Bisogni, SusannaSusannaBisogniMarconi, AlessandroAlessandroMarconiRISALITI, GuidoGuidoRISALITI2020-09-012020-09-0120170035-8711http://hdl.handle.net/20.500.12386/27011We present an analysis of the orientation effects in Sloan Digital Sky Survey (SDSS) quasar composite spectra. In a previous work, we have shown that the equivalent width (EW) of the [O III] λ5007 Å (vacuum rest wavelength 5008.24 Å) line is a reliable indicator of the inclination of the accretion disc. Here, we have selected a sample of ∼12 000 quasars from the SDSS 7th Data Release and divided it in subsamples with different values of EW_{[{O {III}]}}. 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_{[{O {III}]}} as an orientation indicator. Moreover, we suggest that orientation effects could explain, at least partially, the origin of the anticorrelation between [O III] and Fe II intensities, I.e. the well-known eigenvector 1.STAMPAenArticle10.1093/mnras/stw23242-s2.0-85014795992000393646300029https://academic.oup.com/mnras/article/464/1/385/21946872017MNRAS.464..385BFIS/05 - ASTRONOMIA E ASTROFISICA