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

TL;DR

This study used Suzaku observations to analyze the hard X-ray emissions of the merging cluster Abell 3667, revealing a very hot thermal component and setting limits on non-thermal emissions, magnetic fields, and relativistic particles.

Contribution

First detection of a very hot thermal component (>13.2 keV) in Abell 3667's core using Suzaku, and constraints on non-thermal emissions and magnetic fields in the radio relic region.

Findings

Detected a very hot (kT > 13.2 keV) thermal component in the cluster core.

No significant non-thermal emission detected in the radio relic region.

Estimated magnetic field strength within the relic exceeds 1.6 microGauss.

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 the wide energy band from 0.5 to 40 keV. The hard X-ray (> 10 keV) flux observed by the HXD around the cluster center cannot be explained by a simple extension of the thermal emission with average temperature of ~7 keV. The emission is most likely an emission from a very hot (kT > 13.2 keV) thermal component around the cluster center, produced via a strong heating process in the 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'x34' field-of-view around the relic is derived to be 5.3e-12 erg s-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 7.3e-13 erg s-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 uG. The non-thermal pressure due to magnetic fields and relativistic electrons may be as large as ~20% of the thermal pressure in the region.