2007MNRAS.377..300P

We present CCD photometry in the Washington C and T₁ filters for six star clusters (B34, NGC256, NGC265, NGC294, IC1611 and NGC376) in the Small Magellanic Cloud (SMC) and their surrounding fields. The resultant colour-magnitude diagrams (CMDs) extend from T₁∼ 14 to as faint as T₁∼ 22 revealing the main-sequence turnoffs of the clusters. Adopting a metallicity of Z = 0.004, we compare our cluster photometry with theoretical isochrones in the Washington system in order to derive ages. To facilitate age determination of the surrounding fields, we use the magnitude difference between the helium-burning red clump stars and the main-sequence turnoff. Finally, we estimate mean metallicities for the field stars by comparing the location of the field red giant branch with standard giant branches for Galactic globular clusters of known abundance, corrected for age effects. Combining these results with our previous work, we find a clear trend of younger clusters being located closer to the centre of the SMC. In addition, there is a tendency for the mean metallicity and its dispersion to be greater inside 4° of the SMC's centre as compared to outside this radius. As far as the properties of the field stars are concerned, we find little correlation between the ages of the clusters and those of the field stars against which they are projected. Clearly, more work needs to be done to clarify these trends.