A Uniform Contribution of Core-Collapse and Type Ia Supernovae to the Chemical Enrichment Pattern in the Outskirts of the Virgo Cluster

TL;DR

This study measures the distribution of alpha-element abundances in the Virgo Cluster outskirts, revealing a uniform chemical composition shaped by both core-collapse and Type Ia supernovae, indicating early and widespread enrichment.

Contribution

First measurement of alpha-element abundances beyond the virial radius of a galaxy cluster, showing uniform enrichment from both supernova types across large scales.

Findings

Chemical composition is consistent with being constant out to 1.4 Mpc.

Enrichment solely from core-collapse supernovae is ruled out.

SNIa contribute significantly to the metal enrichment, with a ratio of 12-37%.

Abstract

We present the first measurements of the abundances of $\alpha$-elements (Mg, Si, and S) extending out to beyond the virial radius of a cluster of galaxies. Our results, based on Suzaku Key Project observations of the Virgo Cluster, show that the chemical composition of the intra-cluster medium is consistent with being constant on large scales, with a flat distribution of the Si/Fe, S/Fe, and Mg/Fe ratios as a function of radius and azimuth out to 1.4 Mpc (1.3 $r_{200}$). Chemical enrichment of the intergalactic medium due solely to core collapse supernovae (SNcc) is excluded with very high significance; instead, the measured metal abundance ratios are generally consistent with the Solar value. The uniform metal abundance ratios observed today are likely the result of an early phase of enrichment and mixing, with both SNcc and type Ia supernovae (SNIa) contributing to the metal budget during the period of peak star formation activity at redshifts of 2-3. We estimate the ratio between the number of SNIa and the total number of supernovae enriching the intergalactic medium to be between 12-37%, broadly consistent with the metal abundance patterns in our own Galaxy or with the SNIa contribution estimated for the cluster cores.