Identification of a new relatively old star cluster in the Small Magellanic Cloud

TL;DR

This study identifies and characterizes a previously unstudied, relatively old star cluster in the Small Magellanic Cloud, providing new insights into its age, metallicity, and possible orbital history.

Contribution

First detailed age and metallicity estimates for the SMC cluster ESO 51-SC09, establishing it as one of the oldest in the SMC with implications for its orbital motion.

Findings

ESO 51-SC09 is approximately 7 Gyr old.

The cluster's metallicity is [Fe/H] = -1.00.

It is located about 4 degrees north of the SMC center.

Abstract

We present results on the age and metallicity estimates of the astonishingly unstudied SMC cluster ESO 51-SC09, from CCD BVI photometry obtained at the ESO NTT with the EMMI attached. ESO 51-SC09 turns out to be a relatively small cluster (FWHM = (10 +- 1) pc) located ~ 4 deg northward from the galaxy center. We report for the first time a mean cluster age of (7.0 +- 1.3) Gyr and a mean cluster metallicity of [Fe/H] = (-1.00 +- 0.15) dex, concluding that ESO 51-SC09 belongs to the group of the oldest SMC clusters. We found that the cluster is projected onto a dominant field stellar population older (age ~ 10-13 Gyr) and more metal-poor ([Fe/H] = -1.3 +- 0.2 dex), so that the cluster could reach its current location because of its orbital motion.