Maps of Magnetic Field Strength in the OMC-1 using HAWC+ FIR Polarimetric data

TL;DR

This study maps the magnetic field strength in OMC-1 using FIR polarimetry data and the Davis-Chandrasekhar-Fermi method, revealing the 3D magnetic field structure and its role in star formation.

Contribution

It applies a multi-wavelength polarimetric analysis combined with Zeeman measurements to map the 3D magnetic field in OMC-1 for the first time.

Findings

Magnetic field strengths up to 2 mG near BN/KL.

The OMC-1 bar shows magnetic fields of a few hundred microgauss.

Maps of mass-to-flux ratio indicate regions of sub- and super-criticality.

Abstract

Far-infrared (FIR) dust polarimetry enables the study of interstellar magnetic fields via tracing of the polarized emission from dust grains that are partially aligned with the direction of the field. The advent of high quality polarimetric data has permitted the use of statistical methods to extract both the direction and magnitude of the magnetic field. In this work, the Davis-Chandrasekhar-Fermi technique is used to make maps of the plane-of-sky (POS) component of the magnetic field in the Orion Molecular Cloud (OMC-1) by combining polarization maps at 53, 89, 154 and 214 \micron\ from HAWC+/SOFIA with maps of density and velocity dispersion. In addition, maps of the local dispersion of polarization angles are used in conjuction with Zeeman measurements to estimate a map of the strength of the line-of-sight (LOS) component of the field. Combining these maps, information about the three-dimensional magnetic field configuration (integrated along the line-of-sight) is inferred over the OMC-1 region. POS magnetic field strengths of up to 2 mG are observed near the BN/KL object, while the OMC-1 bar shows strengths of up to a few hundred $\mu$G. These estimates of the magnetic field components are used to produce maps of the mass-to-magnetic flux ratio ($M/\Phi$) -- a metric for probing the conditions for star formation in molecular clouds -- and determine regions of sub- and super-criticality in OMC-1. Such maps can provide invaluable input and comparison to MHD simulations of star formation processes in filamentary structures of molecular clouds.