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Session 24 - Star Formation in the Galaxy & the LMC.
Display session, Tuesday, June 10
South Main Hall,

[24.07] The Star Formation History of the LMC from Field Stars

K. Olsen, P. Hodge, A. Dolphin (U. Wash.), N. Suntzeff, A. Walker (CTIO)

The star formation history of the Large Magellanic Cloud is recorded in its numerous field stars. Through analysis of the distribution of stars in color-magnitude diagrams of the field, it is possible to recover the parameters that determine the star formation history. We have used HST WFPC2 images of fields near six old LMC clusters to produce V-I,V color-magnitude diagrams. After removing the comtaminating cluster stars, we are left with color-magnitude diagrams of only the field stars. Previous studies of LMC field stars have used observed color-magnitude diagrams and luminosity functions to test simple models of the evolution of the star formation rate, the chemical evolution, and the slope of the IMF. A more detailed analysis of the star formation history requires the testing of a large number of possible models, a daunting task if done by the usual approach of assembling and testing each model by hand. However, recent work has made it possible to use automated techniques for finding the best solutions to the star formation parameters. We present the results of tests to measure SFR(t) and Z(t) of the field stars from our observations with a resolution of \sim10% in age by using a new automated program that finds the most likely values of these parameters.

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Program listing for Tuesday