paper

Is Multiphase Gas Cloudy or Misty?

arXiv:1912.07808 · doi:10.1093/mnrasl/slaa033

Abstract

Cold 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 gas `droplets' 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 (), and has a large final overdensity , 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.

published version; 5 pages, 5 figures; videos available at http://max.lyman-alpha.com/shattering

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