2026ApJ..1000..126B

We present near-infrared (NIR) and optical linear polarimetry toward the partially embedded cluster AFGL 6366S. The polarization ranges from 0.44% to 10.3% in NIR and from 0.16% to 11.22% in the optical bands. The position angle spans 1°-179° in both the NIR and optical bands. About 22 stars exhibit intrinsic polarization signatures. A polarization hole is evident toward the densest (∼3.4 × 10²³ cm^–2) and warmest (∼28.8 K) central cluster region. It is attributable to depolarization induced by radiative torque disruption of large grains and a modest contribution from magnetic field tangling. The local magnetic field toward the cluster's central region is significantly misaligned with both the large-scale Galactic field and the long axis of the filament present in the region. The field morphology wraps around two dense molecular clumps with radii 0.34 and 0.22 pc and N(H₂) = (7.9 ± 1.1) × 10²² cm^–2 and (4.3 ± 0.5) × 10²² cm^–2, respectively. The clumps are embedded in the filamentary structure and represent locally accelerated stages of mass accumulation. Gravitationally driven mass flows, largely perpendicular to the local magnetic field, produce a U-shaped field curvature across the filament axis. The plane-of-sky magnetic field strengths toward the two clumps are 447.91 ± 83.81 μG and 396.66 ± 73.64 μG. The corresponding mass-to-flux ratios (λ ∼ 1.34 and 0.82) indicate that one clump is magnetically supercritical and the other is subcritical. The Alfvén Mach numbers ${{ \mathcal M }}_{{\rm{A}}}$ ∼ 0.395 and 0.393 indicate that both clumps are in the sub-Alfvénic state.