Unravelling the complex structure of AGN-driven outflows III. The outflow size-luminosity relation

TL;DR

This study measures the sizes of ionized gas outflows in 23 AGNs and finds a shallower size-luminosity relation than the photoionization size, highlighting the importance of kinematic measurements for understanding AGN feedback.

Contribution

The paper presents the first systematic measurement of outflow sizes in a sizable sample of AGNs using spatially-resolved kinematics, refining the size-luminosity relation.

Findings

Outflow sizes range from 0.60 to 7.45 kpc.

The size-luminosity relation has a slope of 0.28±0.03.

Kinematic outflow sizes are smaller than photoionization sizes.

Abstract

Energetic gas outflows driven by active galactic nuclei (AGNs) are considered as one of the mechanisms, by which supermassive black holes affect their host galaxies. To probe the impact of AGN-driven outflows, it is essential to quantify the size of the region under the influence of outflows. In the third of a series of papers, we present the spatially-resolved kinematics of ionized gas for 3 additional type 2 AGNs based on the Gemini Multi-Object Spectrograph (GMOS) integral field spectroscopy. Along with the 6 AGNs presented in our previous works and the 14 AGNs with available GMOS IFU data, we construct a sample of 23 luminous type 2 AGNs at z < 0.2, and kinematically measure the size of ionized gas outflows by tracing the radial decrease of the velocity dispersion of the [O iii] {\lambda}5007 emission line. The kinematically-measured outflow size ranges from 0.60 to ~7.45 kpc, depending on AGN luminosity. We find that the size of the photoionized region is larger than the kinematically-measured outflow size, while the flux-weighted photoionization size is significantly smaller. Thus, using the photoionization size as a proxy for the outflow size will lead to overestimation or underestimation, and introduce a large uncertainty of the mass outflow rate and the energy output rate. We report the outflow size-luminosity relation with a slope of 0.28{\pm}0.03, which is shallower than the slope of the correlation between the photoionization size and luminosity.