论文标题
在原恒星形成的嵌入阶段的线性灰尘极化
Linear dust polarization during the embedded phase of protostar formation
论文作者
论文摘要
测量从热灰尘发射的极化可以对嵌入式质子周围的磁场结构产生约束。但是，解释观测值是具有挑战性的，没有始终如一地说明原prot体的出生环境和极化机制的复杂性的模型。我们的目标是通过比较观测的合成极化图与观测值的合成极化图，以重点关注桥梁样结构（例如对ProtoStellar Moless IRAS 16293--2422）的关注，以提供更好的理解。我们根据理想的MHD 3D Zoom-In模拟使用RAMSES代码进行了与原始倍数形成相关的磁场特性。为了与观测值进行比较，我们后处理了类似桥梁结构的快照，该结构与形成三星级系统具有辐射传输代码极北极星并产生多波长的灰尘极化图。在我们样品中最突出的桥上，典型的密度约为10^（-16）g cm^（-3），磁场强度约为1至2 mg。磁场结构具有细长的环形形态，灰尘极化图追踪复杂的形态。相比之下，与非对称双极流出的发射相关的磁场强度明显更磁化（〜100 mg）。在λ= 1.3 mm时，与与磁场线的完美对齐相比，桥梁中晶粒的方向相似。然而，与假设完美对齐相比，大鼠场景中桥的极化分数小三倍。在较短的波长（λ<200μm）下，灰尘极化不会追踪磁场，因为其他效果（例如自散射和二分法灭绝）主导了极化的方向。
Measuring polarization from thermal dust emission can provide constraints on the magnetic field structure around embedded protostars. However, interpreting the observations is challenging without models that consistently account for both the complexity of the protostellar birth environment and polarization mechanisms. We aim to provide a better understanding with a focus on bridge-like structures such as that observed towards the protostellar multiple IRAS 16293--2422 by comparing synthetic polarization maps of thermal reemission with observations. We analyze the magnetic field properties associated with the formation of a protostellar multiple based on ideal MHD 3D zoom-in simulations carried out with the RAMSES code. To compare with observations, we post-process a snapshot of a bridge-like structure that is associated with a forming triple star system with the radiative transfer code POLARIS and produce multi-wavelength dust polarization maps. In the most prominent bridge of our sample, the typical density is about 10^(-16) g cm^(-3), and the magnetic field strength is about 1 to 2 mG. The magnetic field structure has an elongated toroidal morphology and the dust polarization maps trace the complex morphology. In contrast, the magnetic field strength associated with the launching of asymmetric bipolar outflows is significantly more magnetized (~100 mG). At λ=1.3 mm, the orientation of grains in the bridge is similar for the case accounting for radiative alignment torques (RATs) compared to perfect alignment with magnetic field lines. However, the polarization fraction in the bridge is three times smaller for the RAT scenario compared to assuming perfect alignment. At shorter wavelengths (λ < 200 μm), dust polarization does not trace the magnetic field because other effects such as self-scattering and dichroic extinction dominate the orientation of the polarization.
