"Grandeur in this view of life": N-body simulation models of the
  Galactic habitable zone
  We present an isolated Milky Way-like simulation in GADGET2 N-body SPH code.
The Galactic disk star formation rate (SFR) surface densities and stellar mass
indicative of Solar neighbourhood are used as thresholds to model the
distribution of stellar mass in life friendly environments. SFR and stellar
component density are calculated averaging the GADGET2 particle properties on a
2D grid mapped on the Galactic plane. The peak values for possibly habitable
stellar mass surface density move from $10$ to $15$ kpc cylindrical
galactocentric distance in $10$ Gyr simulated time span. At $10$ Gyr the
simulation results imply the following. Stellar particles which have spent
almost all of their life time in habitable friendly conditions reside typically
at $\sim16$ kpc from Galactic centre and are $\sim 3$ Gyr old. Stellar
particles that have spent $\ge 90 \%$ of their $4-5$ Gyr long life time in
habitable friendly conditions, are also predominantly found in the outskirts of
the Galactic disk. Less then $1 \%$ of these particles can be found at a
typical Solar system galactocentric distance of $8-10$ kpc. Our results imply
that the evolution of an isolated spiral galaxy is likely to result in galactic
civilizations emerging at the outskirts of the galactic disk around stellar
hosts younger than the Sun.
