The influence of the bar on the chaotic dynamics of globular clusters in the central region of the Galaxy

TL;DR

This study investigates how the galactic bar affects the orbital chaos of globular clusters near the Galaxy's center, revealing that the bar can both induce and suppress chaotic motion in these clusters.

Contribution

It provides a detailed analysis of the bar's influence on globular cluster dynamics using Gaia data and frequency methods, highlighting the bar's role in orbital chaos.

Findings

8 clusters changed from regular to chaotic motion due to the bar

9 clusters changed from chaotic to regular motion due to the bar

The bar significantly influences the orbital dynamics of clusters within 3.5 kpc

Abstract

The paper is devoted to the analysis of the influence of the galactic bar on the nature of the orbital motion (chaotic or regular) of globular clusters in the central region of the Galaxy with a radius of 3.5 kpc, which are subject to the greatest influence of the bar. The sample includes 45 globular clusters. To form the 6D phase space required for integrating the orbits, the most accurate astrometric data to date from the Gaia satellite (Vasiliev, Baumgardt, 2021) were used, as well as new refined average distances (Baumgardt, Vasiliev, 2021). The orbits of the globular clusters were obtained both in an axisymmetric potential and in a potential including the bar. The following, most realistic, bar parameters were adopted: mass $10^{10} M_\odot$, semi-major axis length 5 kpc, bar axis rotation angle 25$^o$, angular rotation velocity 40 km s$^{-1}$ kpc$^{-1}$. The analysis of the chaoticity/regularity of the orbital motion in both potentials was carried out using one of the most effective methods, namely, the frequency method, which consists in calculating the drift of fundamental frequencies. As a result, the influence of the bar on the dynamics of each GC of the sample was assessed. It is established that 8 GCs changed regular dynamics to chaotic under the influence of the bar, and 9 GCs changed chaotic dynamics to regular one.