Helical magnetic fields in molecular clouds?

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

doi:10.1051/0004-6361/201732219

Cited by 58 publications

(115 citation statements)

References 90 publications

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“…We note that the B-field angle derived from polarization observations is the true 3D angle projected onto the POS. To understand the actual structure of the B-field and its relationship with surrounding ISM, we need to take into account their respective 3D structures (e.g., Tomisaka 2015;Planck Collaboration et al 2016b;Tahani et al 2018). Moreover, Planck and BLASTPol observations have limited spatial resolutions (>2 5) that are not sufficient to trace the B-field orientation within filaments.…”

Section: Introductionmentioning

confidence: 99%

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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Section: Introductionmentioning

confidence: 99%

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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“…Regarding the effect of magnetic helicity on dust polarization power spectra, our first intuition is conservative within the interpretation frame of the correlation between density filaments and the magnetic field in the ISM. The existence of helical magnetic fields wrapped around the main axis of molecular filaments has been observed (Bally et al 1987;Matthews & Wilson 2002;Poidevin et al 2011;Tahani et al 2018), and is suggested to regulate the dynamics of such clouds against gravitational fragmentation (Fiege & Pudritz 2000;Toci & Galli 2015).…”

Section: Introductionmentioning

confidence: 99%

Is there a left-handed magnetic field in the solar neighborhood?

Bracco

Candelaresi

Sordo

et al. 2019

A&A

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Context. The analysis of the full-sky Planck polarization data at 850 μm revealed unexpected properties of the E- and B-mode power spectra of dust emission in the interstellar medium (ISM). The positive cross-correlations over a wide range of angular scales between the total dust intensity, T, and both E and (most of all) B modes has raised new questions about the physical mechanisms that affect dust polarization, such as the Galactic magnetic field structure. This is key both to better understanding ISM dynamics and to accurately describing Galactic foregrounds to the polarization of the cosmic microwave background (CMB). In particular, in the quest to find primordial B modes of the CMB, the observed positive cross-correlation between T and B for interstellar dust requires further investigation towards parity-violating processes in the ISM. Aims. In this theoretical paper we investigate the possibility that the observed cross-correlations in the dust polarization power spectra, and specifically the one between T and B, can be related to a parity-odd quantity in the ISM such as the magnetic helicity. Methods. We produce synthetic dust polarization data, derived from 3D analytical toy models of density structures and helical magnetic fields, to compare with the E and B modes of observations. We present several models. The first is an ideal fully helical isotropic case, such as the Arnold-Beltrami-Childress field. Second, following the nowadays favored interpretation of the T–E signal in terms of the observed alignment between the magnetic field morphology and the filamentary density structure of the diffuse ISM, we design models for helical magnetic fields wrapped around cylindrical interstellar filaments. Lastly, focusing on the observed T–B correlation, we propose a new line of interpretation of the Planck observations advocating the presence of a large-scale helical component of the Galactic magnetic field in the solar neighborhood. Results. Our analysis shows that: I) the sign of magnetic helicity does not affect E and B modes for isotropic magnetic-field configurations; II) helical magnetic fields threading interstellar filaments cannot reproduce the Planck results; and III) a weak helical left-handed magnetic field structure in the solar neighborhood may explain the T–B correlation seen in the Planck data. Such a magnetic-field configuration would also account for the observed large-scale T–E correlation. Conclusions. This work suggests a new perspective for the interpretation of the dust polarization power spectra that supports the imprint of a large-scale structure of the Galactic magnetic field in the solar neighborhood.

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“…filament. More robust measurements of the field strength are needed (note the recent progress by Pattle et al 2017;Tahani et al 2018).…”

Section: Filament and Core Dynamicsmentioning

confidence: 99%

The CARMA-NRO Orion Survey: Core Emergence and Kinematics in the Orion A Cloud

Kong

Arce

Sargent

et al. 2019

ApJ

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We have investigated the formation and kinematics of sub-mm continuum cores in the Orion A molecular cloud. A comparison between sub-mm continuum and near infrared extinction shows a continuum core detection threshold of A V ∼ 5-10 mag. The threshold is similar to the star formation extinction threshold of A V ∼ 7 mag proposed by recent work, suggesting a universal star formation extinction threshold among clouds within 500 pc to the Sun. A comparison between the Orion A cloud and a massive infrared dark cloud G28.37+0.07 indicates that Orion A produces more dense gas within the extinction range 15 mag A V 60 mag. Using data from the CARMA-NRO Orion Survey, we find that dense cores in the integral-shaped filament (ISF) show sub-sonic core-to-envelope velocity dispersion that is significantly less than the local envelope line dispersion, similar to what

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Helical magnetic fields in molecular clouds?

Cited by 58 publications

References 90 publications

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

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

Is there a left-handed magnetic field in the solar neighborhood?

The CARMA-NRO Orion Survey: Core Emergence and Kinematics in the Orion A Cloud

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