Considerable observational evidence suggests that the activity of supermassive black holes in galactic nuclei is transient. The term "active galactic nuclei archaeology" has even been coined. This implies the possibility of reconstructing the history of activity, such as changes in the nuclear luminosity over time across various ranges of the electromagnetic spectrum, by analysing how this activity manifested itself on galactic and extragalactic spatial scales. These phenomena include relic radio structures, gas clouds illuminated by the 'ionising echo' of past activity, and Fermi/eROSITA bubbles. We provide a review of the results galactic nucleus activity studies, focusing on its observable impact on the intergalactic medium and circumgalactic environment. Our main focus is on optical observations of ionisation cones and evidence of switching between radiative (ionisation cones) and kinetic (radio jets) modes of nuclear activity.

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Keywords: active galactic nuclei, galaxies, interstellar medium, high energy physics PACS: 98.54.Cm DOI: 10.3367/UFNe.2025.03.040022 URL: https://ufn.ru/en/articles/2026/3/e/ Citation: Moiseev A V, Arshinova A, Smirnova A A "Archaeology of galactic nuclei activity" Phys. Usp. 69 (3) (2026) Accepted: 19th, March 2025 Оригинал: Моисеев А В, Аршинова А, Смирнова А А «Археология активности ядер галактик» УФН 196 257–263 (2026); DOI: 10.3367/UFNr.2025.03.040022