University of Cologne
Diffusion mixing in molecular clouds
In order to understand the structure and dynamics of a star-forming cloud, one should understand the nature of material transport and hence the mechanism which seeds the star-forming cores. The chemistry of photo-dissociation regions( PDRs) will be affected by the transport of materials between the regions with different UV fields, densities, and temperatures. We studied dynamic mixing in the irradiated molecular clouds using the KOSMA-$\tau$ PDR model. We estimated the magnitude of turbulent, molecular, and thermal diffusion coefficients. In a detailed study of the transport of species, we try to comprehend its significance for the chemical structure of the PDRs. We analyzed the effect of different temperature profiles on diffusion and the resulting chemistry. We tested various diffusion coefficients and determined their limits. The diffusion process modifies the predicted abundances, and some would act as tracers to this mixing process in multiple environments. C/CO ratio depends on the diffusion coefficients. Turbulent mixing in the outer edge of the cloud could affect the chemical composition inside the cloud and create a moving PDR. This mixing process can create additional chemical pathways and be part of the chemical models of the molecular clouds.