Ordered and chaotic spirals in disk galaxies

TL;DR

This paper explores how ordered and chaotic stellar flows influence the spiral structures in disk galaxies, linking flow dynamics to observed morphologies and pattern speeds.

Contribution

It reviews flow patterns in response models for different spiral potentials, highlighting the roles of order and chaos in shaping galaxy morphologies.

Findings

Ordered flows are associated with slowly rotating spirals with corotation beyond their end.

Chaotic regions can support spiral structures at corotation zones.

Different spiral potentials produce distinct flow regimes influencing galaxy appearance.

Abstract

The pattern speeds of spiral galaxies are closely related to the flow of material in their disks. Flows that follow the `precessing ellipses' paradigm (see e.g., Kalnajs 1973) are likely associated with slowly rotating spirals, which have corotation beyond their end. Such a flow can be secured by material trapped around stable, elliptical, x_1 periodic orbits precessing as their Jacobi constant varies. Contrarily, if part of the spiral arms is located at a corotation region then the spiral structure has to `survive' in chaotic regions. Barred-spiral systems with a single pattern speed and a bar ending before, but close to, corotation are candidates for having spirals supported by stars in chaotic motion. In this work we review the flows we have found in response models for various types of spiral potentials and indicate the cases, where order or chaos shapes the observed morphologies.