The Warp and Spiral Arms of the Milky Way

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