1998/02/03 by R. P. Olling, M. R. Merrifield · 128 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Galactic Center #Galactic tide #Galaxy rotation curve #Milky Way #Radial velocity #Rotation (mathematics) #Scientific Research and Discoveries #Stars #Stellar kinematics #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1046/j.1365-8711.1998.01577.x
published in Monthly Notices of the Royal Astronomical Society 297(3), 943-952 (Oxford University Press) · 11 pages, LaTeX, including 5 figures, using mn and epsf style files. Accepted for publication in MNRAS
arxiv created 1998/02/03 · openalex publication_date 1998/07/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
The local stellar kinematics of the Milky Way offer a useful tool for studying the rotation curve of the Galaxy. These kinematics -- usually parameterized by the Oort constants A and B -- depend on the local gradient of the rotation curve as well as its absolute value (Theta0), and the Sun's distance to the Galactic center (R0). The density of interstellar gas in the Milky Way is shown to vary non-monotonically with radius, and so contributes significantly to the local gradient of the rotation curve. We have therefore calculated mass models for the Milky Way that include this component, and have derived the corresponding radial variation in the Oort constants. Between 0.9R0 and 1.2R0, the Oort functions, A(R) and B(R), differ significantly from the general Theta/R dependence. Various previously-inexplicable observations are shown to be consistent with these predictions. These models can explain the 40% difference between the values for 2 A R0 derived from radial velocity data originating in the inner and outer Galaxy. They also go some way toward explaining the different shapes of the velocity ellipsoids of giant and dwarf stars in the solar neighbourhood. However, a consistent picture only emerges if one adopts small values of R0 = 7.1 +/- 0.4 kpc and Theta0 = 184 +/- 8 km/s. With these Galactic constants, the Milky Way's rotation curve declines slowly in the outer Galaxy; Vrot(20 kpc) = 166 kms. Our low value for R0 agrees well with the only direct determination (7.2 +/- 0.7 kpc, Reid 1993). Using these Galactic constants, we find that the proper motion of Sgr A^* is consistent with the observational constraints. The radial velocities and proper motions of our best fit model are entirely consistent with the radial velocities of Cepheids and the Hipparcos measurements of their proper motions.