Morphology-dependent trends of galaxy age with environment in A 901/2 seen with COMBO-17

We investigate correlations between galaxy age and environment in the A 901/2 supercluster for separate morphologies. Using COMBO-17 data, we define a sample of 530 galaxies, complete at MV− 5 log h < −18 on an area of 3.5 × 3.5 (Mpc h−1)2. We explore several age indicators including an extinction-corrected residual from the colour–magnitude relation. As a result, we find a clear trend of age with density for galaxies of all morphologies that include a spheroidal component, in the sense that galaxies in denser environments are older. This trend is not seen among Scd/Irr galaxies since they all have young ages. However, the trend among the other types is stronger for fainter galaxies. While we also see an expected age–morphology relation, we find no evidence for a morphology–density relation at fixed age.