Near-Infrared Polarization from Unresolved Disks Around Brown Dwarfs and Young Stellar Objects

TL;DR

This study used near-infrared polarimetry to detect and analyze the intrinsic polarization of unresolved disks around brown dwarfs and young stellar objects, revealing disk orientations and their relation to magnetic fields.

Contribution

It demonstrates the effectiveness of NIR polarimetry in identifying disk orientations and their environmental context around brown dwarfs and YSOs, including a binary system.

Findings

Intrinsic polarization detected in one BD and two YSOs

Disk orientations are aligned with each other and perpendicular to magnetic fields

System's multiplicity and disk properties suggest formation in a misaligned magnetic environment

Abstract

Wide-field near-infrared (NIR) polarimetry was used to examine disk systems around two brown dwarfs (BD) and two young stellar objects (YSO) embedded in the Heiles Cloud 2 (HCl2) dark molecular cloud in Taurus as well as numerous stars located behind HCl2. Inclined disks exhibit intrinsic NIR polarization due to scattering of photospheric light which is detectable even for unresolved systems. After removing polarization contributions from magnetically aligned dust in HCl2 determined from the background star information, significant intrinsic polarization was detected from the disk systems of of one BD (ITG~17) and both YSOs (ITG~15, ITG~25), but not from the other BD (2M0444). The ITG~17 BD shows good agreement of the disk orientation inferred from the NIR and from published ALMA dust continuum imaging. ITG~17 was also found to reside in a 5,200~au wide binary (or hierarchical quad star system) with the ITG~15 YSO disk system. The inferred disk orientations from the NIR for ITG~15 and ITG~17 are parallel to each other and perpendicular to the local magnetic field direction. The multiplicity of the system and the large BD disk nature could have resulted from formation in an environment characterized by misalignment of the magnetic field and the protostellar disks.