2024MNRAS.531..259P

Radiative cooling and active galactic nucleus heating are thought to form a feedback loop that regulates the evolution of low-redshift cool-core galaxy clusters. Numerical simulations suggest that the formation of multiphase gas in the cluster core imposes a floor on the ratio of cooling time (t_cool) to free-fall time (t_ff) at min(t_cool/t_ff) ≈ 10. Observations of galaxy clusters show evidence for such a floor, and usually the cluster cores with min(t_cool/t_ff) ≲ 30 contain abundant multiphase gas. However, there are important outliers. One of them is Abell 2029 (A2029), a massive galaxy cluster (M₂₀₀ ≳ 10¹⁵ M_⊙) with min(t_cool/t_ff) ∼ 20, but little apparent multiphase gas. In this paper, we present high-resolution 3D hydrodynamic adaptive mesh refinement simulations of a cluster similar to A2029 and study how it evolves over a period of 1-2 Gyr. Those simulations suggest that A2029 self-regulates without producing multiphase gas because the mass of its central black hole (${\sim} 5 \times 10^{10} \, \mathrm{ M}_\odot$) is great enough for Bondi accretion of hot ambient gas to produce enough feedback energy to compensate for radiative cooling.