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

Jia-Wei Wang , Shih-Ping Lai , Chakali Eswaraiah , Kate Pattle , James Di Francesco , Doug Johnstone , Patrick M. Koch , Tie Liu , Motohide Tamura , Ray S. Furuya , Takashi Onaka , Derek Ward-Thompson , Archana Soam , Kee-Tae Kim , Chang Won Lee , Chin-Fei Lee , Steve Mairs , Doris Arzoumanian , Gwanjeong Kim , Thiem Hoang , Jihye Hwang , Sheng-Yuan Liu , David Berry , Pierre Bastien , Tetsuo Hasegawa , Woojin Kwon , Keping Qiu , Philippe André , Yusuke Aso , Do-Young Byun , Huei-Ru Chen , Michael C. Chen , Wen Ping Chen , Tao-Chung Ching , Jungyeon Cho , Minho Choi , Antonio Chrysostomou , Eun Jung Chung , Simon Coudé , Yasuo Doi , C. Darren Dowell , Emily Drabek-Maunder , Hao-Yuan Duan , Stewart P. S. Eyres , Sam Falle , Lapo Fanciullo , Jason Fiege , Erica Franzmann , Per Friberg , Rachel K. Friesen , Gary Fuller , Tim Gledhill , Sarah F. Graves , Jane S. Greaves , Matt J. Griffin , Qilao Gu , Ilseung Han , Jennifer Hatchell , Saeko S. Hayashi , Wayne Holland , Martin Houde , Tsuyoshi Inoue , Shu-Ichiro Inutsuka , Kazunari Iwasaki , Il-Gyo Jeong , Yoshihiro Kanamori , Ji-Hyun Kang , Miju Kang , Sung-Ju Kang , Akimasa Kataoka , Koji S. Kawabata , Francisca Kemper , Jongsoo Kim , Kyoung Hee Kim , Mi-Ryang Kim , Shinyoung Kim , Jason M. Kirk , Masato I. N. Kobayashi , Vera Konyves , Jungmi Kwon , Kevin M. Lacaille , Hyeseung Lee , Jeong-Eun Lee , Sang-Sung Lee , Yong-Hee Lee , Dalei Li , Di Li , Hua-Bai Li , Hong-Li Liu , Junhao Liu , A. -Ran Lyo , Masafumi Matsumura , Brenda C. Matthews , Gerald H. Moriarty-Schieven , Tetsuya Nagata , Fumitaka Nakamura , Hiroyuki Nakanishi , Nagayoshi Ohashi , Geumsook Park , Harriet Parsons , Enzo Pascale , Nicolas Peretto , Andy Pon , Tae-Soo Pyo , Lei Qian , Ramprasad Rao , Mark G. Rawlings , Brendan Retter , John Richer , Andrew Rigby , Jean-François Robitaille (1) , Sarah Sadavoy , Hiro Saito , Giorgio Savini , Anna M. M. Scaife , Masumichi Seta , Hiroko Shinnaga , Ya-Wen Tang , Kohji Tomisaka , Yusuke Tsukamoto , Sven van Loo , Hongchi Wang , Anthony P. Whitworth , Hsi-Wei Yen , Hyunju Yoo , Jinghua Yuan , Hyeong-Sik Yun , Tetsuya Zenko , Chuan-Peng Zhang , Guoyin Zhang , Ya-Peng Zhang , Jianjun Zhou , Lei Zhu

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

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 (≲1.0 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.

Keywords: ISM: individual objects: IC 5146; ISM: magnetic fields; ISM: structure; polarization; radio continuum: ISM; stars: formation; Astrophysics - Astrophysics of Galaxies

Domains: Sciences of the Universe [physics]

Jia-Wei Wang, Shih-Ping Lai, Chakali Eswaraiah, Kate Pattle, James Di Francesco, et al.. JCMT BISTRO Survey: Magnetic Fields within the Hub-filament Structure in IC 5146. The Astrophysical Journal, 2019, 876, ⟨10.3847/1538-4357/ab13a2⟩. ⟨insu-03703878⟩