GMC Origins and Turbulent Motions in Spiral and Dwarf Galaxies

TL;DR

This paper investigates the origins and turbulent motions of giant molecular clouds (GMCs) across different galaxy types, revealing how environmental factors influence GMC formation, structure, and dynamics.

Contribution

It provides a comparative analysis of GMC formation and turbulence in spiral and dwarf galaxies, highlighting the role of environment and gas accretion processes.

Findings

GMC formation involves gas and cloud accretion independent of molecular content.

Virial parameter decreases with cloud mass, indicating turbulence-driven small-scale structure.

Large clouds form hierarchically through accretion, with turbulence shaping their internal structure.

Abstract

CO clouds can be non-self-gravitating in high pressure environments, while most should be strongly self-gravitating at low metallicities and ambient pressures. In the LMC, which is HI-rich, GMC formation and destruction should generally include molecule formation and destruction. In M51, which is CO-rich, GMCs grow by coalescence. The Milky Way is between these two situations. In all cases, large clouds form by accretion of gas and smaller clouds independently of the presence of molecules. GMCs in the Milky Way are analogous to dust lanes and spurs in other galaxies. The virial parameter alpha usually decreases monotonically with increasing cloud mass in surveys, which implies that small scale structure is formed by turbulence. Hierarchies of sequences with decreasing alpha should be present in cloud complexes from sub-solar masses up to the ambient Jeans mass (10^7 Msun).