The galactic habitable zone of the Milky Way and M31 from chemical
  evolution models with gas radial flows
  The galactic habitable zone is defined as the region with sufficient
abundance of heavy elements to form planetary systems in which Earth-like
planets could be born and might be capable of sustaining life, after surviving
to close supernova explosion events. Galactic chemical evolution models can be
useful for studying the galactic habitable zones in different systems. We apply
detailed chemical evolution models including radial gas flows to study the
galactic habitable zones in our Galaxy and M31. We compare the results to the
relative galactic habitable zones found with "classical" (independent ring)
models, where no gas inflows were included. For both the Milky Way and
Andromeda, the main effect of the gas radial inflows is to enhance the number
of stars hosting a habitable planet with respect to the "classical" model
results, in the region of maximum probability for this occurrence, relative to
the classical model results. These results are obtained by taking into account
the supernova destruction processes. In particular, we find that in the Milky
Way the maximum number of stars hosting habitable planets is at 8 kpc from the
Galactic center, and the model with radial flows predicts a number which is 38%
larger than what predicted by the classical model. For Andromeda we find that
the maximum number of stars with habitable planets is at 16 kpc from the center
and that in the case of radial flows this number is larger by 10 % relative to
the stars predicted by the classical model.
