Dr. Scalo's research follows both empirical and theoretical approaches to study structural features in interstellar gas complexes and the relation of these features to turbulence and the process of star formation. The empirical work is directed toward a quantitative understanding of the existence and nature of the hierarchical structure in cloud complexes. The theoretical work includes the temporal behavior of star formation and numerical solutions of the hydrodynamic cloud fluid equations to study the ability of star formation bursts to deplete and expel gas from galaxies. Star formation is a phenomenon which involves the coupling of processes over a large range of spatial scales, from individual protostars to coherent star formation on scales of 200 to 1000 parsecs. The interstellar gas complexes in which stars form exhibit substructure on all scales from 100 parsecs down to less than 0.1 parsec, and the structure often appears to be hierarchically arranged. This coupling between the local and global aspects of star formation manifests itself in the fact that our understanding of galaxy evolution depends crucially on the largely unknown dependence of the star formation rate and initial mass function of forming stars on both local and global physical conditions.
