Impact of Jet Density on Intracluster Medium Heating in Self-Regulated AGN Feedback Simulations

TL;DR

This study addresses how AGN jet density influences intracluster medium heating and heating isotropy in cool-core clusters. Using 3D hydrodynamic simulations of a Perseus-like cluster, the authors compare single-jet and self-regulated feedback across light, fiducial, and heavy jet densities. They find that lighter jets produce more spherical bubbles and more isotropic heating but require higher average jet power to sustain self-regulation, while heavier jets heat more efficiently in the core but with more anisotropic energy deposition. The results highlight jet density as a critical parameter in AGN feedback models and underscore the need to incorporate magnetic fields, viscosity, and cosmic rays for realistic comparisons with observations.

Abstract

Active galactic nucleus (AGNs) feedback is widely accepted as the key mechanism to suppress cooling flows in galaxy clusters. However, the dependence of heating efficiency on jet properties is not fully understood. In this work, we present three-dimensional hydrodynamic simulations of a Perseus-like cluster, including both single-jet and self-regulated models, to investigate how jet density affects bubble evolution and the thermal balance of the intracluster medium. Our results confirm previous findings that lighter jets inflate more spherical bubbles and are more easily deflected by cold gas, enabling isotropic energy deposition throughout the cluster core. However, despite their broader spatial impact, lighter jets display lower overall heating efficiency, requiring higher average jet power to maintain self-regulation compared to heavier jets. We also find that the distribution and amount of cold gas significantly influence the effectiveness of jet heating. These results highlight jet density as a critical parameter in AGN feedback and emphasize the need to incorporate additional physical processes such as magnetic fields, viscosity, and cosmic rays in future studies for realistic comparisons with observations.

Figures (8)

• Figure 1: Temperature slice plots at 18 Myr after ejection, comparing different jet density cases in the single-jet model. Lighter jets produce more spherical and hotter bubbles near the cluster center, while heavier jets fail to maintain clear bubbles and penetrate the ICM more quickly.
• Figure 2: Enclosed mass profiles for single-jet simulations with different jet densities, normalized by radius squared in order to emphasize the differences close to the cluster center. This figure shows the efficiency of the ICM uplifting by jets in difference cases. The black dashed line represents the initial profile at $t = 0$.
• Figure 3: Entropy profiles for the three single-jet simulations: the different colors represent the different simulation times. This figure shows that the fiducial case has the highest heating efficiency in the central region.
• Figure 4: Density slices at $t =$740 Myrs for the self-regulated cases with varied mass loading factors $\eta$ (see Table \ref{['tab: jet density']}). The bubbles formed by lighter jets have a larger angle of deviation from the jet precession axis than those formed by heavier jets.
• Figure 5: Evolution of jet power for the self-regulated simulations with varied mass loading factors. When $t \gtrsim 500$ Myr, the cluster enters a self-regulated state, as the jet power approaches a quasi-equilibrium value. The time-averaged jet power after $t = 500$ Myr is plotted using the horizontal dashed lines and is indicated in the legend for each case. This figure shows that the lighter jets have higher time-averaged jet power and thus lower heating efficiency compared to heavier jets.