Interstellar Turbulence. I. Retrieval of Velocity Field Statistics
C. M. Brunt, M. H. Heyer;
ApJ, 2002, 566, 276
ABSTRACT:We demonstrate the capability of principal component analysis (PCA) as applied by Heyer & Schloerb to extract the statistics of turbulent
interstellar velocity fields as measured by the energy spectrum,
E(k)~k-β.
Turbulent velocity and density fields with known statistics are generated from
fractional Brownian motion simulations.
These fields are translated to the
observational domain, T(x,y,v), considering the excitation of molecular
rotational energy levels and radiative transfer.
Using PCA and the
characterization of velocity and spatial scales from the eigenvectors and eigenimages,
respectively, a relationship is identified that describes the magnitude of line
profile differences, δv, and the scale, L, over which these differences
occur, δv~Lα.
From a series of models with varying
values of β, we find α=0.33β-0.05 for
1<β<3.
This provides the basic calibration between the intrinsic velocity field
statistics to observational measures and a diagnostic for turbulent flows in the
interstellar medium.
We also investigate the effects of noise, line opacity, and
finite resolution on these results.
KEYWORDS: hydrodynamics, ism: clouds, ism: kinematics and dynamics, line: profiles, methods: statistical, turbulence
PERSOKEY:turbulence, ,
CODE: brunt2002a