We also confirm the decrease of \alpha-element over-abundance with increasing metallicity.Dredge up from under is a phrasal verb that means to bring something back to the surface, especially something that has been forgotten or buried. We present evidence that the metallicity distribution function depends on the evolutionary state of the sample stars, suggesting that enhanced mass loss preferentially removes metal-rich stars. The RV dispersion agrees well with predictions of the Besancon Galaxy model, but the metallicity of the "thick bulge" model component should be shifted to lower metallicity by 0.2 to 0.3dex to well reproduce the observations. We do not find a significant difference in metallicity or RV between the two RCs, a small difference in metallicity being probably due to a selection effect. We identify this population as the carrier of the double RC feature. The metal-rich population could be connected to the Galactic bar. We confirm the presence of two populations among our sample stars: i) a metal-rich one at ~+0.3, comprising about 30% of the sample, with low RV dispersion and low alpha-abundance, and ii) a metal-poor population at ~-0.6 with high RV dispersion and high alpha-abundance. These measurements as well as photometric data are compared to simulations with the Besancon and TRILEGAL models of the Galaxy. From these spectra we measure general metallicities, abundances of Fe and the alpha-elements, and radial velocities (RV) of the stars. Stars of luminosities down to below the two bulge red clumps (RCs) are included.
Spectra of 401 red giant stars in a field at (l,b)=(0) were obtained with FLAMES at the VLT. We aim at studying the abundances and kinematics of stars in the outer bulge, thereby providing additional constraints on models of its formation. The presence of two stellar populations in the Milky Way bulge has been reported recently.
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