Systematic effects in the estimate of the local gamma-ray emissivity
  We show in this letter that estimates of the local emissivity of
{\gamma}-rays in the GeV-TeV range suffer uncertainties which are of the same
order of magnitude as the current Fermi results. Primary cosmic-ray fluxes,
cosmic-ray propagation, interstellar helium abundance and {\gamma}-ray
production crosssections all affect the estimate of this quantity. We also show
that the so-called nuclear enhancement factor -- though widely used so far to
model the {\gamma}-ray emissivity -- is no longer a relevant quantity given the
latest measurements of the primary cosmic ray proton and helium spectra.
