Other
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...21114805l&link_type=abstract
American Astronomical Society, AAS Meeting #211, #148.05; Bulletin of the American Astronomical Society, Vol. 39, p.1001
Other
Scientific paper
In galaxies, the gas distribution and kinematics are a reflection of the gravitational potential and the relevant physical processes. To better understand the dynamics of galactic systems, we investigated the atomic gas in the Milky Way. Using the Leiden/Argentine/Bonn (LAB) survey, we mapped the vertical structure of the Milky Way in atomic hydrogen. We reduced the complex structure of the warp to three simple Fourier spatial frequencies, and we showed that the vertical oscillations known as scalloping are local rather than global. We then used unsharp masking to produce perturbed surface density and thickness maps of the outer Milky Way disk. These maps show the presence of spiral arms out to at least 25 kpc from the Galactic center, and demonstrate that overdensities in the surface density are coincident with regions of reduced gas thickness. Using observations from the VLA Galactic Plane Survey (VGPS) and the Southern Galactic Plane Survey (SGPS), we constrained the rotation curve of the inner Galaxy and its first two vertical derivatives. We used global and local models to find the falloff in the rotation speed with distance from the plane is approximately -20 km/s/kpc. This result is consistent with the falloff measured in the halos of other galaxies, but is too large to be explained by gravitational physics alone.
ESL and LB are supported by NSF grant AST-0540567. CH is supported by NSF grant AST-0406987.
Blitz Leo
Heiles Carl
Levine Evan S.
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