Black-hole activity feedback across vast scales

TL;DR

This paper reviews the extensive range of black-hole activity feedback, from small-scale accretion processes to large-scale galaxy cluster impacts, highlighting ongoing challenges and recent collaborative efforts.

Contribution

It synthesizes observational and theoretical insights across scales and reports on a collaborative meeting addressing open problems in AGN feedback.

Findings

AGN feedback operates across eight orders of magnitude in scale.

Recent collaborative efforts aim to connect different scales of black-hole activity.

Open problems remain in understanding the mechanisms of feedback across these scales.

Abstract

Both observational and theoretical studies of black-hole activity or active galactic nucleus (AGN) feedback have been ongoing since the first indication of supermassive black holes powering quasar activity in the 1960s. Although several crucial astrophysical questions have been answered in the following decades, a number of open problems remain, in particular how AGN feedback operates over nearly eight orders of magnitude - from scales of $\sim 10^{-3}\,{\rm pc}$ to the galaxy-cluster scales of a few hundred kiloparsecs. At the beginning of June 2022, about 50 junior as well as senior researchers met in Brno for the post-lockdown edition of the Cologne-Prague-Brno meeting to try to connect the dots.