the core ($r > 100\,\rmn{kpc}$). For reference we also provide a comparison with results from the single isothermal $\beta$ model. We confirm previous results that the single isothermal $\beta$ model can result in significant biases in derived cluster properties.'
author:
- |
    J. R. Allison$^{1}$[^1], A. C. Taylor$^{1}$, M. E. Jones$^{1}$, S. Rawlings$^{1}$, and S. T. Kay$^{2}$\
    $^{1}$Oxford Astrophysics, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, U.K.\
    $^{2}$Jodrell Bank Centre 