2012ApJ...756L..32P

We present results on the age and metallicity estimates of the astonishingly unstudied Small Magellanic Cloud (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° 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 an older (age ∼10-13 Gyr) and more metal-poor ([Fe/H] = -1.3±0.2 dex) dominant field stellar population, so that the cluster could have reached its current location because of its orbital motion.