2013A&A...560A..44V

This paper compares the chemical evolution of the Large Magellanic Cloud to that of the Milky Way and investigates the relation between the bar and the inner disc of the Large Magellanic Cloud in the context of the formation of the bar. We obtained high-resolution and mid signal-to-noise ratio spectra with FLAMES/GIRAFFE at ESO/VLT and performed a detailed chemical analysis of 106 and 58 Large Magellanic Cloud field red giant stars (mostly older than 1Gyr), located in the bar and the disc of the LMC respectively. To validate our stellar parameter determinations and abundance measurement procedures, we performed thorough tests using the well-known mildly metal-poor Milky-Way thick disc giant Arcturus (HD 124897, α Boo). We measured elemental abundances for O, Mg, Si, Ca, Ti (α-elements), Na (light odd element), Sc, V, Cr, Co, Ni, Cu (iron-peak elements), Y, Zr, Ba, La, and Eu (s- and r-elements). We find that the α-element ratios [Mg/Fe] and [O/Fe] are lower in the LMC than in the MW while the LMC has similar [Si/Fe], [Ca/Fe], and [Ti/Fe] to the MW. As for the heavy elements, [Ba,La/Eu] exhibit a strong increase with increasing metallicity starting from [Fe/H]≃-0.8dex, and the LMC has lower [Y+Zr/Ba+La] ratios than the MW. Cu is almost constant over all metallicities and about 0.5dex lower in the LMC than in the MW. The LMC bar and inner disc exhibit differences in their [α/Fe] (slightly larger scatter for the bar in the metallicity range [-1,-0.5]), their Eu (the bar trend is above the disc trend for [Fe/H]≥-0.5dex), their Y and Zr, their Na and their V (offset between the bar and the disc distributions). Our results show that the chemical history of the LMC experienced a strong contribution from type Ia supernovae as well as a strong s-process enrichment from metal-poor AGB winds. Massive stars made a smaller contribution to the chemical enrichment compared to the MW. The observed differences between the bar and the disc speak in favour of an episode of enhanced star formation a few Gyr ago, occurring in the central parts of the LMC and leading to the formation of the bar. This is in agreement with recently derived star formation histories.