The evolution of QSO host colours

Wisotzki, Lutz; Jahnke, Knud; Sanchez, Sebastian F.;Schramm, Malte. The evolution of QSO host colours. New Astronomy Reviews. 2006, Vol. Volume 50, Issue 9-10, p. 829-832, p. -2006.

We summarise the evidence that the hosts of luminous QSOs are systematically bluer than normal (inactive) galaxies of comparable morphological type. We particularly emphasize the importance of performing such studies in a comparative way, placing QSO hosts in a context of the overall galaxy population.