Metallicity distribution of ω Cen Red Giants based on the Strömgren m1 metallicity index

We adopted uvby Strömgren photometry to investigate the metallicity distribution of ω Cen Red Giant (RG) stars. We provided a new empirical calibration of the Strömgren m₁≡(v − b) − (b − y) metallicity index based on cluster stars. The new calibration has been applied to a sample of ω 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.