Systematic X-Ray Analysis of Radio Relic Clusters with Suzaku

We undertook a systematic X-ray analysis of six giant radio relics in four clusters of galaxies using the Suzaku satellite. The sample included CIZA 2242.8+5301, Zwcl 2341.1-0000, the South-East part of A 3667 and previously published results of the North-West part of A 3667 and A 3376. Especially, we first observed the narrow (50 kpc) relic of CIZA 2242.8+5301 by the Suzaku satellite, which enabled us to reduce the projection effect. We report on X-ray detections of shocks at the positions of the relics in CIZA 2242.8+5301 and A 3667 SE. At the positions of the two relics in ZWCL 2341.1-0000, we did not detect shocks. From spectroscopic temperature profiles across the relic, we found that the temperature profiles exhibit significant jumps across the relics for CIZA 2242.8+5301, A 3376, A 3667 NW, and A 3667 SE. We estimated the Mach number from the X-ray temperature or pressure profile using the Rankine-Hugoniot jump condition, and compared it with the Mach number derived from the radio spectral index. The resulting Mach numbers (M = 1.5-3) are almost consistent with each other, while the Mach number of CIZA 2242.8+5301, derived from the X-ray data, tends to be lower than that of the radio observation. These results indicate that the giant radio relics in merging clusters are related to the shock structure, as suggested by previous studies of individual clusters.