Presentation #208.07D in the session “Star Formation on Galactic Scales”.
Molecular clouds are the immediate sites of star formation. Yet despite decades of observational efforts, we still lack a complete understanding of the demographics of molecular cloud populations in full environmental context. I will showcase the latest results from PHANGS-ALMA, an ALMA large program mapping CO emission at arcsecond resolution in ~70 local star-forming galaxies. With its linear resolution (50-150 pc) matching the typical size of individual giant molecular clouds, PHANGS-ALMA is offering the most detailed and complete view of molecular cloud populations throughout typical star-forming environments in the present day universe. I will present population statistics of over 100,000 independent molecular cloud measurements derived from the PHANGS-ALMA CO data. This unprecedented dataset reveals substantial variations in molecular cloud characteristics with global properties of the host galaxy as well as local dynamical structures in them. Complementing these measurements with multiwavelength ancillary data, I will further illustrate an important mechanism regulating the molecular cloud population in a galaxy — the dynamical balance between the hydrostatic weight of the ISM gas and its internal (turbulent) pressure. Finally, I will put these results in the context of a galactic scale star formation model and demonstrate how molecular clouds fit in the broader picture of a self-regulated galaxy ecosystem.