What Shapes the Structure of Molecular Clouds: Turbulence or Gravity?

Abstract

We revisit the origin of Larson's scaling relations, which describe the structure and kinematics of molecular clouds, based on recent observations and large-scale simulations of supersonic turbulence. Using dimensional analysis, 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 or detailed energy balance 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.

5 pages, 4 color figures; revised version to appear in ApJ Letters

References in corpus (1)

• The Two States of Star Forming Clouds

Cited by in corpus (4)

• The PdBI Arcsecond Whirlpool Survey (PAWS): Environmental Dependence of Giant Molecular Cloud Properties in M51
• The Two States of Star Forming Clouds
• The effect of ISM turbulence on the gravitational instability of galactic discs
• Probing the multi-scale interplay between gravity and turbulence - Power-law like gravitational energy spectra of the Orion Complex