Galactic Spiral Arms: Structure and Dynamics Given by an Equation of Motion

TL;DR

This paper presents a new model explaining how galactic spiral arms form and persist by combining differential rotation and self-gravity, supported by numerical experiments and consistent with observations.

Contribution

It introduces an equation of motion for self-gravitating filaments to describe spiral arm formation and links spiral structure to galaxy rotation curves.

Findings

Spiral arms can be generated and maintained by differential rotation and self-gravity.

The model aligns with observed spiral structures and rotation curves.

Numerical experiments support the theoretical approach.

Abstract

Using an equation of motion for a self-gravitating filament, we show how galactic spiral arms might be created and sustained. We find that the combination of differential rotation of the galactic disk and the self-gravity of the arm (as given by the equation) leads to a rotating spiral structure. Moreover, using this analysis, we then find a second differential equation that explicitly relates this spiral structure to the rotation curve of the galaxy -- it connects several factors, including spiral shape and pattern speed. We also describe a simple many-body numerical experiment that supports our approach. The findings are with consistent with observational evidence concerning arm structure and rotation curves, including leading arm structures.