Unveiling an Hourglass-Shaped Magnetic Field toward IRDC G351.77-0.53

TL;DR

This study reveals an hourglass-shaped magnetic field in the IRDC G351.77-0.53, highlighting magnetic regulation in star formation through polarimetric observations and energy analysis.

Contribution

It provides the first detailed magnetic field morphology of G351.77-0.53, demonstrating magnetic influence on cloud dynamics and star formation processes.

Findings

Hourglass magnetic field observed toward clump c1.

Magnetic field strength estimated at ~147 μG, up to 0.8 mG in c1.

The filament is magnetically transcritical, with magnetic and gravitational energies comparable.

Abstract

We present the SOFIA/HAWC+ 214 $\mu$m polarimetric observations toward the infrared dark cloud G351.77-0.53 (hereafter G351), complemented by existing multi-wavelength 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-of-the-sky magnetic field lines from Planck observations are predominantly oriented perpendicular to the filament's major axis. Magnetic field orientations from SOFIA/HAWC+ 214 $\mu$m observations reveal distinct hourglass-shaped field configuration toward c1, while the field lines remain perpendicular to the rest of the filament. Using the Davis-Chandrasekhar-Fermi method, we estimate a mean plane-of-the-sky magnetic field strength of $\sim$147 $\pm$ 60 $\mu$G in the G351 filament, with values reaching $\sim$0.8 mG toward c1. The mass-to-flux ratio analysis indicates that 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.