Small Magellanic Cloud Field Stars Meddling in Star Cluster Age Estimates

Abstract

I revisited the age of the Small Magellanic Cloud (SMC) cluster HW 42, whose previous estimates differ in more than 6 Gyr, thus challenging the most updated knowledge of the SMC star formation history. I performed an analysis of number stellar density profiles at different brightness levels; carried out a field star decontamination of the cluster color–magnitude diagram; and estimated the cluster fundamental parameters from the minimization of likelihood functions and their uncertainties from standard bootstrap methods. I conclude that HW 42 is a Gyr old ([Fe/H] = −0.89 dex) SMC cluster projected on to a SMC composite star field population which shows variations in magnitude, color, and stellar density of Main Sequence stars. The present outcome solves the conundrum of the previous age discrepancies and moves HW 42 to a region in the SMC age–metallicity relationship populated by star clusters.