Galactic Chaos and the Circular Velocity at the Sun
Abstract
Our galaxy has a substantial nucleus that exhibits itself as a strong rise in the rotation curve inside of 2 kpc, peaking around 500 pc. Stars with very eccentric orbits that pass through the nuclear region generally cannot be confined to a flattened disk distribution; instead, they spend most of their time in the halo. In a local sample of high-velocity-dispersion disk stars, there should be an apparent deficiency of stars with very low angular momenta, because they are scattered to much higher scale heights. The deficiency or gap will be centered on the circular velocity as reflected in the motion of the LSR. Using a new galactic model, the authors calibrate the predicted depression in the distribution of tangential velocities, finding a half-width of 40 km s-1 with a depth greater than 80%. They present evidence that the expected deficiency of low-angular-momentum stars does exist in the local stars. The available data favor a scale and model-free circular velocity at the sun in the range 225 - 245 km s-1 with a most probable value of 235 km s-1.
- Publication:
-
The Astronomical Journal
- Pub Date:
- September 1987
- DOI:
- 10.1086/114503
- Bibcode:
- 1987AJ.....94..666C
- Keywords:
-
- Angular Momentum;
- Circular Orbits;
- Galactic Nuclei;
- Solar Velocity;
- Velocity Distribution;
- Cylindrical Coordinates;
- Disk Galaxies;
- Stellar Orbits;
- Astrophysics;
- STARS: STELLAR STATISTICS;
- GALAXIES: CLUSTERING