HAWC+/SOFIA Multiwavelength Polarimetric Observations of OMC-1

TL;DR

This study presents multiwavelength polarimetric maps of OMC-1, revealing magnetic field structures at different scales and their relation to star formation and explosive outflows, using SOFIA's HAWC+ instrument.

Contribution

First multiwavelength polarimetric analysis of OMC-1 revealing wavelength-dependent magnetic field morphologies and their connection to star formation and outflow dynamics.

Findings

Magnetic field shows hourglass shape at longer wavelengths, consistent with magnetically-regulated star formation.

Shorter wavelengths reveal magnetic fields aligned with the BN/KL outflow structure.

Magnetic field strength varies, dominated by explosion near the center and in equilibrium farther out.

Abstract

We report new polarimetric and photometric maps of the massive star-forming region OMC-1 using the HAWC+ instrument on the Stratospheric Observatory for Infrared Astronomy (SOFIA). We present continuum polarimetric and photometric measurements of this region at 53, 89, 154, and 214 microns at angular resolutions of 5.1, 7.9, 14.0, and 18.7 arcseconds for the four bands, respectively. The photometric maps enable the computation of improved SEDs for the region. We find that at the longer wavelengths, the inferred magnetic field configuration matches the `hourglass' configuration seen in previous studies, indicating magnetically-regulated star formation. The field morphology differs at the shorter wavelengths. The magnetic field inferred at these wavelengths traces the bipolar structure of the explosive Becklin-Neugebauer (BN)/Kleinman-Low (KL) outflow emerging from OMC-1 behind the Orion Nebula. Using statistical methods to estimate the field strength in the region, we find that the explosion dominates the magnetic field near the center of the feature. Farther out, the magnetic field is close to energetic equilibrium with the ejecta and may be providing confinement to the explosion. The correlation between polarization fraction and the local polarization angle dispersion indicates that the depolarization as a function of unpolarized intensity is a result of intrinsic field geometry as opposed to decreases in grain alignment efficiency in denser regions.