The impact of turbulence on supernovae shockwaves

Abstract: The momentum and energy injection from supernovae is one of the main feedback modes, and is therefore key to the understanding of galaxy evolution and star formation. However, due to low resolution, large scale galaxy simulations often have issues with accurately modelling supernovae, and therefore rely on sub-grid models. This is especially true for the injected momentum, where capturing the momentum generating adiabatic phase of SNe, although important, is impossible to self-consistently model in large scale simulations. Previous studies have shown that the final momentum injected only has a weak dependence on the surrounding density, and that the detailed structure of the interstellar medium (ISM) is at large irrelevant when considering the momentum. However these studies lacked accurate modelling of the turbulence in the ISM, and instead resorted to static models, where the velocities of the gas were ignored. In this work, we start by retrieving a known semi-analytic solution of the early and important adiabatic Sedov-Taylor stage, responsible for most of the momentum generation. This solution is then compared to a series of full hydrodynamical simulations using an adaptive mesh refinement code, called RAMSES, with varying mean density of the surrounding ISM. With the inclusion of atomic cooling, the evolutionary stages of supernovae remnants are recovered, with the final momentum $p$ found depending on the surrounding hydrogen density $n$ as $p\propto n^{-0.15}$, in agreement with previous studies. We then adopt a model of turbulence by \cite{turb}, which was calibrated to produce power spectra, density and velocity distributions based on the conditions in giant molecular clouds (GMCs). With this model of the surrounding ISM, the geometry of the SNe shocks changes drastically, preferring channels of less dense gas, leaving higher density filaments mostly intact. However the evolution of momentum and energy of the system still follows the same trend as in the homogeneous case, reaching a similar peak momentum. The momentum was found to decrease with time, which is not predicted in the homogeneous case, but the decay appears to be on longer time scales. This reaffirms the previous results, stating that the detailed structure of the ISM only has a negligible effect on the momentum and energy of the early stages of SNe. Nevertheless, the SNe does show a tendency of generating outflows of low density gas rather than affecting the high density regions, which could have further impacts on SFR and galaxy evolution as a whole.