Evolution of [OIII]5007 emission-line profiles in narrow emission-line galaxies

TL;DR

This study investigates how the [OIII]5007 emission-line profiles evolve in narrow emission-line galaxies, revealing links between line shape, host galaxy properties, and AGN activity, suggesting co-evolution of NLR kinematics and galaxy evolution.

Contribution

It introduces a detailed analysis of [OIII] line profile evolution in a large galaxy sample, incorporating shape parameters and host properties to understand AGN-host co-evolution.

Findings

Transition galaxies have narrower lines and weaker broad wings than AGNs.

Stronger blue asymmetries in AGNs correlate with younger stellar populations.

NLR kinematics and outflow feedback co-evolve with host galaxy evolution.

Abstract

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.