The global properties of the Galaxy. I. The H I distribution outside the solar circle.
Abstract
We have searched for high-velocity 21-cm emission from a possible extended Galactic neutral hydrogen disk. The HI surface density at 50 kpc from the Galactic center is less than 10-2 M0/pc2. This limit is consistent with the HI surface density in M3 1, but well below observed densities in M63, M8 1, or M101 at this radius. The Galactic HI surface density distribution for R > R is consistent with an exponential model whose scale length is 0.4 R . There is no observational evidence for a "cutoff" in the Hi distribution. The agreement with observations is best for a value of the solar circular velocity e0 of 220 km s'.
- Publication:
-
The Astronomical Journal
- Pub Date:
- December 1978
- DOI:
- 10.1086/112367
- Bibcode:
- 1978AJ.....83.1585K
- Keywords:
-
- Gas Density;
- Hydrogen Clouds;
- Milky Way Galaxy;
- Neutral Gases;
- Spatial Distribution;
- Brightness Temperature;
- Centimeter Waves;
- Density Distribution;
- Galactic Rotation;
- Radio Astronomy;
- Astrophysics;
- Galactic Structure:High-Velocity Gas;
- Galaxy:Neutral Hydrogen