Physical properties and scaling relations of molecular clouds: the effect of stellar feedback

TL;DR

This study uses high-resolution hydrodynamical simulations to show that stellar feedback is essential for realistic molecular cloud properties and scaling relations, aligning well with Milky Way observations.

Contribution

The paper demonstrates that stellar feedback is crucial for reproducing observed GMC properties and scaling relations in simulated galactic disks, highlighting the importance of feedback in ISM modeling.

Findings

Stellar feedback leads to realistic GMC mass, size, and velocity dispersion.

Observed GMC scaling relations are reproduced in simulations with feedback.

3D analysis reveals steeper GMC scaling relations, indicating observational limitations.

Abstract

Using hydrodynamical simulations of entire galactic discs similar to the Milky Way, reaching 4.6pc resolution, we study the origins of observed physical properties of giant molecular clouds (GMCs). We find that efficient stellar feedback is a necessary ingredient in order to develop a realistic interstellar medium (ISM), leading to molecular cloud masses, sizes, velocity dispersions and virial parameters in excellent agreement with Milky Way observations. GMC scaling relations observed in the Milky Way, such as the mass-size ($M$--$R$), velocity dispersion-size ($\sigma$--$R$), and the $\sigma$--$R\Sigma$ relations, are reproduced in a feedback driven ISM when observed in projection, with $M\propto R^{2.3}$ and $\sigma\propto R^{0.56}$. When analysed in 3D, GMC scaling relations steepen significantly, indicating potential limitations of our understanding of molecular cloud 3D structure from observations. Furthermore, we demonstrate how a GMC population's underlying distribution of virial parameters can strongly influence the scatter in derived scaling relations. Finally, we show that GMCs with nearly identical global properties exist in different evolutionary stages, where a majority of clouds being either gravitationally bound or expanding, but with a significant fraction being compressed by external ISM pressure, at all times.