摘要：We combine a semi-analytic model of galaxy evolution with constraints on circumstellar
habitable zones and the distribution of terrestrial planets in order to probe the
suitability of galaxies of different mass and type to host habitable planets, and how it
evolves with time. We find that the fraction of stars with terrestrial planets in their
habitable zone (known as habitability) depends only weakly on galaxy mass, with a maximum
around 4 ×
1010M⊙. We estimate that 0.7%
of all stars in Milky Way-type galaxies to host a terrestrial planet within their
habitable zone, consistent with the value derived from Kepler
observations. On the other hand, the habitability of passive galaxies is slightly
but systematically higher, unless we assume an unrealistically high sensitivity of planets
to supernovae. We find that the overall habitability of galaxies has not changed
significantly in the last ~8 Gyr, with most of the habitable planets in local disk galaxies
having formed ~1.5 Gyr
before our own solar system. Finally, we expect that ~1.4 ×109 planets similar to present-day Earth have existed so
far in our galaxy.
关键词：planets and satellites: terrestrial planets;galaxies: evolution;galaxies: star formation;galaxies: abundances;astrobiology
