The NGC 1399 globular cluster system: Washington photometry revisited

A new analysis and discussion of Washington CCD photometry for some 500 glo bular cluster candidates associated with the Fornax cluster cD galaxy NGC 1 399 are presented. The image handling in this work includes improved method s for the removal of both the galaxy halo and fringing effects over that em ployed in a previous work of ours. The analysis of the globular cluster can didates inside an annular region between 0.'5 and 4' from the galaxy center using two-color diagrams shows a clear bimodal distribution for objects fa inter than T-1 = 21.0 (V approximate to 21.5). The modal colors of the glob ular clusters belonging to the red population are coincident, within the me asuring uncertainties, with those of the galaxy halo. In turn, the average integrated colors of the blue population are comparable to those of the blu est non-star-forming low surface brightness galaxies in Fornax. Red cluster s appear more centrally concentrated than the blue clusters. A new determin ation of the integrated luminosity function turnover (T-1 = 23.24) leads to a distance modulus for NGC 1399 of V-o - M-v = 31.02 +/- 0.2. The total nu mber of globular clusters, combined with our preliminary photometry of the galaxy halo, leads to an overall specific frequency S-N = 5.6 +/- 1.0, whic h is considerably lower than previous estimates available in the literature . We note that these last values have been based on an extrapolation of ape rture photometry of the inner regions of the galaxy.