Why study quasar hosts?
HST studies of local (z < 0.3) quasars show that their hosts tend to be dominated by a massive spheroidal component. At z = 2.5 a significant fraction of all massive black holes were active. Very likely all large elliptical galaxies contain massive black holes and are potential quasar hosts. Quasar evolution and the starformation history of the universe share similar properties growth & fuelling of black holes is closely linked to the evolution of large-scale structure.
