Subparsec-Size H i Cloudlets Associated with Orion A
Abstract
Five previously unknown H I components have been detected in absorption toward the H II region Orion A. These features, which cover only a small fraction of the area of M42, are all located around the H II region core. Evidence indicates that they are physically associated with Orion A. Analysis of the ionization balance in the neutral clumps indicates that the clumps cannot be located deeply within the ionized region, but must be located close to the ionization boundary. The anomalous velocities of these components can be explained by rocket acceleration, or by momentum transfer from high-velocity ionized material in the H II region to the neutral clumps. The interaction of an H II region ionization front with the ambient gas is shown to depend on the density of the ambient medium.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1990
- DOI:
- 10.1086/169397
- Bibcode:
- 1990ApJ...364..157V
- Keywords:
-
- H I Regions;
- H Ii Regions;
- Molecular Clouds;
- Interstellar Gas;
- Interstellar Matter;
- Ionized Gases;
- Radio Emission;
- Astrophysics;
- INTERFEROMETRY;
- NEBULAE: H II REGIONS;
- NEBULAE: INDIVIDUAL NAME: ORION A;
- RADIO SOURCES: 21 CM RADIATION