  An objective classification of the globular clusters of NGC 5128 has been
carried out by using a model-based approach of cluster analysis. The set of
observable parameters includes structural parameters, spectroscopically
determined Lick indices and radial velocities from the literature. The optimum
set of parameters for this type of analysis is selected through a modified
technique of Principal Component Analysis, which differs from the classical one
in the sense that it takes into consideration the effects of outliers present
in the data. Then a mixture model based approach has been used to classify the
globular clusters into groups. The efficiency of the techniques used is tested
through the comparison of the misclassification probabilities with those
obtained using the K-means clustering technique. On the basis of the above
classification scheme three coherent groups of globular clusters have been
found. We propose that the clusters of one group originated in the original
cluster formation event that coincided with the formation of the elliptical
galaxy, and that the clusters of the two other groups are of external origin,
from tidally stripped dwarf galaxies on random orbits around NGC 5128 for one
group, and from an accreted spiral galaxy for the other.
