Observations of magnetic fields surrounding LkH$\alpha$ 101 taken by the BISTRO survey with JCMT-POL-2

Abstract

We report the first high spatial resolution measurement of magnetic fields surrounding LkH$\alpha$ 101, a part of the Auriga-California molecular cloud. The observations were taken with the POL-2 polarimeter on the James Clerk Maxwell Telescope within the framework of the B-fields In Star-forming Region Observations (BISTRO) survey. Observed polarization of thermal dust emission at 850 $\mu$m is found to be mostly associated with the red-shifted gas component of the cloud. The magnetic field displays a relatively complex morphology. Two variants of the Davis-Chandrasekhar-Fermi method, unsharp masking and structure function, are used to calculate the strength of magnetic fields in the plane of the sky, yielding a similar result of $B_{\mathrm{POS}}\sim 115$ $\mu$G. The mass-to-magnetic-flux ratio in critical value units, $\lambda \sim 0.3$, is the smallest among the values obtained for other regions surveyed by POL-2. This implies that the LkH$\alpha$ 101 region is sub-critical and the magnetic field is strong enough to prevent gravitational collapse. The inferred $\delta B/B_0\sim 0.3$ implies that the large scale component of the magnetic field dominates the turbulent one. The variation of the polarization fraction with total emission intensity can be fitted by a power-law with an index of $\alpha =0.82\pm 0.03$, which lies in the range previously reported for molecular clouds. We find that the polarization fraction decreases rapidly with proximity to the only early B star (LkH$\alpha$ 101) in the region. The magnetic field tangling and the joint effect of grain alignment and rotational disruption by radiative torques are potential of explaining such a decreasing trend.

25 pages, 19 figures, Accepted for publication in The Astrophysical Journal

References in corpus (23)

• Radiative torques: Analytical Model and Basic Properties
• Planck intermediate results. XIX. An overview of the polarized thermal emission from Galactic dust
• Tracing Magnetic Fields with Aligned Grains
• SCUBA-2: iterative map-making with the Sub-Millimetre User Reduction Facility
• A Compendium of Distances to Molecular Clouds in the Star Formation Handbook
• The Efficiency of Grain Alignment in Dense Interstellar Clouds: A Reassessment of Constraints from Near Infrared Polarization
• A Galactic-scale gas wave in the Solar Neighborhood
• The JCMT BISTRO Survey: The magnetic field strength in the Orion A filament
• ALMA observations of dust polarization and molecular line emission from the Class 0 protostellar source Serpens SMM1
• On the radiation driven alignment of dust grains: Detection of the polarization hole in a starless core
• Unveiling the Role of the Magnetic Field at the Smallest Scales of Star Formation
• Magnetized filamentary gas flows feeding the young embedded cluster in Serpens South
• Submillimeter and Far-Infrared Polarimetric Observations of Magnetic Fields in Star-Forming Regions
• Grain Alignment in Starless Cores
• Polarization measurements analysis I. Impact of the full covariance matrix on polarization fraction and angle measurements
• The JCMT BISTRO Survey: The Magnetic Field of the Barnard 1 Star-Forming Region
• The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333
• The JCMT BISTRO Survey: The Magnetic Field In The Starless Core $\rho$ Ophiuchus C
• Dust Polarization Toward Embedded Protostars in Ophiuchus with ALMA. II. IRAS 16293-2422
• A statistical analysis of dust polarization properties in ALMA observations of Class 0 protostellar cores
• Filament L1482 in the California molecular cloud
• Understanding polarized dust emission from $\rho$ Ophiuchi A in light of grain alignment and disruption by radiative torques
• The JCMT Gould Belt Survey: A First Look at the Auriga-California Molecular Cloud with SCUBA-2

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• Magnetic fields in star formation: a complete compilation of all the DCF estimations
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• The JCMT BISTRO Survey: A Spiral Magnetic Field in a Hub-filament Structure, Monoceros R2
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• Studying magnetic fields and dust in M17 using polarized thermal dust emission observed by SOFIA/HAWC+
• SOFIA observations of 30 Doradus: II -- Magnetic fields and large scale gas kinematics
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• SOFIA observations of 30 Doradus: I -- Far-Infrared dust polarization and implications for grain alignment and disruption by radiative torques
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• Mapping and characterizing magnetic fields in the Rho Ophiuchus-A molecular cloud with SOFIA/HAWC$+$
• Synthetic Modelling of Polarized Dust Emission in Intermediate-Mass YSOs: I: Constraining the Role of Iron Inclusions and Inelastic Relaxation on Grain Alignment with ALMA Polarization
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• The Formation of Filaments and Dense cores in the Cocoon Nebula (IC~5146)
• Dust destruction by the supernova remnant forward shock in a turbulent interstellar medium
• Far-infrared Polarization of the Supernova Remnant Cassiopeia A with SOFIA HAWC+