A toy model of giant molecular clouds

We idealize giant molecular clouds as flattened sheets, incorporating the concepts of strong magnetization, star formation from dense cores, and efficient bipolar outflows. This toy model reproduces the observed tendency of molecular clouds to form filaments without the need to invoke large-scale overall gravitational collapse that would yield a rate of star formation far in excess of empirical Galactic values. It yields line width-size relationships that are in rough accord with observations, although better simulations are needed that remove the imposition of periodic boundary conditions and allow for a more systematic treatment of subgrid turbulence. The model lends credence to earlier ideas concerning the self-regulation of star formation by turbulence and photoionization.