Hard X-Ray Properties of the Merging Cluster Abell 3667 as Observed with Suzaku

Abstract

Abstract Wide-band Suzaku data on the merging cluster Abell 3667 were examined for hard X-ray emission in excess to the known thermal component. Suzaku detected X-ray signals in a wide energy band from 0.5 to 40 keV. The hard X-ray ($\gt$10 keV) flux observed by the HXD around the cluster center cannot be explained by a simple extension of the thermal emission with an average temperature of $\sim$7 keV. The emission is most likely to be from a very hot ($kT$$\gt$ 13.2 keV) thermal component around the cluster center, produced via a strong heating process in a merger. In the north-west radio relic, no signature of non-thermal emission was observed. Using the HXD, the overall upper-limit flux within a 34$^\prime$$\times$ 34$^\prime$ field-of-view around the relic was derived to be 5.3 $\times$ 10$^{-12}$ergs$^{-1}$cm$^{-2}$ in the 10–40 keV band, after subtracting the ICM contribution estimated using the XIS or the XMM-Newton spectra. Directly on the relic region, the upper limit is further tightened by the XIS data to be less than 7.3 $\times$ 10$^{-13}$ergs$^{-1}$cm$^{-2}$, when converted into the 10–40 keV band. The latter value suggest that the average magnetic field within the relic is higher than 1.6 $\mu$G. The non-thermal pressure due to magnetic fields and relativistic electrons may be as large as $\sim$20% of the thermal pressure in the region.