Distances to Populous Clusters in the LMC via the K-Band Luminosity of the Red Clump

TL;DR

This study uses K-band luminosity of red clump stars in 17 LMC clusters to determine their distances, revealing the cluster distribution aligns with the LMC's disk and estimating the galaxy's distance at approximately 48 kpc.

Contribution

It provides new distance measurements to LMC clusters using near-infrared photometry and confirms their distribution aligns with the galaxy's disk structure.

Findings

Cluster distribution matches the LMC's thick, inclined disk.

Old globular clusters share the same distribution as younger clusters.

Distance to the LMC center is estimated at approximately 48 kpc.

Abstract

We present results from a study of the distances and distribution of a sample of intermediate-age clusters in the Large Magellanic Cloud. Using deep near-infrared photometry obtained with ISPI on the CTIO 4m, we have measured the apparent K-band magnitude of the core helium burning red clump stars in 17 LMC clusters. We combine cluster ages and metallicities with the work of Grocholski & Sarajedini to predict each cluster's absolute K-band red clump magnitude, and thereby calculate absolute cluster distances. An analysis of these data shows that the cluster distribution is in good agreement with the thick, inclined disk geometry of the LMC, as defined by its field stars. We also find that the old globular clusters follow the same distribution, suggesting that the LMC's disk formed at about the same time as the globular clusters, ~ 13 Gyr ago. Finally, we have used our cluster distances in conjunction with the disk geometry to calculate the distance to the LMC center, for which we find (m-M)o = 18.40 +/- 0.04_{ran} +/- 0.08_{sys}, or Do = 47.9 +/- 0.9 +/- 1.8 kpc.