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

We studied the intracluster medium (ICM) 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.