Filament Fragmentation in High-Mass Star Formation
Filament Fragmentation in High-Mass Star Formation
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DOI：
10.1051/0004-6361/201527108
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发表时间：
2015-10
期刊：
影响因子：
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通讯作者：
H. Beuther;S. Ragan;K. Johnston;T. Henning;Á. Hacar;J. Kainulainen
中科院分区：
文献类型：
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作者：
H. Beuther;S. Ragan;K. Johnston;T. Henning;Á. Hacar;J. Kainulainen
目的：我们解决了长丝形成和破碎的长度尺度（res. <=0.1pc），特别是牛仔裤长度和圆柱体破碎尺度。研究方法：我们用3.2mm连续谱和1-0视场镶嵌图观测了原型的高质量恒星形成暗条IRDC 18223，空间分辨率为~ 4“（~ 14000 AU）。结果：尘埃连续辐射将灯丝分解成至少12个相对规则间隔的核的链。岩芯之间的平均间隔约为0.40（± 0.18）pc。虽然这与无限的、等温的、重力束缚的气体圆柱体的碎裂大致一致，但是M/l~1000M_sun/pc的高质量-长度比需要额外的湍流和/或磁性支撑来抵抗细丝的径向塌陷。N_2H ~+（1-0）数据揭示了垂直于主丝的速度梯度。虽然不能排除灯丝的旋转，但数据也与主灯丝由几个速度相干的子灯丝组成一致。此外，这种垂直于灯丝的速度梯度类似于最近的结果，对巨蛇座南部被解释为在磁化和湍流片状结构内的灯丝形成的签名。低密度气体示踪剂（[CI]和C18 O）在IRDC 18223暗条东西60“附近的尺度上揭示了类似的红/蓝移速度结构。这可能暂时被解释为一个签名的大规模云和较小规模的灯丝被运动学耦合。我们不能确定沿灯丝轴沿着的速度梯度。这可能是由于没有显著的气体沿大气轴线沿着流动，但它也可能部分地由灯丝相对于天空平面的低倾斜角引起，该低倾斜角可以使这种特征最小化。
Aims: We resolve the length-scales for filament formation and fragmentation (res. <=0.1pc), in particular the Jeans length and cylinder fragmentation scale. Methods: We observed the prototypical high-mass star-forming filament IRDC18223 with the Plateau de Bure Interferometer (PdBI) in the 3.2mm continuum and N2H+(1-0) line emission in a ten field mosaic at a spatial resolution of ~4'' (~14000AU). Results: The dust continuum emission resolves the filament into a chain of at least 12 relatively regularly spaced cores. The mean separation between cores is ~0.40(+-0.18)pc. While this is approximately consistent with the fragmentation of an infinite, isothermal, gravitationally bound gas cylinder, a high mass-to-length ratio of M/l~1000M_sun/pc requires additional turbulent and/or magnetic support against radial collapse of the filament. The N2H+(1-0) data reveal a velocity gradient perpendicular to the main filament. Although rotation of the filament cannot be excluded, the data are also consistent with the main filament being comprised of several velocity-coherent sub-filaments. Furthermore, this velocity gradient perpendicular to the filament resembles recent results toward Serpens south that are interpreted as signatures of filament formation within magnetized and turbulent sheet-like structures. Lower-density gas tracers ([CI] and C18O) reveal a similar red/blueshifted velocity structure on scales around 60'' east and west of the IRDC18223 filament. This may tentatively be interpreted as a signature of the large-scale cloud and the smaller-scale filament being kinematically coupled. We do not identify a velocity gradient along the axis of the filament. This may either be due to no significant gas flows along the filamentary axis, but it may partly also be caused by a low inclination angle of the filament with respect to the plane of the sky that could minimize such signature.