CONSTRAINTS ON THE NUCLEOSYNTHESIS OF CU AND ZN FROM MODELS OF CHEMICAL EVOLUTION OF THE GALAXY

The observed abundances of Cu and Zn in stars of different metalliciti es are compared with chemical evolution models for the Galaxy adopting current stellar nucleosynthesis results. Cu and Zn are both produced by s-processing in massive stars (weak component) and by s-processing in low mass stars (main component) as well as by explosive nucleosynth esis in supemovae. The most important contributions to Cu and Zn are t hose from supemovae and the weak component, while the contribution fro m the main component is negligible. The stellar yields for the weak co mponent are now fairly well established, whereas those for the explosi ve nucleosynthesis are still affected by large uncertainties. We sugge st that a satisfactory agreement between theory and observations canno t be obtained without assuming that a substantial fraction of these is otopes is produced by type la supernovae (SNIa). We also show that the best model to fit the majority of observational constraints requires that SNIa already influenced the chemical evolution of halo stars and globular clusters formed in the range of metallicity -2.0 less-than-or -equal-to [Fe/H] less-than-or-equal-to -1.0.