KINEMATICS OF BULGE GIANTS IN F588

摘要

Radial velocities for 331 stars in the F588 bulge field at l, b = (8°, 7°) are obtained. The mean Galacto-centric velocity for 319 stars with R ≤ 12.3 is < V > = 54.4 ± 4.7 km s~(-1), and the velocity dispersion is σ = 84.4 ± 3.3 km s~(-1). These stars have metal abundances based on a set of spectral indices calibrated against a grid of ～400 standard stars. Dividing the sample according to metallicity, the halo and bulge components are kinematically distinct. The 65 K giants with [Fe/H] ?- 1 (mostly halo giants) have < V > =-7.0±13.6 km s~(-1) and σ = 109.4 ± 9.6 km s~(-1). The 31 "pure" halo giants (with [Fe/ H] ≤ -1.5) have < V > = -5.8 ± 20.4 km s~(-1) and σ = 113.5 ± 14.4 km s~(-1). The mean Galactocentric velocity and velocity dispersion for 194 bulge K giants (stars with [Fe/H] ≥ —1.0) are < V > = 65.9 ±5.1 km s~(-1) and σ_V = 71.9 ± 3.6 km s~(-1). The difference between halo and bulge kinematics is of very high statistical significance. The Galactic bulge and halo are distinct components, defined by consistency among [Fe/H], ), and σ.