Iron in X-COP: tracing enrichment in cluster outskirts with high accuracy abundance profiles

TL;DR

This study provides the first high-accuracy, representative metal abundance profiles for massive galaxy clusters extending to their outskirts, revealing uniform enrichment and minimal scatter, with implications for feedback processes.

Contribution

It offers the first systematic, corrected abundance profiles for a representative sample of massive clusters extending to R500, showing uniform enrichment and minimal scatter.

Findings

Profiles flatten at large radii, consistent with previous results.

No segregation between cool-core and non-cool-core systems beyond 0.3 R500.

Mean abundance within R500 shows less than 15% scatter.

Abstract

We present the first metal abundance profiles for a representative sample of massive clusters. Our measures extend to $R_{500}$ and are corrected for a systematic error plaguing previous outskirt estimates. Our profiles flatten out at large radii, admittedly not a new result, however the radial range and representative nature of our sample extends its import well beyond previous findings. We find no evidence of segregation between cool-core and non-cool-core systems beyond $\sim 0.3 R_{500}$, implying that, as was found for thermodynamic properties (Ghirardini et al, 2019), the physical state of the core does not affect global cluster properties. Our mean abundance within $R_{500}$ shows a very modest scatter, $< $15%, suggesting the enrichment process must be quite similar in all these massive systems. This is a new finding and has significant implications on feedback processes. Together with results from thermodynamic properties presented in a previous X-COP paper, it affords a coherent picture where feedback effects do not vary significantly from one system to another. By combing ICM with stellar measurements we have found the amount of Fe diffused in the ICM to be about ten times higher than that locked in stars. Although our estimates suggest, with some strength, that the measured iron mass in clusters is well in excess of the predicted one, systematic errors prevent us from making a definitive statement. Further advancements will only be possible when systematic uncertainties, principally those associated to stellar masses, both within and beyond $R_{500}$, can be reduced.