Based on Suzaku X-ray observations , we study the hot gas around the NGC4839 group of galaxies and the radio relic in the outskirts of the Coma cluster .
We find a gradual decline in the gas temperature from 5 keV around NGC4839 to 3.6 keV at the radio relic , across which there is a further , steeper drop down to 1.5 keV .
This drop as well as the observed surface brightness profile are consistent with a shock with Mach number { \cal M } = 2.2 \pm 0.5 and velocity v _ { s } = ( 1410 \pm 110 ) ~ { } km~ { } s ^ { -1 } .
A lower limit of B > 0.33 ~ { } \mu G is derived on the magnetic field strength around the relic from upper limits to inverse Compton X-ray emission .
Although this suggests that the non-thermal electrons responsible for the relic are generated by diffusive shock acceleration ( DSA ) , the relation between the measured Mach number and the electron spectrum inferred from radio observations are inconsistent with that expected from the simplest , test-particle theory of DSA .
Nevertheless , DSA is still viable if it is initiated by the injection of a pre-existing population of non-thermal electrons .
Combined with previous measurements , the temperature profile of Coma in the southwest direction is shallower outside NGC4839 and also slightly shallower in the outermost region .
The metal abundance around NGC4839 is confirmed to be higher than in its vicinity , implying a significant peak in the abundance profile that decreases to 0.2 solar toward the outskirts .
We interpret these facts as due to ram pressure stripping of metal-enriched gas from NGC4839 as it falls into Coma .
The relic shock may result from the combined interaction of pre-existing intracluster gas , gas associated with NGC 4839 , and cooler gas flowing in from the large-scale structure filament in the southwest .