The MEGARA view of outflows in LINERs

¹ Instituto de Astrofísica de Andalucía – CSIC, Glorieta de la Astronomía s/n, 18008 Granada, Spain
² Centro de Astrobiología (CAB, CSIC-INTA), Camino Bajo el Castillo s/n, 28692 Villanueva de la Cañada, Madrid, Spain
e-mail: lhermosa@cab.inta-csic.es
³ Departamento de Física de la Tierra y Astrofísica, Universidad Complutense de Madrid, 28040 Madrid, Spain
⁴ Instituto de Física de Partículas y del Cosmos IPARCOS, Facultad de Ciencias Físicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
⁵ Instituto Nacional de Astrofísica, Óptica y Electrónica, Luis Enrique Erro 1, 72840 Tonantzintla, Puebla, Mexico
⁶ FRACTAL S.L.N.E., Calle Tulipán 2, Portal 13, 1A, 28231 Las Rozas de Madrid, Spain

Received: 8 August 2023
Accepted: 18 November 2023

Abstract

Context. Feedback processes, in particular those driven by outflows, are believed to play a major role in galaxy evolution. Outflows are believed to be ubiquitous in all active galactic nuclei (AGNs), although their presence in low luminosity AGNs, in particular for Low-Ionisation Nuclear Emission line Regions (LINERs), has only started to be explored. Their properties (geometry, mass, and energetics) are still far from being properly characterised.

Aims. The main goal is to use integral field spectroscopic data from the MEGARA instrument at the Gran Telescopio Canarias (GTC) to analyse a small sample of nine LINERs, candidates of hosting ionised gas outflows. We aim to study the main emission lines in the optical wavelength range to identify their properties and physical origin.

Methods. We obtained data cubes in several bands at the lowest (R ∼ 6000) and highest (R ∼ 20 000) spectral resolution of MEGARA. We modelled and subtracted the stellar continuum to obtain the ionised gas contribution, and then fitted the emission lines to extract their kinematics (velocity and velocity dispersion). We identified outflows as a secondary component in the emission lines and obtained their main properties.

Results. The primary component of the emission lines was typically associated with gas in the galactic disc. For some objects, there is an enhanced-σ region typically co-spatial with the secondary component. We associated it to turbulent gas produced due to the interaction with the outflows. We find signatures of outflows in six LINERs, with mass outflow rates ranging from 0.004 to 0.4 M_⊙ yr⁻¹ and energy rates from ∼10³⁸ to ∼10⁴⁰ erg s⁻¹. Their mean electronic density is 600 cm⁻³, extending to distances of ∼400 pc at an (absolute) velocity of ∼340 km s⁻¹ (on average). They tend to be compact and unresolved, although for some sources they are extended with a bubble-like morphology.

Conclusions. Our results confirm the existence of outflows in the best LINER candidates identified using previous long-slit spectroscopic and imaging data. These outflows do not follow the scaling relations obtained for more luminous AGNs. For some objects we discuss jets as the main drivers of the outflows.