The Chemical Evolution of Galaxy Clusters: Dissecting the Iron Mass
  Budget of the Intracluster Medium
  We study the chemical evolution of galaxy clusters by measuring the iron mass
in the ICM after dissecting the abundance profiles into different components.
We use Chandra archival observations of 186 morphologically regular clusters in
the redshift range [0.04, 1.07]. For each cluster we compute the iron abundance
and gas density profiles. We aim at identifying in the iron distribution a
central peak associated with the BCG, and an approximately constant plateau
associated with early enrichment. We are able to firmly identify the two
components in a significant fraction of the sample, simply relying on the fit
of the abundance profile. We compute the iron mass included in the iron peak
and plateau, and the gas mass-weighted iron abundance out to $r_{500}$. While
the iron plateau shows no evolution, we find marginal decrease with redshift in
the iron peak. We measure that the fraction of iron peak mass is typically a
few percent (~1%) of the total iron mass within $r_{500}$. Therefore, since the
total iron mass budget is dominated by the plateau, we find consistently that
the global gas mass-weighted iron abundance does not evolve significantly. We
are also able to reproduce past claims of evolution in the global iron
abundance, which turn out to be due to the use of cluster samples with
different selection methods combined to the use of emission-weighted instead of
gas mass-weighted abundance values. Finally, while the intrinsic scatter in the
iron plateau mass is consistent with zero, the iron peak mass exhibits a large
scatter, in line with the fact that the peak is produced after the
virialization of the halo and depends on the formation of the hosting cool core
and the associated feedback processes. We conclude that only a
spatially-resolved approach can resolve the issue of the ICM iron evolution,
reconciling the contradictory results obtained in the last ten years.
