  Luminous blue compact galaxies, common at z~1 but now relatively rare, show
disturbed kinematics in emission lines. As part of a programme to understand
their formation and evolution, we have investigated the stellar dynamics of a
number of nearby objects in this class. We obtained long-slit spectra with
VLT/FORS2 in the spectral region covering the near-infrared calcium triplet. In
this paper we focus on the well-known luminous blue compact galaxy ESO 338-IG04
(Tololo 1924-416). A previous investigation, using Fabry-Perot interferometry,
showed that this galaxy has a chaotic H-alpha velocity field, indicating that
either the galaxy is not in dynamical equilibrium or that H-alpha does not
trace the gravitational potential due to feedback from star formation. Along
the apparent major axis, the stellar and ionised gas velocities for the most
part follow each other. The chaotic velocity field must therefore be a sign
that the young stellar population in ESO 338-IG04 is not in dynamical
equilibrium. The most likely explanation, which is also supported by its
morphology, is that the galaxy has experienced a merger and that this has
triggered the current starburst. Summarising the results of our programme so
far, we note that emission-line velocity fields are not always reliable tracers
of stellar motions, and go on to assess the implications for kinematic studies
of similar galaxies at intermediate redshift.
