The Statistics of Supersonic Isothermal Turbulence

Kritsuk, Alexei G.; Norman, Michael L.; Padoan, Paolo; Wagner, Rick

doi:10.1086/519443

Cited by 555 publications

(961 citation statements)

References 88 publications

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“…Heithausen et al (1998) found M ∝ r 2.31 for scales ranging from 0.01 to 1 pc. A similar mass-size relation is seen in numerical simulations where there is no gravity, and with or without heating and cooling processes included (Kritsuk et al 2007;Federrath et al 2009;Audit & Hennebelle 2010). Because of the fact that this relation is seen in different physical conditions, including isothermal gas, it is often attributed to turbulence.…”

Section: Masssupporting

confidence: 64%

Structure formation in a colliding flow: The Herschel view of the Draco nebula

Miville-Deschênes

Salomé

Martín

et al. 2017

A&A

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Context. The Draco nebula is a high Galactic latitude interstellar cloud observed at velocities corresponding to the intermediate velocity cloud regime. This nebula shows unusually strong CO emission and remarkably high-contrast small-scale structures for such a diffuse high Galactic latitude cloud. The 21 cm emission of the Draco nebula reveals that it is likely to have been formed by the collision of a cloud entering the disk of the Milky Way. Such physical conditions are ideal to study the formation of cold and dense gas in colliding flows of diffuse and warm gas. Aims. The objective of this study is to better understand the process of structure formation in a colliding flow and to describe the effects of matter entering the disk on the interstellar medium. Methods. We conducted Herschel-SPIRE observations of the Draco nebula. The clumpfind algorithm was used to identify and characterize the small-scale structures of the cloud. Results. The high-resolution SPIRE map reveals the fragmented structure of the interface between the infalling cloud and the Galactic layer. This front is characterized by a Rayleigh-Taylor (RT) instability structure. From the determination of the typical length of the periodic structure (2.2 pc) we estimated the gas kinematic viscosity. This allowed us to estimate the dissipation scale of the warm neutral medium (0.1 pc), which was found to be compatible with that expected if ambipolar diffusion were the main mechanism of turbulent energy dissipation. The statistical properties of the small-scale structures identified with clumpfind are found to be typical of that seen in molecular clouds and hydrodynamical turbulence in general. The density of the gas has a log-normal distribution with an average value of 10 3 cm −3 . The typical size of the structures is 0.1−0.2 pc, but this estimate is limited by the resolution of the observations. The mass of these structures ranges from 0.2 to 20 M and the distribution of the more massive structures follows a power-law dN/dlog(M) ∼ M −1.4 . We identify a mass-size relation with the same exponent as that found in molecular clouds (M ∼ L 2.3 ). On the other hand, we found that only 15% of the mass of the cloud is in gravitationally bound structures. Conclusions. We conclude that the collision of diffuse gas from the Galactic halo with the diffuse interstellar medium of the outer layer of the disk is an efficient mechanism for producing dense structures. The increase of pressure induced by the collision is strong enough to trigger the formation of cold neutral medium out of the warm gas. It is likely that ambipolar diffusion is the mechanism dominating the turbulent energy dissipation. In that case the cold structures are a few times larger than the energy dissipation scale. The dense structures of Draco are the result of the interplay between magnetohydrodynamical turbulence and thermal instability as self-gravity is not dominating the dynamics. Interestingly they have properties typical of those found in more classical molecular clouds.

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Section: Masssupporting

confidence: 64%

Structure formation in a colliding flow: The Herschel view of the Draco nebula

Miville-Deschênes

Salomé

Martín

et al. 2017

A&A

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“…This might explain that the gradientsubtracted PDF still shows a weak second peak at a velocity of -v 4 km s 1 to the right of the main peak (v = 0). Finally, turbulence has intrinsic non-Gaussian features, broadly referred to as "intermittency," leading to deviations from Gaussian statistics, especially in the tails of the PDFs (Falgarone & Phillips 1990;Passot & Vázquez-Semadeni 1998;Kritsuk et al 2007;Hily-Blant et al 2008;Schmidt et al 2008Schmidt et al , 2009Burkhart et al 2009;Falgarone et al 2009;Federrath et al 2009Federrath et al , 2010Federrath 2013;Hopkins 2013b). In summary, the Gaussian fit in Figure 4 and the standard deviation of the velocity data (without fitting) yield a consistent 1D turbulent velocity dispersion of s =  -3.9 0.1 km s…”

Section: Velocity Pdfmentioning

confidence: 79%

The Link Between Turbulence, Magnetic Fields, Filaments, and Star Formation in the Central Molecular Zone Cloud G0.253+0.016

Federrath

Rathborne

Longmore

et al. 2016

ApJ

186

235

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Star formation is primarily controlled by the interplay between gravity, turbulence, and magnetic fields. However, the turbulence and magnetic fields in molecular clouds near the Galactic center may differ substantially compared to spiral-arm clouds. Here we determine the physical parameters of the central molecular zone (CMZ) cloud G0.253 +0.016, its turbulence, magnetic field, and filamentary structure. Using column density maps based on dust

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“…For compressible, isothermal and subsonic turbulence, Kim & Ryu (2005), Kritsuk et al (2007), Saury et al (2014) showed that the power spectrum of density follows that of the velocity (P k (n) ∼ k −11/3 ). This would produce a column density power spectrum with γ = −3.7, far from what is observed.…”

Section: The Power Spectrum Of Density Fluctuationsmentioning

confidence: 99%

Probing interstellar turbulence in cirrus with deep optical imaging: no sign of energy dissipation at 0.01 pc scale

Miville-Deschênes

Duc

Marleau

et al. 2016

A&A

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Diffuse Galactic light has been observed in the optical since the 1930s. We propose that, when observed in the optical with deep imaging surveys, it can be used as a tracer of the turbulent cascade in the diffuse interstellar medium (ISM), down to scales of about 1 arcsec. Here we present a power spectrum analysis of the dust column density of a diffuse cirrus at high Galactic latitude (l ≈ 198 • , b ≈ 32 • ) as derived from the combination of a MegaCam g-band image, obtained as part of the MATLAS large programme at the CFHT, with Planck radiance and WISE 12 µm data. The combination of these three datasets have allowed us to compute the density power spectrum of the H i over scales of more than three orders of magnitude. We found that the density field is well described by a single power law over scales ranging from 0.01 to 50 pc. The exponent of the power spectrum, γ = −2.9±0.1, is compatible with what is expected for thermally bi-stable and turbulent H i. We did not find any steepening of the power spectrum at small scales indicating that the typical scale at which turbulent energy is dissipated in this medium is smaller than 0.01 pc. The ambipolar diffusion scenario that is usually proposed as the main dissipative agent, is consistent with our data only if the density of the cloud observed is higher than the typical values assumed for the cold neutral medium gas. We discuss the new avenue offered by deep optical imaging surveys for the study of the low density ISM structure and turbulence.

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The Statistics of Supersonic Isothermal Turbulence

Cited by 555 publications

References 88 publications

Structure formation in a colliding flow: The Herschel view of the Draco nebula

Structure formation in a colliding flow: The Herschel view of the Draco nebula

The Link Between Turbulence, Magnetic Fields, Filaments, and Star Formation in the Central Molecular Zone Cloud G0.253+0.016

Probing interstellar turbulence in cirrus with deep optical imaging: no sign of energy dissipation at 0.01 pc scale

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