The Role of Turbulence and Magnetic Fields in Simulated Filamentary Structure

Kirk, Helen; Klassen, Mikhail; Pillsworth, Samantha

doi:10.1088/0004-637x/802/2/75

Cited by 60 publications

(102 citation statements)

References 77 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…6c (bin size = 0.05 pc), the filament population is highly peaked with a median value of ≈0.13 pc and a standard deviation of 0.05 pc. This characteristic width and dispersion are somewhat larger than those quoted for filaments in nearby fields of the Gould Belt Survey (e.g., 0.09 ± 0.04 pc; André et al 2013), and are possibly more in tune with predictions from other observational and theoretical studies (e.g., Juvela et al 2012b;Kirk et al 2015).…”

Section: Filament Widthscontrasting

confidence: 45%

Galactic cold cores

Rivera-Ingraham

Ristorcelli

Juvela

et al. 2016

A&A

View full text Add to dashboard Cite

Context. The association of filaments with protostellar objects has made these structures a priority target in star formation studies. However, little is known about the link between filament properties and their local environment. Aims. The datasets from the Herschel Galactic Cold cores key programme allow for a statistical study of filaments with a wide range of intrinsic and environmental characteristics. Characterisation of this sample can therefore be used to identify key physical parameters and quantify the role of the environment in the formation of supercritical filaments. These results are necessary to constrain theoretical models of filament formation and evolution. Methods. Filaments were extracted from fields at distance D < 500 pc with the getfilaments algorithm and characterised according to their column density profiles and intrinsic properties. Each profile was fitted with a beam-convolved Plummer-like function, and the filament structure was quantified based on the relative contributions from the filament "core", represented by a Gaussian, and "wing" component, dominated by the power-law behaviour of the Plummer-like function. These filament parameters were examined for populations associated with different background levels. Results. Filaments increase their core (M line,core ) and wing (M line,wing ) contributions while increasing their total linear mass density (M line,tot ). Both components appear to be linked to the local environment, with filaments in higher backgrounds having systematically more massive M line,core and M line,wing . This dependence on the environment supports an accretion-based model of filament evolution in the local neighbourhood (D ≤ 500 pc). Structures located in the highest backgrounds develop the highest central A V , M line,core , and M line,wing as M line,tot increases with time, favoured by the local availability of material and the enhanced gravitational potential. Our results indicate that filaments acquiring a significantly massive central region with M line,core > ∼ M crit /2 may become supercritical and form stars. This translates into a need for filaments to become at least moderately self-gravitating to undergo localised star formation or become star-forming filaments.

show abstract

Section: Filament Widthscontrasting

confidence: 45%

Galactic cold cores

Rivera-Ingraham

Ristorcelli

Juvela

et al. 2016

A&A

View full text Add to dashboard Cite

show abstract

“…Such structures are readily produced in simulations of turbulent gas with and without magnetic fields (Padoan 1995;Mac Low & Klessen 2004;Federrath 2016;Smith et al 2014Smith et al , 2016Kirk et al 2015;Chen & Ostriker 2015). The fact that plausible representations of filaments can be produced even without magnetic fileds makes turbulence a leading candidate for the formation of molecular clouds.…”

Section: Molecular Cloud Formationmentioning

confidence: 99%

Slingshot mechanism in Orion: Kinematic evidence for ejection of protostars by filaments

