标题： JCMT BISTRO巡天：奥菲斯座C无星核心中的磁场$ρ$ 显示英文标题

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

摘要： 我们报告了利用詹姆斯·克拉克·麦克斯韦望远镜（JCMT）上的POL-2仪器对蝘蜓座Ophiuchus云中一个低质量（$\sim$12$M_{\odot}$）的无星核心$\rho$进行的850~$\mu$米尘埃极化观测结果，该观测是JCMT恒星形成区磁场观测（BISTRO）调查的一部分。我们在无星核心中探测到了投射到天空平面上的有序磁场。 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$, indicating that the field in the core is well aligned with the magnetic field in lower-density regions of the cloud probed by near-infrared observations and also the cloud-scale magnetic field traced by Planck observations. 极化百分比（$P$）随着总强度（$I$）的增加按幂律指数为$-$1.03$\pm$0.05 的规律减小。 我们利用基于结构函数（SF）、自相关函数（ACF）和非锐化掩模（UM）分析的改进型 Davis-Chandrasekhar-Fermi (DCF) 方法估算天空平面磁场强度（$B_{\mathrm{pos}}$）。 我们发现，SF、ACF和UM方法得到的强度估计值分别为103 $\pm$ 46 $\mu$G、136 $\pm$ 69 $\mu$G和213 $\pm$ 115 $\mu$G。我们的计算表明，蛇夫座C核心接近磁临界状态或略微超磁临界状态（即不稳定且可能塌缩）。从SF方法计算出的总磁场能量与蛇夫座C中的湍动能量相当，而由于存在较大的不确定性，ACF方法和UM方法只能给出总磁场能量的上限。 显示英文摘要

摘要： 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.