The Role of the IGIMF in the chemical evolution of the solar
  neighbourhood
  The integrated galactic initial mass function (IGIMF) is computed from the
combination of the stellar initial mass function (IMF) and the embedded cluster
mass function, described by a power law with index beta. The result of the
combination is a time-varying IMF which depends on the star formation rate. We
applied the IGIMF formalism to a chemical evolution model for the solar
neighbourhood and compared the results obtained by assuming three possible
values for beta with the ones obtained by means of a standard, well-tested,
constant IMF. In general, a lower absolute value of beta implies a flatter
IGIMF, hence a larger number of massive stars, higher Type Ia and II supernova
rates, higher mass ejection rates and higher [alpha/Fe] values at a given
metallicity. Our suggested fiducial value for beta is 2, since with this value
we can account for most of the local observables. We discuss our results in a
broader perspective, with some implications regarding the possible universality
of the IMF and the importance of the star formation threshold.
