A study of major mergers using a multi-phase ISM code

TL;DR

This paper investigates major galaxy mergers using a multi-phase ISM simulation code, revealing how interactions influence star formation and mass exchange processes, providing new insights into galaxy evolution.

Contribution

It introduces a multi-phase ISM code applied to galaxy mergers, offering a novel approach to modeling star formation beyond the traditional Schmidt law.

Findings

Star formation efficiency is affected by galaxy interactions.

Evaporation and condensation rates vary during mergers.

Mass exchange between stars, ISM, and clouds is influenced by interactions.

Abstract

Galaxy interactions are a common phenomenon in clusters of galaxies. Especially major mergers are of particular importance, because they can change the morphological type of galaxies. They have an impact on the mass function of galaxies and they trigger star formation - the main driver of the Galactic Matter Cycle. Therefore, we conducted a study of major mergers by means of a multi-phase ISM code. This code is based on a TREE-SPH-code combined with a sticky particle method allowing for star formation controlled by the properties of a multi-phase ISM. This is in contrast to the usually implemented Schmidt law depending mainly on the gas density. Previously, this code was used on isolated galaxies. Since our star formation recipe is not restricted to a special type of galaxy, it is interesting to apply it to interacting galaxies, too. Our study on major mergers includes a research of global properties of the interacting system, namely the star formation rate and the star formation efficiency, the evaporation and condensation rates, as well as the mass exchange of distinct components, namely stars, diffuse ISM, and clouds. Investigating these properties provides insight to interrelations between various physical processes. The results indicate that the star formation efficiency as well as the evaporation and condensation rates are influenced by the interaction.