Magnetic field structure of OMC-3 in the far infrared revealed by SOFIA/HAWC+

Abstract

We report the SOFIA/HAWC+ band D (154$\mu$m) and E (214$\mu$m) polarimetric observations of the filamentary structure OMC-3 that is part of the Orion molecular cloud. The polarization pattern is uniform for both bands and parallel to the filament structure. The polarization degree decreases toward regions with high intensity for both bands, revealing a so called "polarization hole." We identified an optical depth effect in which polarized emission and extinction act as counteracting mechanisms as a potential contributor to this phenomenon. Assuming that the detected polarization is caused by the emission of magnetically aligned non-spherical dust grains, the inferred magnetic field is uniform and oriented perpendicular to the filament. The magnetic field strength derived from the polarization patterns at 154$\mu$m and 214$\mu$m amounts to 202$\mu$G and 261$\mu$G, respectively. The derived magnetic field direction is consistent with that derived from previous polarimetric observations in the far infrared and submillimeter (submm) wavelength range. Investigating the far-infrared polarization spectrum derived from the SOFIA/HAWC+ observations, we do not find a clear correlation between the polarization spectrum and cloud properties, namely, the column density, $N(H_2$), and temperature, $T$.

arXiv commentAccepted for publication in A&A, 13 pages, 13 figures

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• Probing Three-Dimensional Magnetic Fields: I -- Polarized Dust Emission
• Parsec-scale cosmic-ray ionisation rate in Orion
• The Role of Magnetic Fields in the Stability and Fragmentation of Filamentary Molecular Clouds: Two Case Studies at OMC-3 and OMC-4
• Magnetic Field of Molecular Gas Measured with the Velocity Gradient Technique I. Orion A
• A Tale of Three: Magnetic Fields along the Orion Integral-Shaped Filament as Revealed by JCMT BISTRO survey
• Limitations of the modified blackbody fit method for determining molecular cloud properties
• Wavelength-dependent far-infrared polarization of HL Tau observed with SOFIA/HAWC+