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arXiv · 2511.14351

Hubble Space Telescope proper motions of Large Magellanic Cloud star clusters -- II. Kinematic structure of young and intermediate-age clusters

F. Niederhofer·L. Cullinane·D. Massari·N. Bastian·A. Bellini·F. Aguado-Agelet·S. Cassisi·D. Erkal·M. Libralato·N. Kacharov·I. Cabrera-Ziri·E. Ceccarelli·M. -R. L. Cioni·F. Dresbach·M. Häberle·S. Martocchia·S. Saracino
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Abstract

In this paper, we explore the kinematic properties of a sample of 19 young (<1 Gyr) and intermediate-age (1-2.5 Gyr) massive star clusters within the Large Magellanic Cloud (LMC). We analyse the proper motions of the clusters, which have been measured based on multi-epoch Hubble Space Telescope (HST) observations. Additionally, we infer from the HST data homogeneous and robust estimates for the distances, ages and metallicities of the clusters. This collection of information, in combination with literature line-of-sight velocities, allows us to investigate the full 3D dynamics of our sample of clusters within the frame of the LMC in a self-consistent way. While most young clusters orbit the LMC close to the stellar disc plane, NGC 1850 (~100 Myr old) depicts a peculiar case. Depending on the exact distance from the disc, it follows either a highly inclined, retrograde orbit or an eccentric orbit along the bar structure. The orbits of young clusters that formed North of the LMC centre show signs that might be connected to the resettling motion of the LMC bar structure. Based on the dynamic properties in combination with the positions of the clusters in the age-metallicity space, we find no clear-cut evidence for clusters in our sample that could have been stripped from the Small Magellanic Cloud (SMC) onto the LMC. We finally compare the kinematics of the intermediate-age clusters with a suite of simple numerical simulations of the Magellanic system to interpret the cluster motions. A possible interaction history of the LMC with the SMC, where the SMC had two past crossings of the LMC disc plane (about 300 and 900 Myr ago), in combination with the recent SMC pericentre passage, can qualitatively explain the observed kinematic structure of the clusters analysed in this work.

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F. Niederhofer, L. Cullinane, D. Massari, N. Bastian, A. Bellini, F. Aguado-Agelet, S. Cassisi, D. Erkal, M. Libralato, N. Kacharov, I. Cabrera-Ziri, E. Ceccarelli, M. -R. L. Cioni, F. Dresbach, M. Häberle, S. Martocchia, S. Saracino. 2025-11-18. Hubble Space Telescope proper motions of Large Magellanic Cloud star clusters -- II. Kinematic structure of young and intermediate-age clusters. https://doi.org/10.1051/0004-6361%2F202557397

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