Small Magellanic Cloud field stars meddling in star cluster age estimates

TL;DR

This study accurately determines the age of the Small Magellanic Cloud cluster HW 42, resolving previous discrepancies by accounting for field star contamination and analyzing stellar density profiles, thus refining the SMC's star formation history.

Contribution

The paper introduces a comprehensive method combining density profiles, field star decontamination, and likelihood analysis to accurately estimate cluster ages in the SMC.

Findings

HW 42 is approximately 6.2 Gyr old with metallicity [Fe/H] = -0.89.

The analysis resolves previous age discrepancies for HW 42.

The results align HW 42 with the SMC's age-metallicity relation.

Abstract

I revisited the age of the Small Magellanic Cloud 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 6.2$^{\rm +1.6}_{\rm -1.3}$ Gyr old ([Fe/H] = -0.89$^{\rm +0.10}_{\rm -0.11}$ 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.