巴纳德335中磁场的畸变
Distortion of Magnetic Fields in Barnard 335
AI总结：
本研究通过近红外背景星偏振观测首次揭示B335原恒星核的沙漏形畸变磁场，测定其磁场强度、倾角及临界质量，证明该星核从近平衡状态开始收缩。
摘要：
本研究基于对背景恒星的近红外偏振观测，通过测量星核内磁排列尘埃颗粒产生的二向色性偏振光，揭示了致密原恒星核巴纳德335（B335）的详细磁场结构。在扣除无关的环境偏振成分后，利用24颗恒星绘制了贯穿B335的磁场图，首次揭示其磁场朝原恒星核方向具有轴对称畸变的沙漏形结构。基于简单的二维和三维磁场模型，确定磁场在天空平面方向和视线方向的倾角分别为90°±7°和50°±10°。B335的总磁场强度确定为30.2±17.7 μG。利用磁场支撑和热/湍流支撑共同抵抗坍缩来评估，B335的临界质量确定为M_cr=3.37±0.94 M_⊙，这与观测到的星核质量M_core=3.67 M_⊙一致。因此我们得出结论：B335是从接近平衡的状态开始收缩的。在偏振-消光图中，我们发现直到A_V~15 mag、朝向遮蔽最严重恒星的范围内存在线性关系，这验证了我们的观测和分析准确刻画了该星核。
英文摘要：
In this study, the detailed magnetic field structure of the dense protostellar core Barnard 335 (B335) was revealed based on near-infrared polarimetric observations of background stars to measure dichroically polarized light produced by magnetically aligned dust grains in the core. Magnetic fields pervading B335 were mapped using 24 stars after subtracting unrelated ambient polarization components, for the first time revealing that they have an axisymmetrically distorted hourglass-shaped structure toward the protostellar core. On the basis of simple two- and three-dimensional magnetic field modeling, magnetic inclination angles in the plane-of-sky and line-of-sight directions were determined to be $90^{\circ} \pm 7^{\circ}$ and $50^{\circ} \pm 10^{\circ}$, respectively. The total magnetic field strength of B335 was determined to be $30.2 \pm 17.7$ $μ{\rm G}$. The critical mass of B335, evaluated using both magnetic and thermal/turbulent support against collapse, was determined to be $M_{\rm cr} = 3.37 \pm 0.94$ ${\rm M}_{\odot}$, which is identical to the observed core mass of $M_{\rm core}=3.67$ M$_{\odot}$. We thus concluded that B335 started its contraction from a condition near equilibrium. We found a linear relationship in the polarization versus extinction diagram, up to $A_V \sim 15$ mag toward the stars with the greatest obscuration, which verified that our observations and analysis provide an accurate depiction of the core.
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