The chemical evolution of galaxy clusters: Dissecting the iron mass budget of the intracluster medium

Abstract

Aims. We study the chemical evolution of galaxy clusters by measuring the iron mass in the ICM after dissecting the abundance profiles into different components. Methods. We use Chandra archival observations of 186 morphologically regular clusters in the redshift range [0.04, 1.07]. For each cluster we compute the azimuthally-averaged iron abundance and gas density profiles. In particular, we aim at identifying a central peak in the iron distribution, associated with the central galaxy, and an approximately constant plateau reaching the largest observed radii, possibly associated with early enrichment occurred before and/or shortly after the virialization of the cluster. We are able to firmly identify the two components in the iron distribution in a significant fraction of the sample, simply relying on the fit of the iron abundance profile. From the abundance and ICM density profiles we compute the iron mass included in the iron peak and iron plateau, and the gas mass-weighted iron abundance of the ICM, out to an extraction radius of 0.4 r 500 and, extending the abundance profile as a constant, to r 500 . Results. We find that the iron plateau shows no evolution with redshift. On the other hand, we find marginal (< 2σ c.l.) decrease with redshift in the iron mass included in the iron peak rescaled by the gas mass. 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 across our sample. 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 history of the hosting cool core and the strength of the associated feedback processes. Conclusions. We conclude that only a spatially-resolved approach can resolve the issue of the iron abundance evolution in the ICM, reconciling the contradictory results obtained in the last ten years. Evolutionary effects below z ∼ 1 are marginally measurable with present-day data, while at z > 1 the constraints are severely limited by the poor knowledge of the high-z cluster population. The path towards a full and comprehensive chemical history of the ICM necessarily requires the use of high-angular resolution X-ray bolometers and a dramatic increase in the statistics of faint, extended X-ray sources.

X-Ray Studies of the Abell 3158 Galaxy Cluster with eROSITA

“…The M 500 was estimated to be 3.50 ± 0.40 × 10 14 M . This is not consistent with the value determined by Liu et al (2020) of M 500 = 4.53 ± 0.11 × 10 14 M which was determined using the same method. However, Liu et al (2020) utilised Chandra data to determine the mass from the M-T relation.…”

“…This is not consistent with the value determined by Liu et al (2020) of M 500 = 4.53 ± 0.11 × 10 14 M which was determined using the same method. However, Liu et al (2020) utilised Chandra data to determine the mass from the M-T relation. Schellenberger et al (2015) show that the temperature measurements from Chandra are higher than those from XMM-Newton and as shown in this work, the eROSITA telescope temperature measurements are also lower than the Chandra results.…”

“…Moretti et al (2017) calculated a mass of 1.79 × 10 15 M using the M 200 -σ v relation from Finn et al (2005). Liu et al (2020) have estimated the mass from the temperature obtained in X-ray with the M-T relation while Piffaretti et al (2011) have estimated the mass using the M-L relation. The hydrostatic mass has also been determined eg.…”

The eROSITA Final Equatorial-Depth Survey (eFEDS)

“…6 for an example). Therefore we fixed the metallicity to 0.3 Z (see, e.g., Liu et al 2020) for all clusters for a uniform treatment of the data. The redshift of the cluster was set at the value provided by MCMF, as described in Sect.…”

Origin of metals in old Milky Way halo stars based on GALAH and Gaia

“…How the SN Ia rate changes as a function of cosmic time or of environments remains elusive because there is no consensus about the progenitor systems and the mechanisms which make the system to finally explode. The observed lack of evolution of the Fe content in the ICM of clusters of galaxies out to redshift ∼2 (McDonald et al 2016;Mantz et al 2017;Liu et al 2020;Mantz et al 2020) suggests that metal enrichment by SN Ia was already important early during cosmic history. This is further confirmed by measurements of the metal abundances in the outskirts of nearby galaxy clusters (Werner et al 2013;Urban et al 2017); the remarkably uniform distribution of Fe over large spatial scales, and the small cluster-to-cluster scatter, suggest that the ICM was enriched more than 10 billion years ago, before these clusters developed a strongly stratified entropy gradient that would prevent the efficient mixing of metals.…”