Metallicities and ages for star clusters and their surrounding fields in the Large Magellanic Cloud

Abstract

Aims. We study 147 star clusters in the Large Magellanic Cloud (LMC) in order to determine their mean metallicities and ages, as well as the mean metallicities of 80 surrounding fields. We construct an age-metallicity relation (AMR) for the clusters in the LMC. Methods. For this purpose, we used Strömgren photometry obtained with the SOI camera on the 4.1 m SOAR telescope. We derived the metallicities of individual stars utilizing a metallicity calibration of the Strömgren (b-y) and m1 colors from the literature. Cluster ages were determined from the isochrone fitting. Results. We found the mean metallicity and age for 110 star clusters. For the remaining 37, we provide an age estimation only. To the best of our knowledge, for 29 clusters from our sample, we provide both the metallicity and age for the first time, whereas for 66 clusters, we provide a first determination of the metallicity, and for 43 clusters, the first estimation of the age. We also calculated the mean metallicities for stars from 80 fields around the clusters. The results were then analyzed for spatial metallicity and age distributions of clusters in the LMC, as well as their AMR. The old, metal-poor star clusters occur both in and out of the LMC bar region, while intermediate-age clusters are located mostly outside of the bar. The majority of star clusters younger than 1 Gyr are located in the bar region. We find a good agreement between our AMR and theoretical models of the LMC chemical enrichment, as well as with AMRs for clusters from the literature. Next, we took advantage of 26 stellar clusters from our sample which host Cepheid variables and used them as an independent check of the correctness of our age determination procedure. We used period-age relations for Cepheids to calculate the mean age of a given cluster and compared it with the age obtained from isochrone fitting. We find good agreement between these ages, especially for models taking into account additional physical processes (e.g., rotation). We also compared the AMR of the LMC and Small Magellanic Cloud (SMC) derived in a uniform way and we note that they indicate possible former interaction between these two galaxies. The Strömgren photometry obtained for this study has been made publicly available.