High resolution HI observations of HII regions. I. Orion A.
Abstract
H I observations toward the H II region of Orion A are presented, and three detected large-scale H I components are mapped and discussed. The morphology and kinematics of component A at a velocity of 6 km/s indicate that the component represents the H I in the envelope of the background molecular cloud. Component C, at a velocity of -2 km/s, is located in a layer between the ionization front and the shock front that precedes it. Component B, at a velocity of 3 km/s, is probably located between the other two components. This model can explain the observed velocity structure in terms of a layer of photodissociated atomic gas between the ionized and the molecular gas. Part of this layer has been overtaken by the shock front associated with the H II region and is observed as component C. Component B represents the remainder of the photodissociated layer.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- October 1989
- Bibcode:
- 1989A&A...224..209V
- Keywords:
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- H I Regions;
- H Ii Regions;
- Interstellar Matter;
- Radio Waves;
- Very Large Array (Vla);
- Angular Resolution;
- High Resolution;
- Molecular Clouds;
- Astrophysics