The impact of rare events on the chemical enrichment in dwarf galaxies

TL;DR

This study models how rare astrophysical events like neutron star mergers influence the chemical composition of dwarf galaxies, revealing oscillations in element ratios at low metallicities and emphasizing the importance of rare events in chemical enrichment.

Contribution

It introduces a chemical evolution model incorporating the rarity of enrichment sources, highlighting the impact of rare events on element abundance oscillations in dwarf galaxies.

Findings

Oscillations in trans-iron element ratios at low metallicities due to r-process events.

Rare neutron star mergers affect chemical enrichment at higher metallicities in low-mass galaxies.

Both r-process and s-process contribute to element dispersion in dwarf galaxies.

Abstract

In the environments where the abundance of heavy elements is low, rare events are expected to impact the chemical enrichment. Dwarf galaxies have small masses, low average metallicities and in general low star formation rates, and thus investigating the chemical enrichment provides understanding on the impact of each source of elements on the chemical abundance. Using a chemical evolution model in which the rarity is introduced, we investigate the impact of rare events on the chemical enrichment for Local Group dwarf galaxies. In the model, the occurrence of individual sources of elements is estimated with the star formation history derived by the colour-magnitude diagram. The abundance ratios of trans-iron elements to iron predicted by the model show the oscillation at the lowest metallicities because of the r-process events. In the case of a galaxy of a lower mass, the oscillation caused by neutron star mergers is also seen at higher metallicities, which suggests that the rarity can be important in lower-mass systems. Regarding the source of the chemical enrichment, we observe that the r-process sites seem to contribute more to the production of trans-iron elements at low metallicities, but massive stars of different rotating velocities also contribute to create part of the dispersion of the abundance ratios through the s-process. Both observational and theoretical data, including nucleosynthesis calculations and the chemical abundance of metal-poor stars, are needed to obtain deeper insights into the sources of the chemical enrichment at low metallicities.