Sánchez, Nestor; Alfaro, Emilio J.
Lecture Notes and Essays in Astrophysics, vol. 4, Name of the proceedings book: Lecture Notes and Essays in Proceedings of the conference held 7-11 September, 2009 at Ciudad Real (Spain). Edited by A. Ulla and M. Manteiga. Tórculo Press (Vigo, Spain). ISBN: 978-84-936098-8-7, p. 1-11.
The Interstellar Medium has a fractal structure, in the sense that gas and dust distribute in a hierarchical and selfsimilar manner. Stars in new-born clusters probably follow the same fractal patterns of their parent molecular clouds. Moreover, it seems that older clusters tend to distribute their stars with radial density profiles. Thus, it is expected that clusters form with an initial fractal distribution of stars that eventually evolves toward centrally concentrated distributions. Is this really the case? This simple picture on to the origin and early evolution of star clusters and associations is very far from being clearly understood. There can be both young clusters exhibiting radial patterns and evolved clusters showing fractal structure. Additionally, the fractal structure of some open clusters is very different from that of the Interstellar Medium in the Milky Way. Here we summarize and discuss observational and numerical evidences concerning this subject.