"Collective processes and structures in spiral galaxies"
E. Polyachenko
Abstract:
1. A new approach to studying global structures in thin stellar disks,
which allows to describe universally both bar and spiral modes, is
presented. They are considered as the low-frequency normal modes in a
disc of orbits precessing at different angular speeds.
The problem of determining the normal modes is reduced to a simple
integral equation in the form of the classical eigen-value problem, where the
eigen-value is directly equal to the pattern speed of the mode.
http://xxx.lanl.gov/abs/astro-ph/0312595
2. Study of line-of sight velocity maps of gaseous disk in spiral
galaxies allows, under some conditions, to reconstruct 3 components of
gas velocity in the galactic plane. It is demonstrated, that there are
exponentially diverging trajectories of gas motion in the galaxy NGC
3631. The Lyapunov characteristic numbers, calculated for these
trajectories, are evidences of the local stochastic instability,
leading to fast mixing of gas in the galaxy.