Galaxy Formation: Merger vs Gas Accretion

TL;DR

This paper compares the roles of galaxy mergers and gas accretion in galaxy formation using high-resolution cosmological simulations, emphasizing the importance of structure detection and merger trees.

Contribution

It introduces a method to analyze the relative impact of mergers and gas accretion on galaxy growth through detailed simulation analysis.

Findings

Cold gas accretion is a significant contributor to galaxy mass assembly.

Merger events are less frequent but still crucial for galaxy evolution.

The study highlights the importance of structure detection in understanding galaxy formation.

Abstract

According to the hierarchical model, small galaxies form first and merge together to form bigger objects. In parallel, galaxies assemble their mass through accretion from cosmic filaments. Recently, the increased spatial resolution of the cosmological simulations have emphasised that a large fraction of cold gas can be accreted by galaxies. In order to compare the role of both phenomena and the corresponding star formation history, one has to detect the structures in the numerical simulations and to follow them in time, by building a merger tree.