The VISCACHA survey - V. Rejuvenating three faint SMC clusters

E. BICA; F. MAIA; R. A. P. OLIVEIRA; B. DIAS; J.F.C. SANTOS JR.; J.P. ROCHA; L. KERBER; J.F. GARDIN; T. ARMOND; M.C. PARISI; S.O. SOUZA; B. BARBUY

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2022 vol. 517 p. 41 - 45

0035-8711

We present the analysis of three faint clusters of the Small Magellanic Cloud RZ 82, HW 42 andRZ 158. We employed the SOAR telescope instrument SAM with adaptive optics, allowing usto reach to 𝑉 ∼ 23−24 mag, unprecedentedly, a depth sufficient to measure ages of up to about10-12 Gyr. All three clusters are resolved to their centres, and the resulting colour-magnitudediagrams (CMDs) allow us to derive ages of 3.9, 2.6, and 4.8 Gyr respectively. These resultsare significantly younger than previous determinations (7.1, 5.0, and 8.3 Gyr, respectively),based on integrated photometry or shallower CMDs. We rule out older ages for these clustersbased on deep photometry and statistical isochrone fitting. We also estimate metallicities forthe three clusters of [Fe/H] = −0.68, −0.57 and −0.90, respectively. These updated agesand metallicities are in good agreement with the age-metallicity relation for the bulk of SMCclusters. Total cluster masses ranging from ∼ 7 − 11 · 103 𝑀 were estimated from integratedflux, consistent with masses estimated for other SMC clusters of similar ages. These resultsreduce the number of SMC clusters known to be older than about 5 Gyr and highlight the needof deep and spatially resolved photometry to determine accurate ages for older, low-luminositySMC star clusters.