Are external perturbations responsible for chaotic motion in galaxies?

TL;DR

This study investigates how external perturbations influence chaotic motion in galactic models, revealing linear relationships between chaos extent and system parameters, supported by numerical and theoretical analysis.

Contribution

It demonstrates the role of external perturbations combined with dense nuclei in inducing chaos, providing new linear relationships and insights into galactic dynamics.

Findings

External perturbations and dense nuclei induce chaos.

Linear relationships between chaos and system parameters.

Chaos extent increases with perturbation strength and flattening.

Abstract

We study the nature of motion in a logarithmic galactic dynamical model, with an additional external perturbation. Two different cases are investigated. In the first case the external perturbation is fixed, while in the second case it is varying with the time. Numerical experiments suggest, that responsible for the chaotic phenomena is the external perturbation, combined with the dense nucleus. Linear relationships are found to exist, between the critical value of the angular momentum and the dynamical parameters of the galactic system that is, the strength of the external perturbation, the flattening parameter and the radius of the nucleus. Moreover, the extent of the chaotic regions in the phase plane, increases linearly as the strength of the external perturbation and the flattening parameter increases. On the contrary, we observe that the percentage covered by chaotic orbits in the phase plane, decreases linearly, as the scale length of the nucleus increases, becoming less dense. Theoretical arguments are used to support and explain the numerically obtained outcomes. A comparison of the present outcomes with earlier results is also presented.