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