Metallicities, Relative Ages, and Kinematics of Stellar Populations in ω Centauri

We present results of an extensive spectroscopic survey of Subgiant stars inthe stellar system omega Centauri. Using infrared CaII triplet lines, wederived metallicities and radial velocities for more than 250 stars belongingto different stellar populations of the system. We find that the most metalrich component, the anomalous Sub Giant Branch (SGB-a), has a metallicity of[Fe/H] -0.6 fully compatible with that determined along the anomalous Red GiantBranch (RGB-a). Our analysis suggests that the age of this component and of theother metal-intermediate (-1.4 < [Fe/H] < -1.0) stellar populations of thesystem are all comparable to that of the dominant metal poor population within2 Gyr regardless of any choice of helium abundance. These results impose severeconstraints on the time-scale of the enrichment process of this stellar system,excluding the possibility of an extended star formation period. The radialvelocity analysis of the entire sample demonstrates that only themetal-intermediate populations are kinematically cooler than the others.Comment: 33 pages, 12 figures, accepted by Ap