A Keck/LRIS Spatially-Resolved Spectroscopic Study of a LINER Galaxy SDSS J091628.05+420818.7

TL;DR

This study uses spatially-resolved spectroscopy to analyze the ionization sources and gas kinematics in a nearby LINER galaxy, revealing a nuclear ionization source and complex gas motions including counter-rotation and possible outflows.

Contribution

First spatially-resolved spectroscopic analysis of a LINER galaxy revealing ionization sources and detailed gas kinematics, including counter-rotation and outflow indications.

Findings

Emission-line gas is slightly extended and centrally concentrated.

Ionization likely driven by a nuclear source, not old stars.

Gas exhibits counter-rotation and possible outflow signatures.

Abstract

Using spatially-resolved spectra obtained with the Low Resolution Imaging Spectrometer at the Keck I telescope, we investigate the nature of ionizing sources and kinematic properties of emission-line gas in a LINER galaxy SDSS J091628.05+420818.7, which is a nearby (z = 0.0241) and bright (M_r = -20.2) early-type galaxy. After subtracting stellar absorption features using a combination of simple stellar population models, we measure the flux, line-of-sight velocity, and velocity dispersion of four emission lines, i.e., H{\alpha}, H{\beta}, [O III] {\lambda}5007, and [N II] {\lambda}6584, to study radial change of emission-line fluxes and velocities. Compared to the point-spread-function of the observation, the emission-line region is slightly extended but comparable to the seeing size. The central concentration of emission-line gas suggests that ionization is triggered by a nuclear source, excluding old stellar population as ionizing sources. We find that emission-line gas is counter-rotating with respect to stellar component and that the [O III] {\lambda}5007 line is blueshifted compared to other emission lines, possibly due to an outflow.