  Based on the photometric survey of the inner region of the Centaurus cluster
(Jerjen & Dressler 1997a) we measured redshifts for a deep, surface brightness
limited sample of galaxies using the MEFOS multifibre spectrograph at the ESO
3.6m telescope. With the new data set radial velocities for 120 centrally
located cluster members become available which is equivalent to 78% of all
known cluster galaxies in the region brighter than B_T=18.5. The relevant
aspect of this investigation is that new redshifts for 32 dwarf galaxies have
been measured, rising the total number to 48. We investigate the prominent
bimodal velocity distribution of Centaurus in more detail, discussing the very
different characteristics of the velocity distributions for the main Hubble
types E&S0, spirals, Im&BCD, and dE&dS0. The nucleated, bright dwarf
ellipticals are the only galaxies with a Gaussian-like distribution centred at
3148+/-98 km/s. The remarkable coincidence of this velocity with the mean
velocity of Cen30 and the redshift of NGC 4696 in particular strongly suggests
a connection of the dE&dS0s to the gravitational centre of the Centaurus
cluster and/or to the cluster dominant E galaxy. The application of statistical
tests reveals the existence of a population dwarf galaxies bound to NGC 4696.
The dynamical parameters for the two velocity components suggest that Cen30 is
the real Centaurus cluster whereas Cen45 can only be a loosely bound group of
galaxies. This conclusion is followed up with a type-mixture analysis. All
results are fully consistent with the cluster-group scenario. Whether Cen45 is
merging with the cluster or is located in the close background remains unclear.
We show that the poorness of Cen45 represents an intrinsic problem which makes
it difficult to approach this question.
