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Title: MAGNETIZED GAS IN THE SMITH HIGH VELOCITY CLOUD

We report the first detection of magnetic fields associated with the Smith High Velocity Cloud. We use a catalog of Faraday rotation measures toward extragalactic radio sources behind the Smith Cloud, new H I observations from the Robert C. Byrd Green Bank Telescope, and a spectroscopic map of Hα from the Wisconsin H-Alpha Mapper Northern Sky Survey. There are enhancements in rotation measure (RM) of ≈100 rad m{sup –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 ≈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 H I 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 (≈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 cloudsmore » 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.« less
Authors:
;  [1] ;  [2] ;  [3] ;  [4]
  1. CSIRO Astronomy and Space Science, Marsfield, NSW (Australia)
  2. Department of Astronomy, University of Wisconsin-Madison, Madison, WI (United States)
  3. Department of Physics, University of Wisconsin-Whitewater, Whitewater, WI (United States)
  4. National Radio Astronomy Observatory, Green Bank, WV (United States)
Publication Date:
OSTI Identifier:
22270624
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 777; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASTRONOMY; ASTROPHYSICS; COMPUTERIZED SIMULATION; COSMIC RADIO SOURCES; FARADAY EFFECT; HYDROGEN 1; INTERSTELLAR MAGNETIC FIELDS; INTERSTELLAR SPACE; MAGNETOHYDRODYNAMICS; MORPHOLOGY; PHOTOIONIZATION; ROTATION; TELESCOPES; VELOCITY