Hierarchical fragmented structure of molecular clouds produced by supersonic turbulence

Abstract

For GMC's the two prominent properties are typical. They consist of dense molecular gas clumps concentrating to the GMC centre and filling only a few percent of a total volume. And these clumps participate in chaotic motions with velocities vt exceeding as a rule the sound velocity co at the temperature of molecular gas. This phenomenon is considered as a supersonic molecular cloud's turbulence. The compressibility of turbulent matter becomes very important with such velocities. Thus in application to GMC it is necessary to develop the theory of turbulence and fragmentation under transsonic and supersonic random motions. The hydrodynamic flow velocity field can be divided into the potential and vortical components. When transsonic or supersonic motions prevail the potential component is become more important that stimulates the shock wave's stochastic field development. Ohul'chansky (1988, Kinematics and Physics of Celestial Bodies 4,3) has described this process on the base of Burgers' equation treatment. In this paper we apply this approach for conditions of GMCs that permit the supersonic turbulence' spectrum evolution, the large density fluctuations development, and clumps formation to consider.