Metallicity distribution of Omega Cen Red Giants based on the Stroemgren m1 metallicity index

Abstract

We adopted uvby Stroemgren photometry to investigate the metallicity distribution of Omega Cen Red Giant (RG) stars. We provided a new empirical calibration of the Stroemgren m1 = (v-b)-(b-y) metallicity index based on cluster stars. The new calibration has been applied to a sample of Omega Cen RGs. The shape of the estimated metallicity distribution is clearly asymmetric, with a sharp cut-off at low metallicities ([Fe/H] < -2.0) and a metal-rich tail up to [Fe/H] ~ 0.0. Two main metallicity peaks have been identified, around [Fe/H] ~ -1.9 and -1.3 dex, and a metal-rich shoulder at ~ 0.2 dex.

4 pages, 3 figures. To appear in the Proceedings of IAU Symposium 241: "Stellar Populations as Building Blocks of Galaxies", 10-16 December, 2006 at La Palma, Canary Islands, Spain