  The investigation of the feedback cycle in galaxy clusters has historically
been performed for systems where feedback is ongoing ("mature-feedback"
clusters), that is where the central radio galaxy has inflated radio lobes,
pushing aside the intracluster medium (ICM). In this pilot study we present
results from "pre-feedback" clusters, where the central newly active radio
galaxies (age $<10^{3}$ yr) may not yet have had time to alter the
thermodynamic state of the ICM. We analyze $Chandra$ and MUSE observations of
two such systems, evaluating the hot gas entropy and cooling time profiles, and
characterizing the morphology and kinematics of the warm gas. Based on our
exploratory study of these two sources, we find that the hot gas meets the
expectations for an as-yet unheated ICM. Specifically, the entropy and cooling
time of pre-feedback clusters within 20 kpc from the center fall below those of
mature-feedback clusters by a factor $\sim$2. We speculate that with an
estimated mechanical power of $\sim10^{44} - 10^{45}$ erg s$^{-1}$, the two
young radio galaxies may restore the entropy levels in a few tens of Myr, which
are typical values of power outbursts and lifetimes for radio galaxies in
clusters. Conversely, the properties of the gas at $\sim10^{4}$ K seem to
remain invariant between the two feedback stages, possibly suggesting that the
warm gas reservoir accumulates over long periods ($10^{7}$ - $10^{8}$ yr)
during the growth of the radio galaxy. We conclude that the exploratory results
obtained from our analysis of two cluster-central young radio galaxies are
crucial in the context of understanding the onset of active galactic nuclei
feedback, and they provide enough motivation for further investigation of
similar cases.
