B-fields in Star-forming Region Observations (BISTRO): Magnetic Fields in the Filamentary Structures of Serpens Main
Woojin Kwon, Kate Pattle, Sarah Sadavoy, Charles L. H. Hull, Doug Johnstone, D. Ward–Thompson, James Di Francesco, Patrick M. Koch, Ray S. Furuya, Yasuo Doi, Valentin J. M. Le Gouellec, Jihye Hwang, A-Ran Lyo, Archana Soam, Xindi Tang, Thiem Hoang, Florian Kirchschlager, Chakali Eswaraiah, Lapo Fanciullo, Kyoung Hee Kim, Takashi Onaka, V. Könyves, Ji‐hyun Kang, Chang Won Lee, Motohide Tamura, Pierre Bastien, Tetsuo Hasegawa, S. Lai, Keping Qiu, David Berry, D. Arzoumanian, Tyler L. Bourke, Do‐Young Byun, Wen Chen, Huei-Ru Vivien Chen, Mike Chen, Zhiwei Chen, Tao-Chung Ching, Jungyeon Cho, Yunhee Choi, Minho Choi, A. Chrysostomou, Eun Jung Chung, Simon Coudé, Sophia Dai, Pham Ngoc Diep, Yan Duan, Hao-Yuan Duan, David Eden, Jason Fiege, Laura M. Fissel, Erica Franzmann, Per Friberg, Rachel Friesen, G. A. Fuller, T. M. Gledhill, Sarah Graves, J. S. Greaves, Matt Griffin, Qilao Gu, Ilseung Han, J. Hatchell, Saeko S. Hayashi, Martin Houde, Tsuyoshi Inoue, Shu‐ichiro Inutsuka, Kazunari Iwasaki, Il-Gyo Jeong, Miju Kang, Janik Karoly, Akimasa Kataoka, Koji S. Kawabata, F. Kemper, Kee‐Tae Kim, Gwanjeong Kim, Mi-Ryang Kim, Shinyoung Kim, Jongsoo Kim, J. M. Kirk, Masato I. N. Kobayashi, Takayoshi Kusune, Jungmi Kwon, Kevin Lacaille, Chi-Yan Law, Chin‐Fei Lee, Yong-Hee Lee, Hyeseung Lee, Jeong‐Eun Lee, Sang-Sung Lee, Dalei Li, Di Li, Hua-bai Li, Sheng-Jun Lin, Sheng‐Yuan Liu, Hongli Liu, Junhao Liu, Tie Liu, Xing Lu, Steve Mairs, M. Matsumura
Abstract
Abstract We present 850 μ m polarimetric observations toward the Serpens Main molecular cloud obtained using the POL-2 polarimeter on the James Clerk Maxwell Telescope as part of the B-fields In STar-forming Region Observations survey. These observations probe the magnetic field morphology of the Serpens Main molecular cloud on about 6000 au scales, which consists of cores and six filaments with different physical properties such as density and star formation activity. Using the histogram of relative orientation (HRO) technique, we find that magnetic fields are parallel to filaments in less-dense filamentary structures where <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> <mml:mo><</mml:mo> <mml:mn>0.93</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>22</mml:mn> </mml:mrow> </mml:msup> </mml:math> cm −2 (magnetic fields perpendicular to density gradients), while they are perpendicular to filaments (magnetic fields parallel to density gradients) in dense filamentary structures with star formation activity. Moreover, applying the HRO technique to denser core regions, we find that magnetic field orientations change to become perpendicular to density gradients again at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> <mml:mo>≈</mml:mo> <mml:mn>4.6</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>22</mml:mn> </mml:mrow> </mml:msup> </mml:math> cm −2 . This can be interpreted as a signature of core formation. At <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:msub> <mml:mrow> <mml:mi>N</mml:mi> </mml:mrow> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi mathvariant="normal">H</mml:mi> </mml:mrow> <mml:mrow> <mml:mn>2</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:msub> <mml:mo>≈</mml:mo> <mml:mn>16</mml:mn> <mml:mo>×</mml:mo> <mml:msup> <mml:mrow> <mml:mn>10</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>22</mml:mn> </mml:mrow> </mml:msup> </mml:math> cm −2 , magnetic fields change back to being parallel to density gradients once again, which can be understood to be due to magnetic fields being dragged in by infalling material. In addition, we estimate the magnetic field strengths of the filaments ( B POS = 60–300 μ G)) using the Davis–Chandrasekhar–Fermi method and discuss whether the filaments are gravitationally unstable based on magnetic field and turbulence energy densities.