The star field age-metallicity relationship in the Small Magellanic Cloud

A.E. PIATTI

Bol. Asoc. Arg. Astron.

AAA Editorial board

Año: 2012 vol. 55 p. 325 - 328

0571?3285

              We present for the first time CCD Washington CT1 photom-etry for the unprecedented data base of some 3.3 million stars distributedthroughout the entire Small Magellanic Cloud (SMC) main body. We ob-tain ages and metallicities for representative field stellar populations andproduce a star field age-metallicity relationship (AMR) from the birth ofthe galaxy until ∼ 1 Gyr ago, independent of any other previous approach.The SMC star field is featured by no gradients in age and metallicity, andby stellar populations younger than ∼ 2 Gyr more metal rich than [Fe/H]∼ -0.8 dex, which are confined to the innermost region (semi-major axis≤ 1◦ ). When comparing this AMR with that for clusters with ages andmetallicities in the same star field scales, we find that clusters and starfields have experienced two enhanced formation processes: the most re-cent peaked at an age of ∼3.5 Gyr, and an earlier one detected at an ageof ∼ 5-6 and 7.5 Gyr for clusters and star fields, respectively.