Abstract
We present the results of radial velocity measurements of 770 thick disk red giants toward the South Galactic Pole, vertically distributed from 0.5 kpc to 5 kpc with respect to the Galactic plane. We find a small gradient in the vertical velocity dispersion (σ_{W}) of 3.8+/-0.8 km s^{-1} kpc^{-1}. Even more noteworthy, our values of σ_{W} are small compared to literature values: in the middle of the vertical height range we find σ_{W,{z=2kpc}}=30 km s^{-1}. We found no possible explanation for this small value of σ_{W} in terms of sample contamination by thin disk stars, nor by wrong assumptions regarding the metallicity distribution and the derived distances.
