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arXiv · 1911.07872

Kinematics and Dynamics of Multiphase Outflows in Simulations of the Star-Forming Galactic ISM

Aditi Vijayan·Chang-Goo Kim·Lucia Armillotta·Eve C. Ostriker·Miao Li
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Abstract

Galactic outflows produced by stellar feedback are known to be multiphase in nature. Both observations and simulations indicate that the material within several kpc of galactic disk mid-planes consists of warm clouds embedded within a hot wind. A theoretical understanding of the outflow phenomenon, including both winds and fountain flows, requires study of the interactions among thermal phases. We develop a method to quantify these interactions via measurements of mass, momentum, and energy flux exchanges using temporally and spatially averaged quantities and conservation laws. We apply this method to a star-forming ISM MHD simulation based on the TIGRESS framework, for Solar neighbourhood conditions. To evaluate the extent of interactions among the phases, we first examine the validity of the ``ballistic model,'' which predicts trajectories of the warm phase ($5050\,\rm{K} 5\times10^5\,\rm{K}$) to the warm phase. The large energy flux from the hot outflow that is transferred to the warm and intermediate phases is quickly radiated away. A simple interaction model implies an effective warm cloud size in the fountain flow of a few 100~pc, showing that warm-hot flux exchange mainly involves a few large clouds rather than many small ones.

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Aditi Vijayan, Chang-Goo Kim, Lucia Armillotta, Eve C. Ostriker, Miao Li. 2019-11-18. Kinematics and Dynamics of Multiphase Outflows in Simulations of the Star-Forming Galactic ISM. https://doi.org/10.3847/1538-4357%2Fab8474

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