How do Galaxies Accrete Gas and Form Stars?

TL;DR

This paper reviews current understanding and challenges in galaxy gas accretion and star formation, emphasizing the need for improved models and observations to resolve key uncertainties in galaxy evolution.

Contribution

It highlights the gaps in current galaxy formation models and proposes directions for future research to better understand baryon accretion and star formation processes.

Findings

Dark matter simulations struggle to reproduce observed galaxies.

Observations are beginning to detect star formation fuel across redshifts.

Understanding gas accretion is crucial for galaxy evolution models.

Abstract

Great strides have been made in the last two decades in determining how galaxies evolve from their initial dark matter seeds to the complex structures we observe at z=0. The role of mergers has been documented through both observations and simulations, numerous satellites that may represent these initial dark matter seeds have been discovered in the Local Group, high redshift galaxies have been revealed with monstrous star formation rates, and the gaseous cosmic web has been mapped through absorption line experiments. Despite these efforts, the dark matter simulations that include baryons are still unable to accurately reproduce galaxies. One of the major problems is our incomplete understanding of how a galaxy accretes its baryons and subsequently forms stars. Galaxy formation simulations have been unable to accurately represent the required gas physics on cosmological timescales, and observations have only just begun to detect the star formation fuel over a range of redshifts and environments. How galaxies obtain gas and subsequently form stars is a major unsolved, yet tractable problem in contemporary extragalactic astrophysics. In this paper we outline how progress can be made in this area in the next decade.