X-ray study of NGC 1399 in the Fornax cluster of galaxies

Abstract

Observations of the cD galaxy NGC 1399 in the Fornax cluster of galaxies with Ginga have detected extended X-ray emission out to a radius of more than ~360 kpc. The energy spectrum of this emission is well fitted with an optically thin thermal spectrum with kT = 1.46^+0.05^_-0.21_ keV with a strong iron emission line corresponding to an iron abundance of 1.1^+1.3^_-0.5_ times solar. The mass of the hot gas responsible for the X-ray emission is nearly the same as the total stellar mass of the cluster. Therefore, the presence of iron at near-solar abundance suggests that the mass of the hot gas ejected from galaxies is comparable to the total stellar mass. This result indicates that most of the hot gas in a very poor cluster is created through ejections from galaxies, rather than being primordial.