On the globular cluster formation history of NGC 5128

Abstract

We deduce the globular cluster formation history of the nearby elliptical galaxy, NGC 5128, by using a chemical enrichment model to accurately reproduce its observed metallicity distribution function (MDF). We derive the observed MDF using recently obtained U and B photometry of the NGC 5128 GC system, with (U - B) used as the metallicity indicator. Our results indicate that the GC system in this galaxy could be the product of two major GC formation episodes. The initial formation episode occured 11-12 Gyr ago creating 65-75 percent of the mass in the GC system. This was followed by a second late formation episode which peaked 2-4 Gyr ago and produced the remaining 25-35 percent of GC mass.