We present new intermediate-band Stromgren photometry based on more than 300 u, v, b, y images of the Galactic globular cluster {omega} Cen. Optical data were supplemented with new multiband near-infrared (NIR) photometry (350 J, H, Ks images). The final optical-NIR catalog covers a region of more than 20x20arcmin squared across the cluster center. We use different optical-NIR color-color planes together with proper-motion data available in the literature to identify candidate cluster red-giant (RG) stars. By adopting different Stromgren metallicity indices, we estimate the photometric metallicity for ~4000 RGs, the largest sample ever collected. We identify four distinct subpopulations, namely, MP ([Fe/H]<=-1.49), metal-intermediate (MI; -1.49<[Fe/H]<=-0.93), metal-rich (MR; -0.95<[Fe/H]<=-0.15), and solar metallicity ([Fe/H]~0). The last group includes only a small fraction of stars (~8%+/-5%) and should be confirmed spectroscopically. Moreover, using the difference in metallicity based on different photometric indices, we find that the 19%+/-1% of RGs are candidate CN-strong stars.

Cone search capability for table J/ApJ/706/1277/table7 (Set of Stroemgren standard stars observed by F. Grundahl (FG))