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

Wang, J. -W.; Lai, S. -P.; Eswaraiah, C.; Pattle, K.; Francesco, J. D.; Johnstone, D.; Koch, P. M.; Liu, T.; Tamura, M.; Furuya, R. S.; Onaka, T.; Ward-Thompson, D.; Soam, A.; Kim, K. -T.; Lee, C. W.; Lee, C. -F.; Mairs, S.; Arzoumanian, D.; Kim, G.; Hoang, T.; Hwang, J.; Liu, S. -Y.; Berry, D.; Bastien, P.; Hasegawa, T.; Kwon, W.; Qiu, K.; Andre, P.; Aso, Y.; Byun, D. -Y.; Chen, H. -R.; Chen, M. C.; Chen, W. P.; Ching, T. -C.; Cho, J.; Choi, M.; Chrysostomou, A.; Chung, E. J.; Coude, S.; Doi, Y.; Dowell, C. D.; Drabek-Maunder, E.; Duan, H. -Y.; Eyres, S. P. S.; Falle, S.; Fanciullo, L.; Fiege, J.; Franzmann, E.; Friberg, P.; Friesen, R. K.; Fuller, G.; Gledhill, T.; Graves, S. F.; Greaves, J. S.; Griffin, M. J.; Gu, Q.; Han, I.; Hatchell, J.; Hayashi, S. S.; Holland, W.; Houde, M.; Inoue, T.; Inutsuka, S. -I.; Iwasaki, K.; Jeong, I. -G.; Kanamori, Y.; Kang, J. -H.; Kang, M.; Kang, S. -J.; Kataoka, A.; Kawabata, K. S.; Kemper, F.; Kim, J.; Kim, K. H.; Kim, M. -R.; Kim, S.; Kirk, J. M.; Kobayashi, M. I. N.; Konyves, V.; Kwon, J.; Lacaille, K. M.; Lee, H.; Lee, J. -E.; Lee, S. -S.; Lee, Y. -H.; Li, D.; Li, D.; H. -B., Li; Liu, H. -L.; Liu, J.; Lyo, A. -R.; Matsumura, M.; Matthews, B. C.; Moriarty-Schieven, G. H.; Nagata, T.; Nakamura, F.; Nakanishi, H.; Ohashi, N.; Park, G.; Parsons, H.; Pascale, E.; Peretto, N.; Pon, A.; Pyo, T. -S.; Qian, L.; Rao, R.; Rawlings, M. G.; Retter, B.; Richer, J.; Rigby, A.; Robitaille, J. -F.; Sadavoy, S.; Saito, H.; Savini, G.; Scaife, A. M. M.; Seta, M.; Shinnaga, H.; Tang, Y. -W.; Tomisaka, K.; Tsukamoto, Y.; Loo, S. V.; Wang, H.; Whitworth, A. P.; Yen, H. -W.; Yoo, H.; Yuan, J.; Yun, H. -S.; Zenko, T.; Zhang, C. -P.; Zhang, G.; Zhang, Y. -P.; Zhou, J.; Zhu, L.

doi:10.3847/1538-4357/ab13a2

We present the 850 mu m 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 (less than or similar to 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) similar to 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 similar to 1.3 +/- 0.4 and an Alfvenic 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.

JCMT BISTRO Survey: Magnetic Fields within the Hub-filament Structure in IC 5146 / Wang, J.-W., Lai, S.-P., Eswaraiah, C., Pattle, K., Francesco, J.D., Johnstone, D., Koch, P.M., Liu, T., Tamura, M., Furuya, R.S., Onaka, T., Ward-Thompson, D., Soam, A., Kim, K.-T., Lee, C.W., Lee, C.-F., Mairs, S., Arzoumanian, D., Kim, G., Hoang, T., et al.. - In: THE ASTROPHYSICAL JOURNAL. - ISSN 0004-637X. - 876:1(2019), p. 42. [10.3847/1538-4357/ab13a2]