Spatial Distribution of Metals in the ICM: Evolution of the Iron Excess in Relaxed Galaxy Clusters

TL;DR

This study analyzes the evolution of iron distribution in the intra-cluster medium of relaxed galaxy clusters over cosmic time, revealing an increasing spatial extent of iron and a stable iron mass excess since redshift 1.

Contribution

It provides the first detailed deprojected analysis of iron profiles in a large sample of relaxed clusters across a wide redshift range, highlighting the evolution of iron distribution.

Findings

Iron distribution extent increases by a factor of ~3 from z~1 to z~0.1.

Emission-weighted iron abundance is ~25% higher than mass-weighted within 0.2r500.

Iron mass excess normalized to baryonic mass remains constant since z~1.

Abstract

We investigate the spatial distribution of iron in the intra-cluster medium in a selected sample of 41 relaxed clusters in the redshift range $0.05 < z < 1.03$ using {\sl Chandra} archival data. We compute the azimuthally-averaged, deprojected $Z_{\rm Fe}$ profile of each cluster out to $\sim 0.4r_{500}$, and identify a peak in the distribution of iron followed by a flatter distribution at larger radii. Due to the steep gradient both in gas density and abundance, we find that the emission-weighted iron abundance within $0.2r_{500}$, which entirely includes the iron peak in most of the cases, is on average $\sim$25\% higher than the mass-weighted value, showing that spatially resolved analysis and accurate deprojection are key to study the evolution of iron enrichment in the very central regions of cool core clusters. We quantify the extent of the iron distribution in each cluster with a normalized scale parameter $r_{\rm Fe}$, defined as the radius where the iron abundance excess is half of its peak value. We find that $r_{\rm Fe}$ increases by a factor of $\sim 3$ from $z\sim 1$ to $z\sim 0.1$, suggesting that the spatial distribution of iron in the ICM extends with time, possibly due to the mixing with the mechanical-mode feedback from the central galaxy. We also find that the iron mass excess within $0.3r_{500}$, when normalized to the total baryonic mass within the same region, does not evolve significantly, showing that this iron mass component is already established at $z\sim 1$.