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

A.E. PIATTI, R. SALINAS, E.K. GREBEL

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2019 vol. 482 p. 980 - 987

0035-8711

We present results from photometric and spectroscopic data obtainedwith 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 innermostLMC star cluster population. We assigned radial velocity (RV) memberships to starsobserved spectroscopically, and derived the cluster age and distance fromtheoretical 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 theinnermost 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 metallicitywith that expected for an outside-in galaxy formation scenario, by consideringthe clusterinternal dynamical stage as inferred from its derived structural parameters andby 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.