Nonlinear Density Wave Theory in a Gaseous Disk

Abstract

A nonlinear solution for the gaseous component of a galactic disk has been derived self-consistently using fluid description and reductive perturbation theory. We show that gas follows a spiral pattern, similarly to the stellar component; but the spirals are slightly separated due to different relevant parameters, as observations suggest. This analytical solution provides an additional contribution to a better understanding of rotation velocity curves of spiral galaxies. Since the proposed approach, and consequently solution, can be used in various astrophysical dynamical systems, we keep as general as possible a form of the calculus. We underline differences between the stellar and gaseous cases, and we apply this solution roughly on the gaseous disk component dynamics pointing out the importance of the nonlinear approach.