X-ray shocks in the cool cores of galaxy clusters: insights from TNG-Cluster

ABSTRACT Shock fronts driven by active galactic nuclei in galaxy cluster cores represent a promising mechanism for heating the intracluster medium and offsetting radiative cooling. Despite their potential importance, they are challenging to detect and have been identified in only about ten massive clusters. We present the first systematic detection and characterization of active galactic nuclei (AGN)-driven shocks in simulated clusters from the TNG-Cluster magnetohydrodynamic cosmological zoom-in simulations of galaxies. TNG-Cluster exhibits a rich variety of spatially resolved X-ray structures, including realistic populations of X-ray cavities, as well as shocks, produced by its AGN feedback model, without collimated, relativistic jets, nor cosmic rays. We produce mock Chandra observations with 600 ks exposures for 100 clusters, mass-matched (M$_{\text{500c}} = 1.2$–$8.5 \times 10^{14}$ M$_\odot$) to the ten observed clusters exhibiting shocks. Using observational techniques, we detect 50 shocks in 30 of the 100 clusters, with $\sim$35 per cent hosting multiple shocks. These shocks typically lie within a hundred kiloparsec of the central supermassive black holes, are weak (Mach $<$ 2, median $\sim$ 1.1), and are associated with X-ray cavities in about half of the cases. Both in observations and in TNG-Cluster, shocks tend to be located at larger radii than cavities, with median offsets of 46 and 27 kpc, respectively. The observationally inferred shock powers are comparable to the cluster cooling luminosities (10$^{44-46}$ erg s$^{-1}$), suggesting that shocks in the simulation are a crucial heating mechanism. Our results indicate that shocks play a role as important as cavities in balancing cooling in cluster cores, acting isotropically and up to larger distances.