X-ray study of hot interstellar medium in early-type galaxies Original Research Article

We have analyzed ASCA data of about 30 early type galaxies, and studied their X-ray emitting ISM (InterStellar Medium) properties. By carefully examining the abundance ratios and uncertainties in the Fe-L complex, we have concluded that the ISM abundances in X-ray luminous galaxies are in fact about 1 solar. Therefore, the severe discrepancy between the ISM and stellar abundance has been relaxed. The ISM metallicity of X-ray fainter galaxies are uncertain, but at least SNe Ia contribution to the ISM abundance is smaller than in the X-ray luminous ones.We have also discovered that X-ray emissions from X-ray luminous galaxies are very extended, and expressed with two beta models of different angular scales. This means that the X-ray luminous ellipticals are central galaxies of some larger-scale potential structures. We show that presence/absence of such a larger-scale potential can consistently account for several unsolved problems with the ISM.