The Prevalence of Gas Outflows in Type 2 AGNs
  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.
