Using the adaptive mesh refinement code MG, we perform hydrodynamic simulations of the interaction of a shock with a molecular cloud evolving due to thermal instability and gravity. To explore the relative importance of these processes, three case studies are presented. The first follows the formation of a molecular cloud out of an initially quiescent atomic medium due to the effects of thermal instability and gravity. The second case introduces a shock whilst the cloud is still in the warm atomic phase, and the third scenario introduces a shock once the molecular cloud has formed. The shocks accelerate the global collapse of the clouds with both experiencing local gravitational collapse prior to this. When the cloud is still atomic, the evolution is shock dominated and structures form due to dynamical instabilities within a radiatively cooled shell. While the transmitted shock can potentially trigger the thermal instability, this is prevented as material is shocked multiple times on the order of a cloud crushing time-scale. When the cloud is molecular, the post-shock flow is directed via the pre-existing structure through low-density regions in the inter-clump medium. The clumps are accelerated and deformed as the flow induces clump-clump collisions and mergers that collapse under gravity. For a limited period, both shocked cases show a mixture of Kolmogorov and Burgers turbulence-like velocity and logarithmic density power spectra, and strongly varying density spectra. The clouds presented in this work provide realistic conditions that will be used in future feedback studies.

中文翻译：

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由于热不稳定性和重力，激波与分子云在其演化的各个阶段的相互作用

使用自适应网格细化代码 MG，我们对冲击与由于热不稳定性和重力而演变的分子云的相互作用进行流体动力学模拟。为了探讨这些过程的相对重要性，我们介绍了三个案例研究。第一个是由于热不稳定性和重力的影响，从最初静止的原子介质中形成分子云。第二种情况在云仍处于温暖原子阶段时引入了冲击，而第三种情况在分子云形成后引入了冲击。冲击加速了云的全球坍塌，在此之前两者都经历了局部引力坍塌。当云还是原子的时候，由于辐射冷却壳内的动力学不稳定性，演化以冲击为主，结构形成。虽然传输的冲击可能会触发热不稳定性，但由于材料在云压碎时间尺度上受到多次冲击，因此可以防止这种情况发生。当云是分子云时，冲击后的流动通过预先存在的结构被引导通过团间介质中的低密度区域。当流动引起在重力作用下坍塌的团块碰撞和合并时，团块被加速和变形。在有限的时间内，这两个冲击案例都显示出 Kolmogorov 和 Burgers 湍流状速度和对数密度功率谱以及强烈变化的密度谱的混合。