Inflow velocities of cold flows streaming into massive galaxies at high
  redshifts
  We study the velocities of the accretion along streams from the cosmic web
into massive galaxies at high redshift with the help of three different suites
of AMR hydrodynamical cosmological simulations. The results are compared to
free-fall velocities and to the sound speeds of the hot ambient medium. The
sound speed of the hot ambient medium is calculated using two different methods
to determine the medium's temperature. We find that the simulated cold stream
velocities are in violent disagreement with the corresponding free-fall
profiles. The sound speed is a better albeit not always correct description of
the cold flows' velocity. Using these calculations as a first order
approximation for the gas inflow velocities vinflow = 0.9 vvir is given. We
conclude from the hydrodynamical simulations as our main result that the
velocity profiles for the cold streams are constant with radius. These constant
inflow velocities seem to have a "parabola-like" dependency on the host halo
mass in units of the virial velocity that peaks at Mvir = 10^{12} Msun and we
also propose that the best fit functional form for the dependency of the inflow
velocity on the redshift is a square root power law relation: vinflow is
proportional to sqrt(z + 1) vvir.
