Could bow-shaped magnetic morphologies surround filamentary molecular clouds?

Tahani, Mehrnoosh; Plume, R.; Brown, J. C.; Soler, J. D.; Kainulainen, J.

doi:10.1051/0004-6361/201936280

Cited by 47 publications

(60 citation statements)

References 46 publications

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“…In this scenario, the flow of matter would be initially generated by the bending of the ambient Bfield lines induced by an interstellar shock compression. Such a bent structure of the B-field lines around elongated molecular clouds is compatible with the observational findings of Tahani et al (2018) and Tahani et al (2019). Large scale CO molecular line observations have suggested that NGC 6334 may be located at the shock front of the collision of two clouds (Fukui et al 2018).…”

Section: The B-field Structure Of a High-mass Star Forming Hub-filamesupporting

confidence: 78%

Dust polarized emission observations of NGC 6334

Arzoumanian¹,

Furuya²,

Hasegawa³

et al. 2021

A&A

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Context. Molecular filaments and hubs have received special attention recently thanks to new studies showing their key role in star formation. While the (column) density and velocity structures of both filaments and hubs have been carefully studied, their magnetic field (B-field) properties have yet to be characterized. Consequently, the role of B-fields in the formation and evolution of hub-filament systems is not well constrained. Aims. We aim to understand the role of the B-field and its interplay with turbulence and gravity in the dynamical evolution of the NGC 6334 filament network that harbours cluster-forming hubs and high-mass star formation. Methods. We present new observations of the dust polarized emission at 850 μm toward the 2 pc × 10 pc map of NGC 6334 at a spatial resolution of 0.09 pc obtained with the James Clerk Maxwell Telescope (JCMT) as part of the B-field In STar-forming Region Observations (BISTRO) survey. We study the distribution and dispersion of the polarized intensity (PI), the polarization fraction (PF), and the plane-of-the-sky B-field angle (χB_POS) toward the whole region, along the 10 pc-long ridge and along the sub-filaments connected to the ridge and the hubs. We derived the power spectra of the intensity and χBPOS along the ridge crest and compared them with the results obtained from simulated filaments. Results. The observations span ~3 orders of magnitude in Stokes I and PI and ~2 orders of magnitude in PF (from ~0.2 to ~ 20%). A large scatter in PI and PF is observed for a given value of I. Our analyses show a complex B-field structure when observed over the whole region (~ 10 pc); however, at smaller scales (~1 pc), χBPOS varies coherently along the crests of the filament network. The observed power spectrum of χBPOS can be well represented with a power law function with a slope of − 1.33 ± 0.23, which is ~20% shallower than that of I. We find that this result is compatible with the properties of simulated filaments and may indicate the physical processes at play in the formation and evolution of star-forming filaments. Along the sub-filaments, χBPOS rotates frombeing mostly perpendicular or randomly oriented with respect to the crests to mostly parallel as the sub-filaments merge with the ridge and hubs. This variation of the B-field structure along the sub-filaments may be tracing local velocity flows of infalling matter in the ridge and hubs. Our analysis also suggests a variation in the energy balance along the crests of these sub-filaments, from magnetically critical or supercritical at their far ends to magnetically subcritical near the ridge and hubs. We also detect an increase in PF toward the high-column density (NH2 ≳ 1023 cm−2) star cluster-forming hubs. These latter large PF values may be explained by the increase in grain alignment efficiency due to stellar radiation from the newborn stars, combined with an ordered B-field structure. Conclusions. These observational results reveal for the first time the characteristics of the small-scale (down to ~ 0.1 pc) B-field structure of a 10 pc-long hub-filament system. Our analyses show variations in the polarization properties along the sub-filaments that may be tracing the evolution of their physical properties during their interaction with the ridge and hubs. We also detect an impact of feedback from young high-mass stars on the local B-field structure and the polarization properties, which could put constraints on possible models for dust grain alignment and provide important hints as to the interplay between the star formation activity and interstellar B-fields.

