Extragalactic globular clusters in the near-infrared

Abstract

Visual and near-infrared colours are used to identify intermediate-age globular cluster in early-type galaxies. In NGC5846 and NGC4365 colour-colour diagrams (V-I vs. V-K) reveal a sub-population in the globular cluster systems with an age much younger than the expected old populations (13-15 Gyr). A comparison with SSP models dates the formation of this younger population 2-7 Gyr back. Further evidence for multiple star formation events is given by the age distribution in both systems and the comparison to models. Our photometric age determination was confirmed by spectroscopy for a small sample of the clusters in NGC4365.