http://arxiv.org/abs/1912.07808

Cold $T \sim 10^{4}$K gas morphology could span a spectrum ranging from large discrete clouds to a fine mist' in a hot medium. This has myriad implications, including dynamics and survival, radiative transfer, and resolution requirements for cosmological simulations. Here, we use 3D hydrodynamic simulations to study the pressure-driven fragmentation of cooling gas. This is a complex, multi-stage process, with an initial Rayleigh-Taylor unstable contraction phase which seeds perturbations, followed by a rapid, violent expansion leading to the dispersion of small cold gasdroplets’ in the vicinity of the gas cloud. Finally, due to turbulent motions, and cooling, these droplets may coagulate. Our results show that a gas cloud `shatters’ if it is sufficiently perturbed out of pressure balance ($\delta P/P\sim 1$), and has a large final overdensity $\chi_{\mathrm{f}}\gtrsim 300$, with only a weak dependence on the cloud size. Otherwise, the droplets reassemble back into larger pieces. We discuss our results in the context of thermal instability, and clouds embedded in a shock heated environment.

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M. Gronke and S. Oh
Wed, 18 Dec 19
65/71

Comments: 5 pages, 5 figures; videos available at this http URL