JCMT POL-2 and BISTRO Survey Observations of Magnetic Fields in the L1689 Molecular Cloud
Kate Pattle, Shih-Ping Lai, James Di Francesco, Sarah Sadavoy, Derek Ward-Thompson, Doug Johnstone, Thiem Hoang, Doris Arzoumanian, Pierre Bastien, Tyler L. Bourke, Simon Coudé, Yasuo Doi, Chakali Eswaraiah, Lapo Fanciullo, Ray S. Furuya, Jihye Hwang, Charles L. H. Hull, Jihyun Kang, Kee-Tae Kim, Florian Kirchschlager, Jungmi Kwon, Woojin Kwon, Chang Won 창원 Lee 이, Tie 铁 Liu 刘, Matt Redman, Archana Soam, Mehrnoosh Tahani, Motohide Tamura, Xindi Tang
Abstract
Abstract We present 850 μ m polarization observations of the L1689 molecular cloud, part of the nearby Ophiuchus molecular cloud complex, taken with the POL-2 polarimeter on the James Clerk Maxwell Telescope (JCMT). We observe three regions of L1689: the clump L1689N which houses the IRAS 16293-2433 protostellar system, the starless clump SMM-16, and the starless core L1689B. We use the Davis–Chandrasekhar–Fermi method to estimate plane-of-sky field strengths of 366 ± 55 μ G in L1689N, 284 ± 34 μ G in SMM-16, and 72 ± 33 μ G in L1689B, for our fiducial value of dust opacity. These values indicate that all three regions are likely to be magnetically transcritical with sub-Alfvénic turbulence. In all three regions, the inferred mean magnetic field direction is approximately perpendicular to the local filament direction identified in Herschel Space Telescope observations. The core-scale field morphologies for L1689N and L1689B are consistent with the cloud-scale field morphology measured by the Planck Space Observatory, suggesting that material can flow freely from large to small scales for these sources. Based on these magnetic field measurements, we posit that accretion from the cloud onto L1689N and L1689B may be magnetically regulated. However, in SMM-16, the clump-scale field is nearly perpendicular to the field seen on cloud scales by Planck, suggesting that it may be unable to efficiently accrete further material from its surroundings.