The Warp and Spiral Arms of the Milky Way

  • Evan S. Levine
  • Leo Blitz
  • Carl Heiles
  • Martin Weinberg
Part of the Astrophysics and Space Science Proceedings book series (ASSSP)

We examine the outer Galactic HI disk for deviations from the b=0°plane by constructing maps of disk surface density, mean height, and thickness.We find that the Galactic warp is well described by a vertical offset plus two Fourier modes of frequency 1 and 2, all of which grow with Galactocentric radius. A perturbation theory calculation demonstrates that the tidal influence of the Magellanic Clouds creates distortions in the dark matter halo, which combine to produce disk warp amplitudes comparable to the observations. We also construct a detailed map of the perturbed surface density of HI in the outer disk demonstrating that the Galaxy is a non-axisymmetric multi-armed spiral. Overdensities in the surface density are coincident with regions of reduced gas thickness.


Surface Density Fourier Mode Spiral Structure Galactic Disk Outer Disk 
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Copyright information

© Springer Science+Business Media, LLC 2008

Authors and Affiliations

  • Evan S. Levine
    • 1
  • Leo Blitz
    • 1
  • Carl Heiles
    • 1
  • Martin Weinberg
    • 2
  1. 1.UC Berkeley Astronomy DeptBerkeleyUSA
  2. 2.Amherst Astronomy DeptUniversity of MassachussettsAmherstUSA

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