# 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…

## Figures from this paper

## 53 Citations

Velocity centroids as tracers of the turbulent velocity statistics

- Physics
- 2005

We use the results of magnetohydrodynamic (MHD) simulations to emulate spectroscopic observations and use maps of centroids to study their statistics. In order to assess under which circumstances the…

Interstellar cloud structure: the statistics of centroid velocities

- Physics
- 2006

Context. The statistical properties of maps of line centroids have been used for almost 50 years, but there is still no general agreement on their interpretation. Aims. We have tried to quantify…

Obtaining Statistics of Turbulent Velocity from Astrophysical Spectral Line Data

- Physics
- 2004

Turbulence is a crucial component of dynamics of astrophysical fluids dynamics, including those of ISM, clusters of galaxies and circumstellar regions. Doppler shifted spectral lines provide a unique…

Study of velocity centroids based on the theory of fluctuations in position–position–velocity space

- Physics
- 2017

We study possibility of obtaining velocity spectra by studying turbulence in an optically thick medium using velocity centroids (VCs).We find that the regime of universal, i.e. independent of…

Turbulence Statistics from Spectral Line Observations

- Physics
- 2004

Turbulence is a crucial component of dynamics of astrophysical fluids dynamics, including those of ISM, clusters of galaxies and circumstellar regions. Doppler shifted spectral lines provide a unique…

Velocity centroids and the structure of interstellar turbulence. I. Analytical study

- Physics
- 2004

We present an analytical study of the statistical properties of integrated emission and velocity centroids for a slightly compressible turbulent slab model, to retrieve the underlying statistics of…

Statistics of velocity centroids: effects of density–velocity correlations and non‐Gaussianity

- Physics
- 2007

We continue with our previous work on statistics of velocity centroids, to retrieve information about the scaling properties of an underlying turbulent velocity field from spectroscopic observations.…

STUDYING TURBULENCE USING DOPPLER-BROADENED LINES: VELOCITY COORDINATE SPECTRUM

- Physics
- 2005

We discuss a new technique for studying astrophysical turbulence that utilizes the statistics of Doppler-broadened spectral lines. The technique relates the power velocity coordinate spectrum (VCS),…

Modification of Projected Velocity Power Spectra by Density Inhomogeneities in Compressible Supersonic Turbulence

- Physics
- 2004

The scaling of velocity fluctuation ?v as a function of spatial scale L in molecular clouds can be measured from size-line width relations, principal component analysis, or line centroid variation.…

Obtaining Spectra of Turbulent Velocity from Observations

- Physics
- 2009

We discuss a long-standing problem of how turbulence can be studied using observations of Doppler broadened emission and absorption lines. The focus of the present review is on two new techniques,…

## References

SHOWING 1-10 OF 24 REFERENCES

Velocity statistics from spectral line data: effects of density–velocity correlations, magnetic field and shear

- Physics
- 2003

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.…

Velocity and density spectra of the small magellanic cloud

- Physics
- 2001

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 the…

Velocity field statistics in star-forming regions. I. Centroid velocity observations

- Physics
- 1998

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 several…

EMISSIVITY STATISTICS IN TURBULENT COMPRESSIBLE MAGNETOHYDRODYNAMIC FLOWS AND THE DENSITY-VELOCITY CORRELATION

- Physics
- 2001

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 —elds…

Velocity Modification of H I Power Spectrum

- Physics
- 2000

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. We…

Spectral Properties of Compressible Magnetohydrodynamic Turbulence from Numerical Simulations

- Physics
- 2003

We analyze the spectral properties of driven, supersonic, compressible, magnetohydrodynamic (MHD) turbulence obtained via high-resolution numerical experiments, for application to understanding the…

High-resolution observations of turbulence in the subcondensation TMC-1C in Heiles' cloud 2 : estimation of the velocity spectrum of turbulence

- Physics
- 1993

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.…

Anisotropic three-dimensional MHD turbulence

- Physics
- 1996

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 a…

Power Spectrum of the Density of Cold Atomic Gas in the Galaxy toward Cassiopeia A and Cygnus A

- Physics
- 2000

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, based…

Inertial range structures in decaying compressible turbulent flows

- Physics
- 1998

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 been…