Balloon-Borne Submillimeter Polarimetry of the Vela C Molecular Cloud: Systematic Dependence of Polarization Fraction on Column Density and Local Polarization-Angle Dispersion

Fissel, Laura M.; Angilè, Francesco E.; Ashton, Peter; Benton, S. J.; Devlin, Mark J.; Dober, Bradley; Fukui, Y.; Galitzki, Nicholas; Gandilo, N. N.; Klein, J.; Korotkov, Andrei; Li, Zhi-Yun; Martín, P. G.; Matthews, Tristan G.; Nakamura, Fúmitaka; Netterfield, C. B.; Novak, Giles; Pascale, Enzo; Poidevin, F.; Santos, Fábio P.; Savini, G.; Scott, Douglas; Shariff, J. A.; Soler, J. D.; Thomas, Nicholas E.; Tucker, C.; Tucker, Gregory S.; Ward-Thompson, Derek

doi:10.3847/0004-637x/824/2/134

Cited by 110 publications

(186 citation statements)

References 58 publications

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“…Fiege & Pudritz 2000;Soler et al 2013) and has some support from observations. BLASTPol (Fissel et al 2016) reveals a flat spectrum of polarization fraction between 250−500 µm for Vela C molecular cloud (Gandilo et al 2016), suggesting the radiative environment of the gas is not playing a huge role in this region. From previously published starlight polarization data in molecular clouds, Soler et al (2016) also concluded that the magnetic field structure is more important in controlling polarization fraction and dispersion than grain alignment efficiency.…”

Section: Derivation Of Polarized Emissionmentioning

confidence: 99%

“…Since most polarization observations of molecular clouds trace only dense gas, and the diffuse background has been removed from the observed thermal emission (e.g. Li et al 2006;Fissel et al 2016), applying a density limit makes the simulated polarization maps more comparable to observations (see e.g. Falceta- Gonçalves et al 2008).…”

Section: Derivation Of Polarized Emissionmentioning

confidence: 99%

“…Benoît et al 2004;Planck Collaboration Int. XX 2015;Fissel et al 2016) and ∼ 1 % in dense cores (e.g. Ward-Thompson et al 2000;Matthews et al 2009;Tang et al 2009;Hull et al 2014).…”

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confidence: 99%

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Change of Magnetic Field-Gas Alignment at the Gravity-Driven Alfvénic Transition in Molecular Clouds: Implications for Dust Polarization Observations

Chen

King

2016

ApJ

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Diffuse striations in molecular clouds are preferentially aligned with local magnetic fields whereas dense filaments tend to be perpendicular to them. When and why this transition occurs remain uncertain. To explore the physics behind this transition, we compute the histogram of relative orientation (HRO) between the density gradient and the magnetic field in 3D MHD simulations of prestellar core formation in shock-compressed regions within GMCs. We find that, in the magnetically-dominated (sub-Alfvénic) post-shock region, the gas structure is preferentially aligned with the local magnetic field. For overdense sub-regions with super-Alfvénic gas, their elongation becomes preferentially perpendicular to the local magnetic field instead. The transition occurs when self-gravitating gas gains enough kinetic energy from the gravitational acceleration to overcome the magnetic support against the cross-field contraction, which results in a power-law increase of the field strength with density. Similar results can be drawn from HROs in projected 2D maps with integrated column densities and synthetic polarized dust emission. We quantitatively analyze our simulated polarization properties, and interpret the reduced polarization fraction at high column densities as the result of increased distortion of magnetic field directions in trans-or super-Alfvénic gas. Furthermore, we introduce measures of the inclination and tangledness of the magnetic field along the line of sight as the controlling factors of the polarization fraction. Observations of the polarization fraction and angle dispersion can therefore be utilized in studying local magnetic field morphology in star-forming regions.

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Section: Derivation Of Polarized Emissionmentioning

confidence: 99%

Section: Derivation Of Polarized Emissionmentioning

confidence: 99%

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Change of Magnetic Field-Gas Alignment at the Gravity-Driven Alfvénic Transition in Molecular Clouds: Implications for Dust Polarization Observations

Chen

King

2016

ApJ

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“…Optical polarization and (sub)millimeter observations have revealed that magnetic fields at large (1 pc) scales tend to be relatively uniform and correlated with the molecular cloud morphology (Pereyra & Magalhães 2004;Li et al 2006;Alves et al 2008;Goldsmith et al 2008;Franco et al 2010;Palmeirim et al 2013;Fissel et al 2016). The magnetic fields seem to have a bimodal behavior, where the field is either parallel or perpendicular to the major axis of the cloud (Li et al 2009(Li et al , 2013Soler et al 2013;Planck Collaboration et al 2016a.…”

