We present the spatially-resolved star formation and chemical enrichment history of the Small Magellanic Cloud ( SMC ) across the entire central 4 ^ { \circ } \times 4.5 ^ { \circ } area of the main body , based on UBVI photometry from our Magellanic Clouds Photometric Survey .
We find that 1 ) approximately 50 % of the stars that ever formed in the SMC formed prior to 8.4 Gyr ago ( z > 1.2 for WMAP cosmology ) , 2 ) the SMC formed relatively few stars between 8.4 and 3 Gyr ago , 3 ) there was a rise in the mean star formation rate during the most recent 3 Gyr punctuated by “ bursts ” at ages of 2.5 , 0.4 , and 0.06 Gyr , 4 ) the bursts at 2.5 and 0.4 Gyr are temporally coincident with past perigalactic passages of the SMC with the Milky Way , 5 ) there is preliminary evidence for a large-scale annular structure in the 2.5 Gyr burst , and 6 ) the chemical enrichment history derived from our analysis is in agreement with the age-metallicity relation of the SMC ’ s star clusters .
Consistent interpretation of the data required an ad hoc correction of 0.1–0.2 mag to the B-V colors of 25 % of the stars ; the cause of this anomaly is unknown , but we show that it does not strongly influence our results .