Magnetic Fields toward Ophiuchus-B Derived from SCUBA-2 Polarization Measurements
Authors: Soam Archana , Pattle Kate , Ward-Thompson Derek , Lee Chang Won , Sadavoy Sarah , Koch Patrick M. , Kim Gwanjeong , Kwon Jungmi , Kwon Woojin , Arzoumanian Doris , Berry David , Hoang Thiem , Tamura Motohide , Lee Sang-Sung , Liu Tie , Kim Kee-Tae , Johnstone Doug , Nakamura Fumitaka , Lyo A-Ran , Onaka Takashi , Kim Jongsoo , Furuya Ray S. , Hasegawa Tetsuo , Lai Shih-Ping , Bastien Pierre , Chung Eun Jung , Kim Shinyoung , Parsons Harriet , Rawlings Mark G. , Mairs Steve , Graves Sarah F. , Robitaille Jean-Franois , Liu Hong-Li , Whitworth Anthony P. , Eswaraiah Chakali , Rao Ramprasad , Yoo Hyunju , Houde Martin , Kang Ji-hyun , Doi Yasuo , Choi Minho , Kang Miju , Coudé Simon , Li Hua-bai , Matsumura Masafumi , Matthews Brenda C. , Pon Andy , Francesco James Di , Hayashi Saeko S. , Kawabata Koji S. , Inutsuka Shu-ichiro , Qiu Keping , Franzmann Erica , Friberg Per , Greaves Jane S. , Kirk Jason M. , Li Di , Shinnaga Hiroko , Loo Sven van , Aso Yusuke , Byun Do-Young , Chen Huei-Ru , Chen Mike C.-Y. , Chen Wen Ping , Ching Tao-Chung , Cho Jungyeon , Chrysostomou Antonio , Drabek-Maunder Emily , Eyres Stewart P. S. , Fiege Jason , Friesen Rachel K. , Fuller Gary , Gledhill Tim , Griffin Matt J. , Gu Qilao , Hatchell Jennifer , Holland Wayne , Inoue Tsuyoshi , Iwasaki Kazunari , Jeong Il-Gyo , Kang Sung-ju , Kemper Francisca , Kim Kyoung Hee , Kim Mi-Ryang , Lacaille Kevin M. , Lee Jeong-Eun , Li Dalei , Liu Junhao , Liu Sheng-Yuan , Moriarty-Schieven Gerald H. , Nakanishi Hiroyuki , Ohashi Nagayoshi , Peretto Nicolas , Pyo Tae-Soo , Qian Lei , Retter Brendan , Richer John , Rigby Andrew , Savini Giorgio , Scaife Anna M. M. , Tang Ya-Wen , Tomisaka Kohji , Wang Hongchi , Wang Jia-Wei , Yen Hsi-Wei , Yuan Jinghua , Zhang Chuan-Peng , Zhang Guoyin , Zhou Jianjun , Zhu Lei , André Philippe , Dowell C. Darren , Falle Sam , Tsukamoto Yusuke , Kanamori Yoshihiro , Kataoka Akimasa , Kobayashi Masato I. N. , Nagata Tetsuya , Saito Hiro , Seta Masumichi , Hwang Jihye , Han Ilseung , Lee Hyeseung , Zenko Tetsuya 
Published: July 2018

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.