Structure and Evolution of Hot Gas in 30 Dor

Abstract

We have investigated the structure and evolution of hot gas in the 30 Dor nebula, based on recent X-ray observations. Our deep ROSAT HRI image shows that diffuse X-ray emission arises in blister-shaped regions outlined by loops of HII gas. X-ray spectroscopic data from ASCA confirm the thermal nature of the emission and indicate that hot gas temperature decreases from the core to the halo of the nebula. The structure of the nebula can be understood as outflows of hot and HII gases from the parent giant molecular cloud of the central OB association. The dynamic mixing between the two gas phases is likely responsible for the mass loading to the hot gas, as required to explain the observed thermal structure and X-ray luminosity of the nebula. Such processes should also be important in the formation of similar giant HII regions and in their subsequent evolution into supergiant bubbles or galactic chimneys.