Location of HII regions in molecular clouds
Abstract
The relationship of H II regions to molecular clouds is considered on a local scale. Emphasis is placed on the Orion complex, considering the 'blister model' in which apparently an OB star or association forms on the edge of a dense molecular region and proceeds to ionize the surroundings. Selection effects with regard to the study of H II regions are considered, and it is noted that the majority of sources for which such a model has been suggested appear to have the blister expanding towards the observer. Other molecular clouds having associated H II emission, such as the Cygnus X region, the M8E source, the Rho Oph cloud, and the radio source W58 are discussed, considering peaks of molecular emission and CO hot spots. It is indicated that molecular clouds have density enhancements and centers of activity at random locations within them, and that on a local scale, there is a tendency for H II regions to be displaced from the actual molecular cores.
- Publication:
-
Giant Molecular Clouds in the Galaxy
- Pub Date:
- 1980
- Bibcode:
- 1980gmcg.work..201H
- Keywords:
-
- H Ii Regions;
- Molecular Gases;
- Radio Astronomy;
- Stellar Evolution;
- B Stars;
- Blisters;
- O Stars;
- Orion Nebula;
- Radio Emission;
- Radio Sources (Astronomy);
- Thermal Emission;
- Astrophysics