无星核中磁场的畸变：FeSt 1-457的近红外偏振测量
Distortion of Magnetic Fields in a Starless Core: Near-Infrared Polarimetry of FeSt 1-457
摘要：
磁场被认为在控制致密气体和尘埃凝聚的稳定性和收缩方面起着重要作用，导致恒星和行星系统的形成。在本研究中，FeSt 1-457是一个冷的无星分子云核，它的磁场是根据185颗背景恒星在被尘埃二向色吸收后的偏振近红外线与核中的磁场对准而成的。一个明显的“沙漏形”磁场被确定在核心的区域，这被解释为磁场结构扭曲的质量凝聚在一个无星的核心的第一个证据。本研究中获得的磁场线的陡峭曲率表明，畸变主要是在致密核的形成阶段产生的。推导出的质量-磁通量比表明，核心是在磁超临界状态。但是，如果考虑到热支持和湍流支持的额外贡献，则可以认为核心的稳定性处于近临界状态。磁场的进一步扩散和/或湍流耗散将导致核心动力学坍缩的开始。磁场线的方向和核的伸长之间的几何关系被发现与在磁场的影响下形成类太阳恒星的理论预测非常一致。
英文摘要：
Magnetic fields are believed to play an important role in controlling the stability and contraction of dense condensations of gas and dust leading to the formation of stars and planetary systems. In the present study, the magnetic field of FeSt 1-457, a cold starless molecular cloud core, was mapped on the basis of the polarized near-infrared light from 185 background stars after being dichroically absorbed by dust aligned with the magnetic field in the core. A distinct "hourglass-shaped" magnetic field was identified in the region of the core, which was interpreted as the first evidence of a magnetic field structure distorted by mass condensation in a starless core. The steep curvature of the magnetic field lines obtained in the present study indicates that the distortion was mainly created during the formation phase of the dense core. The derived mass-to-magnetic flux ratio indicates that the core is in a magnetically supercritical state. However, the stability of the core can be considered to be in a nearly critical state if the additional contributions from the thermal and turbulent support are included. Further diffusion of the magnetic field and/or turbulent dissipation would cause the onset of dynamical collapse of the core. The geometrical relationship between the direction of the magnetic field lines and the elongation of the core was found to be in good agreement with the theoretical predictions for the formation of Sun-like stars under the influence of a magnetic field.
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