Physical properties of star clusters in the outer LMC as observed by the Dark Energy Survey

TL;DR

This study uses Dark Energy Survey data to identify and analyze star clusters in the outer Large Magellanic Cloud, providing new physical parameters and revealing their distribution and properties.

Contribution

It introduces a new pipeline for measuring stellar and cluster parameters, increasing the known cluster census and characterizing their physical properties.

Findings

Identified 109 new star clusters in the outer LMC.

Derived ages, metallicities, and structural parameters for 117 clusters.

Found a radial metallicity gradient with no clusters more metal-rich than -0.7 beyond 8 kpc.

Abstract

The Large Magellanic Cloud (LMC) harbors a rich and diverse system of star clusters, whose ages, chemical abundances, and positions provide information about the LMC history of star formation. We use Science Verification imaging data from the Dark Energy Survey to increase the census of known star clusters in the outer LMC and to derive physical parameters for a large sample of such objects using a spatially and photometrically homogeneous data set. Our sample contains 255 visually identified cluster candidates, of which 109 were not listed in any previous catalog. We quantify the crowding effect for the stellar sample produced by the DES Data Management pipeline and conclude that the stellar completeness is < 10% inside typical LMC cluster cores. We therefore develop a pipeline to sample and measure stellar magnitudes and positions around the cluster candidates using DAOPHOT. We also implement a maximum-likelihood method to fit individual density profiles and colour-magnitude diagrams. For 117 (from a total of 255) of the cluster candidates (28 uncatalogued clusters), we obtain reliable ages, metallicities, distance moduli and structural parameters, confirming their nature as physical systems. The distribution of cluster metallicities shows a radial dependence, with no clusters more metal-rich than [Fe/H] ~ -0.7 beyond 8 kpc from the LMC center. The age distribution has two peaks at ~ 1.2 Gyr and ~ 2.7 Gyr.