非均匀YSO喷流的冲击动力学：三维模拟符合多历元观测
The Shock Dynamics of Heterogeneous YSO Jets: 3-D Simulations Meet Multi-Epoch Observations
摘要：
对年轻星体喷流的高分辨率观测表明，它们是由许多小尺度的结或团块组成的。在本文中，我们报告的3-D数值模拟的结果，旨在研究这些团块如何相互作用，并创建发射线观测中看到的形态和运动模式。我们的模拟集中在团块规模的动力学施加球形，过密区域之间的速度差异，然后导致形成弓冲击更快的团块超过较慢的材料。我们发现，大部分的空间结构明显的发射线图像的射流产生的动力学和相互作用，这些弓冲击。我们的模拟显示了各种随时间变化的功能，包括明亮的结与马赫茎的冲击相交，一个“泡沫”的排放结构，所产生的非线性薄壳不稳定性（NTSI）的存在下沿弓激波的表面，并合并和破碎的团块。我们的模拟使用一种新的非平衡冷却方法来产生H $α$和[S II]中的合成发射图。这些直接与多历元哈勃太空望远镜（HST）的赫比格-哈罗（HH）喷流的观测。我们发现在模拟中看到的功能和观察的自行和形态之间的良好协议。因此，我们的结论是，YSO喷流可能是由异质结构和这些结构之间的相互作用，它们产生的冲击可以解释许多细节的YSO喷流演化。
英文摘要：
High resolution observations of Young Stellar Object (YSO) jets show them to be composed of many small-scale knots or clumps. In this paper we report results of 3-D numerical simulations designed to study how such clumps interact and create morphologies and kinematic patterns seen in emission line observations. Our simulations focus on clump scale dynamics by imposing velocity differences between spherical, over-dense regions which then lead to the formation of bow shocks as faster clumps overtake slower material. We show that much of the spatial structure apparent in emission line images of jets arises from the dynamics and interactions of these bow shocks. Our simulations show a variety of time-dependent features, including bright knots associated with Mach stems where the shocks intersect, a "frothy" emission structure that arises from the presence of the Non-linear Thin Shell Instability (NTSI) along the surfaces of the bow shocks, and the merging and fragmentation of clumps. Our simulations use a new non-equilibrium cooling method to produce synthetic emission maps in H$α$ and [S II]. These are directly compared with multi-epoch Hubble Space Telescope (HST) observations of Herbig-Haro (HH) jets. We find excellent agreement between features seen in the simulations and the observations in terms of both proper motion and morphologies. Thus we conclude that YSO jets may be dominated by heterogeneous structures and that interactions between these structures and the shocks they produce can account for many details of YSO jet evolution.
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