The Velocity Dispersion of the Giant Molecular Clouds: A Viscous Origin
Abstract
The authors propose the energy source and study the details of the acceleration mechanism for the random motion of the Giant Molecular Clouds (GMCs) in the Galaxy. Gravitational scattering of the massive clouds off each other in the differentially rotating galactic disk constitutes an effective "gravitational" viscosity, which causes an increase in the random kinetic energy of the GMCs at the expense of their ordered, rotational kinetic energy in the galactic disk. The authors calculate the rate of increase, due to this effect, of the random kinetic energy of a GMC with a nonzero initial random velocity. Locally the fraction of the rotational kinetic energy lost in supporting inelastic cloud motions for ≡10 billion years is small, ≡0.1. As a result of the viscous interaction among the clouds, the clouds drift inward. Thus, the dynamics as well as the radial distribution in the Galaxy of the GMCs is determined by their gravitational viscous interaction, which operates because of their location in the differentially rotating galactic disk.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 1988
- DOI:
- 10.1086/166302
- Bibcode:
- 1988ApJ...328..404J
- Keywords:
-
- Hydrodynamics;
- Interstellar Gas;
- Milky Way Galaxy;
- Molecular Clouds;
- Velocity Distribution;
- Computational Astrophysics;
- Harmonic Oscillators;
- Kinetic Energy;
- Random Processes;
- Time Dependence;
- Astrophysics;
- GALAXIES: INTERNAL MOTIONS;
- HYDRODYNAMICS;
- INTERSTELLAR: MOLECULES;
- NEBULAE: GENERAL