  Close to its center, the bulgeless galaxy NGC 2139 hosts a star cluster that
is younger and less massive than any actual nuclear star cluster (NC) studied
so far. We have measured the H-alpha velocity field around the photometric
center of this galaxy using the VLT ARGUS integral field unit and GIRAFFE
spectrograph in order to constrain different proposed theories of NC formation.
We observe that the best-fit kinematic center and the candidate NC appear to be
separated by 2.8 arcsec (320 pc). Indeed, the kinematic center also is offset
from the galaxy's photometric center and a possible bar or extended region of
star formation in which the young cluster resides, implying that this galaxy is
not in dynamic equilibrium. The H-alpha flux map also reveals other regions of
strong star formation in the possible bar. These observations suggest that a
nascent NC is forming away from the kinematic center of NGC 2139 which may come
to rest there on a time scale of a few 100 Myr.
