Possible Extragalactic Origins of Five LMC Globular Clusters: Proper Motion Deviations in Gaia DR3

TL;DR

This study analyzes Gaia DR3 proper motion data of LMC clusters to identify potential extragalactic origins, revealing five globular clusters with motions suggesting past interactions or mergers with dwarf galaxies.

Contribution

It provides evidence for extragalactic origins of certain LMC globular clusters through proper motion analysis, indicating past galaxy interactions.

Findings

Five globular clusters show proper motion deviations indicating possible extragalactic origins.

One cluster (NGC 1978) is a statistically significant outlier outside 99.96% confidence.

The direction of motion deviations aligns with the Tarantula Nebula, suggesting a merger-related star formation trigger.

Abstract

We use kinematic data of proper motions from Gaia of forty-two globular and open clusters from Large Magellanic Cloud (LMC) to explore the possibility of them having extragalactic origins. We find the difference between the proper motions of cluster stars and a surrounding patch of young LMC stars in each case. We find five globular clusters towards the north-east showing a high difference (> 0.11 mas/yr, or > 25 km/s). We also examine the statistical significance of this difference taking into account both measurement errors of cluster and surrounding stars as well as inherent dispersion of stellar motions in the local galactic environment. The five globular clusters (NGC 2005, NGC 2210, NGC 1978, Hodge 3 and Hodge 11) have mean proper motions that lie outside the 85% confidence interval of the mean of surrounding young stars, with a clear outlier (NGC 1978 outside 99.96% confidence) whose difference cannot be accounted for by statistical noise. A young cluster (NGC 2100) also fitting the criteria is ruled out owing to contrary evidence from literature. This indicates a possible interaction with a dwarf galaxy resulting in the accretion/disruption in path of the five globular clusters, or possibly one or more past merger(s) of smaller galaxy/galaxies with LMC from its north-eastern region. This direction also coincides with the location of Tarantula Nebula, suggesting the possibility of the interaction event or merger having triggered its star formation activity.