EPoS Contribution

Gravity or turbulence? The star formation law in turbulent and collapsing clouds and the kinematical signatures of the newborn stars Javier Ballesteros-Paredes IRyA-UNAM, Morelia, MX
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 "efficiency per free-fall time" arise naturally when the clouds collapse. Our results imply that locally, 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 a slight modification over the primary 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 also show that the kinematic properties of young stars observed with Gaia are consistent with their being born from collapsing clouds rather than clouds supported by turbulence.

Caption: Velocity dispersion per mass bin for the stars in (a) a simulation of a molecular cloud in collapse; (b) a simulation of a turbulent cloud: (c) the Orion Nebula Cluster; (d) and the Lagoon Nebula Cluster. Stars from collapsing clouds exhibit constant velocity dispersion. Instead, stars in turbulent clouds have time to undergo dynamic relaxation, resulting in massive stars with larger velocity dispersion.
Collaborators: M. Zamora-Avilés, INAOE, MX A. Bonilla-Barroso, IRyA-UNAM	Key publication Relevant topic(s): Collapse Fragmentation Turbulence
Relevant Big Question: The dynamical state of molecular clouds