Proper-Motion Based Kinematics Study of Galactic RR Lyraes

We use the UCAC4 and SDSS proper motions of about 7500 RR Lyrae type variables located within ~10 kpc from the Sun to study the dependence of their velocity ellipsoid on Galactocentric distance in the R _G = 3-17 kpc interval. The radial velocity dispersion, σ _VR , decreases from ~190 km/s at R _G = 3.5-5.5 kpc down to ~100 km/s at R _G = 13-15 kpc, and the σ _VT /σ _VR ratio remains virtually constant (σ _VT /σ _VR ~0.54-0.64) in the Galactocentric distance interval from R _G = 4.5 kpc to R _G = 10.5 kpc increasing to ~0.9 both toward the Galactic center and beyond R _G = 11 kpc.