Detecting metal-rich intermediate-age Globular Clusters in NGC 4570   using K-band photometry
  Globular Cluster Systems (GCSs) of most early-type galaxies feature two peaks in their optical colour distributions. Blue-peak GCs are believed to be old and metal-poor, whereas the ages, metallicities, and the origin of the red-peak GCs are still being debated. We obtained deep K-band photometry and combined it with HST observations in g and z to yield a full SED from optical to near-infrared. This now allows us to break the age-metallicity degeneracy. We used our evolutionary synthesis models GALEV for star clusters to compute a large grid of models with different metallicities and a wide range of ages. Comparing these models to our observations revealed a large population of intermediate-age (1-3 Gyr) and metalrich (~ solar metallicity) globular clusters, that will give us further insights into the formation history of this galaxy. 
R. Kotulla, U. Fritze, P. Anders