Gas dynamics in whole galaxies: SPH

TL;DR

This paper reviews SPH simulations of gas dynamics in galaxies, highlighting the formation of substructure in spiral arms and exploring effects of thermodynamics, self-gravity, and realistic spiral models.

Contribution

It provides a comprehensive overview of SPH galaxy simulations, emphasizing the emergence of substructure and the impact of various physical processes.

Findings

Substructure along spiral arms persists at high resolution.

Smaller clouds can merge into larger GMCs via dissipative collisions.

Inclusion of thermodynamics and self-gravity alters gas dynamics.

Abstract

I review the progress of SPH calculations for modelling galaxies, and resolving gas dynamics on GMC scales. SPH calculations first investigated the response of isothermal gas to a spiral potential, in the absence of self gravity and magnetic fields. Surprisingly though, even these simple calculations displayed substructure along the spiral arms. Numerical tests indicate that this substructure is still present at high resolution (100 million particles, ~10 pc), and is independent of the initial particle distribution. One interpretation of the formation of substructure is that smaller clouds can agglomerate into more massive GMCs via dissipative collisions. More recent calculations have investigated how other processes, such as the thermodynamics of the ISM, and self gravity affect this simple picture. Further research has focused on developing models with a more realistic spiral structure, either by including stars, or incorporating a tidal interaction.