Near-infrared Polarization From Unresolved Disks Around Brown Dwarfs And Young Stellar Objects

Near-infrared (NIR) polarimetry, using the Mimir instrument on the Perkins Telescope Observatory, was used to examine two brown dwarf (BD) and two young stellar object (YSO) disk systems in Heiles Cloud 2 (HCl2) in Taurus. 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, intrinsic polarization was detected from all of the BD (ITG 17, 2M0444) and YSO (ITG 15, ITG 25) disk systems. Three of the inferred disk orientations (for ITG 15, ITG 17, ITG 25) are parallel, even across 0.25 pc of separation. For all four systems, the local magnetic field is perpendicular to the intrinsic NIR polarizations and so to the disk angular momenta. One BD, ITG 17, shows close agreement between disk orientations inferred here and from ALMA imaging. It is in a 5,200 au wide binary with the ITG 15 YSO disk system. The other BD, 2M0444, shows weaker intrinsic NIR polarization and a roughly 45 degree difference between NIR and ALMA resolved continuum orientations. The parallel disk orientations argue for shared specific angular momentum during quiescent formation, potentially constraining the role of magnetic fields during their star forming periods.

This study was supported by grant AST 18-14531 from NSF/MPS to Boston University.