SMC: Stellar Populations through deep CMDs

Abstract

We present deep color-magnitud diagrams (CMDs) reaching the oldest main-sequence turnoffs for 12 fields in the SMC. The {\it B}-band and {\it R}-band observations were performed using the 100-inch Irénée du Pont telescope at Las Campanas Observatory, Chile, during four different campaigns (2001-2004). Our fields cover a wide range of galactocentric distance ranging from $\sim1°$ to $\sim4°$ from the center of the galaxy and are located a different position angles. Photometry was carried out using DAOPHOT II/ALLSTAR/ALLFRAME. Teramo isochrones have been overlapped. All our unprecedented deep ground-based CMDs reach the old MS turnoffs with very good photometric accuracy. They clearly show stellar population gradients as a function of both galactocentric distance and position angle. The most conspicuous difference involves the young population (age$<$1 Gyr): the young MS is much more populated on the eastern fields, located on the SMC wing area, than on the western fields located at similar galactocentric radius. In addition, the main stellar population gets progresively older on average as we go to larger galactocentric radius.