Trouble for AGN Feedback ? The puzzle of the core of the Galaxy Cluster AWM 4

TL;DR

The paper examines the unusual properties of galaxy cluster AWM 4, which challenge existing models of AGN feedback by showing signs of recent black hole activity despite a history of major heating that erased the cool core.

Contribution

It presents observational evidence that questions the standard AGN feedback paradigm in galaxy clusters, highlighting the complex interplay of heating and feeding processes.

Findings

AWM 4 has a flat temperature profile indicating past major heating.

Presence of active radio galaxy suggests recent black hole feeding.

Contradicts expectations of no radio emission if feedback solely regulates AGN activity.

Abstract

The core of the relaxed cluster AWM 4 is characterized by a unique combination of properties which defy a popular scenario for ANG heating of cluster cores. A flat inner temperature profile is indicative of a past, major heating episode which completely erased the cool core, as testified by the high central cooling time (~ 3 Gyr) and by the high central entropy level (~ 60 keV cm^2). Yet the presence of a 1.4 GHz active central radio galaxy with extended radio lobes out to 100 kpc, reveals recent feeding of the central massive black hole. A system like AWM 4 should have no radio emission at all if only feedback from the cooling hot gas regulates the AGN activity.