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 \sim 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 .