The Star Formation History of the Small Magellanic Cloud

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Abstract
We present the spatially resolved star formation and chemical enrichment history of the Small Magellanic Cloud (SMC) across the entire central 4° × 45 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.
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