Suzaku observation of HCG 62: Temperature, abundance, and extended hard X-ray emission profiles

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 ∼ 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 (5-12 keV) 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 5-12 keV intensity in the r < 3′.3 region turned out to be 70±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 T = 1.38 ±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. © 2008. Astronomical Society of Japan.