Gravitational Collapse of Filamentary Clouds

Kawachi, Takeshi; Hanawa, Tomoyuki

doi:10.1093/pasj/50.6.577

Cited by 47 publications

(49 citation statements)

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“…This free-fall estimate is an upper limit since it neglects any form of support against gravity. A more conservative estimate can be obtained by considering the similarity solution found by Kawachi & Hanawa (1998) for the gravitational collapse of a cylindrical filament supported by a polytropic pressure gradient with γ < ∼ 1. In this model, the radial infall velocity in the outer parts of the collapsing filament is expected to be v inf ∼ 0.6-1 km s −1 when γ = 0.9-0.999 and the gas temperature is ∼10 K (see Figs.…”

Section: Discussion: Contraction and Accretion In B211?mentioning

confidence: 99%

“…Kawachi & Hanawa (1998) have shown that the outer density profile of such a collapsing cylinder approaches the power law ρ ∝ r − 2 2−γ . For γ values close to unity, the model column density profile thus approaches ρ ∝ r −2 at large radii, which is consistent with the observed profile of the B211 filament.…”

Section: Density and Temperature Structure Of The B211 Filamentmentioning

confidence: 98%

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Herschelview of the Taurus B211/3 filament and striations: evidence of filamentary growth?

Palmeirim¹,

André²,

Kirk³

et al. 2013

A&A

546

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814

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We present first results from the Herschel Gould Belt survey for the B211/L1495 region in the Taurus molecular cloud. Thanks to their high sensitivity and dynamic range, the Herschel images reveal the structure of the dense, star-forming filament B211 with unprecedented detail, along with the presence of striations perpendicular to the filament and generally oriented along the magnetic field direction as traced by optical polarization vectors. Based on the column density and dust temperature maps derived from the Herschel data, we find that the radial density profile of the B211 filament approaches power-law behavior, ρ ∝ r −2.0 ± 0.4 , at large radii and that the temperature profile exhibits a marked drop at small radii. The observed density and temperature profiles of the B211 filament are in good agreement with a theoretical model of a cylindrical filament undergoing gravitational contraction with a polytropic equation of state: P ∝ ρ γ and T ∝ ρ γ−1 , with γ = 0.97 ± 0.01 < 1 (i.e., not strictly isothermal). The morphology of the column density map, where some of the perpendicular striations are apparently connected to the B211 filament, further suggests that the material may be accreting along the striations onto the main filament. The typical velocities expected for the infalling material in this picture are ∼0.5-1 km s −1 , which are consistent with the existing kinematical constraints from previous CO observations.

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Section: Discussion: Contraction and Accretion In B211?mentioning

confidence: 99%

Section: Density and Temperature Structure Of The B211 Filamentmentioning

confidence: 98%

Herschelview of the Taurus B211/3 filament and striations: evidence of filamentary growth?

Palmeirim¹,

André²,

Kirk³

et al. 2013

A&A

546

111

814

View full text Add to dashboard Cite

show abstract

“…This radial structure is reminiscent of many self-gravitating objects such as Bonnor-Ebert spheres. More precisely, filaments that are collapsing in a self-similar manner are expected to present an envelope with a profile ∝r −2/(2−γ) where γ is the adiabatic index A&A 560, A68 (2013) of the gas (Kawachi & Hanawa 1998). As it is likely that selfgravitating filaments are collapsing in a way not too different from, although not identical to, a self-similar collapse, assuming an r −2 profile is thus a well-motivated assumption, both from observations and theory.…”

Section: Characteristics Of the Filamentmentioning

confidence: 99%

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

Hennebelle

André

2013

A&A

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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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“…The same result has been obtained by Viala & Horedt (1974;see their Tables 11−13). It is also interesting to remark that values of γ < 1 are expected for polytropic filaments in gravitational collapse, according to simulations (Kawachi & Hanawa 1998). As a result, the observation of these temperature profiles has been interpreted as a signature of instability.…”

Section: Equilibrium Solutions For Nonisothermal Filamentsmentioning

confidence: 69%

Nonisothermal filaments in equilibrium

Recchi

Hacar

Палестини

2013

A&A

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Context. The physical properties of the so-called Ostriker isothermal filament have been classically used as a benchmark to interpret the stability of the filaments observed in nearby clouds. However, recent continuum studies have shown that the internal structure of the filaments depart from the isothermality, typically exhibiting radially increasing temperature gradients. Aims. The presence of internal temperature gradients within filaments suggests that the equilibrium configuration of these objects should be therefore revisited. The main goal of this work is to theoretically explore how the equilibrium structure of a filament changes in a nonisothermal configuration. Methods. We solve the hydrostatic equilibrium equation by assuming temperature gradients similar to those derived from observations. Results. We obtain a new set of equilibrium solutions for nonisothermal filaments with both linear and asymptotically constant temperature gradients. For sufficiently large internal temperature gradients, our results show that a nonisothermal filament could present significantly larger masses per unit length and shallower density profiles than the isothermal filament without collapsing by its own gravity. Conclusions. We conclude that filaments can reach an equilibrium configuration under nonisothermal conditions. Detailed studies of both the internal mass distribution and temperature gradients within filaments are then needed to judge the physical state of filaments.

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Gravitational Collapse of Filamentary Clouds

Cited by 47 publications

References 0 publications

Herschelview of the Taurus B211/3 filament and striations: evidence of filamentary growth?

Herschelview of the Taurus B211/3 filament and striations: evidence of filamentary growth?

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

Nonisothermal filaments in equilibrium

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