Orientation effects on spectral emission features of quasars
  We present an analysis of the orientation effects in SDSS quasar composite
spectra. In a previous work we have shown that the equivalent width EW of the
[OIII] {\lambda}5008{\AA} line is a reliable indicator of the inclination of
the accretion disk. Here, we have selected a sample of ~15,000 quasars from the
SDSS 7th Data Release and divided it in sub-samples with different values of
EW([OIII]). We find inclination effects both on broad and narrow quasars
emission lines, among which an increasing broadening from low to high EW for
the broad lines and a decreasing importance of the blue component for the
narrow lines. These effects are naturally explained with a variation of source
inclination from nearly face-on to edge-on, confirming the goodness of
EW([OIII]) as an orientation indicator. Moreover, we suggest that orientation
effects could explain, at least partially, the origin of the anticorrelation
between [OIII] and FeII intensities, i.e. the well known Eigenvector 1.
