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Lookup NU author(s): Dr David RosarioORCiD, Daniel Hill
This work is licensed under a Creative Commons Attribution 4.0 International License (CC BY 4.0).
© 2026. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. We present a detailed, spatially resolved Veilleux and Osterbrock (VO) diagram analysis of ESO 137-G034, a Compton-thick active galactic nucleus (AGN), based on narrowband Hubble Space Telescope imaging in [O III], [S II], Hα, and Hβ emission lines. The narrowband optical emission exhibits a biconical morphology and traces the diffuse X-ray emission observed with Chandra. We dissect the interstellar medium (ISM) into Seyfert-, LINER-, and H II-dominated regions with a resolution of ∼0 (Formula presented) .″ 1 (∼20 pc at z = 0.009). To visualize the fine spatial structure of the ISM excitation, we introduce a new parameter: the Seyfert/LINER Index (SLI), defined as the perpendicular distance of each point in the VO diagram from the Seyfert/LINER division line. SLI mapping reveals fine spatial structures in the ISM excitation especially in the Seyfert ionization bicones where the statistical significance of our data is higher. Most of the emission within the bicones is Seyfert-like, with SLI values consistent with regions of the VO diagram that can be modeled with AGN photoionization. In the northwest Seyfert cone three radial SLI peaks suggest episodic nuclear outbursts, with estimated timescales of a few 103 yrs and <100 yrs duration. The southeast cone shows inhomogeneous excitation, with a higher SLI region in its inner part, coinciding with a wider region of enhanced soft X-ray emission at the radio lobe inner edge. This region is characterized by line ratios consistent with mechanical excitation from fast shocks (>1000 km s−1) induced excitation. The northwest cone is surrounded by a smooth LINER “cocoon.” The LINER region in the southeast cone appears more irregular, with intercone LINER points likely shaped by both local ISM structure and shocks. Our findings highlight the complex interplay of different AGN feedback mechanisms in the ISM.
Author(s): Krol DL, Fabbiano G, Elvis M, Falcao AT, Zhu P, Kewley LJ, Middei R, Rosario D, Davies R, Shimizu T, Hill D
Publication type: Article
Publication status: Published
Journal: Astrophysical Journal
Year: 2026
Volume: 1005
Issue: 2
Print publication date: 10/07/2026
Online publication date: 08/07/2026
Acceptance date: 03/06/2026
Date deposited: 21/07/2026
ISSN (print): 0004-637X
ISSN (electronic): 1538-4357
Publisher: American Astronomical Society
URL: https://doi.org/10.3847/1538-4357/ae78d2
DOI: 10.3847/1538-4357/ae78d2
Data Access Statement: Some of the data presented in this article were obtained from the Mikulski Archive for Space Telescopes (MAST) at the Space Telescope Science Institute. The specific observations analyzed can be accessed via doi: 10.17909/gdjr-yc45.
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