Orbit classification in the meridional plane of a disk galaxy model with a spherical nucleus

TL;DR

This paper analyzes how various parameters affect the regular or chaotic nature of star orbits in a galactic model with a disk and spherical nucleus, introducing a new method to distinguish chaos from regularity.

Contribution

It provides a detailed study of orbit behavior in a galactic model and proposes a novel combined approach using Lyapunov and SALI indicators to identify chaos thresholds.

Findings

Identified how nucleus mass and scale length influence orbit regularity.

Quantified the percentage of chaotic versus regular orbits under different parameters.

Developed a new method combining Lyapunov and SALI to detect chaos thresholds.

Abstract

We investigate the regular or chaotic nature of star orbits moving in the meridional plane of an axially symmetric galactic model with a disk and a spherical nucleus. We study the influence of some important parameters of the dynamical system, such as the mass and the scale length of the nucleus, the angular momentum or the energy, by computing in each case the percentage of chaotic orbits, as well as the percentages of orbits of the main regular resonant families. Some heuristic arguments to explain and justify the numerically derived outcomes are also given. Furthermore, we present a new method to find the threshold between chaos and regularity for both Lyapunov Characteristic Numbers and SALI, by using them simultaneously.