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CIZA J2242.8+5301, a merging galaxy cluster at z=0.19, hosts a double-relicsystem and a faint radio halo. Radio observations at frequencies ranging from afew MHz to several GHz have shown that the radio spectral index at the outeredge of the N relic corresponds to a shock of Mach number 4.6+/-1.1, under theassumptions of diffusive shock acceleration of thermal particles in the testparticle regime. Here, we present results from new Chandra observations of thecluster. The Chandra surface brightness profile across the N relic only hintsto a surface brightness discontinuity (<2-sigma detection). Nevertheless, ourreanalysis of archival Suzaku data indicates a temperature discontinuity acrossthe relic that is consistent with a Mach number of 2.5+/-0.5, in agreement withpreviously published results. This confirms that the Mach number at the shocktraced by the N relic is much weaker than predicted from the radio. Puzzlingly,in the Chandra data we also identify additional inner small densitydiscontinuities both on and off the merger axis. Temperature measurements onboth sides of the discontinuities do not allow us to undoubtedly determinetheir nature, although a shock front interpretation seems more likely. Wespeculate that if the inner density discontinuities are indeed shock fronts,then they are the consequence of violent relaxation of the dark matter cores ofthe clusters involved in the merger.

Multiple density discontinuities in the merging galaxy cluster CIZA J2242.8+5301