JCMT BISTRO Survey: Magnetic Fields within the Hub-filament Structure in IC 5146

Wang, Jia-Wei, Lai, Shih-Ping, Eswaraiah, Chakali, Pattle, Kate, Francesco, James Di, Ward-Thompson, Derek orcid iconORCID: 0000-0003-1140-2761, Eyres, Stewart Paul shore, Kirk, Jason Matthew orcid iconORCID: 0000-0002-4552-7477 and Konyves, Vera (2019) JCMT BISTRO Survey: Magnetic Fields within the Hub-filament Structure in IC 5146. The Astrophysical Journal, 876 (1). ISSN 0004-637X

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Official URL: https://doi.org/10.3847/1538-4357/ab13a2


We present the 850 μm polarization observations toward the IC 5146 filamentary cloud taken using the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) and its associated polarimeter (POL-2), mounted on the James Clerk Maxwell Telescope, as part of the B-fields In STar forming Regions Observations. This work is aimed at revealing the magnetic field morphology within a core-scale (lesssim1.0 pc) hub-filament structure (HFS) located at the end of a parsec-scale filament. To investigate whether the observed polarization traces the magnetic field in the HFS, we analyze the dependence between the observed polarization fraction and total intensity using a Bayesian approach with the polarization fraction described by the Rice likelihood function, which can correctly describe the probability density function of the observed polarization fraction for low signal-to-noise ratio data. We find a power-law dependence between the polarization fraction and total intensity with an index of 0.56 in A V ~ 20–300 mag regions, suggesting that the dust grains in these dense regions can still be aligned with magnetic fields in the IC 5146 regions. Our polarization maps reveal a curved magnetic field, possibly dragged by the contraction along the parsec-scale filament. We further obtain a magnetic field strength of 0.5 ± 0.2 mG toward the central hub using the Davis–Chandrasekhar–Fermi method, corresponding to a mass-to-flux criticality of ~1.3 ± 0.4 and an Alfvénic Mach number of <0.6. These results suggest that gravity and magnetic field are currently of comparable importance in the HFS and that turbulence is less important.

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