论文标题
具有Zeeman效果的原星磁盘中的磁复杂性
Untangling Magnetic Complexity in Protoplanetary Disks with the Zeeman Effect
论文作者
论文摘要
随着最近在Atacama大毫米/亚毫米阵列（ALMA）处的圆极化能力的出现，现在可以将光谱线的Zeeman效应测量值作为直接探测Protoplanetary磁盘（PPDS）中的视线线磁场的一种手段。我们提出了一项建模研究，旨在指导对这些预期观察的物理解释。使用基于典型环盘的基准密度结构，我们使用Polaris辐射传输代码模拟了CN $ j = 1-0 $过渡的超精细分量的线发射。由于PPD中的预期磁场和典型的CN分布在很大程度上不受限制，因此我们生产具有几种不同构型的模型。提出了相应的集成Stokes $ i $和$ V $配置文件和0.4 km/s/s的分辨率，1''光束卷曲的通道图。我们证明，基于通道图的形态，来自环形主导的磁场的发射特征与垂直支配的磁场可区分。由于视线和横梁取消效果，带有环形$ \ boldsymbol {b} $ - 字段配置的磁盘会大大减少Stokes $ V $排放。因此，复杂的磁场使传统上使用的方法用于推断磁场强度（即，将Stokes $ i $的衍生物拟合到Stokes $ v $ profiles的衍生物）含糊不清，因为根据磁场的微音，给定的固有场强可能会产生各种Stokes $ V $ amplites。此外，气体间隙可以在可能模仿磁性子结构的集成Stokes $ V $配置文件中创建结构。因此，应在PPD环境中谨慎应用此方法，并且只有在磁盘的磁场构型被充分了解时，才能自信地用作磁场强度的量度。
With the recent advent of circular polarization capabilities at the Atacama Large Millimeter/submillimeter Array (ALMA), Zeeman effect measurements of spectral lines are now possible as a means to directly probe line-of-sight magnetic fields in protoplanetary disks (PPDs). We present a modeling study that aims to guide physical interpretation of these anticipated observations. Using a fiducial density structure based on a typical ringed disk, we simulate line emission for the hyperfine components of the CN $J = 1-0$ transition with the POLARIS radiative transfer code. Since the expected magnetic field and typical CN distribution in PPDs remain largely unconstrained, we produce models with several different configurations. Corresponding integrated Stokes $I$ and $V$ profiles and 0.4 km/s resolution, 1'' beam convolved channel maps are presented. We demonstrate that the emission signatures from toroidally dominated magnetic fields are distinguishable from vertically dominated magnetic field based on channel map morphology. Due to line-of-sight and beam cancellation effects, disks with toroidal $\boldsymbol{B}$-field configurations result in significantly diminished Stokes $V$ emission. Complex magnetic fields therefore render the traditionally used method for inferring line-of-sight magnetic field strengths (i.e., fitting the derivative of the Stokes $I$ to the Stokes $V$ profile) ambiguous, since a given intrinsic field strength can yield a variety of Stokes $V$ amplitudes depending on the magnetic field geometry. In addition, gas gaps can create structure in the integrated Stokes $V$ profile that might mimic magnetic substructure. This method should therefore be applied with caution in PPD environments, and can only confidently be used as a measure of magnetic field strength if the disk's magnetic field configuration is well understood.
