Statistics of Velocity from Spectral Data: Modified Velocity Centroids

@article{ALazarian2003StatisticsOV,
  title={Statistics of Velocity from Spectral Data: Modified Velocity Centroids},
  author={A.Lazarian and Alejandro Esquivel},
  journal={The Astrophysical Journal},
  year={2003},
  volume={592}
}
We address the problem of studying interstellar turbulence using spectral line data. We find a criterion when the velocity centroids may provide trustworthy velocity statistics. To enhance the scope of centroid applications, we construct a measure that we term "modified velocity centroids" (MVCs) and derive an analytical solution that relates the two-dimensional spectra of the modified centroids with the underlying three-dimensional velocity spectrum. We test our results using synthetic maps… Expand

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References

SHOWING 1-10 OF 24 REFERENCES
Velocity statistics from spectral line data: effects of density–velocity correlations, magnetic field and shear
In a previous work, Lazarian and Pogosyan suggested a technique to extract velocity and density statistics, of interstellar turbulence, by means of analysing statistics of spectral line data cubes.Expand
Velocity and density spectra of the small magellanic cloud
This Letter reports results on the statistical analysis of H I turbulence in the Small Magellanic Cloud (SMC). We use 21 cm channel maps, obtained with the Australia Telescope Compact Array and theExpand
Velocity field statistics in star-forming regions. I. Centroid velocity observations
The probability density functions (pdfs) of molecular line centroid velocity fluctuations, and of line centroid velocity fluctuation differences at different spatial lags, are estimated for severalExpand
EMISSIVITY STATISTICS IN TURBULENT COMPRESSIBLE MAGNETOHYDRODYNAMIC FLOWS AND THE DENSITY-VELOCITY CORRELATION
In this paper we test the results of a recent analytical study by Lazarian and Pogosyan on the statistics of emissivity in velocity channel maps, in the case of realistic density and velocity —eldsExpand
Velocity Modification of H I Power Spectrum
The distribution of atomic hydrogen in the Galactic plane is usually mapped using the Doppler shift of 21 cm emission line, and this causes the modification of the observed emission spectrum. WeExpand
Spectral Properties of Compressible Magnetohydrodynamic Turbulence from Numerical Simulations
We analyze the spectral properties of driven, supersonic, compressible, magnetohydrodynamic (MHD) turbulence obtained via high-resolution numerical experiments, for application to understanding theExpand
High-resolution observations of turbulence in the subcondensation TMC-1C in Heiles' cloud 2 : estimation of the velocity spectrum of turbulence
We have made mapping observations of 4'×4' and 8'×8' areas of the subcondensation TMC-1C in Heiles'cloud 2 of the Taurus complex (140 pc) by using the 45 m telescope of Nobeyama Radio Observatory.Expand
Anisotropic three-dimensional MHD turbulence
Direct spectral method simulation of the three-dimensional magnetohydrodynamics (MHD) equations is used to explore anisotropy that develops from initially isotropic fluctuations as a consequence of aExpand
Power Spectrum of the Density of Cold Atomic Gas in the Galaxy toward Cassiopeia A and Cygnus A
We have obtained the power spectral description of the density and opacity fluctuations of the cold H I gas in the Galaxy toward Cas A and Cygnus A. We have employed a method of deconvolution, basedExpand
Inertial range structures in decaying compressible turbulent flows
Simulations of decaying compressible turbulent flows have been performed using the PPM algorithm on grids of 5123 and 10243 computational cells. Although the run on the finer grid has not yet beenExpand
...
1
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3
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