标题： 建模低质量原恒星盘和大质量原恒星包层的CN塞曼效应观测 显示英文标题

标题： Modeling CN Zeeman Effect Observations of the Envelopes of a Low-Mass Protostellar Disk and a Massive Protostar

摘要： 我们使用 POLARIS 辐射传递代码生成了两种原恒星包层磁流体力学模拟的 CN $J = 1 - 0$分子线跃迁的模拟圆偏振塞曼发射图。 我们的第一个模型是低质量盘状包层系统（盒子长度$L = 200\text{ au}$），而第二个模型是具有原恒星风和增强的 CN 出流壳的高质量原恒星包层（$L = 10^4\text{ au}$）。 我们在模拟发射图的每个探测器像素位置计算了 Stokes $I$和 $V$的速度积分值，以及由此推导出的$V/I$偏振百分比。 我们的结果显示，当前的圆偏振仪器原则上可以观测这两种类型的原恒星环境，每种环境都包含大量包层区域，其百分比偏振超过了阿塔卡马大型毫米/亚毫米阵列 (ALMA) 圆偏振实验的 1.8% 额定灵敏度极限。 在这两个系统中，高偏振率（$\gtrsim$1.8%）的像素倾向于位于距离中心恒星中间距离的位置，并且 CN 发射线中心附近的吸收度适度为光学薄（$\tau_{LC} \sim 0.1-1$）。 此外，我们计算得到的 $V/I$ 值大致与密度加权平均视线磁感应强度成比例，这表明塞曼效应观测能够有效诊断包层尺度上的磁场强度。 我们还发现，具有较大 $V/I$ 的像素倾向于与速度积分的 $V$ 绝对值也较大的位置重合，这意味着有利的百分比偏振率的位置在原始信号方面也是有利的。 显示英文摘要

摘要： We use the POLARIS radiative transfer code to produce simulated circular polarization Zeeman emission maps of the CN $J = 1 - 0$ molecular line transition for two types of protostellar envelope magnetohydrodynamic simulations. Our first model is a low mass disk envelope system (box length $L = 200\text{ au}$), and our second model is the envelope of a massive protostar ($L = 10^4\text{ au}$) with a protostellar wind and a CN enhanced outflow shell. We compute the velocity-integrated Stokes $I$ and $V$, as well as the implied $V/I$ polarization percentage, for each detector pixel location in our simulated emission maps. Our results show that both types of protostellar environment are in principle accessible with current circular polarization instruments, with each containing swaths of envelope area that yield percentage polarizations that exceed the 1.8\% nominal sensitivity limit for circular polarization experiments with the Atacama Large Millimeter/submillimeter Array (ALMA). In both systems, high polarization ($\gtrsim$1.8\%) pixels tend to lie at an intermediate distance away from the central star and where the line-center opacity of the CN emission is moderately optically thin ($\tau_{LC} \sim 0.1-1$). Furthermore, our computed $V/I$ values scale roughly with the density weighted mean line-of-sight magnetic field strength, indicating that Zeeman observations can effectively diagnose the strength of envelope-scale magnetic fields. We also find that pixels with large $V/I$ are preferentially co-located where the absolute value of the velocity-integrated $V$ is also large, suggesting that locations with favorable percentage polarization are also favorable in terms of raw signal.