THE SEARCH FOR PROTOSTELLAR INFLOW

Very few protostellar clouds show direct evidence for infall. This rev iew discusses the plausibility of the detection of infall in the conte xt of both dynamic and quasi-static (magnetic) collapse models. The se arch for infall has been based on the study of spectral energy distrib utions (which form the basis of the protostellar classification scheme ), the relative spatial distribution of molecular material and the ana lysis of spectral line profiles. Only the latter method gives direct e vidence for velocity structure and the presence of inflow. The interpr etation of line profiles is complicated by chemical effects but, with a self-consistent approach to the modelling, powerful diagnostics of t he infall dynamics may be obtained.