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The presence of two stellar populations in the Milky Way bulge has beenreported recently. We aim at studying the abundances and kinematics of stars inthe outer bulge, thereby providing additional constraints on models of itsformation. Spectra of 401 red giant stars in a field at(l,b)=(0{\deg},-10{\deg}) were obtained with FLAMES at the VLT. Stars ofluminosities down to below the two bulge red clumps (RCs) are included. Fromthese spectra we measure general metallicities, abundances of Fe and thealpha-elements, and radial velocities (RV) of the stars. These measurements aswell as photometric data are compared to simulations with the Besancon andTRILEGAL models of the Galaxy. We confirm the presence of two populations amongour sample stars: i) a metal-rich one at [M/H] ~+0.3, comprising about 30% ofthe sample, with low RV dispersion and low alpha-abundance, and ii) ametal-poor population at [M/H] ~-0.6 with high RV dispersion and highalpha-abundance. The metal-rich population could be connected to the Galacticbar. We identify this population as the carrier of the double RC feature. We donot find a significant difference in metallicity or RV between the two RCs, asmall difference in metallicity being probably due to a selection effect. TheRV dispersion agrees well with predictions of the Besancon Galaxy model, butthe metallicity of the "thick bulge" model component should be shifted to lowermetallicity by 0.2 to 0.3dex to well reproduce the observations. We presentevidence that the metallicity distribution function depends on the evolutionarystate of the sample stars, suggesting that enhanced mass loss preferentiallyremoves metal-rich stars. We also confirm the decrease of \alpha-elementover-abundance with increasing metallicity.

astronomy and astrophysics

Constraining the structure and formation of the Galactic bulge from a  field in its outskirts. FLAMES-GIRAFFE spectra of about 400 red giants around  (l,b)=(0{\deg},-10{\deg})