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

We report the SOFIA/HAWC+ band D (154$\,μ$m) and E (214$\,μ$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$\,μ$m and 214$\,μ$m amounts to 202$\,μ$G and 261$\,μ$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, $T$.