Rings, spirals and manifolds

TL;DR

This paper explores how the dynamics around Lagrangian points in barred galaxies can explain the formation of rings and spirals through manifold-guided orbits, linking theoretical models to observed galaxy structures.

Contribution

It provides a detailed theoretical framework for understanding galaxy rings and spirals via manifold dynamics near Lagrangian points, including effects of mass concentrations.

Findings

Manifolds explain the formation of rings and spirals in barred galaxies.

Mass concentrations at bar ends can stabilize Lagrangian points.

Material circulation within manifolds accounts for observed galaxy morphologies.

Abstract

Two-armed, grand design spirals and inner and outer rings in barred galaxies can be due to orbits guided by the manifolds emanating from the vicinity of the L1 and L2 Lagrangian points, located at the ends of the bar. We first summarise the necessary theoretical background and in particular we describe the dynamics around the unstable equilibrium points in barred galaxy models, and the corresponding homoclinic and heteroclinic orbits. We then discuss two specific morphologies and the circulation of material within the corresponding manifolds. We also discuss the case where mass concentrations at the end of the bar can stabilise the L1 and L2 and the relevance of this work to the gas concentrations in spirals and rings.