Mass spectrum of giant molecular clouds in a coagulation model

Solutions of Smoluchovski’ equation, describing merging processes in a system of giant molecular clouds, are investigated in detail. Both the case of a constant spatial gas density in the clouds and the case of a constant radial gas density are considered. It is shown that the solution of the coagulation equation is not expressed by a power law that is the same for the entire mass range under consideration. It is also demonstrated that the form of the solution depends on the width of the mass range of the clouds. A comparison with observations shows that the Oort model and the coagulation mechanism can describe the observed cloud mass spectrum quite adequately. Ways of improving the Oort model are suggested.