On the discrete nature of the Red Giant Branch of omega Centauri

Abstract

We report the results of an extensive VLT high-resolution imaging campaign of the central region of the giant globular cluster omega Centauri. More than 100,000 stars have been measured in the inner 9'x 9' region of the cluster. On the basis of multiband Colour Magnitude Diagrams (CMD), we confirm the existence of multiple stellar populations along the Red Giant Branch (RGB). Moreover, thanks to the high-precision of this dataset, we conclude that the RGB does not present a smooth and continuous distribution, but shows a discrete structure: besides the metal-poor and the extreme metal-rich population (RGB-a), the existence of three metal intermediate populations is shown.