The Formation History of Omega Cen

Omega Centauri is the nearest nuclear star cluster to us and is the likely stripped nucleus of the Gaia-Enceladus merger. The oMEGACat surveys pairs MUSE spectroscopy for 300,000 stars with HST photometry in Omega Centauri. We combine these measurements to determine individual stellar ages for more than 8000 subgiant branch stars with a median age precision of 0.7 Gyr. These stars formed over ~3 Gyr, with metal-rich populations having younger mean ages and larger age spreads than metal-poor stars. There is also a clear dichotomy of ages at a fixed metallicity for lower metallicity stars. Finally, we also use the HST photometry and spectroscopic metallicities to separate subpopulations across the full CMD and show the increasing enrichment of Helium abundance for metal-rich stars. Together these results present the first clear picture of the formation history of the Omega Cen.