"Gravity or turbulence? Understanding the star formation law from molecular clouds to galaxies."

In this talk, I will show that the variety of Kennicutt-Schmidt (KS) relations reported in the literature, from molecular clouds in the Milky Way (MW) to resolved and unresolved galaxies, is naturally explained by the very collapse of the molecular clouds. I will also show that the low values and the constancy of the (wrongly named) “efficiency per free-fall time” arise naturally when the clouds collapse. Putting all together, our results imply that star formation is fast and efficient and that molecular cloud turbulence, the pressure in the midplane of the galaxies, their rotation, or other physical agents are not the primary drivers of the star formation law but only slight modification over the main law, namely, that the star formation rate is proportional to the mass in collapsing gas. However, stellar feedback is crucial to halt star formation, keeping the gas depletion time low on galactic levels. I will show, finally, that the properties of collapsing clouds and the kinematical properties of their newborn stellar clusters, as inferred from Gaia DR3 data, are consistent with these KS relations.