Suzaku Observation of HCG 62: Temperature, Abundance, and Extended Hard X-Ray Emission Profiles

Abstract

Abstract The compact group of galaxies HCG 62 ($z=$ 0.0145) was observed for 120ks with Suzaku XIS and HXD-PIN. The XIS spectra for four annular regions were fitted with a two-temperature vapec model with variable abundance, combined with the foreground Galactic component. The Galactic component was described by a two-temperature apec model, and constrained to have a common surface brightness among the four annuli. We confirmed the multi-temperature nature of the intra-group medium, as reported previously, with a doughnut-like high temperature ring at radii 3.3'-6.5'. Abundances of Mg, Si, S, and Fe were well-constrained. We examined the possible “high-abundance arc” at $\sim 2'$ southwest from the center; however, Suzaku data did not confirm it. We suspect that it is a misidentification of an excess hot component in this region as the Fe line. Neither XIS (5-12keV) nor HXD-PIN (12-40keV) gave positive detection of the extended hard X-rays previously reported with ASCA, although our upper limit did not exclude the ASCA result. The 5-12keV intensity in the $r <$ 3.3' region turned out to be 70$\pm$19% higher than the nominal CXB level, and Chandra and Suzaku data suggest a concentration of hard X-ray sources with an average photon index of $\Gamma=$ 1.38$\pm$0.06. The cumulative mass of O, Fe, and Mg in the intra-group medium and the metal mass-to-light ratio were compared with those in other groups. The possible role of AGN or galaxy mergers in this group is also discussed.