  We present UV rest frame spectra of 3 powerful narrow line radio galaxies and
the hyperluminous type 2 active galaxy SMM02399-0136, all at high redshift
(z>2).
  We find high velocities (FWHM>1000, km/s) in the extended gas of all objects.
A natural explanation is the interaction between the radio jet and the ambient
gas, that drives shocks into the gas and accelerates the clouds. However, the
existence of high velocities in regions where such interactions are not taking
place implies that other processes can play a role. We discuss here several
possible mechanisms.
