Identifying AGN Balmer absorptions and stratified narrow emission-line region kinematics in SDSS J112611.63+425246.4

Abstract

Context. Balmer absorption is a rare phenomenon in active galactic nuclei (AGNs). So far, only seven Balmer-absorption AGNs have been reported in the literature.
Aims: 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).
Methods: We modeled the continuum by a linear combination of a starlight component, a power law from the central AGN, and the emission from the FeII complex. After subtracting the modeled continuum, each emission or absorption line profile is a sum of multi-Gaussian functions. All the line shifts were determined with respect to the modeled starlight component.
Results: By using the host starlight as a reference for the local system, both Hα and Hβ show AGN absorptions with a blueshift of ~300 km s^-1. We identify a strong anticorrelation between the inferred velocity shifts and the ionization potential for various narrow emission lines, which suggests a stratified NLR kinematics. A de-accelerated outflow is implied for the inner NLR gas, an accelerated inflow for the outer NLR gas. This complicated NLR kinematics additionally implies that AGN narrow emission lines, even for the low-ionized lines, might not be a reliable substitute for the velocity of the local system.