How do different spiral arm models impact the ISM and GMC population?

TL;DR

This study uses simulations to compare how different spiral arm models influence the interstellar medium and giant molecular cloud populations, finding minimal differences in cloud properties but variations in mass spectra and velocity dispersions.

Contribution

It provides a comparative analysis of various spiral arm models' effects on galactic ISM and GMCs, highlighting subtle differences linked to pattern speed variations.

Findings

Little variation in cloud populations across models

Differences in interarm/arm mass spectra observed

Radial velocity dispersion variations linked to spiral models

Abstract

The nature of galactic spiral arms in disc galaxies remains elusive. Regardless of the spiral model, arms are expected to play a role in sculpting the star-forming interstellar medium. As such, different arm models may result in differences in the structure of the interstellar medium and molecular cloud properties. In this study we present simulations of galactic discs subject to spiral arm perturbations of different natures. We find very little difference in how the cloud population or gas kinematics vary between the different grand-design spirals, indicting that the interstellar medium on cloud scales cares little about where spiral arms come from. We do, however, see a difference in the interarm/arm mass spectra, {and minor differences in tails of the distributions of cloud properties} (as well as radial variations in the stellar/gaseous velocity dispersions). These features can be attributed to differences in the radial dependence of the pattern speeds between the different spiral models, and could act as a metric of the nature of spiral structure in observational studies.