The JCMT BISTRO Survey: A Spiral Magnetic Field in a Hub-filament Structure, Monoceros R2
Authors: Hwang Jihye , Kim Jongsoo , Pattle Kate , Lee Chang Won , Koch Patrick M. , Johnstone Doug , Tomisaka Kohji , Whitworth Anthony , Furuya Ray S. , Kang Ji-hyun , Lyo A-Ran , Chung Eun Jung , Arzoumanian Doris , Park Geumsook , Kwon Woojin , Kim Shinyoung , Tamura Motohide , Kwon Jungmi , Soam Archana , Han Ilseung , Hoang Thiem , Kim Kyoung Hee , Onaka Takashi , Eswaraiah Chakali , Ward-Thompson Derek , Liu Hong-Li , Tang Xindi , Chen Wen Ping , Matsumura Masafumi , Hoang Thuong Duc , Chen Zhiwei , Le Gouellec Valentin J. M. , Kirchschlager Florian , Poidevin Frédérick , Bastien Pierre , Qiu Keping , Hasegawa Tetsuo , Lai Shih-Ping , Byun Do-Young , Cho Jungyeon , Choi Minho , Choi Youngwoo , Choi Yunhee , Jeong Il-Gyo , Kang Miju , Kim Hyosung , Kim Kee-Tae , Lee Jeong-Eun , Lee Sang-Sung , Lee Yong-Hee , Lee Hyeseung , Kim Mi-Ryang , Yoo Hyunju , Yun Hyeong-Sik , Chen Mike , Francesco James Di , Fiege Jason , Fissel Laura M. , Franzmann Erica , Houde Martin , Lacaille Kevin , Matthews Brenda , Sadavoy Sarah , Moriarty-Schieven Gerald , Tahani Mehrnoosh , Ching Tao-Chung , Dai Y. Sophia , Duan Yan , Gu Qilao , Law Chi-Yan , Li Dalei , Li Di , Li Guangxing , Li Hua-bai , Liu Tie , Lu Xing , Qian Lei , Wang Hongchi , Wu Jintai , Xie Jinjin , Yuan Jinghua , Zhang Chuan-Peng , Zhang Guoyin , Zhang Yapeng , Zhou Jianjun , Zhu Lei , Berry David , Friberg Per , Graves Sarah , Liu Junhao , Mairs Steve , Parsons Harriet , Rawlings Mark , Doi Yasuo , Hayashi Saeko , Hull Charles L. H. , Inoue Tsuyoshi , Inutsuka Shu-ichiro , Iwasaki Kazunari , Kataoka Akimasa , Kawabata Koji , Kim Gwanjeong , Kobayashi Masato I. N. , Nagata Tetsuya , Nakamura Fumitaka , Nakanishi Hiroyuki , Pyo Tae-Soo , Saito Hiro , Seta Masumichi , Shimajiri Yoshito , Shinnaga Hiroko , Tsukamoto Yusuke , Zenko Tetsuya , Chen Huei-Ru Vivien , Duan Hao-Yuan , Fanciullo Lapo , Kemper Francisca , Lee Chin-Fei , Lin Sheng-Jun , Liu Sheng-Yuan , Ohashi Nagayoshi , Rao Ramprasad , Tang Ya-Wen , Wang Jia-Wei , Yang Meng-Zhe , Yen Hsi-Wei , Bourke Tyler L. , Chrysostomou Antonio , Debattista Victor , Eden David , Eyres Stewart , Falle Sam , Fuller Gary , Gledhill Tim , Greaves Jane , Griffin Matt , Hatchell Jennifer , Karoly Janik , Kirk Jason , Könyves Vera , Longmore Steven , van Loo Sven , Looze Ilse de , Peretto Nicolas , Priestley Felix , Rawlings Jonathan , Retter Brendan , Richer John , Rigby Andrew , Savini Giorgio , Scaife Anna , Viti Serena , Diep Pham Ngoc , Ngoc Nguyen Bich , Tram Le Ngoc , André Philippe , Coudé Simon , Dowell C. Darren , Friesen Rachel , Robitaille Jean-Franćois 
Published: December 2022

Abstract
We present and analyze observations of polarized dust emission at 850 μm toward the central 1 × 1 pc hub-filament structure of Monoceros R2 (Mon R2). The data are obtained with SCUBA-2/POL-2 on the James Clerk Maxwell Telescope (JCMT) as part of the B-fields in Star-forming Region Observations survey. The orientations of the magnetic field follow the spiral structure of Mon R2, which are well described by an axisymmetric magnetic field model. We estimate the turbulent component of the magnetic field using the angle difference between our observations and the best-fit model of the underlying large-scale mean magnetic field. This estimate is used to calculate the magnetic field strength using the Davis–Chandrasekhar–Fermi method, for which we also obtain the distribution of volume density and velocity dispersion using a column density map derived from Herschel data and the C18O (J = 3 − 2) data taken with HARP on the JCMT, respectively. We make maps of magnetic field strengths and mass-to-flux ratios, finding that magnetic field strengths vary from 0.02 to 3.64 mG with a mean value of 1.0 ± 0.06 mG, and the mean critical mass-to-flux ratio is 0.47 ± 0.02. Additionally, the mean Alfvén Mach number is 0.35 ± 0.01. This suggests that, in Mon R2, the magnetic fields provide resistance against large-scale gravitational collapse, and the magnetic pressure exceeds the turbulent pressure. We also investigate the properties of each filament in Mon R2. Most of the filaments are aligned along the magnetic field direction and are magnetically subcritical.