CHANDRA OBSERVATIONS OF ULTRALUMINOUS INFRARED GALAXIES: EXTENDED HOT GASEOUS HALOS IN MERGING GALAXIES

摘要

We study the properties of hot gaseous halos in 10 nearby ultraluminous IRAS galaxies observed with the ACIS instrument on board Chandra. For all sample galaxies, diffuse soft X-ray emissions are found within ～10 kpc of the central region; their spectra are well fitted by a MEKAL model plus emission lines from α-elements and other ions. The temperature of the hot gas is about 0.7 keV and metallicity is about 1 Z_☉. Outside the central region, extended hot gaseous halos are found for 9 out of the 10 ultraluminous infrared galaxies (ULIRGs). Most spectra of these extended halos can be fitted with a MEKAL model with a temperature of about 0.6 keV and a low metallicity (Z～0.1 Z_☉). We discuss the implications of our results on the origin of X-ray halos in elliptical galaxies and the feedback processes associated with starbursts.