Chemical evolution with rotating massive star yields – I. The solar neighbourhood and the s-process elements

Abstract

We present a comprehensive study of the abundance evolution of the elements\nfrom H to U in the Milky Way halo and local disk. We use a consistent chemical\nevolution model, metallicity dependent isotopic yields from low and\nintermediate mass stars and yields from massive stars which include, for the\nfirst time, the combined effect of metallicity, mass loss and rotation for a\nlarge grid of stellar masses and for all stages of stellar evolution. The\nyields of massive stars are weighted by a metallicity dependent function of the\nrotational velocities, constrained by observations as to obtain a primary-like\n$^{14}$N behavior at low metallicity and to avoid overproduction of s-elements\nat intermediate metallicities. We show that the solar system isotopic\ncomposition can be reproduced to better than a factor of two for isotopes up to\nthe Fe-peak, and at the 10\\% level for most pure s-isotopes, both light ones\n(resulting from the weak s-process in rotating massive stars) and the heavy\nones (resulting from the main s-process in low and intermediate mass stars). We\nconclude that the light element primary process (LEPP), invoked to explain the\napparent abundance deficiency of the s-elements with A< 100, is not necessary.\nWe also reproduce the evolution of the heavy to light s-elements abundance\nratio ([hs/ls]) - recently observed in unevolved thin disk stars - as a result\nof the contribution of rotating massive stars at sub-solar metallicities. We\nfind that those stars produce primary F and dominate its solar abundance and we\nconfirm their role in the observed primary behavior of N. In contrast, we show\nthat their action is insufficient to explain the small observed values of\nC12/C13 in halo red giants, which is rather due to internal processes in those\nstars.\n