Dr. Jason Harris
University of Arizona

University of Florida Astronomy Colloquium - Oct 12th, 2005

Stellar Archaeology in the Magellanic Clouds

The Magellanic Clouds have much to teach us about star formation processes and the drivers of galaxy evolution. Using our comprehensive Magellanic Clouds Photometric Survey as a foundation, I have been undertaking several complementary studies focused on understanding the star formation histories (SFHs) of these important nearby galaxies. From UBVI photometry of 6 million stars in the Small Magellanic Cloud (SMC), I have reconstructed a global map of its past SFH. I found that the SMC experienced a long quiescent epoch until about 3 Gyr ago, and has formed stars more-or-less continuously ever since. In addition, this recent epoch of star formation is punctuated by a few distinct episodes of enhanced activity, which seem to be tantilizingly coincident with past perigalactic encounters between the SMC and the Milky Way. The internal structure of the SMC is thought to be quite complex, with no apparent organized structure, but a very large line-of-sight depth. I have completed a spectroscopic survey of over 2000 red giant branch stars in the SMC, in order to study the kinematics of its stellar population and to constrain its chemical enrichment history. Turning to the Large Magellanic Cloud, I will present preliminary results on our SFH analysis of the enigmatic supergiant shells in the Shapley III region.