Probing the role of magnetic fields in star-forming filaments: NIKA2-Pol commissioning results toward OMC-1

TL;DR

This paper demonstrates the capabilities of NIKA2-Pol in high-resolution polarization observations of star-forming regions, addressing instrumental challenges and revealing detailed magnetic field structures in OMC-1.

Contribution

It introduces a method to correct instrumental polarization effects in NIKA2-Pol data and provides new insights into magnetic field morphology at small scales in star-forming filaments.

Findings

Successful correction of instrumental polarization effects.

Detection of a small-scale hourglass magnetic field pattern near Orion-KL.

Comparison showing consistency between NIKA2-Pol and SCUBA2-Pol2 results.

Abstract

Dust polarization observations are a powerful, practical tool to probe the geometry (and to some extent, the strength) of magnetic fields in star-forming regions. In particular, Planck polarization data have revealed the importance of magnetic fields on large scales in molecular clouds. However, due to insufficient resolution, Planck observations are unable to constrain the B-field geometry on prestellar and protostellar scales. The high angular resolution of 11.7 arcsec provided by NIKA2-Pol 1.15 mm polarimetric imaging, corresponding to $\sim$ 0.02 pc at the distance of the Orion molecular cloud (OMC), makes it possible to advance our understanding of the B-field morphology in star-forming filaments and dense cores (IRAM 30m large program B-FUN). The commissioning of the NIKA2-Pol instrument has led to several challenging issues, in particular, the instrumental polarization or intensity-to-polarization (leakage) effect. In the present paper, we illustrate how this effect can be corrected for, leading to reliable exploitable data in a structured, extended source such as OMC-1. We present a statistical comparison between NIKA2-Pol and SCUBA2-Pol2 results in the OMC-1 region. We also present tentative evidence of local pinching of the B-field lines near Orion-KL, in the form of a new small-scale hourglass pattern, in addition to the larger-scale hourglass already seen by other instruments such as Pol2.