Magnetized Gas in the Smith High Velocity Cloud

Abstract

We report the first detection of magnetic fields associated with the Smith High Velocity Cloud. We use a catalog of Faraday rotation measures towards extragalactic radio sources behind the Smith Cloud, new HI observations from the Green Bank Telescope, and a spectroscopic map of Hα from the Wisconsin H-Alpha Mapper Northern Sky Survey. There are enhancements in rotation measure of approximately 100 rad m^(-2) which are generally well correlated with decelerated Hα emission. We estimate a lower limit on the line-of-sight component of the field of approximately 8 μG along a decelerated filament; this is a lower limit due to our assumptions about the geometry. No RM excess is evident in sightlines dominated by HI or Hα at the velocity of the Smith Cloud. The smooth Hα morphology of the emission at the Smith Cloud velocity suggests photoionization by the Galactic ionizing radiation field as the dominant ionization mechanism, while the filamentary morphology and high (approximately 1 Rayleigh) Hα intensity of the lower-velocity magnetized ionized gas suggests an ionization process associated with shocks due to interaction with the Galactic interstellar medium. The presence of the magnetic field may contribute to the survival of high velocity clouds like the Smith Cloud as they move from the Galactic halo to the disk. We expect these data to provide a test for magnetohydrodynamic simulations of infalling gas.

ApJ accepted. 10 pages, 5 figures in emulateapj format. Replacement corrects title, changing "Ionized" to "Magnetized"

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Cited by in corpus (31)

• The COS/UVES Absorption Survey of the Magellanic Stream. III: Ionization, Total Mass, and Inflow Rate onto the Milky Way
• Magnetic Field Morphology in Interstellar Clouds with the Velocity Gradient Technique
• Comparison of algorithms for determination of rotation measure and Faraday structure I. 1100 - 1400 MHz
• On the Metallicity and Origin of the Smith High-Velocity Cloud
• The Smith Cloud and its dark matter halo: Survival of a Galactic disc passage
• Interacting Large-Scale Magnetic Fields and Ionised Gas in the W50/SS433 System
• A Broadband Spectro-polarimetric View of the NVSS Rotation Measure Catalogue I: Breaking the nπ-ambiguity
• Constraining the Magnetic Field of the Smith High Velocity Cloud using Faraday rotation
• Magnetized High Velocity Clouds in the Galactic Halo: A New Distance Constraint
• Collisions between Dark Matter Confined High Velocity Clouds and Magnetized Galactic Disks: The Smith Cloud
• Tracing Multi-Scale Magnetic Field Structure Using Multiple Chemical Tracers in Giant Molecular Clouds
• Disentangling the Faraday rotation sky
• Physical effects on compact high-velocity clouds in the circumgalactic medium
• Simulating Gas Inflow at the Disk-Halo Interface
• A Search For Star Formation in the Smith Cloud
• The Smith Cloud: surviving a high speed transit of the Galactic disc
• Shattering and growth of cold clouds in galaxy clusters: the role of radiative cooling, magnetic fields and thermal conduction
• A Broadband Spectro-polarimetric View of the NVSS Rotation Measure Catalogue II: Effects of Off-axis Instrumental Polarisation
• Magnetic field draping around clumpy high-velocity clouds in galactic halo
• Interstellar magnetic cannon targeting the Galactic halo : A young bubble at the origin of the Ophiuchus and Lupus molecular complexes
• High-energy radiation from collisions of high velocity clouds and the Galactic disk
• Exploring Hydrodynamic Instabilities along the Infalling High-Velocity Cloud Complex A
• Synchrotron Emission from Dark Matter in Galactic Subhalos. A Look into the Smith Cloud
• Properties of 3D HI Filaments in the Smith High Velocity Cloud
• A Component of the Smith High Velocity Cloud Now Crossing the Galactic Plane
• Distant probes of RM structure -- Where is the Faraday Rotation towards the Magellanic Leading Arm?
• Neutral Gas Accretion onto Nearby Galaxies
• Accretion Onto the Milky Way: The Smith Cloud
• Cosmic Rays and Non-thermal Emission Induced by Accretion of Cool Gas onto the Galactic Disk
• Interaction Between Rogue HI Clouds and the Magnetic Field High Above the Galaxy
• Gamma rays from reaccelerated cosmic rays in high velocity clouds colliding with the Galactic disk