Section: Magnetic Fields At Different Spatial Scalesmentioning

confidence: 99%

ALMA Observations of Dust Polarization and Molecular Line Emission from the Class 0 Protostellar Source Serpens SMM1

Hull

Girart

Tychoniec

et al. 2017

ApJ

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113

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We present high angular resolution dust polarization and molecular line observations carried out with the Atacama Large Millimeter/submillimeter Array (ALMA) toward the Class 0 protostar Serpens SMM1. By complementing these observations with new polarization observations from the Submillimeter Array (SMA) and archival data from the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and the James Clerk Maxwell Telescopes (JCMT), we can compare the magnetic field orientations at different spatial scales. We find major changes in the magnetic field orientation between large (∼0.1 pc) scales-where the magnetic field is oriented E-W, perpendicular to the major axis of the dusty filament where SMM1 is embedded-and the intermediate and small scales probed by CARMA (∼1000 au resolution), the SMA (∼350 au resolution), and ALMA (∼140 au resolution). The ALMA maps reveal that the redshifted lobe of the bipolar outflow is shaping the magnetic field in SMM1 on the southeast side of the source; however, on the northwestern side and elsewhere in the source, lowvelocity shocks may be causing the observed chaotic magnetic field pattern. High-spatial-resolution continuum and spectral-line observations also reveal a tight (∼130 au) protobinary system in SMM1-b, the eastern component of which is launching an extremely high-velocity, one-sided jet visible in both =  (J CO 2 1) and =  (J SiO 5 4); however, that jet does not appear to be shaping the magnetic field. These observations show that with the sensitivity and resolution of ALMA, we can now begin to understand the role that feedback (e.g., from protostellar outflows) plays in shaping the magnetic field in very young, star-forming sources like SMM1.

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“…However, it is at too low resolution (∼4 arcmin at 857 GHz; Planck HFI Core Team 2011) to study the detailed cloud geometries in star-forming regions on the necessary scale of prestellar cores and protostars. At somewhat better resolution (30 arcsec at 250 μm; Pascale et al 2008), the BLASTPol balloon-borne polarimeter has mapped a limited number of star-forming regions in great detail (e.g., Matthews et al 2014;Fissel 2015;Fissel et al 2016). …”

Section: Observing Magnetic Fieldsmentioning

confidence: 99%

First Results from BISTRO: A SCUBA-2 Polarimeter Survey of the Gould Belt

Ward-Thompson

Pattle

Bastien

et al. 2017

ApJ

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We present the first results from the B-fields In STar-forming Region Observations (BISTRO) survey, using the Sub-millimetre Common-User Bolometer Array2 camera, with its associated polarimeter (POL-2), on the James Clerk Maxwell Telescope in Hawaii. We discuss the survey's aims and objectives. We describe the rationale behind the survey, and the questions thatthe survey will aim to answer. The most important of these is the role of magnetic fields in the star formation process on the scale of individual filaments and cores in dense regions. We describe the data acquisition and reduction processes for POL-2, demonstrating both repeatability and consistency with previous data. We present a first-look analysis of the first results from the BISTRO survey in the OMC1 region. We see that the magnetic field lies approximately perpendicular to the famous "integral filament" in the densest regions of that filament. Furthermore, we see an "hourglass" magnetic field morphology extending beyond the densest region of the integral filament into the less-dense surrounding material, and discuss possible causes for this. We also discuss the more complex morphology seen along the Orion Bar region. We examine the morphology of the field along the lower-density northeastern filament. We find consistency with previous theoretical models that predict magnetic fields lying parallel to low-density, non-self-gravitating filaments, and perpendicular to higher-density, self-gravitating filaments.

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Balloon-Borne Submillimeter Polarimetry of the Vela C Molecular Cloud: Systematic Dependence of Polarization Fraction on Column Density and Local Polarization-Angle Dispersion

Cited by 110 publications

References 58 publications

Change of Magnetic Field-Gas Alignment at the Gravity-Driven Alfvénic Transition in Molecular Clouds: Implications for Dust Polarization Observations

Change of Magnetic Field-Gas Alignment at the Gravity-Driven Alfvénic Transition in Molecular Clouds: Implications for Dust Polarization Observations

ALMA Observations of Dust Polarization and Molecular Line Emission from the Class 0 Protostellar Source Serpens SMM1

First Results from BISTRO: A SCUBA-2 Polarimeter Survey of the Gould Belt

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