Formation of dense gas cores in supernova remnant-cloud interactions

星星的形成发生在星际云内致密的、受重力约束的气体聚集体中。这种恒星前的“核心”被认为是由重力和强烈会聚的流动之间的非线性相互作用产生的，这些流动出现在由超新星爆炸等能量输入维持的湍流环境中。在这个项目中，理想化的但基本的问题是研究一个孤立的超新星遗迹与星际云的碰撞是否能够引发原位核心的形成。为了实现这一目标，高层次的数值建模的基础上，国家的最先进的数值，自适应网格细化和并行计算进行使用NIRVANA模拟软件。我们的模型将磁流体动力学与自重力、星际介质的辐射冷却和各向异性热传导结合起来。虽然缺乏其他物理，如非理想的磁流体动力学过程和详细的电离/化学，这种方法意味着一个重大的改进，目前的冲击云相互作用模型。在这方面的主要进展源于一个并行泊松求解器的发展和从一个有效的刚性积分器的各向异性热传导项的实施。传导的刚性积分器使得超新星遗迹膨胀的建模在计算上是可访问的，因此，允许超越通常采用的小云近似。通过探索所有上述物理效应之间的复杂相互作用，三维模拟这个项目的目的是对关键问题作出贡献，在这种条件下，致密的气核可能会在被压碎的云被下列作用破坏之前形成：磁流体动力学不稳定性

Star formation takes place in dense, gravity-bound gas aggregations within interstellar clouds. Such pre-stellar 'cores' are believed to be created by the nonlinear interaction between gravity and strongly converging flows emerging in a turbulent environment sustained by energy input from e.g. supernova explosions. In this project, the idealized but fundamental problem is studied whether the collision of an isolated supernova remnant with an interstellar cloud is able to trigger in-situ core formation. In order to achieve this goal, high-level numerical modeling based on state-of-the-art numerics, adaptive mesh refinement and parallel computing is conducted using the NIRVANA simulation software. Our model couples magnetohydrodynamics with self-gravity, radiative cooling of the interstellar medium and anisotropic thermal conduction. Although lacking other physics like non-ideal magnetohydrodynamical processes and detailed ionisation/chemistry, the approach means a substantial improvement over current shock-cloud interaction models. Major progress in this respect stems from the development of a parallel Poisson solver and from the implementation of an efficient stiff integrator for the anisotropic thermal conduction term. The stiff integrator for conduction makes a modeling of the supernova remnant expansion computationally accessible and, hence, allows to go beyond the usually adopted small-cloud approximation.By exploring the complex interplay between all aforesaid physical effects in three-dimensional simulations the project aims to contribute to the key question under which conditions dense gas cores may be formed before the crushed cloud is disrupted by the action of magnetohydrodynamical instabilities.