SZ and X-ray combined analysis of a distant galaxy cluster, RX J2228+2037

We have performed a combined analysis of X-ray and Sunyaev-Zel'dovich data in the direction of the distant galaxy cluster, RX J2228+2037. Fitting a β-model to the high-resolution HRI data gives r_c = 103 ± 12 h₇₀^-1 kpc and β = 0.54 ± 0.03. The dependency of the Sunyaev-Zel'dovich effect with respect to the gas temperature allows us, through the additional use of the 21 GHz data of the cluster, to determine k_BT_e = 10.4 ± 1.8 h₇₀^1/2 keV. Extrapolating the gas density profile out to the virial radius (R_v = r₁₇₈ = 2.9 Mpc), we derived a gas mass of M_g(r < R_v) = (4.0 ± 0.2) × 10¹⁴ h₇₀^-5/2 M_⊙. Within the hypothesis of hydrostatic equilibrium, the corresponding extrapolated total mass for this source is: M_tot(r < R_v) = (1.8 ± 0.4) × 10¹⁵ h^-1 M_⊙, which corresponds to a gas fraction of f_gas = 0.22 ± 0.06 h₇₀^-3/2. Our results on the temperature and on the cluster mass classify RX J2228+2037 among the distant, hot and very massive galaxy clusters. Our work highlights the power of the association of galaxy cluster mapping observations in X-ray and the SZ effect to derive the cluster's physical properties, even without X-ray spectroscopy.