Twisted magnetic field in star formation processes of L1521F revealed by submillimeter dual-band polarimetry using the James Clerk Maxwell Telescope
Twisted magnetic field in star formation processes of L1521F revealed by submillimeter dual-band polarimetry using the James Clerk Maxwell Telescope
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使用詹姆斯·克拉克·麦克斯韦望远镜通过亚毫米双波段偏振测量揭示了 L1521F 恒星形成过程中的扭曲磁场
DOI：
10.1093/pasj/psac094
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发表时间：
2023
影响因子：
2.3
通讯作者：
Harada Naoto
中科院分区：
文献类型：
--
作者：
Fukaya Sakiko;Shinnaga Hiroko;Furuya Ray S;Tomisaka Kohji;Machida Masahiro N;Harada Naoto
要了解恒星形成的初始条件，需要进行观测研究和理论工作，并考虑磁场，磁场在恒星形成过程中发挥着重要作用。在这里，我们研究了金牛座分子云中年轻的附近致密云核L1521 F[n(H2)∼104−6 cm−3]。这个致密的核心拥有一颗0.2M的⊙原星，被归类为具有复杂速度结构的非常低光度的天体，特别是在原星附近。为了跟踪致密核心内的磁场，我们使用位于James Clerk Maxwell望远镜上Scuba-2亚毫米测辐射热计相机前面的POL-2偏振器，对λ=850 μm和450 μm的尘埃连续谱进行了高灵敏度的亚毫米偏振测量。这与使用ALMA3.3 mm时进行的毫米波偏振测量进行了比较。在沿南北方向穿线的外围区域中，在λ=850 μm处检测到磁场，而在λ=450 μm处跟踪的中心区域显示具有东西方向的磁场，即，与外围区域的磁场垂直。用Davis-Chandrasekhar-Fermi方法估算出外围和中心区域的磁场强度分别为70∼G和200 μG。由此得到的两个区域的质量通量比都比磁临界态的质量通量比大三倍，这表明L 1521 F是磁超临界的，即引力主导于磁湍流力。结合观测数据和磁流体动力学模拟，首次得到了这一令人困惑的天体的形态特征的详细参数。
Understanding the initial conditions of star formation requires both observational studies and theoretical works taking into account the magnetic field, which plays an important role in star formation processes. Herein, we study the young nearby dense cloud core L1521 F [n(H2) ∼104−6cm−3] in the Taurus Molecular Cloud. This dense core hosts a 0.2M⊙protostar, categorized as a very low luminosity object with complex velocity structures, particularly in the vicinity of the protostar. To trace the magnetic field within the dense core, we conducted high-sensitivity submillimeter polarimetry of the dust continuum at λ = 850 μm and 450 μm using the POL-2 polarimeter situated in front of the SCUBA-2 submillimeter bolometer camera on the James Clerk Maxwell Telescope. This was compared with millimeter polarimetry taken at λ = 3.3 mm with ALMA. The magnetic field was detected at λ = 850 μm in the peripheral region, which is threaded in a north–south direction, while the central region traced at λ = 450 μm shows a magnetic field with an east–west direction, i.e., orthogonal to that of the peripheral region. Magnetic field strengths are estimated to be ∼70 μG and 200 μG in the peripheral and central regions, respectively, using the Davis–Chandrasekhar–Fermi method. The resulting mass-to-flux ratio of three times larger than that of magnetically critical state for both regions indicates that L 1521 F is magnetically supercritical, i.e., gravitational forces dominate over magnetic turbulence forces. Combining observational data with magnetohydrodynamic simulations, detailed parameters of the morphological properties of this puzzling object are derived for the first time.