TAGGING THE CHEMICAL EVOLUTION HISTORY OF THE LARGE MAGELLANIC CLOUD DISK

We have used high-resolution spectra obtained with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to derive kinematic properties and chemical abundances of Fe, O, Mg, and Si for 89 stars in the disk of the Large Magellanic Cloud (LMC). The derived metallicity and [alpha/Fe], obtained as the average of O, Mg, and Si abundances, allow us to draw a preliminary scheme of the star formation history of this region of the LMC. The derived metallicity distribution shows two main components: one component (comprising similar to 84% of the sample) peaks at [Fe/H] = -0.48 dex and it shows an [alpha/Fe] ratio slightly under solar ([alpha/Fe] similar to-0.1 dex). This population probably originated in the main star formation event that occurred 3-4 Gyr ago (possibly triggered by tidal capture of the Small Magellanic Cloud). The other component (comprising similar to 16% of the sample) peaks at [Fe/H] similar to-0 dex and it shows an [alpha/Fe] similar to 0.2 dex. This population was probably generated during the long quiescent epoch of star formation between the first episode and the most recent bursts. Indeed, in our sample we do not find stars with chemical properties similar to the old LMC globular clusters nor to the iron-rich and alpha-poor stars recently found in the LMC globular cluster NGC 1718 and also predicted to be in the LMC field, thus suggesting that both of these components are small (<1%) in the LMC disk population.