High luminosity galaxies in the IRAS survey

The IRAS survey has demonstrated the existence of a previously unrecognized class of ultraluminous objects. These ultraluminous infrared galaxies represent the dominant population of extragalactic emitters at luminosities where the only other objects known are quasars. Observations suggest that these objects are all found in merging galaxies, and appear to be dust enshrouded quasars. We suggest that these IR loud quasars represent the formation stage of quasars, with the latter stages in the evolution of such systems being found in the UV excess quasars.