Unveiling an hourglass-shaped magnetic field toward IRDC G351.77-0.53

We present the SOFIA/HAWC + 214 μm polarimetric observationstoward the infrared dark cloud G351.77-0.53 (hereafter G351), complemented by existing multiwavelength data sets. Infrared excess from the embedded sources indicate ongoing star formation activity in the cloud. The G351 cloud hosts two prominent star-forming clumps i.e. c1 and c2. The plane-ofthe-sky magnetic field lines from Planck observations are predominantly oriented perpendicular to the filament’s major axis. Magnetic field orientations from SOFIA/HAWC + 214 μm observations reveal distinct hourglass-shaped field configuration toward c1, while the field lines remain perpendicular to the rest of the filament. Using the Davis-ChandrasekharFermi method, we estimate a mean plane-of-the-sky magnetic field strength of ∼147 ± 60 μG in the G351 filament, with valuesreaching ∼0.8 mG toward c1. The mass-to-flux ratio analysisindicatesthat the filament is magnetically transcritical, where the gravitational and magnetic field energies are comparable. The hourglass-shaped magnetic field observed toward c1 could result from magnetically regulated gravitational collapse, the alignment of converging sub-filaments with the magnetic field, or a combination of both processes. The energy budget analysis further indicates that magnetic fields play an important role in governing the cloud’s gas dynamics, followed by contributions from turbulence and gravity.