Evolution of galactic density waves at the unstable stage
Abstract
A description of the evolution process of galactic density waves from an unstable stage to a quasi-stationary stage is given, starting from an evolutionary mode of the density waves. A primary property, i.e., the 'quasi-material arm property' of the density waves at the unstable stage is indicated. Owing to this property, the wave pattern would 'wind up' when the amplitude rapidly increases, so that trailing waves are formed and their wave numbers increase. When the wave numbers are increased to a certain extent, the rapid increase of the amplitude and the winding of the wave pattern automatically stop, and a quasi-stationary stage follows. Density waves are initiated in the unstable range near the co-rotation and wind up gradually into trailing short waves, which propagate on both sides of the co-rotation with their group velocities after the quasi-stationary stage is reached.
- Publication:
-
Scientia Sinica
- Pub Date:
- December 1976
- Bibcode:
- 1976SciSn..19..779Y
- Keywords:
-
- Cosmology;
- Density Wave Model;
- Galactic Evolution;
- Galactic Rotation;
- Galactic Structure;
- Spiral Galaxies;
- Fluid Mechanics;
- Group Velocity;
- Mathematical Models;
- Perturbation Theory;
- Astrophysics