Speaker
Description
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 arcsec provided by NIKA2-Pol 1.2 mm polarimetric imaging,
corresponding to ∼0.02 pc at the distance of the Orion 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
which will be briefly addressed in the first part of the proposed presentation. In particular,
we will present our current understanding of the instrumental polarization or intensity-topolarization
"leakage" effect with NIKA2-Pol. We will show how this effect can be
corrected for, leading to reliable exploitable data in a structured extended source such as
OMC-1. We will present a statistical comparison between NIKA2-Pol and SCUBA2-Pol2
results in the OMC-1 region. We will also present tentative evidence of a local hourglass
pattern centered on Orion-KL, in addition to a large-scale hourglass already seen by other
instruments such as Pol2. Finally, we will discuss new estimates of the B-field strength in
the OMC-1 region based on, e.g., the Davis-Chandrasekhar-Fermi (DCF) and structurefunction
methods applied to NIKA2-Pol data, along with their associated limitations.
