Globular cluster systems II : On the formation of old globular clusters and their sites of formation

We studied the metal-poor globular cluster populations of a large variety of galaxies and compared their mean metallicity with the properties of the host galaxies. For this purpose, we constructed a comprehensive database of old, metal-poor globular cluster populations, hosted by 47 galaxies spanning about 10 magnitudes in absolute brightness. The mean metallicities of the systems are found to be very similar and to lie in the −1.65 <[Fe/H]≤ −1.20 range (74 % of the population). Using only globular cluster systems with more than 6 objects detected, we find that 85 % of the population are within −1.65 <[Fe/H]≤ −1.20. The relation between the mean metallicity of the metal-poor globular cluster systems and the absolute V magnitude of their host galaxies presents a very low slope which includes zero. An analysis of the correlation of the mean metallicity of the populations with other galaxy properties (such as velocity dispersion, metallicity, environment density) also leads to the conclusion that no strong correlation exists. The lack of correlation with galaxy properties suggests a formation of all metal-poor globular clusters in very similar gas fragments. A weak correlation (to be confirmed) might exist between mean metallicity of the metal-poor clusters and host galaxy metallicity. This would imply that at least some fragments in which metal-poor