INTERACTING ELLIPTIC GALAXIES AS HOSTS OF INTERMEDIATE-REDSHIFT QUASARS

QUASARS are the most luminous objects in the Universe. It has been spe culated that they are the visible evidence for accretion of gas onto s upermassive black holes that reside at the centres of host galaxies. D irect observational confirmation that quasars reside in the centres of galaxies has been hard to obtain, because atmospheric turbulence usua lly scatters the quasar light sufficiently to swamp the signal from th e fainter surrounding galaxy. Despite the difficulties, however, many attempts have been made to observe the host galaxies(1-17), although t he results have not been definitive(18). Here we report observations o f four quasars, made with the refurbished Hubble Space Telescope. In a ll four cases the quasars reside in luminous elliptical galaxies with very close companions. This is in contrast to recent work(19,20) in wh ich host galaxies were not observed (in a sample of quasars that has o ne in common with ours). The elliptical galaxies are featureless, but the presence of close companions is suggestive of continuing interacti ons.