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Section: The B-field Structure Of a High-mass Star Forming Hub-filamesupporting

confidence: 78%

Dust polarized emission observations of NGC 6334

Arzoumanian¹,

Furuya²,

Hasegawa³

et al. 2021

A&A

Self Cite

View full text Add to dashboard Cite

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“…These studies suggest that the the line-of-sight magnetic field in this region (including error bars) might have a maximum strength, 440 μG, that is smaller than 25% of the minimum plane-of-sky magnetic field strength in the OMC-1 region. The magnetic field strength along the line of sight is weaker than that in the plane of the sky, which is consistent with the bow-shaped magnetic field morphology suggested by Tahani et al (2019). Tahani et al (2018) estimated magnetic field strengths in the Orion A cloud using a new technique based on rotation measure.…”

Section: Mass-to-flux Ratiosupporting

confidence: 82%

The JCMT BISTRO Survey: The Distribution of Magnetic Field Strengths toward the OMC-1 Region

Hwang

Kim

Pattle

et al. 2021

ApJ

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Measurement of magnetic field strengths in a molecular cloud is essential for determining the criticality of magnetic support against gravitational collapse. In this paper, as part of the JCMT BISTRO survey, we suggest a new application of the Davis-Chandrasekhar-Fermi (DCF) method to estimate the distribution of magnetic field strengths in the OMC-1 region. We use observations of dust polarization emission at 450 and 850 μm, and C 18 O (3-2) spectral line data obtained with the JCMT. We estimate the volume density, the velocity dispersion, and the polarization angle dispersion in a box, 40″ × 40″ (5×5 pixels), which moves over the OMC-1 region. By substituting three quantities in each box with the DCF method, we get magnetic field strengths over the OMC-1 region. We note that there are very large uncertainties in the inferred field strengths, as discussed in detail in this paper. The field strengths vary from 0.8 to

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“…The LOS velocity distributions of H I and CO lines suggest compression of the molecular cloud by an expanding ISM shell associated with the Per OB2 association (Sancisi 1974;Sun et al 2006;Shimajiri et al 2019). Furthermore, the LOS B-field morphology around the molecular cloud (Tahani et al 2018; see also Tahani et al 2019) hints at deformation of the large-scale B-field by the compressed molecular cloud.…”

Section: Discussionmentioning

confidence: 86%

The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333

Doi¹,

Hasegawa

Furuya

et al. 2020

ApJ

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We present new observations of the active star formation region NGC 1333 in the Perseus molecular cloud complex from the James Clerk Maxwell Telescope B-Fields In Star-forming Region Observations (BISTRO) survey with the POL-2 instrument. The BISTRO data cover the entire NGC 1333 complex (∼1.5 pc×2 pc) at 0.02 pc resolution and spatially resolve the polarized emission from individual filamentary structures for the first time. The inferred magnetic field structure is complex as a whole, with each individual filament aligned at different position angles relative to the local field orientation. We combine the BISTRO data with low-and high-resolution data derived from Planck and interferometers to study the multiscale magnetic field structure in this region. The magnetic field morphology drastically changes below a scale of ∼1 pc and remains continuous from the scales of filaments (∼0.1 pc) to that of protostellar envelopes (∼0.005 pc or ∼1000 au). Finally, we construct simple models in which we assume that the magnetic field is always perpendicular to the long axis of the filaments. We demonstrate that the observed variation of the relative orientation between the filament axes and the magnetic field angles are well reproduced by this model, taking into account the projection effects of the magnetic field and filaments relative to the plane of the sky. These projection effects may explain the apparent complexity of the magnetic field structure observed at the resolution of BISTRO data toward the filament network.

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Could bow-shaped magnetic morphologies surround filamentary molecular clouds?

Cited by 47 publications

References 46 publications

Dust polarized emission observations of NGC 6334

Dust polarized emission observations of NGC 6334

The JCMT BISTRO Survey: The Distribution of Magnetic Field Strengths toward the OMC-1 Region

The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333

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