Colour-Magnitude Diagrams of candidate age-gap filling LMC clusters

TL;DR

This study used colour-magnitude diagrams and isochrone fitting to determine the ages of four LMC clusters, finding they are younger than the 3-10 Gyr age gap, thus unlikely to fill it.

Contribution

First detailed CMD analysis of candidate intermediate-age LMC clusters using SOAR imaging and Padova models to assess their ages.

Findings

Clusters are younger than 2 Gyr, not filling the LMC age gap.

Isochrone fitting suggests ages of 1.3-1.6 Gyr for two clusters.

Remaining cluster under analysis, unlikely to be in the age gap.

Abstract

The LMC has a rich star cluster system spanning a wide range of ages and masses. One striking feature of the LMC cluster system is the existence of an age gap between 3-10 Gyrs. Four LMC clusters whose integrated colours are consistent with those of intermediate age simple stellar populations have been imaged with the Optical Imager (SOI) at the Southern Telescope for Astrophysical Research (SOAR). Their colour-magnitude diagrams (CMDs) reach V ~ 24. Isochrone fits, based on Padova evolutionary models, were carried out to these CMDs, after subtraction of field contamination. The preliminary results are as follows: KMK88-38 has an age of ~ 1.3 Gyr, assuming typical LMC metallicity and distance modulus, and a very low redenning. For OGLE-LMC0531, the best eye fits to isochrones yield an age ~ 1.6 Gyr and E(B-V)=0.03. BSDL917 is younger, ~ 150 yrs, and subjected to larger extinction (E(B-V)=0.08). The remaining cluster is currently under analysis. Therefore, we conclude that these clusers are unlikely to fill in the LMC cluster age gap, even when fitting uncertainties in the parameters are considered.