NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-04-23 T11:59:59 PDT
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For refcode 2007PASJ...59..167N:
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NED Abstract

Copyright by Astronomical Society of Japan. 2007PASJ...59..167N Hard X-Ray Properties of Groups of Galaxies as Observed with ASCA Nakazawa, Kazuhiro; Makishima, Kazuo; Fukazawa, Yasushi Abstract. X-ray spectra of groups of galaxies, obtained with the GIS instrument onboard ASCA, were investigated for diffuse hard X-rays in excess of the soft thermal emission from their inter-galactic medium (IGM). In total, 18 objects with IGM temperatures of 0.7-1.7keV were studied, including HCG 62 in particular. Non X-ray backgrounds in the GIS spectra were carefully estimated and subtracted. The IGM emission was represented by up to two temperature thermal models, which was determined in a soft energy band below 2.5keV, mainly by the SIS data. When extrapolated to a higher energy range of 4--8keV, this thermal model under-predicted the background-subtracted GIS counts in HCG 62 and RGH 80 by > 2{sigma} significance, even though the background uncertainties and the IGM modeling errors were carefully accounted. A hard excess could also be present in NGC 1399. The excess was successfully explained by a power-law model with a photon index of ~ 2, or a thermal emission with a temperature exceeding ~ 3 keV. In HCG 62, the 2-10keV luminosity of the excess hard component was found to be 5.5x10^41^ erg s^-1^ at 2-10keV, which is ~ 30% of the thermal IGM luminosity in 0.7--2.5keV. Non-thermal and thermal interpretations of this excess components are discussed. Key words: galaxies: intergalactic medium -- galaxies: clusters: general -- X-rays: galaxies: clusters
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