The age of early-type galaxies in clusters: an observational perspective

Abstract

Contradictory results on the evolution of lenticular galaxies (S0s) at intermediate redshift have been recently published. A careful analysis of the used methodology shows that in order to gain insights on the evolution of the morphological types it is necessary: (1) to use quantitative morphological types, (2) to propagate morphological errors in the quantity used to measure the evolution of the S0s and (3) to adopt the same morphological classes at high as at low redshift, testing the correspondence with standard types. Some published analysis fail to satisfy at least one of the above three conditions, thus undermining the claim for a young age of S0s of intermediate redshift clusters.