The impact of metallicity on nova populations
  The metallicity of a star affects its evolution in a variety of ways,
changing stellar radii, luminosities, lifetimes, and remnant properties. In
this work, we use the population synthesis code binary_c to study how
metallicity affects novae in the context of binary stellar evolution. We
compute a 16-point grid of metallicities ranging from $Z=10^{-4}$ to 0.03,
presenting distributions of nova white dwarf masses, accretion rates,
delay-times, and initial system properties at the two extremes of our 16-point
metallicity grid. We find a clear anti-correlation between metallicity and the
number of novae produced, with the number of novae at $Z=0.03$ roughly half
that at $Z=10^{-4}$. The white dwarf mass distribution has a strong systematic
variation with metallicity, while the shape of the accretion rate distribution
is relatively insensitive. We compute a current nova rate of approximately 33
novae per year for the Milky Way, a result consistent with observational
estimates relying on extra-Galactic novae but an under-prediction relative to
observational estimates relying on Galactic novae. However, the shape of our
predicted Galactic white dwarf mass distribution differs significantly to
existing observationally derived distributions, likely due to our underlying
physical assumptions. In M31, we compute a current nova rate of approximately
36 novae per year, under-predicting the most recent observational estimate of
$65^{+15}_{-16}$. Finally, we conclude that when making predictions about
currently observable nova rates in spiral galaxies, or stellar environments
where star formation has ceased in the distant past, metallicity can likely be
considered of secondary importance compared to uncertainties in binary stellar
evolution.
