2020MNRAS.496.1554M

We present results from a 577 ks XMM-Newton observation of SPT-CL J0459-4947, the most distant cluster detected in the South Pole Telescope 2500 square degree (SPT-SZ) survey, and currently the most distant cluster discovered through its Sunyaev-Zel'dovich effect. The data confirm the cluster's high redshift, z = 1.71 ± 0.02, in agreement with earlier, less precise optical/IR photometric estimates. From the gas density profile, we estimate a characteristic mass of M₅₀₀=(1.8±0.2)×10¹⁴ M_☉; cluster emission is detected above the background to a radius of ∼2.2 r₅₀₀, or approximately the virial radius. The intracluster gas is characterized by an emission-weighted average temperature of 7.2 ± 0.3 keV and metallicity with respect to Solar of Z/ Z_☉=0.37±0.08. For the first time at such high redshift, this deep data set provides a measurement of metallicity outside the cluster centre; at radii r> 0.3 r₅₀₀, we find Z/ Z_☉=0.33±0.17 in good agreement with precise measurements at similar radii in the most nearby clusters, supporting an early enrichment scenario in which the bulk of the cluster gas is enriched to a universal metallicity prior to cluster formation, with little to no evolution thereafter. The leverage provided by the high redshift of this cluster tightens by a factor of 2 constraints on evolving metallicity models, when combined with previous measurements at lower redshifts.