The Fractal Dimension of Star-forming Regions at Different Spatial Scales in M33 [ Erratum: 2010ApJ...723..969S ]

Sánchez, Néstor; Añez, Neyda; Alfaro, Emilio J.; Crone Odekon, Mary
The Astrophysical Journal, Volume 720, Issue 1, pp. 541-547 (2010).


We study the distribution of stars, H II regions, molecular gas, and individual giant molecular clouds in M33 over a wide range of spatial scales. The clustering strength of these components is systematically estimated through the fractal dimension. We find scale-free behavior at small spatial scales and a transition to a larger correlation dimension (consistent with a nearly uniform distribution) at larger scales. The transition region lies in the range ~500-1000 pc. This transition defines a characteristic size that separates the regime of small-scale turbulent motion from that of large-scale galactic dynamics. At small spatial scales, bright young stars and molecular gas are distributed with nearly the same three-dimensional fractal dimension (D f,3D <~ 1.9), whereas fainter stars and H II regions exhibit higher values, D f,3D ~= 2.2-2.5. Our results indicate that the interstellar medium in M33 is on average more fragmented and irregular than in the Milky Way.