FORMATION OF GIANT MOLECULAR CLOUDS ASSOCIATED WITH SPIRAL STRUCTURE

molecular hydrogen in spiral galaxies is distributed in clumps, i.e., molecular clouds, which have mass between 10(3) M. and 10(6)s M. and a mass spectrum of n(m) is-proportional-to m-1.6. Molecular clouds with masses greater than 105 M., are called giant molecular clouds (GMCs). It is generally accepted that GMCs are formed by the coalescence of molecular clouds through their collision. This process is studied by both numerical simulation and numerical integration. The observation with high resolution identified a great number of CO emission cores in galaxies. Based on this result, the aggregation or clustering formation of GMCs is numerically simulated. In the process of either coalescence or clustering, spiral perturbation plays an important role