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| Paper: |
The Evolution of the Large-Scale ISM: Bubbles, Superbubbles and Non-Equilibrium Ionization |
| Volume: |
438, The Dynamic Interstellar Medium: A Celebration of the Canadian Galactic Plane Survey |
| Page: |
313 |
| Authors: |
de Avillez, M. A.; Breitschwerdt, D. |
| Abstract: |
The ISM, powered by SNe, is turbulent and permeated by a magnetic field (with a mean and a turbulent component). It
constitutes a frothy medium that is mostly out of equilibrium and is ram pressure dominated on most of the temperature
ranges, except for T < 200 K and T > 106K, where magnetic and thermal pressures dominate, respectively. Such lack of
equilibrium is also imposed by the feedback of the radiative processes into the ISM flow. Many models of the ISM or
isolated phenomena, such as bubbles, superbubbles, clouds evolution, etc., take for granted that the flow is in the
so-called collisional ionization equilibrium (CIE). However, recombination time scales of most of the ions below
106 K are longer than the cooling time scale. This implies that the recombination lags behind and the plasma is
overionized while it cools. As a consequence cooling deviates from CIE. This has severe implications on the
evolution of the ISM flow and its ionization structure. Here, besides reviewing several models of the ISM, including
bubbles and superbubbles, the validity of the CIE approximation is discussed, and a presentation of recent developments
in modeling the ISM by taking into account the time-dependent ionization structure of the flow in a full-blown numerical
3D high resolution simulation is presented. |
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