Constraint of Non-Thermal X-Ray Emission from the On-Going Merger Cluster Abell 3376 with Suzaku
Isobe, Naoki; Fukazawa, Yasushi; Kokubun, Motohide; Makishima, Kazuo; Nakazawa, Kazuhiro; Takahashi, Tadayuki; Ohashi, Takaya; Nishino, Sho; Kitaguchi, Takao; Kawano, Naomi; Hornschemeier, Ann; Ota, Naomi; Henry, J. Patrick
Japan, United States
Abstract
Clusters of galaxies are among the best candidates for particle acceleration sources in the universe, a signature of which is non-thermal hard X-ray emission from the accelerated relativistic particles. We present early results on Suzaku observations of non-thermal emission from Abell 3376, which is a nearby on-going merger cluster. Suzaku observed the cluster twice, while focusing on the cluster center containing the diffuse radio emission to the east, and a cluster peripheral region to the west. For both observations, we detected no excess hard X-ray emission above the thermal cluster emission. An upper limit on the non-thermal X-ray flux of 2.1 × 10-11erg cm-2s-1(15--50keV) at the 3σ level from a 34' ×34' region, derived with the Hard X-ray Detector (HXD), is similar to that obtained with the BeppoSAX/PDS. Using the X-ray Imaging Spectrometer (XIS) data, the upper limit on the non-thermal emission from the West Relic is independently constrained to be <1.1 ×10-12erg s-1cm-2 (4--8keV) at the 3σ level from a 122arcmin2 region. Assuming Compton scattering between relativistic particles and the cosmic microwave background photons, the intracluster magnetic field B is limited to be >0.03μG (HXD) and >0.10μG (XIS).