Investigating how feedback is onset; young radio galaxies at the center of cool core clusters
The investigation of the AGN feedback cycle in galaxy clusters has historically been performed for systems where feedback is ongoing (“mature-feedback” systems), that is where the central jetted AGN has inflated radio lobes, pushing aside the intracluster medium (ICM). However, measuring the ICM cooling properties in systems where the gas has already been perturbed by the central activity cannot reveal the conditions that onset feedback. A potential workaround is to investigate systems that are right around the point of triggering feedback, as soon after the AGN begins its activity as possible. This talk is dedicated to recent results on two “pre-feedback” clusters, which harbor newly born radio galaxies (<10^4 yr), too young to have affected their cool cores. Chandra observations of these two systems unveiled an as-yet unheated ICM, whose entropy and cooling time within 20 kpc from the center fall below those of “mature-feedback” clusters by a factor ∼2. Conversely, MUSE data revealed that the properties of the gas at ∼10^4 K seem to remain invariant between the two feedback stages. I will discuss the implications and future perspectives on these results in the context of how feedback from cluster-central AGN is onset.