Аннотация
Using high-resolution simulations with explicit treatment of stellar feedback
physics based on the FIRE (Feedback in Realistic Environments) project, we
study how galaxy formation and the interstellar medium (ISM) are affected by
magnetic fields, anisotropic Spitzer-Braginskii conduction and viscosity, and
sub-grid turbulent metal diffusion. We consider controlled simulations of
isolated (non-cosmological) galaxies but also a limited set of cosmological
"zoom-in" simulations. Although simulations have shown significant effects from
these physics with weak or absent stellar feedback, the effects are much weaker
than those of stellar feedback when the latter is modeled explicitly. The
additional physics have no systematic effect on galactic star formation rates
(SFRs). In contrast, removing stellar feedback leads to SFRs being
over-predicted by factors of \$10 -100\$. Without feedback, neither galactic
winds nor volume filling hot-phase gas exist, and discs tend to runaway
collapse to ultra-thin scale-heights with unphysically dense clumps
congregating at the galactic center. With stellar feedback, a multi-phase,
turbulent medium with galactic fountains and winds is established. At currently
achievable resolutions, the additional physics investigated here (MHD,
conduction, viscosity, metal diffusion) have only weak (\$\sim10\%\$-level)
effects on these properties and do not significantly alter the balance of
phases, outflows, or the energy in ISM turbulence, consistent with simple
equipartition arguments. We conclude that galactic star formation and the ISM
are primarily governed by a combination of turbulence, gravitational
instabilities, and feedback.
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