The link between magnetic fields and filamentary clouds: bimodal cloud orientations in the Gould Belt

Li, Hua-bai; Fang, Min; Henning, Thomas; Kainulainen, J.

doi:10.1093/mnras/stt1849

Cited by 134 publications

(181 citation statements)

References 74 publications

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“…Such alignment of strong magnetic field models and misalignment of weak magnetic field models are also presented in the simulations not including turbulence (Van Loo et al 2014). In observations, the correlation between the orientations of clouds and magnetic fields is found to be either-parallelor-perpendicular in filamentary clouds from few to tens pc scales (Li et al 2013;Planck Collaboration et al 2016) and in massive cores at 0.1-0.01 pc scales Koch et al 2014), suggesting a dynamically important role of magnetic fields in various physical scales (see Li et al 2014 for a review).…”

Section: Introductionsupporting

confidence: 55%

Magnetic Fields in the Massive Dense Cores of the DR21 Filament: Weakly Magnetized Cores in a Strongly Magnetized Filament

Ching

Lai

Zhang

et al. 2017

ApJ

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We present Submillimeter Array 880 µm dust polarization observations of six massive dense cores in the DR21 filament. The dust polarization shows complex magnetic field structures in the massive dense cores with sizes of 0.1 pc, in contrast to the ordered magnetic fields of the parsec-scale filament. The major axes of the massive dense cores appear to be aligned either parallel or perpendicular to the magnetic fields of the filament, indicating that the parsec-scale magnetic fields play an important role in the formation of the massive dense cores. However, the correlation between the major axes of the cores and the magnetic fields of the cores is less significant, suggesting that during the core formation, the magnetic fields below 0.1 pc scales become less important than the magnetic fields above 0.1 pc scales in supporting a core against gravity. Our analysis of the angular dispersion functions of the observed polarization segments yields the plane-of-sky magnetic field strengths of 0.4-1.7 mG of the massive dense cores. We estimate the kinematic, magnetic, and gravitational virial parameters of the filament and the cores. The virial parameters show that in the filament, the gravitational energy is dominant over magnetic and kinematic energies, while in the cores, the kinematic energy is dominant. Our work suggests that although magnetic fields may play an important role in a collapsing filament, the kinematics arising from gravitational collapse must become more important than magnetic fields during the evolution from filaments to massive dense cores.

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Section: Introductionsupporting

confidence: 55%

Magnetic Fields in the Massive Dense Cores of the DR21 Filament: Weakly Magnetized Cores in a Strongly Magnetized Filament

Ching

Lai

Zhang

et al. 2017

ApJ

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“…Furthermore, Fiege & Pudritz (2000) showed that also a toroidal magnetic field could stabilize the filament against radial collapse. However, observations show that the magnetic field in filaments seems to be preferentially perpendicular to the major axis (Chapman et al 2011;Sugitani et al 2011;Planck Collaboration et al 2014a) although also parallel configurations are observed (Li et al 2013;Pillai et al 2015;Planck Collaboration et al 2014b). Under the assumption that there is indeed a universal width for star forming filaments of the order of 0.1 pc as proposed by André et al (2014) (or even larger, see Schisano et al 2014), our results raise the question what mechanism allows to retain this width.…”

Section: A Universal Filament Width?mentioning

confidence: 99%

“…According to Arzoumanian et al (2011), this can be converted into central column densities Observations show that filaments are most likely magnetized with a direction of the magnetic field which is either perpendicular to the major axis 2 of the filament (e.g. Chapman et al 2011;Sugitani et al 2011;Planck Collaboration et al 2014a) or parallel to it (Li et al 2013;Pillai et al 2015;Planck Collaboration et al 2014b). The preferred direction of the magnetic field in the densest parts, however, is still not entirely certain: Dust polarisation maps usually reveal a strong decrease of the polarisation towards the densest regions, which leads to some uncertainty about the field direction within the filament (e.g.…”

Section: Initial Conditionsmentioning

confidence: 99%

The impact of turbulence and magnetic field orientation on star-forming filaments

Seifried

Walch

2015

Mon. Not. R. Astron. Soc.

