Chemical Abundance of the LINER galaxy UGC 4805 with SDSS-IV MaNGA

TL;DR

This study investigates the oxygen abundance in the LINER galaxy UGC 4805 using SDSS-IV MaNGA data, comparing multiple methods and models, and suggests a stellar origin for the ionizing source rather than an active nucleus.

Contribution

It demonstrates that various methods for estimating oxygen abundance in LINERs yield consistent results and supports a stellar ionizing source hypothesis for UGC 4805.

Findings

Abundance estimates from different methods agree within uncertainties.

Nuclear emission-line ratios reliably estimate oxygen abundance.

Stellar sources likely dominate ionization in UGC 4805.

Abstract

Chemical abundance determinations in Low-Ionization Nuclear Line Regions (LINERs) are especially complex and uncertain because the nature of the ionizing source of this kind of object is unknown. In this work, we study the oxygen abundance in relation to the hydrogen abundance (O/H) of the gas phase of the UGC4805 LINER nucleus. Optical spectroscopic data from the Mapping Nearby Galaxies (MaNGA) survey was employed to derive the O/H abundance of the UGC4805 nucleus based on the extrapolation of the disk abundance gradient, on calibrations between O/H abundance and strong emission-lines for Active Galactic Nuclei (AGNs) as well as on photoionization models built with the Cloudy code, assuming gas accretion into a black hole (AGN) and post-Asymptotic Giant Branch (p-AGB) stars with different effective temperatures. We found that abundance gradient extrapolations, AGN calibrations, AGN and p-AGB photoionization models produce similar O/H values for the UGC4805 nucleus and similar ionization parameter values. The study demonstrated that the methods used to estimate the O/H abundance using nuclear emission-line ratios produce reliable results, which are in agreement with the O/H values obtained from the independent method of galactic metallicity gradient extrapolation. Finally, the results from the WHAN diagram combined with the fact that the high excitation level of the gas has to be maintained at kpc scales, we suggest that the main ionizing source of the UGC4805 nucleus probably has a stellar origin rather than an AGN.