Turbulent molecular clouds

Hennebelle, P.; Falgarone, É.

doi:10.1007/s00159-012-0055-y

Cited by 397 publications

(436 citation statements)

References 294 publications

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“…Audit & Hennebelle 2010;Heitsch et al 2008b). The velocity dispersion within the clumps as a function of their size is about σ 1 km s −1 (L/1pc), which is close to the Larson relation (Larson 1981;Hennebelle & Falgarone 2012). The third panel shows that the kinetic β parameter is typically of the order of, or slightly below 1, showing that the magnetic field plays an important role within the clumps.…”

Section: Clump Statisticssupporting

confidence: 74%

“…Although the exact mechanism that leads to the formation of molecular clouds is still under investigation, it seems unavoidable to consider converging streams of diffuse gas (e.g. Hennebelle & Falgarone 2012;Dobbs et al 2014). What exactly triggers these flows is not fully elucidated yet but is most likely due to a combination of gravity, large-scale turbulence, and large-scale shell expansion.…”

Section: Introductionmentioning

confidence: 99%

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H₂distribution during the formation of multiphase molecular clouds

Valdivia

Hennebelle

Gérin

et al. 2016

A&A

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Context. H 2 is the simplest and the most abundant molecule in the interstellar medium (ISM), and its formation precedes the formation of other molecules. Aims. Understanding the dynamical influence of the environment and the interplay between the thermal processes related to the formation and destruction of H 2 and the structure of the cloud is mandatory to understand correctly the observations of H 2 . Methods. We performed high-resolution magnetohydrodynamical colliding-flow simulations with the adaptive mesh refinement code RAMSES in which the physics of H 2 has been included. We compared the simulation results with various observations of the H 2 molecule, including the column densities of excited rotational levels. Results. As a result of a combination of thermal pressure, ram pressure, and gravity, the clouds produced at the converging point of HI streams are highly inhomogeneous. H 2 molecules quickly form in relatively dense clumps and spread into the diffuse interclump gas. This in particular leads to the existence of significant abundances of H 2 in the diffuse and warm gas that lies in between clumps. Simulations and observations show similar trends, especially for the HI-to-H 2 transition (H 2 fraction vs. total hydrogen column density). Moreover, the abundances of excited rotational levels, calculated at equilibrium in the simulations, turn out to be very similar to the observed abundances inferred from FUSE results. This is a direct consequence of the presence of the H 2 enriched diffuse and warm gas. Conclusions. Our simulations, which self-consistently form molecular clouds out of the diffuse atomic gas, show that H 2 rapidly forms in the dense clumps and, due to the complex structure of molecular clouds, quickly spreads at lower densities. Consequently, a significant fraction of warm H 2 exists in the low-density gas. This warm H 2 leads to column densities of excited rotational levels close to the observed ones and probably reveals the complex intermix between the warm and cold gas in molecular clouds. This suggests that the two-phase structure of molecular clouds is an essential ingredient for fully understanding molecular hydrogen in these objects.

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Section: Clump Statisticssupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

H₂distribution during the formation of multiphase molecular clouds

Valdivia

Hennebelle

Gérin

et al. 2016

A&A

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“…SF is known to be due to gravitational collapse of the dense cores of molecular clouds. Supersonic turbulent gas motions, magnetic fields in the molecular cloud, as well as radiative and mechanical feedback from the formed stars each play a role in this process (e.g., Federrath et al 2011, Hennebelle and Falgarone 2012, Renaud et al 2014.…”

Section: Star Formation In the Milky Way And Other Galaxiesmentioning

confidence: 99%

Nonthermal particles and photons in starburst regions and superbubbles

Bykov

2014

Astron Astrophys Rev

111

102

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Starforming factories in galaxies produce compact clusters and loose associations of young massive stars. Fast radiation-driven winds and supernovae input their huge kinetic power into the interstellar medium in the form of highly supersonic and superalfvenic outflows. Apart from gas heating, collisionless relaxation of fast plasma outflows results in fluctuating magnetic fields and energetic particles. The energetic particles comprise a long-lived component which may contain a sizeable fraction of the kinetic energy released by the winds and supernova ejecta and thus modify the magnetohydrodynamic flows in the systems. We present a concise review of observational data and models of nonthermal emission from starburst galaxies, superbubbles, and compact clusters of massive stars. Efficient mechanisms of particle acceleration and amplification of fluctuating magnetic fields with a wide dynamical range in starburst regions are discussed. Sources of cosmic rays, neutrinos and multi-wavelength nonthermal emission associated with starburst regions including potential galactic "PeVatrons" are reviewed in the global galactic ecology context.

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“…The density within the clump is also needed to get the accretion rate and we assume that ρ c = m p n c follows the Larson relations (Larson 1981;Falgarone et al 2009;Hennebelle & Falgarone 2012), m p being the mass per particle n c = n 0 R c 1 pc…”

Section: Gravitational Accretion Ratementioning

confidence: 99%

Ion-neutral friction and accretion-driven turbulence in self-gravitating filaments

Hennebelle

André

2013

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Recent Herschel observations have confirmed that filaments are ubiquitous in molecular clouds and suggest, that irrespective of the column density, there is a characteristic width of about 0.1 pc whose physical origin remains unclear. We develop an analytical model that can be applied to self-gravitating accreting filaments. It is based on the one hand on the virial equilibrium of the central part of the filament and on the other hand on the energy balance between the turbulence driven by accretion onto the filament and dissipation. We consider two dissipation mechanisms, the turbulent cascade and the ion-neutral friction. Our model predicts that the width of the inner part of the filament is almost independent of the column density and leads to values comparable to what is inferred observationally if dissipation is due to ion-neutral friction. On the contrary, turbulent dissipation leads to a structure that is bigger and depends significantly on the column density. Our model provides a reasonable physical explanation which could explain the observed filament width when they are self-gravitating. It predicts the correct order or magnitude though hampered by some uncertainties.

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Turbulent molecular clouds

Cited by 397 publications

References 294 publications

H₂distribution during the formation of multiphase molecular clouds

H₂distribution during the formation of multiphase molecular clouds

Nonthermal particles and photons in starburst regions and superbubbles

Ion-neutral friction and accretion-driven turbulence in self-gravitating filaments

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Turbulent molecular clouds

Cited by 397 publications

References 294 publications

H2distribution during the formation of multiphase molecular clouds

H2distribution during the formation of multiphase molecular clouds

Nonthermal particles and photons in starburst regions and superbubbles

Ion-neutral friction and accretion-driven turbulence in self-gravitating filaments

Contact Info

Product

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H₂distribution during the formation of multiphase molecular clouds

H₂distribution during the formation of multiphase molecular clouds