用AstroBEAR模拟辐射磁流体动力学流动：非平衡冷却的实现和应用
Simulating Radiative Magnetohydrodynamical Flows with AstroBEAR: Implementation and Applications of Non-equilibrium Cooling
摘要：
辐射冷却在许多天体物理流动的动力学中起着至关重要的作用，特别是在赫比格-哈罗（HH）天体和恒星喷流中的致密激波气体中。精确地模拟冷却过程是必要的，以比较数值模拟与现有的和计划的观测HH对象，如那些从哈勃太空望远镜和詹姆斯韦伯太空望远镜。在本文中，我们讨论了一个新的，非平衡冷却计划，我们已经实现了3-D磁流体动力学（MHD）的代码AstroBEAR。新的冷却功能包括电离，复合和激发所有重要的原子物种，冷却到10000 K以下。我们通过将其预测结果与经过良好测试的一维Cox-Raymond激波代码（Raymond 1979）的预测结果进行比较，对该程序进行了测试。结果表明，AstroBEAR准确地跟踪电离分数，温度和其他MHD变量的所有低速（0.90公里/秒）磁化辐射冲击波。新的程序使我们能够预测在恒星喷流中观察到的所有明亮的禁止线和允许线的合成发射图，包括Hα，[NII]，[OI]和[SII]。我们提出了一个例子，这些合成地图如何促进HH对象的窄带图像的直接比较。
英文摘要：
Radiative cooling plays a crucial role in the dynamics of many astrophysical flows, and is particularly important in the dense shocked gas within Herbig-Haro (HH) objects and stellar jets. Simulating cooling processes accurately is necessary to compare numerical simulations with existing and planned observations of HH objects, such as those from the Hubble Space Telescope and the James Webb Space Telescope. In this paper we discuss a new, non-equilibrium cooling scheme we have implemented into the 3-D magnetohydrodynamic (MHD) code AstroBEAR. The new cooling function includes ionization, recombination, and excitation of all the important atomic species that cool below 10000 K. We tested the routine by comparing its predictions with those from the well-tested 1-D Cox-Raymond shock code (Raymond 1979). The results show thatAstroBEAR accurately tracks the ionization fraction, temperature, and other MHD variables for all low-velocity (.90 km/s) magnetized radiative shock waves. The new routine allows us to predict synthetic emission maps in all the bright forbidden and permitted lines observed in stellar jets, including Hα, [NII], [OI], and [SII]. We present an example as to how these synthetic maps facilitate a direct comparison with narrowband images of HH objects.
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