Astronomy Colloquium

We explore the relationship of the hosts of luminous quasars to normal giant elliptical galaxies in order to look for evidence of evolutionary trends. We use measured stellar velocity dispersions combined with effective radii and magnitudes from the literature to place the host galaxies of 8 luminous quasars (MV < -23) on the Fundamental Plane (FP), where their properties are compared to other types of galaxies. We find that the radio-loud (RL) QSO hosts have similar properties to massive elliptical galaxies, while the radio-quiet (RQ) hosts are more similar to intermediate mass galaxies. The RL hosts lie at the upper extreme of the FP due to their large velocity dispersions , low surface brightness , and large effective radii and M/L = 14.1. Our data support previous results that PG QSOs are related to gas-rich galaxy mergers that form intermediate-mass galaxies, while RL QSOs reside in massive early-type galaxies, some of which also show signs of recent mergers. Most previous work has drawn these conclusions by using estimates of the black hole mass and inferring host galaxy properties from that, while here we have relied purely on directly measured host galaxy properties.