Detailed mechanism of AGN feedback in galaxy evolution remains unknown

Determine the detailed physical mechanisms by which active galactic nucleus (AGN) feedback regulates star formation in massive galaxies, specifically how AGN-driven energy couples to and impacts the interstellar and circumgalactic medium to truncate star formation and produce the observed galaxy population.

Background

Cosmological simulations require energy input from active galactic nuclei (AGN) to prevent excessive star formation in massive galaxies and to reproduce the observed galaxy population. While multiple feedback channels have been proposed—such as radiative (quasar-mode) winds and kinetic (radio-mode) jets—the concrete physical pathways and coupling efficiencies by which AGN energy interacts with multiphase gas remain unsettled.

This uncertainty motivates studies like the present work that focus on spatially resolving the kinematics and energetics of outflows and jet–ISM interactions, especially at high redshift, to constrain how feedback operates in detail.

References

However, the detailed mechanism regarding this feedback process is still unknown.

— JWST Reveals Powerful Feedback from Radio Jets in a Massive Galaxy at z = 4.1  (2401.11612 - Roy et al., 2024) in Section 1.1 (Background)

However, we point out that a tension between predictions from simulations and observed stellar content of the most massive halos is shared by different simulations presented in the literature \citep[e.g.][and references therein]{schaye.etal.2023,Nelson.etal.2024}, thus highlighting the relevance of properly addressing this open problem.

— Dianoga simulations of galaxy clusters and groups: Properties of the baryonic components  (2608.17570 - Borgani et al., 18 Aug 2026) in Section 3.2, subsection “Properties of the Brightest Cluster Galaxies”

Despite such significant improvements, several open issues remain that outline future lines of development. First, while our multi-phase gas evaporation model (M4--M6 models) succeeded in regulating star formation, it remains an isotropic thermal implementation acting on a sub-resolution effective model of star formation. Including an explicit treatment of the kinetic mode of AGN feedback to describe the effect of sub-relativistic jets during periods of low accretion, with directionality explicitly provided by a self-consistent description of the SMBH spin evolution \citep[e.g.][]{Sala.etal.2024} represents the first necessary further step. In fact, including the effect of AGN-driven jets \citep[e.g.][]{Barai.etal.2016} has been shown to be a promising avenue to regulate star formation and produce realistic cool-core structures in the cosmological framework of hierarchical assembly of galaxy clusters \citep[e.g.][]{Weinberger.etal.2026,Rosenberg.etal.2026}. Another direction of improvement should involve the description of the SMBH accretion. While the Bondi criterion is the most common accretion model adopted, its validity relies on assumptions that are not expected to be fulfilled in a cosmological environment. Implementing a model in which the BH gas accretion rate is directly related to the amount of gas cooling within halos should allow to effectively establish a self-regulated balance between heating and cooling in the cores of massive halos \citep[e.g.][]{Gaspari2020}. Finally, the results presented in Appendix \ref{app:feed} from the models including cold gas evaporation highlight that the effect of AGN feedback on star formation sensitively depends on how these two sectors interact with each other, and definitely represents a direction of investigation for forthcoming analyses. In this respect, moving to a star formation model that explicitly treats the mass- and energy-flows between the different ISM phases \citep[e.g.][]{Valentini.etal.2020,Valentini.etal.2023}, also incorporating the effect of \mathrm{H}_{2} formed on dust grains \citep{Ragone.etal.2024}, would allow a more direct and self-consistent description of the effect of AGN feedback on star formation.

— Dianoga simulations of galaxy clusters and groups: Properties of the baryonic components  (2608.17570 - Borgani et al., 18 Aug 2026) in Section 5, Conclusions

However, this comparison is model-dependent, and our data do not directly show that AGN feedback removes or heats the central gas.

— Interplay of Compaction, Quenching, and Black Hole Growth in the Most Massive Galaxies since $z\sim5$: Insights from JWST and Chandra Data  (2608.24124 - Haryana et al., 25 Aug 2026) in Section 5.3, Comparison with Theoretical Expectations