SUPERMASSIVE BLACK HOLES WITH HIGH ACCRETION RATES IN ACTIVE GALACTIC NUCLEI. III. DETECTION OF Fe II REVERBERATION IN NINE NARROW-LINE SEYFERT 1 GALAXIES

This is the third in a series of papers reporting on a large reverberation-mapping campaign aimed to study the properties of active galactic nuclei (AGNs) with high accretion rates. We present new results on the variability of the optical Fe II emission lines in 10 AGNs observed by the Yunnan Observatory 2.4 m telescope from. 2012 to 2013. We detect statistically significant time. lags, relative to the AGN continuum, in nine of the sources. This accurate measurement is achieved using a sophisticated spectral fitting scheme that allows for apparent flux variations of the host galaxy, and several narrow. lines, due to the changing observing conditions. Six of the newly detected lags are indistinguishable from the H beta lags measured in the same sources. Two are significantly longer and one is slightly shorter. Combining these findings with the Fe II lags reported in previous studies, we find an Fe II radius-luminosity relationship similar to the one for H beta, although our sample by itself shows no clear correlation. The results support the idea that Fe II emission lines originate in photoionized gas, which, for the majority of the newly reported objects, is indistinguishable from the H beta-emitting gas. We also present a tentative correlation between the lag and intensity of Fe II and H beta and comment on its possible origin.