Escape dynamics and fractal basin boundaries in Seyfert galaxies

TL;DR

This study investigates the escape dynamics of stars in Seyfert galaxies using a gravitational model, revealing fractal basin boundaries and energy-dependent escape behaviors, with implications for understanding spiral structure formation.

Contribution

The paper introduces a detailed numerical analysis of escape basins and fractal boundaries in a Seyfert galaxy model, linking escape properties to energy levels and galaxy structure.

Findings

Escape basins exhibit fractal boundaries across energy regimes.

Higher energy levels lead to faster and more immediate escapes.

The model can simulate the formation of spiral structures in Seyfert galaxies.

Abstract

The escape dynamics in a simple analytical gravitational model which describes the motion of stars in a Seyfert galaxy is investigated in detail. We conduct a thorough numerical analysis distinguishing between regular and chaotic orbits as well as between trapped and escaping orbits, considering only unbounded motion for several energy levels. In order to distinguish safely and with certainty between ordered and chaotic motion, we apply the Smaller ALingment Index (SALI) method. It is of particular interest to locate the escape basins through the openings around the collinear Lagrangian points $L_1$ and $L_2$ and relate them with the corresponding spatial distribution of the escape times of the orbits. Our exploration takes place both in the physical $(x,y)$ and in the phase $(x,\dot{x})$ space in order to elucidate the escape process as well as the overall orbital properties of the galactic system. Our numerical analysis reveals the strong dependence of the properties of the considered escape basins with the total orbital energy, with a remarkable presence of fractal basin boundaries along all the escape regimes. It was also observed, that for energy levels close to the critical escape energy the escape rates of orbits are large, while for much higher values of energy most of the orbits have low escape periods or they escape immediately to infinity. We also present evidence obtained through numerical simulations that our model can describe the formation and the evolution of the observed spiral structure in Seyfert galaxies. We hope our outcomes to be useful for a further understanding of the escape mechanism in galaxies with active nuclei.