Spectroscopic Properties of QSOs Selected from Ultraluminous Infrared Galaxy Samples

We collected an infrared QSO sample with a total of 25 objects and obtained their opt ical spectra to investigate their spectroscopic properties. Compared with optically-selected sample, the infrared-selected sample exhibits remarkably different properties. Stat ist ical analyses show that most infrared QSOs have narrow permitted emission lines (with FWHM of Hβ less than 4000 km s^-1) and more than 60% of them are luminous narrow line Seyfert 1 galaxies. Moderately or extremely strong Fe Ⅱ emitters take a fraction of more than 70%. This is the highest percentage of strong Fe Ⅱ emitters in all subclasses of QSO/ Seyfert 1 samples. The Hβ emission lines in Infrared QSOs are commonly characterized by a blueshifted profile, which is most likely related to outflows, and the blueshift is significantly correlated with the Feto Hβ line ratio.