Angular momentum evolution of galaxies: the perspective of hydrodynamical simulations

TL;DR

Recent hydrodynamical simulations have advanced our understanding of galaxy angular momentum, highlighting the roles of mergers and gas accretion, and suggesting revisions to classical disk formation theories.

Contribution

This review synthesizes recent simulation results, emphasizing the need to revise classical theories of galaxy disk formation based on new insights into angular momentum acquisition.

Findings

Simulations now reproduce observed galaxy angular momentum and morphology.

Galaxy mergers and gas accretion significantly influence angular momentum evolution.

Current challenges include refining feedback models and understanding complex gas dynamics.

Abstract

Until a decade ago, galaxy formation simulations were unable to simultaneously reproduce the observed angular momentum (AM) of galaxy disks and bulges. Improvements in the interstellar medium and stellar feedback modelling, together with advances in computational capabilities, have allowed the current generation of cosmological galaxy formation simulations to reproduce the diversity of AM and morphology that is observed in local galaxies. In this review I discuss where we currently stand in this area from the perspective of hydrodynamical simulations, specifically how galaxies gain their AM, and the effect galaxy mergers and gas accretion have on this process. I discuss results which suggest that a revision of the classical theory of disk formation is needed, and finish by discussing what the current challenges are.