The Galactic habitable zone is defined as the region with highly enough
metallicity to form planetary systems in which Earth-like planets could be born
and might be capable of sustaining life surviving to the destructive effects of
nearby supernova explosion events. Galactic chemical evolution models can be
useful tools for studying the galactic habitable zones in different systems.
Our aim here is to find the Galactic habitable zone using chemical evolution
models for the Milky Way disc, adopting the most recent prescriptions for the
evolution of dust and for the probability of finding planetary systems around M
and FGK stars. Moreover, for the first time, we will express those
probabilities in terms of the dust-to-gas ratio of the ISM in the solar
neighborhood as computed by detailed chemical evolution models. At a fixed
Galactic time and Galactocentric distance we determine the number of M and FGK
stars having Earths (but no gas giant planets) which survived supernova
explosions, using the formalism of our Paper I. The probabilities of finding
terrestrial planets but not gas giant planets around M stars deviate
substantially from the ones around FGK stars for supersolar values of [Fe/H].
For both FGK and M stars the maximum number of stars hosting habitable planets
is at 8 kpc from the Galactic Centre, if destructive effects by supernova
explosions are taken into account. At the present time the total number of M
stars with habitable planets are ≃ 10 times the number of FGK stars.
Moreover, we provide a sixth order polynomial fit (and a linear one but more
approximated) for the relation found with chemical evolution models in the
solar neighborhood between the [Fe/H] abundances and the dust-to-gas ratio.Comment: Accepted for publication in A&A, 10 pages 6 figure
