The Fractal Dimension of Star-forming Regions at Different Spatial Scales in M33
The Astrophysical Journal
Sanchez, Nestor; Anez, Neyda; Alfaro, Emilio J.; and Odekon, Mary Crone, "The Fractal Dimension of Star-forming Regions at Different Spatial Scales in M33" (2010). Physics. 1.
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 (Df,3D 1.9), whereas fainter stars and H ii regions exhibit higher values, Df,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.