The Interstellar Medium and star formation on kpc size scales

TL;DR

This study uses high-resolution simulations to analyze molecular clouds and the interstellar medium on kiloparsec scales, confirming previous findings and exploring internal cloud properties and star formation processes.

Contribution

It provides a detailed comparison of ISM and GMC properties at higher resolution and investigates internal cloud structures and star formation features not resolved in earlier simulations.

Findings

Cloud properties extend to lower masses with similar characteristics.

Velocity dispersions may be underestimated in poorly resolved clouds.

GMCs exhibit Larson relation and multiple star formation episodes.

Abstract

By resimulating a region of a global disc simulation at higher resolution, we resolve and study the properties of molecular clouds with a range of masses from a few 100's M$_{\odot}$ to $10^6$ M$_{\odot}$. The purpose of our paper is twofold, i) to compare the ISM and GMCs at much higher resolution compared to previous global simulations, and ii) to investigate smaller clouds and characteristics such as the internal properties of GMCs which cannot be resolved in galactic simulations. We confirm the robustness of cloud properties seen in previous galactic simulations, and that these properties extend to lower mass clouds, though we caution that velocity dispersions may not be measured correctly in poorly resolved clouds. We find that the properties of the clouds and ISM are only weakly dependent on the details of local stellar feedback, although stellar feedback is important to produce realistic star formation rates and agreement with the Schmidt-Kennicutt relation. We study internal properties of GMCs resolved by $10^4-10^5$ particles. The clouds are highly structured, but we find clouds have a velocity dispersion radius relationship which overall agrees with the Larson relation. The GMCs show evidence of multiple episodes of star formation, with holes corresponding to previous feedback events and dense regions likely to imminently form stars. Our simulations show clearly long filaments, which are seen predominantly in the inter-arm regions, and shells.