Halo Mergers, Galaxy Mergers, and Why Hubble Type Depends on Mass

TL;DR

This paper reviews how galaxy mergers, influenced by dark matter halo mergers, vary with mass and impact galaxy morphology, explaining the dependence of Hubble type on galaxy mass.

Contribution

It highlights the importance of galaxy-halo connection and shows that galaxy merger rates depend strongly on mass, offering insights into galaxy morphology evolution.

Findings

Galaxy mergers are more frequent in massive galaxies.

Dark matter halo mergers differ from galaxy mergers in simulations.

Mass dependence explains Hubble type variation.

Abstract

In the CDM cosmological framework structures grow from merging with smaller structures. Merging should have observable effects on galaxies including destroying disks and creating spheroids. This proceeding aims to give a brief overview of how mergers occur in cosmological simulations. In this regard it is important to understand that dark matter halo mergers are not galaxy mergers; a theory of galaxy formation is necessary to connect the two. Mergers of galaxies in hydrodynamical simulations show a stronger dependence on mass than halo mergers in N-body simulations. If one knows how to connect galaxies to dark matter halos then the halo merger rate can be converted into a galaxy merger rate. When this is done it becomes clear that major mergers are many times more common in more massive galaxies offering a possible explanation of why Hubble type depends on galaxy mass.