FRACTAL 3-D SIMULATIONS OF MOLECULAR CLOUDS

We propose a number of methods to produce tri-dimensional simulations of gas density distribution of molecular clouds. The methods make use of random number generation and of simple recursive construction rules dependent on a few parameters. A large number of simulations were produced by varying the parameters of these rules. The projected two-dimensional images of the simulated clouds were compared to those of observed molecular clouds. The quantitative description of a simulation is approached via the fractal dimension D and the factor K of the contour levels of the images, obtained from the relation (area)1/2 = K x (perimeter)1/D. From our measurements of the fractal dimension of the visual extinction contours of clouds of the Chamaeleon complex and from other results in the literature, D and K are found to be in the range 1.21-1.52 and 0.32-0.45 respectively. The simulated clouds that we obtained with D in the correct range were submitted to additional tests like the study of the normalized-mass versus normalized-radius relation, visual inspection of a perspective representation of the density distribution, and a study of the projected distribution of density peaks. The tests show that the simulated clouds have statistical properties similar to that observed ones. Theoretical reasons for D being in the interval 1.2-1.5 are discussed. Some examples of possible applications of our simulations are briefly discussed.