Galaxy formation hydrodynamics: From cosmic flows to star-forming clouds

TL;DR

This paper reviews recent advances and ongoing challenges in simulating galaxy formation, focusing on hydrodynamical processes, baryon accretion, and star formation modeling at small scales.

Contribution

It highlights the importance of resolved, three-dimensional turbulence modeling in cosmological simulations to better understand star formation and galaxy evolution.

Findings

Resolved turbulence modeling improves star formation predictions.

Small-scale processes significantly influence galaxy evolution.

Current sub-grid models are insufficient for accurate galaxy formation simulations.

Abstract

Major progress has been made over the last few years in understanding hydrodynamical processes on cosmological scales, in particular how galaxies get their baryons. There is increasing recognition that a large part of the baryons accrete smoothly onto galaxies, and that internal evolution processes play a major role in shaping galaxies - mergers are not necessarily the dominant process. However, predictions from the various assembly mechanisms are still in large disagreement with the observed properties of galaxies in the nearby Universe. Small-scale processes have a major impact on the global evolution of galaxies over a Hubble time and the usual sub-grid models account for them in a far too uncertain way. Understanding when, where and at which rate galaxies formed their stars becomes crucial to understand the formation of galaxy populations. I discuss recent improvements and current limitations in "resolved" modelling of star formation, aiming at explicitely capturing star-forming instabilities, in cosmological and galaxy-sized simulations. Such models need to develop three-dimensional turbulence in the ISM, which requires parsec-scale resolution at redshift zero.