Blueshifted [O  iii ] Emission Line Driven by Outflows in Nearby AGNs

The primary objective of this paper is to examine the orientation-based interpretation of the blueshifted [O iii] emission line by comparing the blueshifted velocities of Type 1 and Type 2 Active Galactic Nuclei (AGNs) using a large sample derived from the Sloan Digital Sky Survey Data Release 16 (SDSS DR16). We obtained reliable measurements of both the extended and core [O iii] components, ensuring that their fluxes and line widths are at least five times greater than their corresponding uncertainties. Our analysis includes 6,566 Type 1 AGNs and 3,699 Type 2 AGNs from SDSS DR16. After accounting for the effects of central nuclear activity and orientation-related projection effects, our results indicate that the blueshifted velocity of [O iii] is significantly larger in Type 1 AGNs compared to Type 2 AGNs. This finding aligns with the unified model of AGNs, which suggests that Type 1 AGNs are more likely to exhibit larger blueshift velocities due to their unobscured line of sight, allowing direct observation of high-velocity gas. Therefore, the observed larger blueshifted velocity of [O iii] is most likely associated with orientation-dependent outflows in the narrow-line regions (NLRs).