Shocking interactions of supernova remnants with atomic and molecular clouds - the interplay between shocks, thermal instability and gravity in the large cloud regime

Using the adaptive mesh refinement code MG, we perform 3D hydrodynamic simulations of a supernova–cloud interaction in the ‘large cloud regime’. The cloud is initially atomic and evolving due to the thermal instability (TI) and gravity. We study interactions in a ‘pre-TI’ and ‘post-TI’ stage when cold and dense clumps are present, and compare these results to idealized shock–cloud scenarios in the ‘small cloud regime’, and a scenario without shocks. On aggregate, the supernova disruption is significantly weaker than that from an idealized shock due to the supernova impact being instantaneous, and not continuous. In both supernova–cloud interactions, we observe two shocks impact the cloud, followed by the development of a weak 10 km s−1 upstream flow on the cloud interface, and a global ambient pressure drop. When the cloud is still atomic, it expands due to this drop. Additionally, the TI is triggered at the front of the cloud, causing the formation of a cap-like structure with clumps embedded inside. The upstream flow converges in this region, resulting in a lobe-like cloud morphology. When the cloud is molecular, the transmitted shock disrupts the inter-clump material and causes the clumps’ outer envelopes to expand slightly and form tail-like morphologies. These effects are less pronounced than those in our shock–cloud scenarios, and more pronounced that those in our un-shocked scenario. After ∼ 3.5 Myr, the effects from the supernova decay and the cloud returns to an almost indistinguishable state from an un-shocked cloud, in spite of the global ambient pressure drop. In neither supernova–cloud scenario do we see any local gravitational collapse.