The Metallicity Evolution of Interacting Galaxies

TL;DR

This study uses simulations to explore how galaxy interactions influence nuclear metallicity, revealing that gas inflows and star formation competition determine metallicity changes, with results aligning with observed galaxy relationships.

Contribution

It introduces a new stochastic method for tracking recycled stellar material and analyzes the impact of mergers on metallicity evolution in galaxies.

Findings

Gas-poor interactions lower central metallicity by ~0.07.

Gas-rich interactions can increase central metallicity.

Simulation results agree with observed mass-metallicity trends.

Abstract

Nuclear inflows of metal-poor interstellar gas triggered by galaxy interactions can account for the systematically lower central oxygen abundances observed in local interacting galaxies. Here, we investigate the metallicity evolution of a large set of simulations of colliding galaxies. Our models include cooling, star formation, feedback, and a new stochastic method for tracking the mass recycled back to the interstellar medium from stellar winds and supernovae. We study the influence of merger-induced inflows, enrichment, gas consumption, and galactic winds in determining the nuclear metallicity. The central metallicity is primarily a competition between the inflow of low-metallicity gas and enrichment from star formation. An average depression in the nuclear metallicity of ~0.07 is found for gas-poor disk-disk interactions. Gas-rich disk-disk interactions, on the other hand, typically have an enhancement in the central metallicity that is positively correlated with the gas content. The simulations fare reasonably well when compared to the observed mass-metallicity and separation-metallicity relationships, but further study is warranted.