Dust spectrum and polarisation at 850 m in the massive IRDC G035.39-00.33

Abstract

This study combines JCMT SCUBA‑2/POL‑2 observations at 850 μm with Planck 850 μm data to map polarisation properties of the filamentary cloud G035.39‑00.33, complemented by Herschel and SCUBA‑2 intensity data across multiple bands to derive column densities and dust temperature. The filament shows peak column densities around N(H₂) ≈ 7×10²² cm⁻², dust temperatures ≈ 12 K, and mass ~4300 M☉. The dust opacity spectral index is β ≈ 1.9; the ratio τ(250 μm)/τ(J) ∼ 2.5×10⁻³—more than four times typical diffuse‐ISM values. The polarisation fraction declines with increasing column density, reaching ~1% at the densest regions. Observations suggest grain realignment loss above densities ~10⁴ cm⁻³ or variable radiative torque alignment. Interpretations are limited by SCUBA‑2 spatial filtering and uncertainties in magnetic field geometry. Overall, results indicate dust evolution and low polarisation in dense filament cores.