Misc,
What Shapes the Structure of Molecular Clouds: Turbulence or Gravity?
(2011)cite arxiv:1111.2827Comment: 5 pages, 4 color figures; submitted to ApJ Letters.
Abstract
We discuss the origin of Larson's scaling relations that describe the
structure and kinematics of molecular clouds, based on recent observations and
simulations of supersonic turbulence. Using dimensional analysis and results
from large-scale numerical experiments, we first show that both linewidth--size
and mass--size correlations observed on scales 0.1-50 pc can be explained by a
simple conceptual theory of compressible turbulence without resorting to the
often assumed virial equilibrium condition. The scaling laws can be
consistently interpreted as a signature of supersonic turbulence with no need
to invoke gravity. We then show how self-similarity of structure established by
the turbulence breaks in star-forming clouds through development of
gravitational instabilities in the vicinity of the sonic scale, l_s~0.1 pc,
leading to the formation of prestellar cores.
