Observations of Magnetic Fields Surrounding LkHα 101 Taken by the BISTRO Survey with JCMT-POL-2

Nguyen Bich Ngoc , Pham Ngoc Diep , Harriet Parsons , Kate Pattle , Thiem Hoang , Derek Ward-Thompson , Le Ngoc Tram , Charles L. H. Hull , Mehrnoosh Tahani , Ray Furuya , Pierre Bastien , Keping Qiu , Tetsuo Hasegawa , Woojin Kwon , Yasuo Doi , Shih-Ping Lai , Simon Coudé , David Berry , Tao-Chung Ching , Jihye Hwang , Archana Soam , Jia-Wei Wang , Doris Arzoumanian , Tyler L. Bourke , Do-Young Byun , Huei-Ru Vivien Chen , Zhiwei Chen , Wen Ping Chen , Mike Chen , Jungyeon Cho , Yunhee Choi , Minho Choi , Antonio Chrysostomou , Eun Jung Chung , Sophia Dai , James Di Francesco , Yan Duan , Hao-Yuan Duan , David Eden , Chakali Eswaraiah , Lapo Fanciullo , Jason Fiege , Laura M. Fissel , Erica Franzmann , Per Friberg , Rachel Friesen , Gary Fuller , Tim Gledhill , Sarah Graves , Jane Greaves , Matt Griffin , Qilao Gu , Ilseung Han , Jennifer Hatchell , Saeko Hayashi , Martin Houde , Tsuyoshi Inoue , Shu-Ichiro Inutsuka , Kazunari Iwasaki , Il-Gyo Jeong , Doug Johnstone , Ji-Hyun Kang , Sung-Ju Kang , Miju Kang , Akimasa Kataoka , Koji Kawabata , Francisca Kemper , Kee-Tae Kim , Jongsoo Kim , Tae-Soo Pyo , Lei Qian , Ramprasad Rao , Mark Rawlings , Jonathan Rawlings , Brendan Retter , John Richer , Andrew Rigby , Sarah Sadavoy , Hiro Saito , Giorgio Savini , Anna Scaife , Masumichi Seta , Gwanjeong Kim , Shinyoung Kim , Kyoung Hee Kim , Mi-Ryang Kim , Florian Kirchschlager , Jason Kirk , Masato I. N. Kobayashi , Patrick M. Koch , Vera Konyves , Takayoshi Kusune , Jungmi Kwon , Kevin Lacaille , Chi-Yan Law , Sang-Sung Lee , Yong-Hee Lee , Chin-Fei Lee , Jeong-Eun Lee , Hyeseung Lee , Chang Won Lee , Di Li , Hua-Bai Li , Dalei Li , Hong-Li Liu , Junhao Liu , Tie Liu , Sheng-Yuan Liu , Xing Lu , A. -Ran Lyo , Steve Mairs , Masafumi Matsumura , Brenda Matthews , Gerald Moriarty-Schieven , Tetsuya Nagata , Fumitaka Nakamura , Hiroyuki Nakanishi , Nagayoshi Ohashi , Takashi Onaka , Geumsook Park , Nicolas Peretto , Yoshito Shimajiri , Hiroko Shinnaga , Motohide Tamura , Ya-Wen Tang , Xindi Tang , Kohji Tomisaka , Yusuke Tsukamoto , Serena Viti , Hongchi Wang , Anthony Whitworth , Jinjin Xie , Hsi-Wei Yen , Hyunju Yoo , Jinghua Yuan , Hyeong-Sik Yun , Tetsuya Zenko , Yapeng Zhang , Chuan-Peng Zhang , Guoyin Zhang , Jianjun Zhou , Lei Zhu , Ilse de Looze , Philippe André , C. Darren Dowell , Stewart Eyres , Sam Falle , Jean-François Robitaille (1) , Sven van Loo

1 IPAG - Institut de Planétologie et d'Astrophysique de Grenoble

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 δB/B₀ ∼ 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.

Keywords: Interstellar magnetic fields; Molecular clouds; Star formation; 845; 1072; 1569; Astrophysics - Astrophysics of Galaxies; Astrophysics - Solar and Stellar Astrophysics

Domains: Sciences of the Universe [physics]

Nguyen Bich Ngoc, Pham Ngoc Diep, Harriet Parsons, Kate Pattle, Thiem Hoang, et al.. Observations of Magnetic Fields Surrounding LkHα 101 Taken by the BISTRO Survey with JCMT-POL-2. The Astrophysical Journal, 2021, 908, ⟨10.3847/1538-4357/abd0fc⟩. ⟨insu-03705327⟩