Stutz

Gould

2016

A&A

131

260

View full text Add to dashboard Cite

By comparing three constituents of Orion A (gas, protostars, and pre-main-sequence stars), both morphologically and kinematically, we derive the following conclusions. The gas surface density near the integral-shaped filament (ISF) is very well represented by a power law, Σ(b) = 37 M pc −2 (b/pc) −5/8 , for the entire range to which we are sensitive, 0.05 pc < b < 8.5 pc, of projected separation from the filament ridge. Essentially all Class 0 and Class I protostars lie superposed on the ISF or on identifiable filament ridges farther south, while almost all pre-main-sequence (Class II) stars do not. Combined with the fact that protostars are moving < ∼ 1 km s −1 relative to the filaments, while stars are moving several times faster, this implies that protostellar accretion is terminated by a slingshot-like "ejection" from the filaments. The ISF is the third in a series of identifiable star bursts that are progressively moving south, with separations of several Myr in time and 2-3 pc in space. This, combined with the observed undulations in the filament (both spatial and velocity), suggest that repeated propagation of transverse waves through the filament is progressively digesting the material that formerly connected Orion A and B into stars in discrete episodes. We construct a simple, circularly symmetric gas density profile ρ(r) = 17 M pc −3 (r/pc) −13/8 consistent with the two-dimensional data. The model implies that the observed magnetic fields in this region are subcritical on spatial scales of the observed undulations, suggesting that the transverse waves propagating through the filament are magnetically induced. Because the magnetic fields are supercritical on scales of the filament as a whole (as traced by the power law), the system as a whole is relatively stable and long lived. Protostellar "ejection" (i.e., the slingshot) occurs because the gas accelerates away from the protostars, not the other way around. The model also implies that the ISF is kinematically young, which is consistent with several other lines of evidence. In contrast to the ISF, the southern filament (L1641) has a broken power law, which matches the ISF profile for 2.5 pc < b < 8.5 pc, but is shallower closer in. L1641 is kinematically older than the ISF.

show abstract

“…Turbulent box simulations and colliding flows (e.g. Mac Low & Klessen 2004;Hennebelle et al 2008;Federrath et al 2010;Gómez & Vázquez-Semadini 2014;Moeckel & Burkert 2015;Smith, Glover & Klessen 2014;Kirk et al 2015) produce filaments. Hennebelle & André (2013) demonstrated the formation of filaments through the velocity shear that is common in magnetised turbulent media.…”

Section: Formation Models Of Filamentsmentioning

confidence: 99%

“…Recently, (Smith, Glover & Klessen 2014, hereafter SGK14) and (Kirk et al 2015, hereafter KKPP15) investigated the formation and evolution of filaments in more detail. SGK14 examined the influence of different types of turbulence, keeping the initial mean density constant in simulations without magnetic fields.…”

Section: Formation Models Of Filamentsmentioning

confidence: 99%

Magnetohydrodynamical simulation of the formation of clumps and filaments in quiescent diffuse medium by thermal instability

Wareing

Pittard

Falle

et al. 2016

Mon. Not. R. Astron. Soc.

View full text Add to dashboard Cite

We have used the AMR hydrodynamic code, MG, to perform idealised 3D MHD simulations of the formation of clumpy and filamentary structure in a thermally unstable medium without turbulence. A stationary thermally unstable spherical diffuse atomic cloud with uniform density in pressure equilibrium with low density surroundings was seeded with random density variations and allowed to evolve. A range of magnetic field strengths threading the cloud have been explored, from β = 0.1 to β = 1.0 to the zero magnetic field case (β = ∞), where β is the ratio of thermal pressure to magnetic pressure. Once the density inhomogeneities had developed to the point where gravity started to become important, self-gravity was introduced to the simulation. With no magnetic field, clouds and clumps form within the cloud with aspect ratios of around unity, whereas in the presence of a relatively strong field (β = 0.1) these become filaments, then evolve into interconnected corrugated sheets that are predominantly perpendicular to the magnetic field. With magnetic and thermal pressure equality (β = 1.0), filaments, clouds and clumps are formed. At any particular instant, the projection of the 3D structure onto a plane parallel to the magnetic field, i.e. a line of sight perpendicular to the magnetic field, resembles the appearance of filamentary molecular clouds. The filament densities, widths, velocity dispersions and temperatures resemble those observed in molecular clouds. In contrast, in the strong field case β = 0.1, projection of the 3D structure along a line of sight parallel to the magnetic field reveals a remarkably uniform structure.

show abstract

The Role of Turbulence and Magnetic Fields in Simulated Filamentary Structure

Cited by 60 publications

References 77 publications

Galactic cold cores

Galactic cold cores

Slingshot mechanism in Orion: Kinematic evidence for ejection of protostars by filaments

Magnetohydrodynamical simulation of the formation of clumps and filaments in quiescent diffuse medium by thermal instability

Contact Info

Product

Resources

About