Turbulence Spectra From Doppler-Broadened Spectral Lines: Tests of the Velocity Channel Analysis and Velocity Coordinate Spectrum Techniques

Chepurnov, A. V.; Lazarían, A.

doi:10.1088/0004-637x/693/2/1074

Cited by 60 publications

(73 citation statements)

References 35 publications

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“…The VCS technique, which as been numerically tested in Chepurnov & Lazarian (2009), has a bright future ahead in terms of measuring the properties of turbulence in a number of interesting environments. The technique thus far has been applied primarily in the context of 21 cm data but there is no reason not to apply it to the wealth of molecular line tracers such as CO, as was done in Padoan et al (2009).…”

Section: Discussionmentioning

confidence: 99%

“…This is because the VCA technique is concerned with taking the spatial power spectrum of the two-dimensional (2D) slices of PPV while the VCS studies the fluctuations of PPV intensities along the velocity coordinate of the PPV cube. Both techniques have been applied to multi-wavelength observations as well as having undergone numerical tests (Stanimirović & Lazarian 2001;Chepurnov & Lazarian 2009;.…”

Section: Introductionmentioning

confidence: 99%

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The Turbulence Velocity Power Spectrum of Neutral Hydrogen in the Small Magellanic Cloud

Chepurnov

Burkhart

Lazarían

et al. 2015

ApJ

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We present the results of the Velocity Coordinate Spectrum (VCS) technique to calculate the velocity power spectrum of turbulence in the Small Magellanic Cloud (SMC) in 21 cm emission. We present an updated version of the VCS technique that takes into account regular motions, which is an important factor in our SMC VCS analysis. We have obtained a velocity spectral index of −3.85, a cold phase sonic Mach number of 5.6, and an injection scale of 2.3 kpc. The spectral index is steeper than the Kolmogorov index, which is expected for shock-dominated turbulence. The injection scale of 2.3 kpc suggests that HI supershells or tidal interactions with the Large Magellanic Cloud are the dominant drivers of turbulence in this dwarf galaxy. This implies that turbulence may be driven by multiple mechanisms in galaxies and that galaxy-galaxy interactions may play an important role in addition to supernova feedback.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

The Turbulence Velocity Power Spectrum of Neutral Hydrogen in the Small Magellanic Cloud

Chepurnov

Burkhart

Lazarían

et al. 2015

ApJ

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“…We examined the changes in the distribution of the dendrogram as we vary the threshold parameter δ. This is analogous to changing the corresponding threshold parameter in other techniques that rely on contouring thresholds, e.g., in the Genus analysis (see Chepurnov & Lazarian 2009). By varying δ we obtained a new outlook on the technique; in particular, we found that the dendrogram distribution and hierarchy have a strong dependency on the magnetization and compressibility of the gas and are sensitive to the amount of self-gravity.…”

Section: Discussionmentioning

confidence: 99%

Hierarchical Structure of Magnetohydrodynamic Turbulence in Position-Position-Velocity Space

Burkhart

Lazarían

Goodman

et al. 2013

ApJ

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Magnetohydrodynamic turbulence is able to create hierarchical structures in the interstellar medium (ISM) that are correlated on a wide range of scales via the energy cascade. We use hierarchical tree diagrams known as dendrograms to characterize structures in synthetic position-position-velocity (PPV) emission cubes of isothermal magnetohydrodynamic turbulence. We show that the structures and degree of hierarchy observed in PPV space are related to the presence of self-gravity and the global sonic and Alfvénic Mach numbers. Simulations with higher Alfvénic Mach number, self-gravity and supersonic flows display enhanced hierarchical structure. We observe a strong dependency on the sonic and Alfvénic Mach numbers and self-gravity when we apply the statistical moments (i.e., mean, variance, skewness, kurtosis) to the leaf and node distribution of the dendrogram. Simulations with self-gravity, larger magnetic field and higher sonic Mach number have dendrogram distributions with higher statistical moments. Application of the dendrogram to three-dimensional density cubes, also known as position-position-position (PPP) cubes, reveals that the dominant emission contours in PPP and PPV are related for supersonic gas but not for subsonic. We also explore the effects of smoothing, thermal broadening, and velocity resolution on the dendrograms in order to make our study more applicable to observational data. These results all point to hierarchical tree diagrams as being a promising additional tool for studying ISM turbulence and star forming regions for obtaining information on the degree of self-gravity, the Mach numbers and the complicated relationship between PPV and PPP data.

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“…This yields two distinct power laws, which we fit individually using the segmented linear model described in K16. The fit at larger scales describes bulk gas velocity-dominated motion; the fit at smaller scales describes gas density-dominated motions (Chepurnov & Lazarian 2009). Kowal et al (2007) find that the density-dominated regime is sensitive to the magnetic field strength, where stronger fields correspond to steeper slopes.…”

Section: Spatial Power Spectrummentioning

confidence: 99%

An Exploration of the Statistical Signatures of Stellar Feedback

Boyden

Koch

Rosolowsky

et al. 2016

ApJ

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All molecular clouds are observed to be turbulent, but the origin, means of sustenance, and evolution of the turbulence remain debated. One possibility is that stellar feedback injects enough energy into the cloud to drive observed motions on parsec scales. Recent numerical studies of molecular clouds have found that feedback from stars, such as protostellar outflows and winds, injects energy and impacts turbulence. We expand upon these studies by analyzing magnetohydrodynamic simulations of molecular clouds, including stellar winds, with a range of stellar mass-loss rates and magnetic field strengths. We generate synthetic 12 CO(1-0) maps assuming that the simulations are at the distance of the nearby Perseus molecular cloud. By comparing the outputs from different initial conditions and evolutionary times, we identify differences in the synthetic observations and characterize these using common astrostatistics. We quantify the different statistical responses using a variety of metrics proposed in the literature. We find that multiple astrostatistics, including principal component analysis, the spectral correlation function and the velocity coordinate spectrum, are sensitive to changes in stellar mass-loss rates and/or time evolution. A few statistics, including the Cramer statistic and velocity coordinate spectrum, are sensitive to the magnetic field strength. These findings demonstrate that stellar feedback influences molecular cloud turbulence and can be identified and quantified observationally using such statistics.

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Turbulence Spectra From Doppler-Broadened Spectral Lines: Tests of the Velocity Channel Analysis and Velocity Coordinate Spectrum Techniques

Cited by 60 publications

References 35 publications

The Turbulence Velocity Power Spectrum of Neutral Hydrogen in the Small Magellanic Cloud

The Turbulence Velocity Power Spectrum of Neutral Hydrogen in the Small Magellanic Cloud

Hierarchical Structure of Magnetohydrodynamic Turbulence in Position-Position-Velocity Space

An Exploration of the Statistical Signatures of Stellar Feedback

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