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The asymptotic giant branch (AGB) phase is the penultimate stage of evolutionfor low- and intermediate-mass stars. AGB star outflows inject a significantamount of material into the interstellar medium (ISM), seeding new starformation. AGB mass loss is thus a crucial component of galactic chemicalevolution. The Large Magellanic Cloud (LMC) is an excellent site for AGBstudies. Over 40,000 AGB candidates have been identified using photometric datafrom the Spitzer Space Telescope Surveying The Agents of a Galaxy's Evolution(SAGE) mid-infrared (MIR) survey, including about 35,000 oxygen-rich, 7000carbon-rich and 1400 "extreme" sources. For the first time, SAGE photometryreveals two distinct populations of O-rich sources in the LMC: a faintpopulation that gradually evolves into C-rich stars and a bright, massivepopulation that circumvents this evolution, remaining O-rich. This work aims toquantify the mass-loss return from AGB stars to the LMC, a rough estimate forwhich is derived from the amount of MIR dust emission in excess of that fromstarlight. I show that this excess flux is a good proxy for the mass-loss rate,and I calculate the total AGB injection rate to be (5.9-13) x 10{-3} Msun/yr. Amore accurate determination requires detailed dust radiative transfer (RT)modeling. For this purpose, I present a grid of C-rich AGB models generated bythe RT code 2DUST, spanning a range of effective temperatures, gravities, dustshell radii and optical depths as well as a baseline set of dust propertiesobtained by modeling a carbon star, data for which was acquired as part of thespectroscopic follow-up to SAGE. AGB stars are the best laboratories for duststudies, and the development of a model grid will reinforce future research inthis field.

The Mass-Loss Return From Asymptotic Giant Branch Stars to The Large Magellanic Cloud Using Data From The SAGE Survey