Observations of Magnetic Fields Surrounding LkHα 101 Taken by the BISTRO Survey with JCMT-POL-2
Authors: Ngoc Nguyen Bich , Diep Pham Ngoc , Parsons Harriet , Pattle Kate , Hoang Thiem , Ward-Thompson Derek , Tram Le Ngoc , Hull Charles L. H. , Tahani Mehrnoosh , Furuya Ray , Bastien Pierre , Qiu Keping , Hasegawa Tetsuo , Kwon Woojin , Doi Yasuo , Lai Shih-Ping , Coudé Simon , Berry David , Ching Tao-Chung , Hwang Jihye , Soam Archana , Wang Jia-Wei , Arzoumanian Doris , Bourke Tyler L. , Byun Do-Young , Chen Huei-Ru Vivien , Chen Zhiwei , Chen Wen Ping , Chen Mike , Cho Jungyeon , Choi Yunhee , Choi Minho , Chrysostomou Antonio , Chung Eun Jung , Dai Sophia , Francesco James Di , Duan Yan , Duan Hao-Yuan , Eden David , Eswaraiah Chakali , Fanciullo Lapo , Fiege Jason , Fissel Laura M. , Franzmann Erica , Friberg Per , Friesen Rachel , Fuller Gary , Gledhill Tim , Graves Sarah , Greaves Jane , Griffin Matt , Gu Qilao , Han Ilseung , Hatchell Jennifer , Hayashi Saeko , Houde Martin , Inoue Tsuyoshi , Inutsuka Shu-ichiro , Iwasaki Kazunari , Jeong Il-Gyo , Johnstone Doug , Kang Ji-hyun , Kang Sung-ju , Kang Miju , Kataoka Akimasa , Kawabata Koji , Kemper Francisca , Kim Kee-Tae , Kim Jongsoo , Pyo Tae-Soo , Qian Lei , Rao Ramprasad , Rawlings Mark , Rawlings Jonathan , Retter Brendan , Richer John , Rigby Andrew , Sadavoy Sarah , Saito Hiro , Savini Giorgio , Scaife Anna , Seta Masumichi , Kim Gwanjeong , Kim Shinyoung , Kim Kyoung Hee , Kim Mi-Ryang , Kirchschlager Florian , Kirk Jason , Kobayashi Masato I. N. , Koch Patrick M. , Konyves Vera , Kusune Takayoshi , Kwon Jungmi , Lacaille Kevin , Law Chi-Yan , Lee Sang-Sung , Lee Yong-Hee , Lee Chin-Fei , Lee Jeong-Eun , Lee Hyeseung , Lee Chang Won , Li Di , Li Hua-bai , Li Dalei , Liu Hong-Li , Liu Junhao , Liu Tie , Liu Sheng-Yuan , Lu Xing , Lyo A-Ran , Mairs Steve , Matsumura Masafumi , Matthews Brenda , Moriarty-Schieven Gerald , Nagata Tetsuya , Nakamura Fumitaka , Nakanishi Hiroyuki , Ohashi Nagayoshi , Onaka Takashi , Park Geumsook , Peretto Nicolas , Shimajiri Yoshito , Shinnaga Hiroko , Tamura Motohide , Tang Ya-Wen , Tang Xindi , Tomisaka Kohji , Tsukamoto Yusuke , Viti Serena , Wang Hongchi , Whitworth Anthony , Xie Jinjin , Yen Hsi-Wei , Yoo Hyunju , Yuan Jinghua , Yun Hyeong-Sik , Zenko Tetsuya , Zhang Yapeng , Zhang Chuan-Peng , Zhang Guoyin , Zhou Jianjun , Zhu Lei , Looze Ilse de , André Philippe , Dowell C. Darren , Eyres Stewart , Falle Sam , Robitaille Jean-François , van Loo Sven 
Published: February 2021

Abstract
We report the first high spatial resolution measurement of magnetic fields surrounding LkHα 101, part of the Auriga–California molecular cloud. The observations were taken with the POL-2 polarimeter on the James Clerk Maxwell Telescope within the framework of the B-fields In Star-forming Region Observations (BISTRO) survey. Observed polarization of thermal dust emission at 850 μm is found to be mostly associated with the redshifted gas component of the cloud. The magnetic field displays a relatively complex morphology. Two variants of the Davis–Chandrasekhar–Fermi method, unsharp masking and structure function, are used to calculate the strength of magnetic fields in the plane of the sky, yielding a similar result of B
POS ∼ 115 μG. The mass-to-magnetic-flux ratio in critical value units, λ ∼ 0.3, is the smallest among the values obtained for other regions surveyed by POL-2. This implies that the LkHα 101 region is subcritical, and the magnetic field is strong enough to prevent gravitational collapse. The inferred δ
B/B
0 ∼ 0.3 implies that the large-scale component of the magnetic field dominates the turbulent one. The variation of the polarization fraction with total emission intensity can be fitted by a power law with an index of α = 0.82 ± 0.03, which lies in the range previously reported for molecular clouds. We find that the polarization fraction decreases rapidly with proximity to the only early B star (LkHα 101) in the region. Magnetic field tangling and the joint effect of grain alignment and rotational disruption by radiative torques can potentially explain such a decreasing trend.