Abstract details

High-resolution photometry of more than 100,000 stars in the central regions of Omega Cen has recently shed more light on the complex star formation history of this peculiar Galactic globular cluster, with up to five separate components having been identified on its RGB (Sollima et al. 2005). We take advantage of the results of this extensive imaging campaign to construct detailed chemical evolution models for Omega Cen. The model predictions are then compared with a wealth of chemical abundance data collected from the literature. We demonstrate that the abundances and abundance ratios of the stars in this cluster can be explained only if it is the remnant of a dwarf satellite galaxy evolved in isolation and then accreted by the Milky Way some 10 Gyr ago. Particular attention is paid to the problem of the large helium enhancement required in order to explain the double main sequence of Omega Cen.