Identification of a new relatively old star cluster in the small magellanic cloud

Abstract

We present results on the age and metallicity estimates of the astonishingly unstudied Small Magellanic Cloud (SMC) cluster (ESO51-SC09), from CCD BVI photometry obtained at the ESO NTT with the EMMI attached. ESO51-SC09 turns out to be a relatively small cluster (FWHM = 10± 1pc) located ∼4° northward from the galaxy center. We report for the first time a mean cluster age of 7.0± 1.3Gyr and a mean cluster metallicity of [Fe/H]= -1.00± 0.15dex, concluding that ESO51-SC09 belongs to the group of the oldest SMC clusters. We found that the cluster is projected onto an older (age ∼10-13Gyr) and more metal-poor ([Fe/H]= -1.3± 0.2dex) dominant field stellar population, so that the cluster could have reached its current location because of its orbital motion. © 2012 The American Astronomical Society. All rights reserved.