High-resolution CCD spectra of stars in globular clusters. VII - Abundances of 16 elements in 47 Tuc, M4, and M22

Abstract

We have derived elemental abundances from high-resolution CCD echelle spectra of a selection of giant stars in the globular clusters 47 Tuc, M4, and M22. Elements determined include the alpha elements Mg, Si, Ca, and Ti, the light odd-Z elements Na and Al, the iron-peak elements Sc, Fe, and Zn; the s-process elements Y, Zr, Ba, and La, and the r-process element Eu. The alpha elements are slightly overabundant with respect to Fe, indistinguishable from the trend in the field halo stars. However, the globular cluster stars in our sample show strong excesses of Na and Al which are correlated with the C and N abundances: We confirm that the CN-Na, Al correlations in globular clusters are due to abundance anomalies. We argue that these anomalies must be 'primordial' in origin, and discuss implications of these anomalies for the precursor population and the formation of the clusters.