Chemical evolution of the Milky Way: the origin of phosphorus
  Context. Recently, for the first time the abundance of P has been measured in
disk stars. This provides the opportunity of comparing the observed abundances
with predictions from theoretical models. Aims. We aim at predicting the
chemical evolution of P in the Milky Way and compare our results with the
observed P abundances in disk stars in order to put constraints on the P
nucleosynthesis. Methods. To do that we adopt the two-infall model of galactic
chemical evolution, which is a good model for the Milky Way, and compute the
evolution of the abundances of P and Fe. We adopt stellar yields for these
elements from different sources. The element P should have been formed mainly
in Type II supernovae. Finally, Fe is mainly produced by Type Ia supernovae.
Results. Our results confirm that to reproduce the observed trend of [P/Fe] vs.
[Fe/H] in disk stars, P is formed mainly in massive stars. However, none of the
available yields for P can reproduce the solar abundance of this element. In
other words, to reproduce the data one should assume that massive stars produce
more P than predicted by a factor of ~ 3. Conclusions. We conclude that all the
available yields of P from massive stars are largely underestimated and that
nucleosynthesis calculations should be revised. We also predict the [P/Fe]
expected in halo stars.
