Identifying AGN's Balmer-Absorptions and stratified NLR kinematics in SDSS\.J112611.63+425246.4

TL;DR

This paper reports the discovery of a new Balmer-absorption AGN, analyzes its spectral features, and reveals complex stratified kinematics in its narrow emission-line region, indicating outflows and inflows.

Contribution

It introduces the identification of SDSS J112611.63+425246 as a Balmer-absorption AGN and studies its NLR kinematics, highlighting stratified outflow and inflow motions.

Findings

Balmer absorption detected with a blueshift of ~300 km/s

Anti-correlation between velocity shifts and ionization potential

Evidence for stratified NLR kinematics with outflows and inflows

Abstract

Balmer absorption is a rare phenomenon in active galactic nuclei (AGNs). So far, only seven Balmer-absorption AGNs have been reported in literature. We here report the identification of SDSS\,J112611.63+425246 as a new Balmer-absorption AGN through our spectral analysis, and study the kinematics of its narrow emission-line region (NLR). We model the continuum by a linear combination of a starlight component, a powerlaw from the central AGN and the emission from the FeII complex. After the subtraction of the modeled continuum, each emission/absorption line is profiled by a sum of multi Gaussian functions. All the line shifts are determined with respect to the modeled starlight component. By using the host starlight as a reference for the local system, both H$\alpha$ and H$\beta$ show AGN's absorptions with a blueshift of $\sim300\mathrm{km\ s^{-1}}$. We identify a strong anti-correlation between the inferred velocity shifts and ionization potential for various narrow emission lines, which suggests a stratified NLR kinematics. A de-accelerated outflow is implied for the inner NLR gas, while an accelerated inflow for the outer NLR gas. This complicated NLR kinematics additionally implies that AGN's narrow emission lines, even for the low-ionized lines, might not be a reliable surrogate for the velocity of the local system.