HI absorption limits and emission mapping for high-velocity clouds.
Abstract
Systematic emission and absorption surveys have been conducted for high-velocity H I in the direction of 63 bright continuum sources. High-velocity emisison is detected along 18 of these 63 directions with a threshold about a factor of 2 better than previous, much more extensive surveys. No high-velocity absorption was found in any of the directions. The sky distribution of the high-velocity emission and the column density distribution agree with larger surveys. Detailed emission maps in the vicinity of each continuum source show that the variations in column density within a high-velocity cloud are similar to the variations between high-velocity clouds. A previously discovered high-velocity cloud at high galactic latitude, in the direction of part of the Virgo Cluster of galaxies, was mapped. This small cloud is moving away from the galactic plane at v greater than 30 km/s and is probably not self-gravitating.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 1990
- DOI:
- 10.1086/168488
- Bibcode:
- 1990ApJ...351..503C
- Keywords:
-
- H I Regions;
- Hydrogen Clouds;
- Interstellar Gas;
- Absorption Spectra;
- Centimeter Waves;
- Emission Spectra;
- Astrophysics