The distribution of star-forming regions in M33

Sanchez, Nestor; Anez, Neyda; Alfaro, Emilio; Crone Odekon, Mary
Highlights of Spanish Astrophysics VI, Proceedings of the IX Scientific Meeting of the Spanish Astronomical Society (SEA), held in Madrid, September 13 - 17, 2010, Eds.: M. R. Zapatero Osorio, J. Gorgas, J. Maíz Apellániz, J. R. Pardo, and A. Gil de Paz., p. 333-338


We use fractal analysis to systematically study the clustering strength of the distribution of stars, HII regions, molecular gas, and individual giant molecular clouds in M33 over a wide range of spatial scales. We find a clear transition from a scale-free behavior at small spatial scales to a nearly uniform distribution at large scales. The transition region lies in the range ˜ 500-1000 pc and it separates the regime of small-scale turbulent motion from that of large-scale galactic dynamics. The three-dimensional fractal dimension of bright young stars and molecular gas at small spatial scales is D_{f,3D} < 1.9 indicating that the interstellar medium in M33 is on average much more fragmented and irregular than the in the Milky Way.