Evolution of [OIII]5007 emission-line profiles in narrow emission-line
  galaxies
  The AGN-host co-evolution issue is investigated here by focusing on the
evolution of the [\ion{O}{3}]$\lambda5007$ emission-line profile. In order to
simultaneously measure both [\ion{O}{3}] line profile and circumnuclear stellar
population in individual spectrum, a large sample of narrow emission-line
galaxies is selected from the MPA/JHU SDSS DR7 catalog. By requiring that 1)
the [\ion{O}{3}] line signal-to-noise ratio is larger than 30, 2) the
[\ion{O}{3}] line width is larger than the instrumental resolution by a factor
of 2, our sample finally contains 2,333 Seyfert galaxies/LINERs (AGNs), 793
transition galaxies, and 190 starforming galaxies. In additional to the
commonly used profile parameters (i.e., line centroid, relative velocity shift
and velocity dispersion), two dimensionless shape parameters, skewness and
kurtosis, are used to quantify the line shape deviation from a pure Gaussian
function. We show that the transition galaxies are systematically associated
with narrower line widths and weaker [\ion{O}{3}] broad wings than the AGNs,
which implies that the kinematics of the emission-line gas is different in the
two kinds of objects. By combining the measured host properties and line shape
parameters, we find that the AGNs with stronger blue asymmetries tend to be
associated with younger stellar populations. However, the similar trend is not
identified in the transition galaxies. The failure is likely resulted from a
selection effect in which the transition galaxies are systematically associated
with younger stellar populations than the AGNs. The evolutionary significance
revealed here suggests that both NLR kinematics and outflow feedback in AGNs
co-evolve with their host galaxies.
