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| Paper: |
Oort Limit from HIPPARCOS |
| Volume: |
182, Galaxy Dynamics: A Rutgers Symposium |
| Page: |
301 |
| Authors: |
Bienaymé, O.; Crézé, M.; Chereul, E.; Pichon, C. |
| Abstract: |
Hipparcos data provide the first volume-limited and absolute-magnitude-limited homogeneous tracer of stellar density and velocity distributions in the solar neighborhood. The density of A-type stars more luminous than M_v = 2.5 can be accurately mapped within a sphere of 125pc radius, while proper motions in galactic latitude provide the vertical velocity distribution near the galactic plane. The potential well across the galactic plane is traced practically hypothesis-free and model-free. The local dynamical density comes out as ρ_0 = 0.076 +/- 0.015 M_odot pc^{-3} (Crézé et al. 1997), a value well below all previous determinations leaving no room for any disk-shaped component of dark matter. In the frame of Stäckel potentials, we determine explicitly the link between the (v_&thetas;, v_z) tangential-vertical galactic velocity coupling and the local shape of the potential. This is applied to the analysis of the 3D velocity distribution of neighboring stars (Bienaymé 1999). It implies that the galactic potential is not extremely flat and that the dark matter component is not confined to the galactic plane. This is an independent confirmation of the results found from our Oort limit determination. |
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