A sub-parsec resolution simulation of the Milky Way: Global structure of the ISM and properties of molecular clouds

TL;DR

This paper presents a high-resolution hydrodynamical simulation of a Milky Way-like galaxy, revealing detailed ISM structure, molecular cloud properties, and the influence of galactic features like bars and spiral arms on cloud formation and turbulence.

Contribution

It provides a self-consistent, sub-parsec resolution simulation including star formation and stellar feedback, advancing understanding of ISM dynamics and molecular cloud evolution.

Findings

Galactic bar influences central ~100 pc dynamics.

Spiral arms form regularly spaced molecular clouds.

Turbulence and gravity shape hierarchical cloud structures.

Abstract

We present a self-consistent hydrodynamical simulation of a Milky Way-like galaxy, at the resolution of 0.05 pc. The model includes star formation and a new implementation of stellar feedback through photo-ionization, radiative pressure and supernovae. The simulation resolves the structure of the interstellar medium at subparsec resolution for a few cloud lifetimes, and at 0.05 pc for about a cloud crossing time. Turbulence cascade and gravitation from the kpc scales are de facto included in smaller structures like molecular clouds. We show that the formation of a bar influences the dynamics of the central ~100 pc by creating resonances. At larger radii, the spiral arms host the formation of regularly spaced clouds: beads on a string and spurs. These instabilities pump turbulent energy into the gas, generally in the supersonic regime. Because of asymmetric drift, the supernovae explode outside of their gaseous nursery, which diminishes the effect of feedback on the structure of clouds. The evolution of clouds is thus mostly due to fragmentation and gas consumption, regulated mainly by supersonic turbulence. The transition from turbulence supported to self-gravitating gas is detected in the gas density probability distribution function at ~2000 cm^-3. The power spectrum density suggests that gravitation governs the hierarchical organisation of structures from the galactic scale down to a few parsecs.