The Vertical Structure of the Outer Milky Way Hi Disk
نویسنده
چکیده
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. Adding the m = 2 mode accounts for the large asymmetry between the northern and southern warps. We use a Morlet wavelet transform to investigate the spatial and frequency localization of higher frequency modes; these modes are often referred to as “scalloping.” We find that the m = 10 and 15 scalloping modes are well above the noise, but localized; this suggests that the scalloping does not pervade the whole disk, but only local regions. Subject headings: Galaxy: disk — Galaxy: structure — Galaxy: kinematics and dynamics — ISM: structure — radio lines: general
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