Hierarchical stellar clusters in molecular clouds

Observations show that massive stars always form in clusters or associations, and that the most massive stars form in the dense cores of large clusters. This suggests that accretion processes in cluster cores may be responsible for the formation of stars. In addition, young stellar clusters have been found to contain subclusters, so that star formation can be seen to be a hierarchical process that involves clustering on a range of scales. In this paper, we propose a fractal model of the parental molecular cloud, namely that of the Julia set given by f (z) = z2 + c, where z and c are complex numbers and c = — 0.745430 + 0.113008i, to explain this phenomenon and the associated complex structures seen in star-forming regions.