A likely runaway star cluster in the outer disc of the Large Magellanic Cloud

Abstract

We present results from photometric and spectroscopic data obtained with SOAR and Gemini observatory facilities in the field of a recently discovered star cluster. The cluster, projected towards the Eastern side of the outer disc of the Large Magellanic Cloud (LMC), was originally placed nearly 10 kpc behind the LMC with an age and metallicity typical of the innermost LMC star cluster population. We assigned radial velocity (RV) memberships to stars observed spectroscopically, and derived the cluster age and distance from theoretical isochrone fitting to the cluster colour-magnitude diagram. The new object turned out to be a 0.9 Gyr old outer LMC disc cluster, which possibly reached the present position after being scattered from the innermost LMC regions where it might have been born. We arrived at this conclusion by examining the spatial distribution of LMC star clusters of similar age, by comparing the derived spectroscopic metallicity with that expected for an outside-in galaxy formation scenario, by considering the cluster internal dynamical stage as inferred from its derived structural parameters and by estimating the circular velocity of a disc that rotates with the corresponding star cluster radial velocity at the cluster's deprojected distance, which resulted to be nearly 60 per cent higher than that of most of the outer LMC disc clusters.

9 pages, 8 figures. Accepted for publication in Monthly Noticies of the Royal Astronomical Society

References in corpus (11)

• Calcium II Triplet Spectroscopy of LMC Red Giants. I. Abundances and Velocities for a Sample of Populous Clusters
• The Infrared Ca II triplet as metallicity indicator
• SOAR Adaptive Module (SAM): seeing improvement with a UV laser
• The VMC survey - XV. The Small Magellanic Cloud--Bridge connection history as traced by their star cluster populations
• Evidence of differential tidal effects in the old globular cluster population of the Large Magellanic Cloud
• Recent Star Formation in the Leading Arm of the Magellanic Stream
• Isolated ellipticals and their globular cluster systems III. NGC 2271, NGC 2865, NGC 3962, NGC 4240 and IC 4889
• Young stars in the periphery of the Large Magellanic Cloud
• H I Kinematics of the Large Magellanic Cloud revisited : Evidence of possible infall and outflow
• Stellar cluster candidates discovered in the Magellanic System
• Accurate radial velocity and metallicity of the Large Magellanic Cloud old globular clusters NGC 1928 and NGC 1939

Cited by in corpus (5)

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• Metallicity estimates of young clusters in the Magellanic Clouds from Stromgren photometry of supergiant stars
• Astrophysical properties of newly discovered Magellanic Cloud star clusters
• Residual velocities of Small Magellanic Cloud star clusters
• Tracing Milky Way substructure with an RR Lyrae hierarchical clustering forest