Abstract
This study presents the analysis of medium resolution optical spectra of Narrow-Line Seyfert
1 galaxies and investigates the physical conditions in their Fe II emission zone. The sample
includes fourteen bright AGNs from the Southern hemisphere, which shows moderate to strong
iron emission in their spectra. Parameters were determined from spectra of high signal-to-noise
ratio, which were obtained by averaging four up to ten spectra for each target. The parameters
obtained from the fits of Fe II, HV and [O III] 5007Å lines include width, asymmetry, and relative
strength. This study tests the applicability of different standard profiles to HV. The HV profile
is decomposed into broad and narrow components, as seen in all Seyfert 1 galaxies, and also an
intermediate component. A satisfactory fit is achieved when HV is fitted with three Gaussian
functions, while the fit improves when the intermediate component is fitted with a Lorentzian
profile instead of a Gaussian for most of the sample. The HV intermediate component accounted
for the largest fraction of the HV flux when a Lorentzian is used. The width of the HV Lorentzian
was found to be consistent with that of the Fe II lines, also a strong and significant correlation exists
between the Fe II shift and asymmetry of HV intermediate component. Unlike many other types of
AGNs, no drastic optical spectral variations were detected over a period of two years for the NLS1
sample, which includes even objects that are highly variable in X-ray. In particular, the variability
of the Fe II lines relative to the HV intermediate component seems to be minimal. The [O III] line
asymmetries are identified in almost all the targets that could be accounted for a primary central
and a second blue-shifted component. A strong correlation between [O III] 5007Å asymmetry
and the FWHM [O III] core component was also found and are all in agreement with the previous
results. The asymmetry possibly suggests versatile gas dynamics driven by nuclear outflow.
Key words:Active Galactic Nuclei – NLS1s – Optical Fe II emission.