Mapping Seyfert and LINER Excitation Modes in the Inner kpc of NGC 3393

TL;DR

This study maps the ionization structure of NGC 3393's inner kiloparsec, revealing a Seyfert bicone and a LINER cocoon, illustrating feedback effects of a Compton-thick AGN on its circumnuclear environment.

Contribution

It provides the first detailed spatially resolved BPT diagram mapping of the ENLR in NGC 3393, highlighting the morphological dependence of ionization states.

Findings

Seyfert-like emission confined within the ionization bicone

Discovery of a figure 8 shaped LINER cocoon surrounding the bicone

Sharp transition between high and low ionization zones within 100 pc

Abstract

We have mapped the extended narrow line region (ENLR) of NGC 3393 on scales of $r\lesssim4^{\prime\prime}$ ($\sim1\,$kpc) from the nucleus using emission line images of H$\alpha\,\lambda6563$, [O III]$\lambda5007$, and [S II]$\lambda\lambda6717,6731$ taken with HST as part of the CHandra survey of Extended Emission line Regions in nearby Seyfert galaxies (CHEERS). By mapping these lines onto a spatially resolved Baldwin-Phillips-Terlevich (BPT) diagram, we investigate the impact of feedback from a Compton-thick AGN on its circumnuclear ISM. We find the expected Seyfert-like emission within the ionization bicone ($\lesssim3^{\prime\prime}$; 770 pc). We also find a new, figure 8 shaped LINER cocoon enveloping the bicone and defining a sharp ($\lesssim100\;$pc) transition between higher and lower ionization zones. These data illustrate the morphological dependence of ionization states of the ENLR relative to bicone and host gas geometries.