DDO integrated photometry of globular clusters and initial chemical evolution of the galaxy

Integrated photometry of 91 galactic globular clusters was carried out with theUBV and DDO systems. A method to determine reddening is presented. Metal abundances were obtained by means of a calibration ofC(42–45)₀ vs Fe/H]. Thirteen other clusters whose metallicity values were made compatible with those observed here, were added to the sample totalizing a homogenous set of Fe/H] estimates for 104 globular clusters. This sample is used to analyze the spatial distribution of metallicities. An estimate of the intrinsic metal abundance frequency distribution of the globular cluster system is provided. The chemical properties of the globular cluster system are compared with one-zone-chemical-enrichment models which take into account gas loss from star formation regions. It is concluded that these models cannot describe the complete chemical enrichment of the globular cluster system.