A search for ionised gas outflows in an Halpha imaging atlas of nearby LINERs

TL;DR

This study compiles the largest atlas of ionised gas outflow candidates in 70 nearby LINERs using multi-wavelength imaging and kinematic data, revealing a significant incidence of outflows and their correlation with soft X-ray emission.

Contribution

It provides the first comprehensive morphological and kinematic analysis of ionised gas outflows in LINERs, combining new and archival data to estimate outflow incidence.

Findings

Approximately 48% of LINERs show outflows or inflows based on combined morphological and kinematic data.

Ionised gas often coexists spatially with soft X-ray emission, suggesting a common origin.

The study proposes using Halpha imaging as an effective pre-selection tool for outflow candidates.

Abstract

Outflows play a major role in the evolution of galaxies. However, we do not have yet a complete picture of their properties (extension, geometry, orientation and clumpiness). For low-luminosity Active Galactic Nuclei (AGNs), in particular, low-ionisation nuclear emission line regions (LINERs), the rate of outflows and their properties are largely unknown. The main goal of this work is to create the largest, up-to-date atlas of ionised gas outflow candidates in a sample of 70 nearby LINERs. We use narrow-band, imaging data to analyse the morphological properties of the ionised gas nuclear emission of these galaxies and to identify signatures of extended emission with distinctive outflow-like morphologies. We obtained new imaging data from ALFOSC/NOT for 32 LINERs. We complemented it with HST archival data for 6 objects and with results from the literature for other 32 targets. We additionally obtained soft X-ray data from Chandra archive to compare with the ionised gas. The distribution of the ionised gas in these LINER shows that $\sim$32% have bubble-like emission, $\sim$28% show a 'Core-halo', unresolved emission, and $\sim$21% have a disky-like distribution. Dust lanes prevent a detailed classification for $\sim$11% of the sample ('Dusty'). If we account for the kinematical information, available for 60 galaxies, we end up with 48% of the LINERs with detected outflows/inflows (50% considering only kinematical information based on Integral Field Spectroscopy). Our results suggest that the incidence of outflows in LINERs may vary from 41% up to 56%, based on both the Halpha morphology and the kinematical information from the literature. The ionised gas is co-spatial with the soft X-ray emission for the majority of cases ($\sim$60%), so that they may have a common origin. We discuss the use of Halpha imaging for the pre-selection of candidates likely hosting ionised gas outflows.