Orbital structure in barred spiral galaxies

TL;DR

This study analyzes the orbital structures in simulated barred spiral galaxies, identifying orbit types and their roles in supporting galaxy features like bars, rings, and spirals through frequency analysis and phase space mapping.

Contribution

It provides a detailed analysis of orbital dynamics in self-consistent N-body galaxy simulations, highlighting the role of chaotic orbits in galaxy morphology.

Findings

Chaotic orbits support outer bar and spiral structures.

Frequency maps reveal resonances even in chaotic regions.

Phase space analysis shows preferred regions for real particles.

Abstract

We study the orbital structure in a series of self-consistent $N$-body configurations simulating rotating barred galaxies with spiral and ring structures. We perform frequency analysis in order to measure the angular and the radial frequencies of the orbits at two different time snapshots during the evolution of each $N$-body system. The analysis is done separately for the regular and the chaotic orbits. We thereby identify the various types of orbits, determine the shape and percentages of the orbits supporting the bar and the ring/spiral structures, and study how the latter quantities change during the secular evolution of each system. Although the frequency maps of the chaotic orbits are scattered, we can still identify concentrations around resonances. We give the distributions of frequencies of the most important populations of orbits. We explore the phase space structure of each system using projections of the 4D surfaces of section. These are obtained via the numerical integration of the orbits of test particles, but also of the real $N$-body particles. We thus identify which domains of the phase space are preferred and which are avoided by the real particles. The chaotic orbits are found to play a major role in supporting the shape of the outer envelope of the bar as well as the rings and the spiral arms formed outside corotation.