XMM-Newton observations of the merging galaxy cluster CIZA J2242.8+5301

TL;DR

This study uses deep XMM-Newton X-ray observations to analyze the complex merger dynamics of galaxy cluster CIZA J2242.8+5301, revealing shock features, temperature variations, and a hot gas ring that challenge simple merger models.

Contribution

It provides new X-ray evidence of shock structures and complex gas distributions, offering insights into the merger process of this galaxy cluster.

Findings

Detection of a shock with Mach number 1.3 east of the southern relic.

Temperature increase at the northern relic.

Presence of a hot gas 'wall' and elliptical ring indicating complex merger dynamics.

Abstract

We studied the intracluster medium of the galaxy cluster CIZA J2242.8+5301 using deep XMM-Newton observations. The cluster hosts a remarkable 2-Mpc long, ~50-kpc wide radio relic that has been nicknamed the "Sausage". A smaller, more irregular counter-relic is also present, along with a faint giant radio halo. We analysed the distribution of the ICM physical properties, and searched for shocks by trying to identify density and temperature discontinuities. East of the southern relic, we find evidence of shock compression corresponding to a Mach number of 1.3, and speculate that the shock extends beyond the length of the radio structure. The ICM temperature increases at the northern relic. More puzzling, we find a "wall" of hot gas east of the cluster centre. A partial elliptical ring of hot plasma appears to be present around the merger. While radio observations and numerical simulations predict a simple merger geometry, the X-ray results point towards a more complex merger scenario.