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/ \mathrm { \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/ \mathrm { \alpha } ] at low metallicity ( [ Fe/H ] < -1 ) and the [ Eu/ ( Fe , \mathrm { \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 , \mathrm { \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 .