The JCMT BISTRO Survey: The Magnetic Field In The Starless Core $ρ$ Ophiuchus C

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

Published 2019-02-20Version 1

We report 850~$\mu$m dust polarization observations of a low-mass ($\sim$12 $M_{\odot}$) starless core in the $\rho$ Ophiuchus cloud, Ophiuchus C, made with the POL-2 instrument on the James Clerk Maxwell Telescope (JCMT) as part of the JCMT B-fields In STar-forming Region Observations (BISTRO) survey. We detect an ordered magnetic field projected on the plane of sky in the starless core. The magnetic field across the $\sim$0.1~pc core shows a predominant northeast-southwest orientation centering between $\sim$40$^\circ$ to $\sim$100$^\circ$, indicating that the field in the core is well aligned with the magnetic field in lower-density regions of the cloud probed by near-infrared observations and also the cloud-scale magnetic field traced by Planck observations. The polarization percentage ($P$) decreases with an increasing total intensity ($I$) with a power-law index of $-$1.03 $\pm$ 0.05. We estimate the plane-of-sky field strength ($B_{\mathrm{pos}}$) using modified Davis-Chandrasekhar-Fermi (DCF) methods based on structure function (SF), auto-correlation (ACF), and unsharp masking (UM) analyses. We find that the estimates from the SF, ACF, and UM methods yield strengths of 103 $\pm$ 46 $\mu$G, 136 $\pm$ 69 $\mu$G, and 213 $\pm$ 115 $\mu$G, respectively. Our calculations suggest that the Ophiuchus C core is near magnetically critical or slightly magnetically supercritical (i.e. unstable to collapse). The total magnetic energy calculated from the SF method is comparable to the turbulent energy in Ophiuchus C, while the ACF method and the UM method only set upper limits for the total magnetic energy because of large uncertainties.