The fractal dimension of star-forming regions at different spatial
  scales in M33
  We study the distribution of stars, HII 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 <=
1.9), whereas fainter stars and HII regions exhibit higher values (Df =
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.
