Description
We present abundances of Fe, Na and O for 1409 red giant stars in 15 galactic globular clusters (GCs), derived from the homogeneous analysis of high resolution FLAMES/GIRAFFE spectra. The program clusters cover a range in metallicity from [Fe/H]=-2.4dex to [Fe/H]=-0.4dex, with a wide variety of global parameters (morphology of the horizontal branch, mass, concentration, etc.). For all clusters we find the Na-O anticorrelation, classical signature of the operation of proton-capture reactions in H burning at high temperature in a previous generation of more massive stars now extinct. Using quantitative criteria (from the morphology and extension of the Na-O anticorrelation), we can define three different components of the stellar population in GCs.
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