Trojan globular clusters: radial migration via trapping in bar resonances

TL;DR

This study investigates how the Milky Way's bar can trap globular clusters in resonances, significantly altering their orbits and positions, and influencing the structure of their tidal tails, with implications for their origins.

Contribution

It demonstrates that the galactic bar can transport globular clusters via resonances, reshaping their distribution and providing insights into their origins and tidal tail structures.

Findings

Most trapped GCs are in corotation resonance, including M22 and 47 Tuc.

The decelerating bar can move GCs from lower energies and radii to current positions.

Stripped stars form diffuse halos around GCs, matching observations.

Abstract

We search for globular clusters (GCs) trapped in resonances with the bar of the Milky Way. By integrating their orbits in a potential with a decelerating bar, we select 10 whose orbits are significantly changed by its presence. Most of these are trapped in the corotation resonance (CR), including M22 and 47 Tuc. The decelerating bar is capable of transporting these GCs to their current positions from much lower energies, angular momenta, and radii. Our results indicate that the bar is likely to have reshaped the Milky Way's globular cluster system via its resonances. We also discuss implications for the origins of specific GCs, including the possible nuclear star cluster M22. Finally, we consider the effects of the bar on the tidal tails of a trapped GC, by running simulations of stars stripped from 47 Tuc. Instead of forming narrow tails, the stripped stars make up a diffuse extended halo around the cluster, consistent with observations of 47 Tuc.