Optical H II regions in the outer Galaxy.
Abstract
The results of the CO survey of optical H II regions of Blitz, Fich, and Stark (1982) are used to obtain the distribution of H II regions and their associated molecular clouds beyond the solar circle. H II regions are observed in the Milky Way to distances as large as R = 20 kpc, but there are very few beyond this distance. This limiting distance does not appear to be the result of extinction and appears to be the approximate edge of the stellar disk of the Galaxy. The scale height of H II regions at 10 kpc is about 100 pc as measured by the z distance dispersion, but there is considerable variation in this quantity. The smallest scale heights appear to be related to the major spiral arms. Beyond 12 kpc the H II regions follow the warp of the H I plane. H II regions are smaller on average at large R and few very large H II regions are observed beyond 12 kpc.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- April 1984
- DOI:
- 10.1086/161872
- Bibcode:
- 1984ApJ...279..125F
- Keywords:
-
- Astrometry;
- Astronomical Coordinates;
- Galactic Structure;
- H Ii Regions;
- Milky Way Galaxy;
- Molecular Clouds;
- Carbon Monoxide;
- Distance;
- Light Emission;
- Radial Velocity;
- Scale Height;
- Astrophysics