Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002apj...566..276b&link_type=abstract
The Astrophysical Journal, Volume 566, Issue 1, pp. 276-288.
Astronomy and Astrophysics
Astronomy
45
Hydrodynamics, Ism: Clouds, Ism: Kinematics And Dynamics, Line: Profiles, Methods: Statistical, Turbulence
Scientific paper
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.
Brunt Christopher M.
Heyer Mark H.
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