Multidirectional Mass Accretion and Collimated Outflows on Scales of 100–2000 au in Early Stages of High-mass Protostars
Multidirectional Mass Accretion and Collimated Outflows on Scales of 100–2000 au in Early Stages of High-mass Protostars
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DOI：
10.3847/1538-4357/abc88e
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发表时间：
2020-12
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影响因子：
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通讯作者：
C. Goddi;Adam Ginsburg;L. Maud;Q. Zhang;L. Zapata
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作者：
C. Goddi;Adam Ginsburg;L. Maud;Q. Zhang;L. Zapata
我们观察到的W51高质量恒星形成复杂的阿塔卡马大型毫米/亚毫米阵列的最长基线配置，实现了100万质量的角分辨率，对应的线性分辨率为100 Au在D W51 = 5.4 kpc。观测区域包含三颗高质量原恒星，其中1.3 mm处的尘埃连续辐射的光学厚度可达半径Au 1000，亮度温度为200 K。在没有自由-自由辐射的情况下，它的高光度（104 L）表明在其形成的最早阶段存在大质量恒星（M 20 M）。我们的连续图像揭示了从致密核中产生的非常复杂和复杂的结构。分子发射没有显示出明显的迹象，旋转或降落的规模从150至2000 Au，我们没有检测到磁盘。中心源驱动年轻（t dyn 100 yr）、快速（v 100 km s−1）、强大（M yr−1）、准直的外流。这些外流提供了在r = 100-500 Au（取决于物体）尺度上的吸积盘的间接证据。活跃的外流连接到化石流，在更大的空间尺度上有不同的方向，这意味着这些小磁盘的方向随着时间的推移而变化。这些结果共同支持的一个变种的吸积模型的大质量星星形成大规模的原恒星不形成一个大的，稳定的开普勒磁盘在其早期阶段，而是吸积材料从多个大规模的流动与不同的角动量矢量。因此，这种情况下，一个稳定的磁盘+喷流系统，这是低质量星星形成的标准模型的简化的经典范例，并提供了实验确认的大质量星星形成的多方向和不稳定的吸积模型。
We observed the W51 high-mass star-forming complex with the Atacama Large Millimeter/submillimeter Array’s longest-baseline configurations, achieving an angular resolution of ∼20 mas, corresponding to a linear resolution of ∼100 au at D W51 = 5.4 kpc. The observed region contains three high-mass protostars in which the dust continuum emission at 1.3 mm is optically thick up to a radius ≲1000 au and has brightness temperatures ≳200 K. The high luminosity (≳104 L ⊙) in the absence of free–free emission suggests the presence of massive stars (M ≳ 20 M ⊙) at the earliest stages of their formation. Our continuum images reveal remarkably complex and filamentary structures arising from compact cores. Molecular emission shows no clear signs of rotation or infall on scales from 150 to 2000 au; we do not detect disks. The central sources drive young (t dyn ∼ 100 yr), fast (v ∼ 100 km s−1), powerful ( M ⊙ yr−1), collimated outflows. These outflows provide indirect evidence of accretion disks on scales r ≲ 100–500 au (depending on the object). The active outflows are connected to fossil flows that have different orientations on larger spatial scales, implying that the orientations of these small disks change over time. These results together support a variant of an accretion model for high-mass star formation in which massive protostars do not form a large, stable Keplerian disk during their early stages but instead accrete material from multiple massive flows with different angular momentum vectors. This scenario therefore contrasts with the simplified classic paradigm of a stable disk+jet system, which is the standard model for low-mass star formation, and provides experimental confirmation of a multidirectional and unsteady accretion model for massive star formation.