Outflow-Driven Turbulence in Molecular Clouds

Carroll, Jonathan; Frank, Adam; Blackman, Eric G.; Cunningham, A. J.; Quillen, Alice C.

doi:10.1088/0004-637x/695/2/1376

Cited by 87 publications

(106 citation statements)

References 27 publications

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“…This is demonstrated by recent simulations of outflow-driven turbulence which reveal that energy injection by outflows is not capable of creating turbulence at scales comparable to the cloud size. Models of interacting outflows generated either randomly (Carroll et al 2008), or self-consistently (Nakamura & Li 2007) show that turbulence is only injected with an effective driving scale of about 1/5 to 1/10 the size of the cloud (λ D /L c ≈ 0.1-0.2) which is incompatible with our results as summarized in Figs. 1 and 5.…”

Section: Disfavored On Energetic Grounds (Mac Low and Klessen 2004)contrasting

confidence: 91%

Turbulent driving scales in molecular clouds

Brunt¹,

Heyer²,

Low³

2009

A&A

160

151

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Context. Supersonic turbulence in molecular clouds is a dominant agent that strongly affects the clouds' evolution and star formation activity. Turbulence may be initiated and maintained by a number of processes, acting at a wide range of physical scales. By examining the dynamical state of molecular clouds, it is possible to assess the primary candidates for how the turbulent energy is injected. Aims. The aim of this paper is to constrain the scales at which turbulence is driven in the molecular interstellar medium, by comparing simulated molecular spectral line observations of numerical magnetohydrodynamic models and molecular spectral line observations of real molecular clouds. Methods. We use principal component analysis, applied to both models and observational data, to extract a quantitative measure of the driving scale of turbulence. Results. We find that only models driven at large scales (comparable to, or exceeding, the size of the cloud) are consistent with observations. This result applies also to clouds with little or no internal star formation activity. Conclusions. Astrophysical processes acting on large scales, including supernova-driven turbulence, magneto-rotational instability, or spiral shock forcing, are viable candidates for the generation and maintenance of molecular cloud turbulence. Small-scale driving by sources internal to molecular clouds, such as outflows, can be important on small scales, but cannot replicate the observed large-scale velocity fluctuations in the molecular interstellar medium.

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Section: Disfavored On Energetic Grounds (Mac Low and Klessen 2004)contrasting

confidence: 91%

Turbulent driving scales in molecular clouds

Brunt¹,

Heyer²,

Low³

2009

A&A

160

151

View full text Add to dashboard Cite

show abstract

“…If measured outflow extents range from ∼0.1 to 2 pc then they will not contribute driving motions on larger scales. Magnetohydrodynamic simulations of outflow-driven turbulence confirm that the peak of the velocity power spectrum occurs at the maximum length scale of the driving outflows (Carroll et al 2009(Carroll et al , 2010.…”

Section: Discussionmentioning

confidence: 83%

Radiation-Hydrodynamic Simulations of Protostellar Outflows: Synthetic Observations and Data Comparisons

Offner

Lee

Goodman

et al. 2011

ApJ

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We present results from three-dimensional, self-gravitating, radiation-hydrodynamic simulations of low-mass protostellar outflows. We construct synthetic observations in 12 CO in order to compare with observed outflows and evaluate the effects of beam resolution and outflow orientation on inferred outflow properties. To facilitate the comparison, we develop a quantitative prescription for measuring outflow opening angles. Using this prescription, we demonstrate that, in both simulations and synthetic observations, outflow opening angles broaden with time similarly to observed outflows. However, the interaction between the outflowing gas and the turbulent core envelope produces significant asymmetry between the redshifted and blueshifted outflow lobes. We find that applying a velocity cutoff may result in outflow masses that are underestimated by a factor five or more, and masses derived from optically thick CO emission further underpredict the mass of the high-velocity gas by a factor of 5-10. Derived excitation temperatures indicate that outflowing gas is hotter than the ambient gas with temperature rising over time, which is in agreement with the simulation gas temperatures. However, excitation temperatures are otherwise not well correlated with the actual gas temperature.

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“…Recent numerical simulations have demonstrated that protostellar outflows can indeed inject turbulent motions into cluster-forming clumps (Li & Nakamura 2006;Nakamura & Li 2007;Carroll et al 2009Carroll et al , 2010Wang et al 2010;Hansen et al 2012). A common drawback of this type of simulations is the use of periodic boundary conditions, which prevent the outflows from leaving the simulation box, leading to an overestimate of the efficiency of outflow feedback.…”

Section: Analytic Model Of Outflow-regulated Cluster Formationmentioning

confidence: 99%

Confronting the Outflow-Regulated Cluster Formation Model With Observations

Nakamura

2014

ApJ

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Protostellar outflows have been shown theoretically to be capable of maintaining supersonic turbulence in cluster-forming clumps and keeping the star formation rate per free-fall time as low as a few percent. We aim to test two basic predictions of this outflow-regulated cluster formation model, namely (1) the clump should be close to virial equilibrium and (2) the turbulence dissipation rate should be balanced by the outflow momentum injection rate, using recent outflow surveys toward 8 nearby cluster-forming clumps (B59, L1551, L1641N, Serpens Main Cloud, Serpens South, ρ Oph, IC 348, and NGC 1333). We find, for almost all sources, that the clumps are close to virial equilibrium and the outflow momentum injection rate exceeds the turbulence momentum dissipation rate. In addition, the outflow kinetic energy is significantly smaller than the clump gravitational energy for intermediate and massive clumps with M cl a few × 10 2 M ⊙ , suggesting that the outflow feedback is not enough to disperse the clump as a whole. The number of observed protostars also indicates that the star formation rate per free-fall time is as small as a few percent for all clumps. These observationally-based results strengthen the case for outflow-regulated cluster formation.

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Outflow-Driven Turbulence in Molecular Clouds

Cited by 87 publications

References 27 publications

Turbulent driving scales in molecular clouds

Turbulent driving scales in molecular clouds

Radiation-Hydrodynamic Simulations of Protostellar Outflows: Synthetic Observations and Data Comparisons

Confronting the Outflow-Regulated Cluster Formation Model With Observations

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