The UV and optical Fe II emission lines in type 1 AGNs
  We investigate the spectral properties of the UV ($\lambda\lambda$2650-3050
\AA) and optical ($\lambda\lambda$4000-5500 \AA) Fe II emission features in a
sample of 293 type 1 active galactic nuclei (AGNs) from Sloan Digital Sky
Survey (SDSS) database. We explore different correlations between their
emission line properties, as well as the correlations with the other emission
lines from the spectral range. We find several interesting correlations and we
can outline the most interesting results as follows. (i) There is a kinematical
connection between the UV and optical Fe II lines, indicating that the UV and
optical Fe II lines originate from the outer part of the broad line region,
so-called intermediate line region; (ii) The unexplained anticorrelations of
the optical Fe II (EW Fe II$_{opt}$) versus EW [O III] 5007 \AA\ and EW Fe
II$_{opt}$ versus FWHM Hbeta have not been detected for the UV Fe II lines;
(iii) The significant averaged redshift in the UV Fe II lines, which is not
present in optical Fe II, indicates an inflow in the UV Fe II emitting clouds,
and probably their asymmetric distribution. (iv) Also, we confirm the
anticorrelation between the intensity ratio of the optical and UV Fe II lines
and FWHM of Hbeta, and we find the anticorrelations of this ratio with the
widths of Mg II 2800 \AA, optical Fe II and UV Fe II. This indicates a very
important role for the column density and microturbulence in the emitting gas.
We discuss the starburst activity in high-density regions of young AGNs as a
possible explanation of the detected optical Fe II correlations and intensity
line ratios of the UV and optical Fe II lines.
