Age-metallicity relation of {omega} Cen

This distribution is similar to that found for the red giant branch. The distribution shows a sharp rise to a mean of [Fe/H]=-1.7 with a long tail to higher metallicities.

Ages have then been determined for the stars using theoretical isochrones enabling the construction of an age-metallicity diagram. Interpretation of this diagram is complicated by the correlation of the errors in the metallicities and ages. Nevertheless, after extensive Monte Carlo simulations, we conclude that our data show that the formation of the cluster took place over an extended period of time: the most metal-rich stars in our sample ([Fe/H]~-0.6) are younger by 2-4Gyr than the most metal-poor population.