Temperature and abundance profiles of hot gas in galaxy groups - II. Implications for feedback and ICM enrichment

Abstract

We investigate the history of galactic feedback and chemical enrichment within a sample of 15 X‐ray bright groups of galaxies, on the basis of the inferred Fe and Si distributions in the hot gas and the associated metal masses produced by core‐collapse and Type Ia supernovae (SNe). Most of these cool‐core groups show a central Fe and Si excess, which can be explained by prolonged enrichment by SN Ia and stellar winds in the central early‐type galaxy alone, but with tentative evidence for additional processes contributing to core enrichment in hotter groups. Inferred metal mass‐to‐light ratios inside r500 show a positive correlation with total group mass but are generally significantly lower than in clusters, due to a combination of lower global intracluster medium (ICM) abundances and gas‐to‐light ratios in groups. This metal deficiency is present for products from both SN Ia and SN II, and suggests that metals were either synthesized, released from galaxies or retained within the ICM less efficiently in lower mass systems. We explore possible causes, including variations in galaxy formation and metal release efficiency, cooling out of metals, and gas and metal loss via active galactic nuclei (AGN) – or starburst‐driven galactic winds from groups or their precursor filaments. Loss of enriched material from filaments coupled with post‐collapse AGN feedback emerges as viable explanations, but we also find evidence for metals to have been released less efficiently from galaxies in cooler groups and for the ICM in these to appear chemically less evolved, possibly reflecting more extended star formation histories in less massive systems. Some implications for the hierarchical growth of clusters from groups are briefly discussed.

The bow shock, cold fronts and disintegrating cool core in the merging galaxy group RX J0751.3+5012

“…This observed difference in metallicity follows the trend of higher metal abundances in the central regions of higher temperature groups (e.g. Rasmussen & Ponman 2009 for the SW and the NE groups, respectively. Although this is not a significant difference, these results are consistent with the galaxy redshifts z = 0.0218 for UGC 4051 in the SW group and z = 0.0236 and 0.0228 for UGC 4052 E and W, respectively (Crawford et al 1999).…”

Radial metal abundance profiles in the intra-cluster medium of cool-core galaxy clusters, groups, and ellipticals

“…The origin of such a difference of ICM enrichment between cooler and hotter objects is still unclear, and has been already debated in the literature (e.g. Rasmussen & Ponman 2009;Liang et al 2016;Yates et al 2017). For example, in contrast to clusters, galaxy groups may not be closed boxes (e.g.…”

Observational Evidence of Active Galactic Nuclei Feedback

“…Feedback can be seen operating in many of them. Most X-ray luminous groups have cool cores with short central radiative cooling times (< 1 Gyr) and low central entropy (Rasmussen & Ponman 2009;Sun et al 2009). A full range of bubbling behaviour is seen in these objects (see e.g.…”