Poster Presentation Astronomical Society of Australia Annual Scientific Meeting including HWWS 2013

Magnetic fields in the Smith Cloud (#227)

Alex S Hill 1 , Robert A Benjamin 2 , Sui Ann Mao 3 4 , Felix J Lockman 5 , Naomi M McClure-Griffiths 1
  1. CSIRO Astronomy & Space Science, Epping, NSW, Australia
  2. Department of Physics, University of Wisconsin-Whitewater, Whitewater, WI, USA
  3. NRAO, Socorro, NM, USA
  4. Department of Astronomy, University of Wisconsin-Madison, Madison, WI, USA
  5. NRAO, Green Bank, WV, USA

The accretion of gas is an important component of galaxy evolution by providing fresh fuel for star formation. However, it is unknown whether and how infalling gas can reach galactic disks. The Smith Cloud is perhaps the best-studied example of a high velocity cloud interacting with the Galactic halo 3 kpc below the midplane, a case study of the active accretion in the Milky Way. We analyse H I, Hα, and Faraday rotation data for the Smith Cloud. We find filamentary structures in both H I and Hα which suggest shocked and decelerated bow waves from the interaction between the cloud and the halo ISM. There are also enhancements in Faraday rotation measure aligned with the Hα filaments, suggesting a magnetic field of > 3 μG in these filaments which may pervade the rest of the Smith Cloud. This object promises to provide an excellent case study for magnetohydrodynamic simulations of gas accretion.