Magnetic Fields toward Ophiuchus-B Derived from SCUBA-2 Polarization Measurements

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

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Abstract

We present the results of dust emission polarization measurements of Ophiuchus-B (Oph-B) carried out using the Submillimetre Common-User Bolometer Array 2 (SCUBA-2) camera with its associated polarimeter (POL-2) on the James Clerk Maxwell Telescope in Hawaii. This work is part of the B-fields in Star-forming Region Observations survey initiated to understand the role of magnetic fields in star formation for nearby star-forming molecular clouds. We present a first look at the geometry and strength of magnetic fields in Oph-B. The field geometry is traced over ∼0.2 pc, with clear detection of both of the sub-clumps of Oph-B. The field pattern appears significantly disordered in sub-clump Oph-B1. The field geometry in Oph-B2 is more ordered, with a tendency to be along the major axis of the clump, parallel to the filamentary structure within which it lies. The degree of polarization decreases systematically toward the dense core material in the two sub-clumps. The field lines in the lower density material along the periphery are smoothly joined to the large-scale magnetic fields probed by NIR polarization observations. We estimated a magnetic field strength of 630 ± 410 μG in the Oph-B2 sub-clump using a Davis-Chandrasekhar-Fermi analysis. With this magnetic field strength, we find a mass-to-flux ratio λ = 1.6 ± 1.1, which suggests that the Oph-B2 clump is slightly magnetically supercritical.

Original languageEnglish
Article number65
JournalAstrophysical Journal
Volume861
Issue number1
DOIs
StatePublished - 1 Jul 2018

Keywords

  • ISM: individual objects (Ophiuchus)
  • ISM: structure
  • polarization
  • radio continuum: ISM
  • stars: formation

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