CIZA J2242.8+5301 , a merging galaxy cluster at z = 0.19 , hosts a double-relic system and a faint radio halo .
Radio observations at frequencies ranging from a few MHz to several GHz have shown that the radio spectral index at the outer edge of the N relic corresponds to a shock of Mach number 4.6 \pm 1.1 , under the assumptions of diffusive shock acceleration of thermal particles in the test particle regime .
Here , we present results from new Chandra observations of the cluster .
The Chandra surface brightness profile across the N relic only hints to a surface brightness discontinuity ( < 2 \sigma detection ) .
Nevertheless , our reanalysis of archival Suzaku data indicates a temperature discontinuity across the relic that is consistent with a Mach number of 2.54 _ { -0.43 } ^ { +0.64 } , in agreement with previously published results .
This confirms that the Mach number at the shock traced by the N relic is much weaker than predicted from the radio .
Puzzlingly , in the Chandra data we also identify additional inner small density discontinuities both on and off the merger axis .
Temperature measurements on both sides of the discontinuities do not allow us to undoubtedly determine their nature , although a shock front interpretation seems more likely .
We speculate that if the inner density discontinuities are indeed shock fronts , then they are the consequence of violent relaxation of the dark matter cores of the clusters involved in the merger .