# Extended ionized-gas structures in Seyfert 2 galaxy Mrk 78

## TL;DR

This study investigates the extended ionized gas regions in Seyfert 2 galaxy Mrk 78, revealing AGN ionization at large distances and clarifying the nature of nearby optical features.

## Contribution

First detailed spectroscopic analysis of EELRs in Mrk 78, demonstrating AGN ionization at 12-16 kpc and distinguishing a background galaxy from a potential companion.

## Key findings

- Ionized gas clouds are AGN-ionized at 12-16 kpc.
- The nearby optical galaxy is a background object, not a tidal companion.
- Extended ionized structures provide insights into AGN activity history.

## Abstract

Search for and study of extended emission-line regions (EELRs) related to AGN in early-type galaxies is interesting to probe the history of nuclear ionization activity and also to understand the process of external gas accretion. In this work, we present observations of the EELR in Mrk 78 obtained at the 6-m Russian telescope using the long-slit and 3D spectroscopy methods. We show that ionized-gas clouds at the 12-16 kpc projected distances from the nucleus are ionized by the AGN radiation. Also we have checked if the galaxy appearing in the optical images in the immediate neighbourhood of Mrk 78 near the external clouds is a dwarf companion or a part of a tidal structure. However, the spectrum of this galaxy, SDSS J074240.37+651021.4, obtained at the 6-m telescope corresponds to the distant background galaxy.