Strong FeII emission in NLS1s: An unsolved mystery
  The work initially started as a test to retrace the Shen & Ho (2014) Quasar
Main Sequence diagram where they claimed that the parameter RFeII, which
defines the Eigenvector 1 (EV1) is driven by the Eddington ratio alone. We
subsequently construct a refined (error and redshift limited) sample from the
original Shen et al. 2011 QSO catalogue. Based on our hypothesis - the main
driver of the Quasar Main Sequence is the maximum of the accretion disk
temperature defined by the Big Blue Bump on the Spectral Energy Distribution.
We select the four extreme sources that have RFeII $\geq$ 4.0 and use the SED
modelling code CIGALE to fit the multi-band photometric data for these sources.
We also perform detailed spectral fitting including the FeII pseudo-continuum
to estimate and compare the value of RFeII for them. We show the metallicity
dependent FeII strength in the context of this study.
