Comparison of the rich optical Fe II line spectra of selected I Zw 1 type objects from two epochs

Abstract- This paper presents the analysis of medium resolution optical spectra of NLSy1 objects obtained with the 1.9 m telescope at SAAO (Sutherland). Six bright objects were observed during at least two epochs in the two year period from January 2016 to November 2017: ESO 12-G21, Fairall 265, Mkn 1044, H 0707-495, IRAS 03450+0055 and Ton S180. Multiple spectra for each epoch were co-added to achieve exceptionally high signal-to-noise, allowing the resolution and characterization of weak individual Fe II and other lines. Parameters determined from line profiles include relative strength, width and asymmetry. The combined spectra from each epoch were then compared to establish the existence and possible nature and extent of spectral changes in each object. As opposed to many other types of AGN, no dramatic spectral changes were detected between the epochs, and our spectra also do not differ much from decade-old discovery spectra of these objects. Where changes were detected, we detail these and attempt to interpret these in terms of established physical models of NLSy1 galaxies.