MHD Simulations of the ISM: The Importance of the Galactic Magnetic Field on the ISM "Phases"

Abstract

We have carried out 1.25 pc resolution MHD simulations of the ISM, on a Cartesian grid of $0\le (x,y)\le 1$ kpc size in the galactic plane and $-10\le z\le 10$ kpc into the halo, thus being able to fully trace the time-dependent evolution of the galactic fountain. The simulations show that large scale gas streams emerge, driven by SN explosions, which are responsible for the formation and destruction of shocked compressed layers. The shocked gas can have densities as high as 800 cm${}^{-3}$ and lifetimes up to 15 Myr. The cold gas is distributed into filaments which tend to show a preferred orientation due to the anisotropy of the flow induced by the galactic magnetic field. Ram pressure dominates the flow in the unstable branch $10^2<$T$\le 10^{3.9}$ K, while for T$\le 100$ K (stable branch) magnetic pressure takes over. Near supernovae thermal and ram pressures determine the dynamics of the flow. Up to 80% of the mass in the disk is concentrated in the thermally unstable regime $10^2<$T$\le 10^{3.9}$ K with $\sim 30$ of the disk mass enclosed in the T$\le 10^3$ K gas. The hot gas in contrast is controlled by the thermal pressure, since magnetic field lines are swept towards the dense compressed walls.

arXiv comment8 pages, 8 figures (in jpeg format) that include 2 simulations images and 6 plots. Paper accepted by the referee for publication in the proceedings of ``Magnetic fields and star formation: theory versus observations'', kluwer

References in corpus (5)

• Disk-Halo Interaction - I. Three-Dimensional Evolution of the Galactic Disk
• Thermal Instability-Induced Interstellar Turbulence
• The Temperature Distribution in Turbulent Interstellar Gas
• New Temperatures of Diffuse Interstellar Gas: Thermally Unstable Gas
• From Large to Small Scales: Global Models of the ISM

Cited by in corpus (10)

• Science with ASKAP - the Australian Square Kilometre Array Pathfinder
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• Turbulent Structure of a Stratified Supernova-Driven Interstellar Medium
• X-Ray Absorption from the Milky Way Halo and the Local Group
• The ISM in spiral galaxies: can cooling in spiral shocks produce molecular clouds?
• The effect of stellar feedback on the formation and evolution of gas and dust tori in AGN
• Local Turbulence Simulations for the Multiphase ISM
• On the spatial and temporal non-locality of dynamo mean-field effects in supersonic interstellar turbulence
• Galactic breeze origin for the Fermi bubbles emission
• HI Density Distribution Driven by Supernovae: A Simulation Study