The Two-Component Colour-Structure of the gE Galaxy NGC 4472

From the observational point of view the ‘missing link’ in our understanding of the chemical and dynamical evolution of early-type galaxies still lies in the lack of a reliable data set of colour and metallicity distributions for a considerable number of objects. The problem in measuring colours mainly arises from the extremely small amplitude of the expected gradients and the difficulties to remove the sky background precisely. Typical colour-changes of the order of 0.01 mag/□” may be detected down to the brightness level of the sky only if the background determination is accurate to ∆F sky / F sky < 1 %.