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

Abstract

We present the first metal abundance profiles for a representative sample of massive clusters. Our measurements extend to R500 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 ∼0.3 R500, implying that, as was found for thermodynamic properties, the physical state of the core does not affect global cluster properties. Our mean abundance within R500 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 for feedback processes. Together with results from the thermodynamic properties presented in a previous X-COP paper, it affords a coherent picture in which feedback effects do not vary significantly from one system to another. By combining intra-cluster medium with stellar measurements we have found the amount of Fe diffused in the intra-cluster medium 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 with stellar masses, both within and beyond R500, can be reduced.

The Metal Content of the Hot Atmospheres of Galaxy Groups

“…The vast majority of these studies show a gradual metallicity increase towards the core of the systems, with the maximum value spanning from half a Solar to slightly super-Solar values. This picture is qualitatively in line with the centrally peaked Fe abundance profiles that are typically found in relaxed clusters (e.g., References [9,52,[87][88][89]). Quantitatively, samples including groups and clusters are valuable to provide comprehensive comparisons.…”

“…Another important open debate concerns the comparison of clusters' and groups' metallicities in their outskirts (∼R 500 and beyond). Whereas there is now striking evidence for clusters having their metallicity flattening with radius and converging toward an universal value of ∼0.3 Solar [9,101,102], groups and elliptical galaxies have sometimes been measured with an uninterrupted decrease of metallicity down to at most 0.1-0.2 Solar (e.g., References [77,84,103,104]). The trend seems to be followed by the sample results of Rasmussen and Ponman [93,94] and of Sun [33].…”

“…A considerable fraction of the metals (and most of the iron) do not reside in the galaxies of groups and clusters and they have been expelled in their surrounding X-ray emitting hot atmospheres (for the purpose of this review, we will define the hot atmosphere of groups as intra-group medium, IGrM). Indeed, the iron share, i.e., the ratio of iron in the hot atmosphere and the iron locked up in stars in the galaxies, ranges from 1 up to 10 (see, for recent measurements, References [8,9]). Therefore, the key question is to understand the main transport mechanisms responsible for that unbalance (see, for a more detailed discussion, References [10,11]).…”

Iron in X-COP: Tracing enrichment in cluster outskirts with high accuracy abundance profiles (Corrigendum)

“…Their new estimates provide k Ia = 3.1 +1.1 −1.0 × 10 −3 M −1 , which leads to Y Fe, = 2.34 +0.63 −0.56 Z . By chance, the new updated value is not very different from the wrong value reported in Ghizzardi et al (2021), leaving our discussion and main conclusions unchanged.…”

The Cluster HEritage project withXMM-Newton: Mass Assembly and Thermodynamics at the Endpoint of structure formation

“…We can test the uniformity of the metal enrichment in massive clusters as a function of redshift with Tier-2, and as a function of mass with Tier-1. By comparing with stellar masses, we will address the long-standing issue of whether the amount of iron in the ICM is in excess of what can be produced in the stars (e.g., Arnaud et al 1992;Ghizzardi et al 2021); and in particular with Tier-1, address the relation of the iron mass, ICM mass and stellar mass, to the total mass (e.g., Bregman et al 2010;Renzini & Andreon 2014).…”