Strömgren photometry of omega Cen Red Giants

We present new intermediate-band Strömgren photometry based on more than 300 u,v,b,y images of the Galactic globular cluster omega Cen p, covering a region of more than 20×20 arcmin squared across the cluster center. By adopting different Strömgren metallicity indices we estimate the photometric metallicity for ≈ 4,000 Red Giants, the largest sample ever collected. The metallicity distributions show multiple peaks ([Fe/H]phot= -1.69±0.08, -1.28±0.03, -1.07±0.02, -0.88±0.04, -0.71±0.12 and -0.03±0.08 dex) and a sharp cut-off in the metal-poor tail ([Fe/H]phot ≲ -2 dex) that agree quite well with spectroscopic measurements. We identify four distinct sub-populations, namely metal-poor (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 (SM, [Fe/H] ≈ 0). The last group includes only a small fraction of stars (˜; 8±5%) and should be confirmed spectroscopically