The Prevalence of Gas Outflows in Type 2 AGNs

TL;DR

This study analyzes gas outflows in a large sample of type 2 AGNs, revealing that ionized gas outflows are common and linked to AGN luminosity and accretion, but not directly to radio activity.

Contribution

It provides a comprehensive analysis of ionized gas outflows in type 2 AGNs, quantifying their prevalence and relation to AGN properties using a large dataset.

Findings

Ionized gas outflows are prevalent among type 2 AGNs.

Outflow velocity correlates with AGN luminosity and Eddington ratio.

Outflows are not strongly related to radio luminosity.

Abstract

To constrain the nature and fraction of the ionized gas outflows in AGNs, we perform a detailed analysis on gas kinematics as manifested by the velocity dispersion and shift of the [O III] {\lambda}5007 emission line, using a large sample of ~39,000 type 2 AGNs at z<0.3. First, we confirm a broad correlation between [O III] and stellar velocity dispersions, indicating that the bulge gravitational potential plays a main role in determining the [O III] kinematics. However, [O III] velocity dispersion is on average larger than stellar velocity dispersion by a factor of 1.3-1.4 for AGNs with double Gaussian [O III], suggesting that the non-gravitational component, i.e., outflows, is almost comparable to the gravitational component. Second, the increase of the [O III] velocity dispersion (after normalized by stellar velocity dispersion) with both AGN luminosity and Eddington ratio suggests that non-gravitational kinematics are clearly linked to AGN accretion. The distribution in the [O III] velocity - velocity dispersion diagram dramatically expands toward large values with increasing AGN luminosity, implying that the launching velocity of gas outflows increases with AGN luminosity. Third, the majority of luminous AGNs presents the non-gravitational kinematics in the [O III] profile. These results suggest that ionized gas outflows are prevalent among type 2 AGNs. On the other hand, we find no strong trend of the [O III] kinematics with radio luminosity, once we remove the effect of the bulge gravitational potential, indicating that ionized gas outflows are not directly related to radio activity for the majority of type 2 AGNs.