CaT metallicities of SMC star clusters: Tracers of the chemical evolution

Abstract

We present new results based on VLT Ca Triplet (CaT) medium resolution spectroscopy of red giant members of 10 SMC intermediate- old age clusters. We derive mean cluster velocities to a few km s−1 and mean metallicities to 0.05 dex. We combine these results with those from 29 additional clusters previously studied, as well as accurate velocities and metallicities for about 750 surrounding field giants, previously studied. This additional sample was observed with the same instrument and instrumental configuration as in the present work, and their metallicities were obtained following the same prescriptions. We investigate the metallicity distribution, age-metallicity relation and metallicity gradient in great detail for the SMC using this large and homogeneous database. We find some surprising differences between the clusters and their fields.