The JCMT BISTRO Survey: Multi-wavelength polarimetry of bright regions in NGC 2071 in the far-infrared/submillimetre range, with POL-2 and HAWC+

Abstract

Polarized dust emission is a key tracer in the study of interstellar medium and of star formation. The observed polarization, however, is a product of magnetic field structure, dust grain properties and grain alignment efficiency, as well as their variations in the line of sight, making it difficult to interpret polarization unambiguously. The comparison of polarimetry at multiple wavelengths is a possible way of mitigating this problem. We use data from HAWC+/SOFIA and from SCUBA-2/POL-2 (from the BISTRO survey) to analyse the NGC 2071 molecular cloud at 154, 214 and 850 $\mu$m. The polarization angle changes significantly with wavelength over part of NGC 2071, suggesting a change in magnetic field morphology on the line of sight as each wavelength best traces different dust populations. Other possible explanations are the existence of more than one polarization mechanism in the cloud or scattering from very large grains. The observed change of polarization fraction with wavelength, and the 214-to-154 $\mu$m polarization ratio in particular, are difficult to reproduce with current dust models under the assumption of uniform alignment efficiency. We also show that the standard procedure of using monochromatic intensity as a proxy for column density may produce spurious results at HAWC+ wavelengths. Using both long-wavelength (POL-2, 850 $\mu$m) and short-wavelength (HAWC+, $\lesssim 200\mu$m) polarimetry is key in obtaining these results. This study clearly shows the importance of multi-wavelength polarimetry at submillimeter bands to understand the dust properties of molecular clouds and the relationship between magnetic field and star formation.

Main article: 18 pages, 11 figures. Online supplemental material: 2 pages, 3 figures

References in corpus (11)

• Radiative torques: Analytical Model and Basic Properties
• SCUBA-2: iterative map-making with the Sub-Millimetre User Reduction Facility
• Early Science with SOFIA, the Stratospheric Observatory for Infrared Astronomy
• The Efficiency of Grain Alignment in Dense Interstellar Clouds: A Reassessment of Constraints from Near Infrared Polarization
• Properties of the dense core population in Orion B as seen by the Herschel Gould Belt survey
• On the radiation driven alignment of dust grains: Detection of the polarization hole in a starless core
• Grain Alignment in Starless Cores
• Low-temperature MIR to submillimeter mass absorption coefficient of interstellar dust analogues II: Mg and Fe-rich amorphous silicates
• Self-scattering of non-spherical dust grains
• The JCMT BISTRO Survey: An 850/450$\mu$m Polarization Study of NGC 2071IR in OrionB
• Far-Infrared Polarization Spectrum of the OMC-1 Star-Forming Region

Cited by in corpus (8)

• The JCMT BISTRO Survey: A Spiral Magnetic Field in a Hub-filament Structure, Monoceros R2
• The JCMT BISTRO-2 Survey: Magnetic Fields of the Massive DR21 Filament
• Physical Modeling of Dust Polarization from Magnetically Enhanced Radiative Torque (MRAT) Alignment in Protostellar Cores with POLARIS
• Probing Three-Dimensional Magnetic Fields: I -- Polarized Dust Emission
• Understanding the Multi-wavelength Thermal Dust Polarisation from the Orion Molecular Cloud in Light of the Radiative Torque Paradigm
• The origin of dust polarization in the Orion Bar
• Alignment and Rotational Disruption of Dust Grains in the Galactic Centre Revealed by Polarized Dust Emission
• Limitations of the modified blackbody fit method for determining molecular cloud properties