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arXiv · 2309.02298

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

Tamojeet Roychowdhury·Navdha Bhalla
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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.

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Tamojeet Roychowdhury, Navdha Bhalla. 2023-09-05. Possible Extragalactic Origins of Five LMC Globular Clusters: Proper Motion Deviations in Gaia DR3. https://arxiv.org/abs/2309.02298

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