Galactic Simulations of r-process Elemental Abundances

TL;DR

This study uses chemodynamical simulations to analyze the origins of europium in galaxies, comparing different neutron capture processes and matching results with recent observational data.

Contribution

It evaluates the effectiveness of various r-process sites, highlighting the roles of neutron-star mergers and magneto-rotational supernovae in producing heavy elements.

Findings

Neutron-star mergers and magneto-rotational supernovae can produce heavy r-process elements like Eu.

Electron-capture supernovae and neutrino-driven winds are insufficient for Eu production.

Neutron-star mergers alone cannot fully explain observed Eu abundances, but combined with magneto-rotational supernovae, they might.

Abstract

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.