A toy model of giant molecular clouds

We idealize giant molecular clouds as flattened sheets, incorporating the c oncepts of strong magnetization, star formation from dense cores, and effic ient bipolar outflows. This toy model reproduces the observed tendency of m olecular clouds to form filaments without the need to invoke large-scale ov erall gravitational collapse that would yield a rate of star formation far in excess of empirical Galactic values. It yields line width-size relations hips that are in rough accord with observations, although better simulation s are needed that remove the imposition of periodic boundary conditions and allow for a more systematic treatment of subgrid turbulence. The model len ds credence to earlier ideas concerning the self-regulation of star formati on by turbulence and photoionization.