UBV(RI)c phot. of omega Cen (NGC5139) subgiants

GIRAFFE@VLT spectra of 80 stars at R=6400 give metallicities for all of them and abundances of C, N, Ca, Ti, and Ba for a subset of them. The photometric data, which have unusually high accuracy, come from a ~10x10arcmin^2^ mosaic of HST ACS images centered on the cluster center and on multicolor images of a ~34x33arcmin^2^ field, taken with the WFI@ESO2.2m camera.

Stars with [Fe/H]<-1.25 have a large magnitude spread on the flat part of the sub-giant branch (SGB). We interpret this as empirical evidence for an age spread, and from theoretical isochrones we derive a relative age for each star.