The shocking features in the closest rich galaxy cluster Norma

TL;DR

This study detects a merger shock in the Norma galaxy cluster using X-ray data, revealing its significant impact on galaxy evolution, including ram pressure stripping and jet morphology changes.

Contribution

First detection of a merger shock in Norma cluster with detailed analysis of its effects on embedded galaxies and their features.

Findings

Detection of a $ ext{Mach} \, 1.3$ merger shock in Norma.

Identification of ram pressure stripping in galaxy ESO 137-001.

Observation of jet and tail morphology changes due to the shock.

Abstract

The merger shocks generated by the collision of galaxy clusters elevate the pressure within the intracluster medium, significantly influencing the evolution of embedded cluster galaxies. We detect a merger shock (Mach number $\sim 1.3$) on the northwest side of the closest rich galaxy cluster Norma (A3627), using XMM-Newton and Chandra data. The textbook ram pressure stripping (RPS) galaxy ESO 137-001 appears to be located in the post-shock region. The shock boosts RPS and may induce the formation of the brightest known X-ray tail behind a cluster late-type galaxy. Another prominent head-tail radio galaxy ESO 137-007, with one of the longest radio continuum tails ($> 500$ kpc), is also likely in the post-shock region. The shock may have reversed the upstream jet to a one-sided radio head-tail morphology. Moreover, the shock can strip and roll the jet cocoon into a vortex ring structure like a `smoke ring' behind the end of the jet as observed by the ASKAP data. Therefore, the cluster merger shock can remarkably change cluster galaxies. Furthermore, Norma is the second brightest non-cool-core cluster following the Coma cluster, with a cool core remnant on its southeast side. Its original cool core may be disrupted by cluster mergers and/or active galactic nuclei.