On the relation between CO and gamma-ray observations, cosmic rays, and the thickness of the galactic disk.
Abstract
Recent CO observations suggest that dense clouds provide a high mean gas density (mostly H2) at approximately 5 kpc from the galactic center. Gamma-ray observations have been explained as resulting primarily from the interaction of cosmic rays with interstellar matter. The relationship between cosmic-ray density and mean gas density is discussed, and it is argued that the CO clouds must be dynamically independent of the gas that is observed in 21-cm line radiation. A plausible upper limit to the cosmic-ray density at 5 kpc from the galactic center is derived which is based on measurements of galactic-disk thickness and hydrogen turbulent velocities from 21-cm line data. An estimate is also made of the 'distributed' gas density which confines the cosmic rays to the disk. This upper limit is approximately five times the cosmic-ray density near the sun. Observations of the thickness of the galactic disk suggest that the cosmic-ray density increases with distributed gas density.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 1975
- DOI:
- 10.1086/181928
- Bibcode:
- 1975ApJ...201L...5W
- Keywords:
-
- Cosmic Rays;
- Galactic Structure;
- Gamma Rays;
- Interstellar Gas;
- X Ray Astronomy;
- Galactic Nuclei;
- Gas Density;
- Numerical Analysis;
- Solar Atmosphere;
- Synchrotron Radiation;
- Turbulence Effects;
- Astrophysics