Gas-phase metallicity for the Seyfert galaxy NGC 7130

Abstract

Metallicity measurements in galaxies can provide valuable clues about galaxy evolution. One of the mechanisms postulated for metallicity redistribution in galaxies is gas flows induced by active galactic nuclei (AGNs), but the details of this process remain elusive. We report the discovery of a positive radial gradient in the gas-phase metallicity of the narrow-line region of the Seyfert 2 galaxy NGC 7130, which is not found when considering the star-forming (SF) components in the galaxy disc. To determine gas-phase metallicities for each kinematic component, we used both AGN and SF strong-line abundance relations, as well as Baldwin–Phillips–Terlevich diagnostic diagrams. These relations involve sensitive strong emission lines, namely [O III]λ5007, [N II]λ6584, Hα, Hβ, [S II]λ6716, and [S II]λ6731, observed with the adaptive-optics-assisted mode of the Multi Unit Spectroscopic Explorer at the Very Large Telescope. The presence of a positive radial metallicity gradient in only the ionised AGN component suggests that metals may be transported from central areas of a galaxy to its purlieus by AGN activity.