Radial metal abundance profiles in the intra-cluster medium of cool-core galaxy clusters, groups, and ellipticals

Abstract

The hot intra-cluster medium (ICM) permeating galaxy clusters and groups is not pristine, as it is continuously enriched by metals synthesised in Type Ia (SNIa) and core-collapse (SNcc) supernovae since the major epoch of star formation (z ~ 2-3). The cluster/group enrichment history and the mechanisms responsible for releasing and mixing the metals can be probed via the radial distribution of SNIa and SNcc products within the ICM. In this paper, we use deep XMM-Newton/EPIC observations from a sample of 44 nearby cool-core galaxy clusters, groups, and ellipticals (CHEERS) to constrain the average radial O, Mg, Si, S, Ar, Ca, Fe, and Ni abundance profiles. The radial distributions of all these elements, averaged over a large sample for the first time, represent the best constrained profiles available currently. We find an overall decrease of the Fe abundance with radius out to ~$0.9 r_{500}$ and ~$0.6 r_{500}$ for clusters and groups, respectively, in good agreement with predictions from the most recent hydrodynamical simulations. The average radial profiles of all the other elements (X) are also centrally peaked and, when rescaled to their average central X/Fe ratios, follow well the Fe profile out to at least ~0.5$r_{500}$. Using two sets of SNIa and SNcc yield models reproducing well the X/Fe abundance pattern in the core, we find that, as predicted by recent simulations, the relative contribution of SNIa (SNcc) to the total ICM enrichment is consistent with being uniform at all radii, both for clusters and groups. In addition to implying that the central metal peak is balanced between SNIa and SNcc, our results suggest that the enriching SNIa and SNcc products must share the same origin, and that the delay between the bulk of the SNIa and SNcc explosions must be shorter than the timescale necessary to diffuse out the metals.