Observations of magnetic fields surrounding LkHa 101 taken by the BISTRO survey with JCMT-POL-2

BISTRO, 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 Coude, David Berry, Tao-Chung ChingJihye 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

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We report the first high spatial resolution measurement of magnetic fields surrounding LkHa 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 BPOS~ 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 LkHa 101 region is subcritical, and the magnetic field is strong enough to prevent gravitational collapse. The inferred dB/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 a =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 (LkHa 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.

Original languageEnglish
Number of pages20
JournalThe Astrophysical Journal
Issue number10
Early online date8 Feb 2021
Publication statusPublished - 10 Feb 2021


  • astro-ph.GA
  • astro-ph.SR


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