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Date and Time of the Query: 2019-06-16 T22:00:05 PDT
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For refcode 2012ApJ...754L..35H:
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2012ApJ...754L..35H Magnetic Field Transport from Disk to Halo via the Galactic Chimney Process in NGC 6946 Heald, George H. Abstract. The interstellar medium (ISM) in galaxies is directly affected by the mass and energy outflows originating in regions of star formation. Magnetic fields are an essential ingredient of the ISM, but their connection to the gaseous medium and its evolution remains poorly understood. Here, we present the detection of a gradient in Faraday rotation measure (RM), co-located with a hole in the neutral hydrogen (H I) distribution in the disk of the nearby spiral galaxy NGC 6946. The gas kinematics in the same location show evidence for infall of cold gas. The combined characteristics of this feature point to a substantial vertical displacement of the initially plane-parallel-ordered magnetic field, driven by a localized star formation event. This reveals how the large-scale magnetic field pattern in galaxy disks is directly influenced by internal energetic phenomena. Conversely, magnetic fields are observed to be an important ingredient in disk-halo interactions, as predicted in MHD simulations. Turbulent magnetic fields at smaller spatial scales than the observed RM gradient will also be carried from the disk and provide a mechanism for the dynamo process to amplify the ordered magnetic field without quenching. We discuss the observational biases and suggest that this is a common feature of star-forming galaxies with active disk-halo flows. Key words: galaxies: evolution, galaxies: individual: NGC 6946, galaxies: ISM, galaxies: magnetic fields, galaxies: structure
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