Dynamical evolution of high velocity clouds in the intergalactic medium

Abstract

HI observations of high-velocity clouds (HVCs) indicate, that they are interacting with their ambient medium. Even clouds located in the very outer Galactic halo or the intergalactic space seem to interact with their ambient medium. In this paper, we investigate the dynamical evolution of high velocity neutral gas clouds moving through a hot magnetized ambient plasma by means of two-dimensional magnetohydrodynamic plasma-neutral gas simulations. This situation is representative for the fast moving dense neutral gas cloudlets in the Magellanic Stream as well as for high velocity clouds in general. The question on the dynamical and thermal stabilization of a cold dense neutral cloud in a hot thin ambient halo plasma is numerically investigated. The simulations show the formation of a comet-like head-tail structure combined with a magnetic barrier of increased field strength which exerts a stabilizing pressure on the cloud and hinders hot plasma from diffusing into the cloud. The simulations can explain both the survival times in the intergalactic medium and the existence of head-tail high velocity clouds.

11 pages, 19 figures

Cited by in corpus (30)

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• An Interaction of a Magellanic Leading Arm High Velocity Cloud with the Milky Way Disk
• Head-Tail Clouds: Drops to Probe the Diffuse Galactic Halo
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• HI observations of three compact high-velocity clouds around the Milky Way
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• Distant probes of RM structure -- Where is the Faraday Rotation towards the Magellanic Leading Arm?
• HI Clouds Beyond the Galactic Disk