Galactic Simulations of r-process Elemental Abundances
  We present the distributions of elemental abundance ratios using
chemodynamical simulations which include four different neutron capture
processes: magneto-rotational supernovae, neutron star mergers, neutrino driven
winds, and electron capture supernovae. We examine both simple isolated dwarf
disc galaxies and cosmological zoom-in simulations of Milky Way-type galaxies,
and compare the [Eu/Fe] and [Eu/{\alpha}] evolution with recent observations,
including the HERMES-GALAH survey. We find that neither electron-capture
supernovae or neutrino-driven winds are able to adequately produce heavy
neutron-capture elements such as Eu in quantities to match observations. Both
neutron-star mergers and magneto-rotational supernovae are able to produce
these elements in sufficient quantities. Additionally, we find that the scatter
in [Eu/Fe] and [Eu/{\alpha}] at low metallicity ([Fe/H] < -1) and the [Eu/(Fe,
{\alpha})] against [Fe/H] gradient of the data at high metallicity ([Fe/H] >
-1) are both potential indicators of the dominant r-process site. Using the
distribution in [Eu/(Fe, {\alpha}] - [Fe/H] we predict that neutron star
mergers alone are unable to explain the observed Eu abundances, but may be able
to together with magneto-rotational supernovae.
