  Many active galactic nuclei (AGN) and particularly narrow-line Seyfert 1
(NLS1) galaxies, usually exhibit blueshifts and blue wings in several emission
lines, which are mainly associated with outflows and strong winds. In order to
study the radial velocity difference between the narrow component of H$\beta$
and the core component of [OIII]$\lambda$5007 and the asymmetric emission of
this forbidden line, we investigate a sample of NLS1 galaxies . One of the aims
of this paper is to analyze the blue wings of the [OIII]$\lambda$5007 profiles
and their relation with the central engine. We have obtained and studied
medium-resolution spectra (190 km s$^{-1}$ FWHM at H$\beta$) of a sample of 28
NLS1 galaxies in the optical range 4300 - 5200\AA. We performed Gaussian
decomposition to the H$\beta$ and [OIII]$\lambda\lambda$4959,5007 emission
profiles in order to study the distinct components of these lines. A new blue
outlier galaxy is found, in which the center of the core component of [OIII] is
blueshifted by 405 km s$^{-1}$ relative to the center of the narrow component
of H$\beta$ line. We confirmed a previously known correlation between the
blueshift and the full width half maximum (FWHM) of the core component of
[OIII]$\lambda$5007 line. We also corroborated the correlation between the
latter and the velocity of the centroid of the blue wing. On the other hand, by
studying the radial velocity difference between the blue end of the asymmetric
emission and the centroid of the core component of [OIII], we found a
correlation between it and the central black hole mass and, therefore, with the
luminosity of the broad component of H$\beta$. Finally, we found a moderate
correlation between the luminosity of the [OIII] blue wing and the black hole
mass.
