Characterizing Magnetic Field Morphologies in Three Serpens Protostellar Cores with ALMA
Characterizing Magnetic Field Morphologies in Three Serpens Protostellar Cores with ALMA
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DOI：
10.3847/1538-4357/ab43c2
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发表时间：
2019-08
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影响因子：
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通讯作者：
Valentin J. M. Le Gouellec;C. Hull;A. Maury;J. Girart;Ł. Tychoniec;L. Kristensen;Zhi-Yun Li;F. Louvet;P. Cortés;R. Rao
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文献类型：
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作者：
Valentin J. M. Le Gouellec;C. Hull;A. Maury;J. Girart;Ł. Tychoniec;L. Kristensen;Zhi-Yun Li;F. Louvet;P. Cortés;R. Rao
为了表征年轻原恒星形成过程中的动力学过程，我们对0类原恒星核心巨蛇座SMM 1、Emb 8（N）和Emb 8进行了高角分辨率的阿尔马尘埃偏振观测。在870 μm的空间分辨率范围为150到40 Au的情况下，我们发现Serpens Emb 8（N）中沿流出腔壁的偏振分数沿着出乎意料地高。我们使用3毫米和1毫米的分子示踪剂来研究外流和稠密气体的性质及其与偏振的相关性。这些观测结果使我们能够调查的物理过程中涉及的辐射对准扭矩（RAT）作用于尘埃颗粒沿着流出腔壁，经历辐射吸积过程和流出冲击。SMM 1-a的内核在双极流出的两个叶的基部呈现极向磁场的极化图案。在SMM 1-a的南面，我们看到两个极化的细丝，其中一个似乎是沿着红移的流出腔壁。另一个可能是物质的吸积流落在中央原恒星上。我们提出，如果在0类包层中以<500 Au尺度存在的排列颗粒已经长大到大于星际介质中尘埃颗粒的0.1 μm尺寸，那么我们沿着沿着辐照腔壁在毫米波长处看到的偏振发射可以与RAT理论的预期相一致。我们的观察使我们能够约束的磁场形态的恒星形成源的中央核心内，沿着流出腔壁，并在可能的吸积流光。
With the aim of characterizing the dynamical processes involved in the formation of young protostars, we present high-angular-resolution ALMA dust polarization observations of the Class 0 protostellar cores Serpens SMM1, Emb 8(N), and Emb 8. With spatial resolutions ranging from 150 to 40 au at 870 μm, we find unexpectedly high values of the polarization fraction along the outflow cavity walls in Serpens Emb 8(N). We use 3 mm and 1 mm molecular tracers to investigate outflow and dense-gas properties and their correlation with the polarization. These observations allow us to investigate the physical processes involved in the radiative alignment torques (RATs) acting on dust grains along the outflow cavity walls, which experience irradiation from accretion processes and outflow shocks. The inner core of SMM1-a presents a polarization pattern with a poloidal magnetic field at the bases of the two lobes of the bipolar outflow. To the south of SMM1-a we see two polarized filaments, one of which seems to trace the redshifted outflow cavity wall. The other may be an accretion streamer of material infalling onto the central protostar. We propose that the polarized emission we see at millimeter wavelengths along the irradiated cavity walls can be reconciled with the expectations of RAT theory if the aligned grains present at <500 au scales in Class 0 envelopes have grown larger than the 0.1 μm size of dust grains in the interstellar medium. Our observations allow us to constrain the magnetic field morphologies of star-forming sources within the central cores, along the outflow cavity walls, and in possible accretion streamers.