Spectrophotometry of globular clusters in NGC 5128 (Centaurus A): Determination of their metallicities

We have carried out spectrophotometry in the range 3600-9700 Angstrom of five globular clusters in NGC 5128 for which previous photometric studies suggested a high metal content. We compare the equivalent widths of a set of metallic features of the NGC 5128 clusters with those of well-studied Galactic and M31 globular clusters. This enables us to derive a reliable ranking and estimate of the metallicity for the NGC 5128 clusters. The reddening is obtained from the comparison of the continuum distribution of the observed clusters with those of reference clusters. The present spectroscopic study clarifies the question raised in the photometric studies about the NGC 5128 clusters metallicities. We conclude that, in the present NGC 5128 sample, no object has actually a metallicity higher than solar, unlike what happens in M31.