The Blueshifting and Baldwin effects for the [OIII] 5007 Emission Line in Type 1 Active Galactic Nuclei

TL;DR

This study investigates the relationship between the velocity shift and equivalent width of the [OIII] 5007 emission line in Type 1 AGNs, revealing that host galaxy conditions influence these properties more than fundamental AGN parameters.

Contribution

It demonstrates that host galaxy interstellar medium conditions, rather than AGN intrinsic parameters, primarily drive [OIII] emission line variations in active galactic nuclei.

Findings

Negative correlation between EW(core) and blueshift of [OIII]

Weak correlations between [OIII] properties and AGN parameters

Host galaxy ISM conditions significantly influence [OIII] emission

Abstract

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] 5007 emission line, and their correlations with physical parameters of active galactic nuclei (AGNs). We find a significant 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; it is fairly strong for the blueshift of the total profile particularly. However, both quantities (EW and velocity shift) generally have only weak, if any, correlations with fundamental AGN parameters such as the nuclear continuum luminosity at 5100 L_{5100}, black hole mass (M_{BH}), and the Eddington ratio (L/L_{Edd}); these correlations include the classical Baldwin effect of EW(core), an inverse Baldwin effect of EW(wing), and the relationship between velocity shifts and \lratio. 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 L_{5100}, M_{BH} and L/L_{Edd}. 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] 5007 luminosity as proxy of AGN luminosity does not depend strongly on the above-mentioned fundamental AGN parameters.