Article

# The vertical velocity dispersion profile of the Galactic thick disk

01/2008;
Source: arXiv

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 (sigma_W) of 3.8+/-0.8 km/s kpc. Even more noteworthy, our values of $\sigma_W$ are small compared to literature values: in the middle of the vertical height range we find sigma_W(z=2kpc)=30 km/s. We found no possible explanation for this small value of sigma_W in terms of sample contamination by thin disk stars, nor by wrong assumptions regarding the metallicity distribution and the derived distances.

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### Keywords

5 kpc

770 thick disk red giants

derived distances

literature values

small value

South Galactic Pole

thin disk stars

vertical height range

vertical velocity dispersion

vertically