We use homogeneous samples of radio-quiet Seyfert 1 galaxies and QSOs selected from the Sloan Digital Sky Survey to investigate the connection between the velocity shift and the equivalent width (EW) of the [OIII] λ5007 emission line, and their correlations with physical parameters of active galactic nuclei (AGNs). We find a fairly strong and negative correlation between the EW of the core component, EW(core), and the blueshift of either the core (the peak), the wing, or the total profile of [OIII] emission. However, both quantities (EW and velocity shift) have only weak, if any, correlations with fundamental AGN parameters such as the nuclear continuum luminosity at 5100 Å (L5100), black hole mass (MBH), and the Eddington ratio (L/LEdd); these weak correlations include the classical Baldwin effect of EW(core), an inverse Baldwin effect of EW(wing), and the relationship between velocity shifts and L/LEdd. Our findings suggest that both the large object-to-object variation in the strength of [OIII] emission and the blueshift–EW(core) connection are not governed primarily by fundamental AGN parameters such as L5100, MBH and L/LEdd. We propose that the ISM conditions of the host galaxies play a major role instead in the diversity of the [OIII] properties in active galaxies. This suggests that the use of [OIII] λ5007 luminosity as proxy of AGN luminosity does not depend strongly on the above-mentioned fundamental AGN parameters.

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