117

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We present simulations of collapsing filaments studying the impact of turbulence and magnetic field morphologies on their evolution and star formation properties. We vary the mass per unit length of the filaments as well as the orientation of the magnetic field with respect to the major axis. We find that the filaments, which have no or a perpendicular magnetic field, typically reveal a smaller width than the universal width of 0.1 pc proposed by e.g. Arzoumanian et al. (2011). We show that this also holds in the presence of supersonic turbulence and that accretion driven turbulence is too weak to stabilize the filaments along their radial direction. On the other hand, we find that a magnetic field that is parallel to the major axis can stabilize the filament against radial collapse resulting in widths of 0.1 pc. Furthermore, depending on the filament mass and magnetic field configuration, gravitational collapse and fragmentation in filaments occurs either in an edge-on way, uniformly distributed across the entire length, or in a mixed way. In the presence of initially moderate density perturbations, a centralized collapse towards a common gravitational centre occurs. Our simulations can thus reproduce different modes of fragmentation observed recently in star forming filaments. Moreover, we find that turbulent motions influence the distance between individual fragments along the filament, which does not always match the results of a Jeans analysis.

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“…numerical simulation by Vestuto et al 2003;Li et al 2008). Li et al (2013) examined the orientation of the filamentary giant molecular clouds of the Gould Belt (NH ≈ 2 × 10 21 -2 × 10 22 cm −2 ) relative to the magnetic fields of the intercloud medium (ICM) and found a bimodal distribution. Most clouds are oriented either perpendicular or parallel to ICM B-fields, with offsets typically less than 20 degrees.…”

Section: Introductionmentioning

confidence: 99%

“…We have examined scales on the order of a few parsec, smaller than the Gould Belt clouds examined in Li et al (2013), but on the same physical scales as the Serpens South cloud (e.g. Sugitani et al 2011;Kirk et al 2013) and the Taurus B211 filament (Palmeirim et al 2013).…”

Section: Introductionmentioning

confidence: 99%

Filamentary flow and magnetic geometry in evolving cluster-forming molecular cloud clumps

Klassen

Pudritz

Kirk

2016

Mon. Not. R. Astron. Soc.

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We present an analysis of the relationship between the orientation of magnetic fields and filaments that form in 3D magnetohydrodynamic simulations of cluster-forming, turbulent molecular cloud clumps. We examine simulated cloud clumps with size scales of L ∼ 2-4 pc and densities of n ∼ 400-1000 cm −3 with Alfvén Mach numbers near unity. We simulated two cloud clumps of different masses, one in virial equilibrium, the other strongly gravitationally bound, but with the same initial turbulent velocity field and similar mass-to-flux ratio. We apply various techniques to analyze the filamentary and magnetic structure of the resulting cloud, including the DisPerSE filamentfinding algorithm in 3D. The largest structure that forms is a 1-2 parsec-long filament, with smaller connecting sub-filaments. We find that our simulated clouds, wherein magnetic forces and turbulence are comparable, coherent orientation of the magnetic field depends on the virial parameter. Subvirial clumps undergo strong gravitational collapse and magnetic field lines are dragged with the accretion flow. We see evidence of filament-aligned flow and accretion flow onto the filament in the subvirial cloud. Magnetic fields oriented more parallel in the subvirial cloud and more perpendicular in the denser, marginally bound cloud. Radiative feedback from a 16 M star forming in a cluster in one of our simulations ultimately results in the destruction of the main filament, the formation of an H ii region, and the sweeping up of magnetic fields within an expanding shell at the edges of the H ii region.

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The link between magnetic fields and filamentary clouds: bimodal cloud orientations in the Gould Belt

Cited by 134 publications

References 74 publications

Magnetic Fields in the Massive Dense Cores of the DR21 Filament: Weakly Magnetized Cores in a Strongly Magnetized Filament

Magnetic Fields in the Massive Dense Cores of the DR21 Filament: Weakly Magnetized Cores in a Strongly Magnetized Filament

The impact of turbulence and magnetic field orientation on star-forming filaments

Filamentary flow and magnetic geometry in evolving cluster-forming molecular cloud clumps

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