Title

The Fractal Dimension of Star-forming Regions at Different Spatial Scales in M33

Document Type

Article

Publication Date

2010

Abstract

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.

Published In

The Astrophysical Journal

Volume

720

Issue

1

Pages

541-547