Structure and characteristics of diffuse interstellar clouds.
Abstract
Models of spherically symmetric clouds with masses of 100 to 700 solar masses confined by external pressures of 800 to 3000 K/cu cm are calculated numerically. Neutral and singly ionized carbon are assumed to provide the main contribution to cloud cooling. The thermal balance of the clouds is investigated by computing the UV radiation field within a cloud and the chemical equilibrium for the constituent elements. It is found that for conditions typical of the Galactic disk the clouds will have dense (at least 200 per cu cm) and cold (about 20-30 K) central regions consisting mainly of molecular hydrogen. Critical masses for quasi-steady-state clouds are obtained as a function of external pressure. The results show that clouds with masses no greater than 500-600 solar masses can exist in the Galactic disk; this upper limit is about 1.5 times smaller than the isothermal solution.
- Publication:
-
Astrofizika
- Pub Date:
- November 1978
- Bibcode:
- 1978Afz....14..591A
- Keywords:
-
- Clouds;
- Gaseous Diffusion;
- Interstellar Gas;
- Nebulae;
- Ultraviolet Astronomy;
- Astronomical Models;
- Critical Mass;
- Gas Density;
- Gas Temperature;
- Hydrogen Clouds;
- Milky Way Galaxy;
- Astrophysics;
- Interstellar Clouds:Cooling;
- Interstellar Clouds:Masses;
- Interstellar Clouds:Models