Lee Hartmann from the Univerity of Michigan will be the featured speaker at an upcoming Department of Physics and Astronomy colloquium. His talk is titled, "Numerical Experiments on Star Formation: Mass Functions and Angular Momenta."

The initial mass function of stars - the number of stars N formed per interval of mass M - has long been known to be a power law, with power index of -1.3. Many explanations of this distribution have been advanced over the years, including fractal dimensions of star-forming molecular clouds and/or self-similar grouping of clouds. Hartmann will discuss simplified numerical simulations of star formation which show that gravitational accretion onto initial seed masses generates a power law mass distribution approaching power index of -1 asymptotically, irrespective of complications of cloud structure. This mechanism can also explain the mass function of young star clusters, which also has a power law distribution with the index of -1. Finally, he will describe preliminary results concerning the origin of protostellar cloud angular momenta, with implications for the properties of protoplanetary disks that result from cloud collapse.