Isolated Strömgren spheres as a source of galactic Halpha emission.
Abstract
The isolated H alpha emission features reported by Reynolds et al. are identified with Stroemgren spheres surrounding observed O stars; the root mean square electron densities and Stroemgren radii are calculated from the observed emission measure and stellar type. The density has an average value of 2 per cu cm but increases to 3.3 per cu cm for stars within 200 pc of the galactic plane. An analysis of the Catalogue of Galactic O Stars shows that enhanced H alpha emission is observed around all known O stars. The diffuse component of H alpha emission is what one would expect from the line-of-sight overlapping of isolated Stroemgren spheres surrounding B stars and appears to correlate with features on extinction maps, as derived. There is no compelling reason to suggest any large-scale intercloud ionization from H alpha data alone.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1975
- DOI:
- 10.1086/181804
- Bibcode:
- 1975ApJ...198L..31E
- Keywords:
-
- Background Radiation;
- Early Stars;
- Galactic Radiation;
- H Alpha Line;
- Astronomical Maps;
- B Stars;
- Electron Density (Concentration);
- Gas Ionization;
- Hydrogen Clouds;
- Interstellar Matter;
- O Stars;
- Stellar Radiation;
- Astrophysics