SIMBAD references

Extended halo tidal streams from disrupting Milky Way satellites offer new opportunities for gauging fundamental Galactic parameters without challenging observations of the Galactic center. In the roughly spherical Galactic potential, tidal debris from a satellite system is largely confined to a single plane containing the Galactic center, so accurate distances to stars in the tidal stream can be used to gauge the Galactic center distance, R₀, given reasonable projection of the stream orbital pole on the X_GCaxis. Alternatively, a tidal stream with orbital pole near the Y_GCaxis, such as the Sagittarius stream, can be used to derive the speed of the local standard of rest (Θ_LSR). Modest improvements in current astrometric catalogs might allow this measurement to be made, but NASA's SpaceInterferometry Mission (now SIM PlanetQuest) can definitively obtain both R₀and Θ_LSRusing tidal streams.