Context. We present the results of Suzaku observations of a massive galaxy cluster A2744, which is an active merger at z = 0.308. Aims. By using long X-ray observations of A2744, we aim to understand the growth of the cluster and the gas heating process through mass accretion along the surrounding filaments. Methods. We analyzed data from two-pointed Suzaku observations of A2744 to derive the temperature distribution out to the virial radius in three different directions. We also performed a deprojection analysis to study radial profiles of gas temperature, density, and entropy and compared the X-ray results with multiwavelength data to investigate correlations with the surface density of galaxies and with radio relics. Results. The gas temperature was measured out to the virial radius r 200 in the north-eastern region and to about 1.5r 200 in the northwestern and southern regions. The radial profile of the gas temperature is rather flat and the temperature is very high (even near r 200 ), which makes it comparable to the mean temperature of this cluster (kT = 9 keV). These characteristics have not been reported in any other cluster. We find a hint of temperature jump in the north-eastern region whose location coincides with a large radio relic, indicating that the cluster experienced gas heating because of merger or mass accretion onto the main cluster. The temperature distribution is anisotropic and shows no clear positive correlation with the galaxy density, which suggests an inhomogeneous mass structure and a complex merger history in A2744.

Aims. We present the results of Suzaku observations of a nearby galaxy cluster, A76 at z = 0.0395. This cluster is characterized by extremely low X-ray surface brightness and is hereafter referred to as the LSB cluster. We investigate the nature and thermodynamic evolution of the LSB cluster by studying the physical properties of the hot intracluster medium in A76. Methods. We conducted two-pointed Suzaku observations of A76 and examined the global gas properties of the cluster by XIS spectral analysis. We also performed deprojection analysis of annular spectra and derived radial profiles of gas temperature, density, and entropy out to approximately 850 kpc (∼0.6r 200 ) in A76 East and 560 kpc (∼0.4r 200 ) in A76 West. Results. The measured global temperature and metal abundance are approximately 3.3 keV and 0.24 solar, respectively. From the deprojection analysis, the entropy profile is found to be flat with respect to radius. The entropy within the central region (r < 0.2r 200 ) is exceptionally high (∼400 keV cm 2 ), a phenomenon that is not readily explained by either gravitational heating or preheating. The X-ray morphology is clumped and irregular, and the electron density is extremely low (10 −4 −10 −3 cm −3 ) for the observed high temperature, suggesting that A76 is in the early phase of cluster formation and that the gas compression due to gravitational potential confinement is lagging behind the gas heating.

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