Chemical enrichment in LINERs from MaNGA

II. Characterizing the shape of the radial metallicity gradients

¹ Instituto de Astrofísica de Andalucía (IAA-CSIC) Glorieta de la Astronomía s/n 18008 Granada, Spain
² Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg Mönchhofstraße 12-14 D-69120 Heidelberg, Germany
³ Faculty of Physics, Ludwig-Maximilians-Universität Scheinerstr. 1 81679 Munich, Germany
⁴ Main Astronomical Observatory, National Academy of Sciences of Ukraine 27 Akad. Zabolotnoho St 03680 Kyiv, Ukraine
⁵ Institute of Astronomy, Pontificia Universidad Católica de Chile Avenida Vicuña Mackena 4690 Santiago, Chile
⁶ Centro de Astro-Ingeniería, Pontificia Universidad Católica de Chile Avenida Vicuña Mackena 4690 Santiago, Chile
⁷ INAF - Osservatorio Astronomico di Roma via Frascati 33 I-00078 Monte Porzio Catone, Italy

^★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 5 June 2025
Accepted: 8 December 2025

Abstract

Context. Chemical abundance radial gradients provide key information on how the processes that affect chemical enrichment of the gas-phase interstellar medium (ISM) act at different galaxy scales. In the past decades, though there has been an increase in the number of galaxies studied with integral field spectroscopy, there is still not a clear picture on a subsequent characterization of the chemical abundance radial gradients in galaxies hosting active galactic nuclei (AGNs). This lack of studies is even more accentuated in the case of low-ionization nuclear emission-line regions (LINERs).

Aims. For the first time, we analyze the chemical abundance radial gradients in a sample of LINER-like galaxies, whose nuclear emission has been previously discussed (Paper I).

Methods. We used a sample of 97 galaxies from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA), whose nuclear regions show LINER-like emission. We used the open-source code HII-CHI-MISTRY to estimate the chemical abundance ratios 12+log(O/H) and log(N/O) in the HII regions across the disks in our sample as well as in the nuclear parts where the LINER-like activity dominates. To fit the radial profiles, we used a piecewise methodology that uses a non-fixed number of breaks to find the best fit for the data.

Results. We find that a majority of our sample of galaxies exhibit departures from the single linear gradient both in 12+log(O/H) and log(N/O), as expected from the inside-out scenario. We investigated whether these departures are driven by galaxy properties (stellar mass, neutral gas mass, stellar velocity dispersion) but found no correlation at all. We also report that in most cases, there is no correlation between the shape of the 12+log(O/H) and log(N/O) radial profiles. We propose a model in which AGN feed(back), acting at different scales depending on the galaxy and its evolutionary stage, might be responsible for these departures.