Order and chaos in a galactic model with a strong nuclear bar

TL;DR

This paper investigates the dynamics of stars in a galactic model with a strong nuclear bar, revealing how the presence of a massive nucleus influences chaos and resonance phenomena at different energy levels.

Contribution

It introduces a composite galactic model linking global and local dynamics, highlighting the role of a massive nucleus in star motion and chaos.

Findings

Low energy stars exhibit chaos due to the nucleus.

High energy stars show unbounded motion near the galactic center.

Resonance phenomena are observed in low energy local motion.

Abstract

We use a composite gravitational galactic model consisting of a disk, a halo, a massive nucleus and a strong nuclear bar, in order to study the connections between global and local parameters in a realistic dynamical system. The local model is constructed from a two-dimensional perturbed harmonic oscillator and can be derived by expanding the global model in the vicinity of the central stable Lagrange equilibrium point. The frequencies of oscillations are not arbitrary, but they are connected with all the parameters involved with the global model. Moreover, the value of the local energy is also connected with the value of the global energy. Low and high energy stars in the global model display chaotic motion. Comparison with previous research reveals that the presence of the massive nucleus is responsible for the chaotic motion of the low energy stars. In the local motion, the low energy stars show interesting resonance phenomena, but the chaotic motion, if any, is negligible. On the contrary, the high energy stars do not show bounded motion in the local model. This is an indication of particular activity near the center of galaxies possessing massive nuclei.