# A uniform metallicity in the outskirts of massive, nearby galaxy clusters

## TL;DR

This study confirms that the outskirts of massive galaxy clusters have a uniform metallicity around 0.3 Solar, supporting the idea of early, widespread enrichment of the intergalactic medium before cluster formation.

## Contribution

It provides observational evidence that the metallicity in the outskirts of multiple galaxy clusters is consistently uniform, validating predictions of early universal enrichment.

## Key findings

- Iron abundance is approximately 0.316 Solar in cluster outskirts.
- Measured metallicity is consistent across 10 different galaxy clusters.
- Results support early, homogeneous metal enrichment in the universe.

## Abstract

Suzaku measurements of a homogeneous metal distribution of $Z\sim0.3$ Solar in the outskirts of the nearby Perseus cluster suggest that chemical elements were deposited and mixed into the intergalactic medium before clusters formed, likely over 10 billion years ago. A key prediction of this early enrichment scenario is that the intracluster medium in all massive clusters should be uniformly enriched to a similar level. Here, we confirm this prediction by determining the iron abundances in the outskirts ($r>0.25r_{200}$) of a sample of ten other nearby galaxy clusters observed with Suzaku for which robust measurements based on the Fe-K lines can be made. Across our sample the iron abundances are consistent with a constant value, $Z_{\rm Fe}=0.316\pm0.012$ Solar ($\chi^2=28.85$ for 25 degrees of freedom). This is remarkably similar to the measurements for the Perseus cluster of $Z_{\rm Fe}=0.314\pm0.012$ Solar, using the Solar abundance scale of Asplund et al. (2009).