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We present deep direct images of five IRAS-selected QSOs with similar IR luminosities and spectral indices. The redshifts are in the range 0.11-0.44. Radio observations were obtained of three of the objects. Our sample objects have IR luminosities similar to the IRAS flux-limited sample of ultraluminous galaxies, but have IR spectral indices similar to normal QSOs. Four of the objects are in strong tidal interaction, and have blue host galaxies (due to star formation?) and reddened nuclei. Unreddened nuclear magnitudes correspond to QSO luminosities in these four cases. We suggest that these are QSOs and AGN in an intermediate early stage of their activity, which lies between the ultraluminous galaxies and optically selected QSOs. The high fraction of strong tidal events in such objects is noted.
Hutchings et al. (Tue,) studied this question.