Mordecai Mac Low - November 20, 2015

Formation and Evolution of Giant Molecular Clouds: Gravity or Turbulence?

Star formation in galaxies is observed to occur in molecular clouds. 
However, the origins and evolution of these clouds remains unclear, 
impeding the construction of a predictive theory of star formation. 
Indeed, the necessity of molecules for star formation has come into 
question, as it becomes clear that their formation may just be a side 
effect of star formation, correlated with gravitational collapse but 
not causing it. In this talk I will present kiloparsec-scale, well-resolved, 
MHD simulations of the stratified, supernova-driven, interstellar medium 
performed with the Flash code. I will use the results of these simulations 
to argue that gravitational collapse rather than any sort of turbulent 
equilibrium determines the dynamics of molecular clouds, with a focus on 
the relationships between size, velocity dispersion, and surface density 
of the clouds.