  Wide-field photometric data from the Sloan Digital Sky Survey have recently
revealed that the Galactic globular cluster Palomar 5 is in the process of
being tidally disrupted (Odenkirchen et al. 2001). Here we investigate the
kinematics of this sparse remote star cluster using high resolution spectra
from the Very Large Telescope (VLT). Twenty candidate cluster giants located
within 6 arcmin of the cluster center have been observed with the UV-Visual
Echelle Spectrograph (UVES) on VLT-UT2. The spectra provide radial velocities
with a typical accuracy of 0.15 km/s. We find that the sample contains 17
certain cluster members with very coherent kinematics, two unrelated field
dwarfs, and one giant with a deviant velocity, which is most likely a cluster
binary showing fast orbital motion. From the confirmed members we determine the
heliocentric velocity of the cluster as -58.7 +- 0.2 km/s. The total
line-of-sight velocity dispersion of the cluster stars is 1.1 +- 0.2 km/s (all
members) or 0.9 +- 0.2 km/s (stars on the red giant branch only). This is the
lowest velocity dispersion that has so far been measured for a stellar system
classified as a globular cluster. The shape of the velocity distribution
suggests that there is a significant contribution from orbital motions of
binaries and that the dynamical part of the velocity dispersion is therefore
still substantially smaller than the total dispersion. ... (abridged)
