Suzaku Observation of the Radio Halo Cluster Abell 2319: Gas Dynamics and Hard X-Ray Properties

We present the results of a Suzaku observation of the radio halo cluster Abell 2319 (A 2319). The metal abundance in the central cool region is found to be higher than the surrounding region, which was not resolved in former studies. We confirm that the line-of-sight velocities of the intracluster medium in the observed region are consistent with those of the member galaxies of the entire A 2319 and A 2319A subgroup for the first time, though no velocity difference within the region has been detected. On the other hand, we have not found any signs of gas motion relevant to the A 2319B subgroup. Hard X-ray emission from the cluster has clearly been detected, but its spectrum is likely to be thermal. Assuming a simple single-temperature model for the thermal component, we find that the upper limit of the non-thermal inverse Compton component becomes 2.6 × 10^-11 erg s^-1 cm^-2 in the 10-40 keV band, which means that the lower limit of the magnetic field is 0.19μG with a radio spectral index of 0.92. Although the results slightly depend on the detailed spectral modeling, it is robust that the upper limit of the power-law component flux and lower limit of the magnetic field strength become ∼3 × 10^-11 erg s^-1 cm^-2 and ∼0.2μG, respectively. Considering the lack of a significant amount of very hot (∼20 keV) gas and the strong bulk flow motion, it is more likely that the relativistic non-thermal electrons responsible for the radio halo are accelerated through intracluster turbulence rather than shocks.