[O iii] 5007 Å Emission Line Width as a Surrogate for σ ∗ in Type 1 AGNs?

• Published in: The Astrophysical journal 2023-03, Vol.945 (1), p.59
• Main Authors: Le, Huynh Anh N., Xue, Yongquan, Lin, Xiaozhi, Wang, Yijun
• Format: Article
• Language: English
• Subjects: Active galactic nuclei; Active galaxies; Astrophysics; Emission analysis; Emission line galaxies; Emission lines; Galaxy kinematics; Luminosity; Outflow; Red shift; Scattering; Spiral galaxies; Stellar kinematics
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/acb770

We present a study of the relation between the [O iii ] 5007 Å emission line width ( σ [O III ] ) and stellar velocity dispersion ( σ * ), utilizing a sample of 740 type 1 active galactic nuclei (AGNs) with high-quality spectra at redshift z < 1.0. We find the broad correlation between the core component of the [O iii ] emission line width ( σ [ O III , core ] ) and σ * with a scatter of 0.11 dex for the low redshift ( z < 0.1) sample; for redshift (0.3 < z < 1.0) AGNs, the scatter is larger, being 0.16 dex. We also find that the Eddington ratio ( L bol / L Edd ) may play an important role in the discrepancies between σ [ O III , core ] and σ * . As the L bol / L Edd increases, σ [ O III , core ] tends to be larger than σ * . By classifying our local sample with different minor-to-major axis ratios, we find that σ * is larger than σ [ O III , core ] for those edge-on spiral galaxies. In addition, we also find that the effects of outflow strength properties such as maximum outflow velocity ( V max ) and the broader component of the [O iii ] emission line width and line shift ( σ [O III ,out] and V [O III ,out] ) may play a major role in the discrepancies between σ [ O III , core ] and σ * . The discrepancies between σ [ O III , core ] and σ * are larger when V max , V [O III ,out] , and σ [O III ,out] increase. Our results show that the outflow strengths may have significant effects on the differences between narrow-line region gas and stellar kinematics in AGNs. We suggest that caution should be taken when using σ [ O III , core ] as a surrogate for σ * . In addition, the substitute of σ [ O III , core ] for σ * could be used only for low luminosity AGNs.