Ground-based and HST optical-infrared studies of quasar host galaxies at low redshift

Abstract

We describe the results from a series of ground-based and HST programs aimed at investigating the host galaxies of both radio-loud and radio-quiet quasars (RLQs & RQQs) and FRII radio galaxies (RGs) at low redshifts (0.1 < z < 0.3). Our results are in good agreement with those of other recent studies of host galaxies. In general the hosts of powerful AGN are large, luminous (> 2L^*) galaxies, with underlying stellar populations which are predominantly old and red. The host galaxies of RLQs are massive ellipticals, indistinguishable from the FRII radio galaxies, consistent with unification of these sources by viewing angle. Although we find disc-like hosts around two low-luminosity (M_R > -23.5) RQQs, our R-band imaging campaign with HST, though currently incomplete, indicates that all quasars with M_R < -23.5, occur in massive elliptical galaxies regardless of their radio luminosity.