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The Chemical Evolution of the Solar Neighbourhood: the Effect of Binaries

In this paper we compute the time evolution of the elements (4He, 12C, 14N, 16O, 20Ne, 24Mg, 28Si, 32S, 40Ca and 56Fe) and of the supernova rates in the solar neighbourhood by means of a galactic chemical evolutionary code that includes in detail the evolution of both single and binary stars. Special attention is payed to the formation of black holes. Our main conclusions: in order to predict the galactic time evolution of the different types of supernovae, it is essential to compute in detail the evolution of the binary population, the observed time evolution of carbon is better reproduced by a galactic model where the effect is included of a significant fraction of intermediate mass binaries, massive binary mass exchange provides a possible solution for the production of primary nitrogen during the very early phases of galactic evolution, chemical evolutionary models with binaries or without binaries but with a detailed treatment of the SN Ia progenitors predict very similar age-metallicity relations and very similar G-dwarf distributions whereas the evolution of the yields as function of time of the elements 4He, 16O, 20Ne, 24Mg, 28Si, 32S and 40Ca differ by no more than a factor of two or three, the observed time evolution of oxygen is best reproduced when most of the oxygen produced during core helium burning in ALL massive stars serves to enrich the interstellar medium. This can be used as indirect evidence that (massive) black hole formation in single stars and binary components is always preceded by a supernova explosion.