How active galactic nucleus feedback and metal cooling shape cluster entropy profiles

Abstract

Observed clusters of galaxies essentially come in two flavours: non‐cool‐core clusters characterized by an isothermal temperature profile and a central entropy floor, and cool‐core clusters where temperature and entropy in the central region are increasing with radius. Using cosmological resimulations of a galaxy cluster, we study the evolution of its intracluster medium (ICM) gas properties, and through them we assess the effect of different (subgrid) modelling of the physical processes at play, namely gas cooling, star formation, feedback from supernovae and active galactic nuclei (AGNs). More specifically, we show that AGN feedback plays a major role in the pre‐heating of the protocluster as it prevents a high concentration of mass from collecting in the centre of the future galaxy cluster at early times. However, AGN activity during the cluster’s later evolution is also required to regulate the mass flow into its core and prevent runaway star formation in the central galaxy. Whereas the energy deposited by supernovae alone is insufficient to prevent an overcooling catastrophe, supernovae are responsible for spreading a large amount of metals at high redshift, enhancing the cooling efficiency of the ICM gas. As the AGN energy release depends on the accretion rate of gas on to its central black hole engine, the AGNs respond to this supernova‐enhanced gas accretion by injecting more energy into the surrounding gas, and as a result increase the amount of early pre‐heating. We demonstrate that the interaction between an AGN jet and the ICM gas that regulates the growth of the AGN’s black hole can naturally produce cool‐core clusters if we neglect metals. However, as soon as metals are allowed to contribute to the radiative cooling, only the non‐cool‐core solution is produced.

Rhapsody-G simulations I: the cool cores, hot gas and stellar content of massive galaxy clusters

“…Upon closer inspection one notices that a similar but slightly weaker offset also exists in the power-law part of the entropy profile, where the simulated profiles are systematically offset to lower entropy. A similar discrepancy can be seen also, e.g., in Figure 7 of Dubois et al (2011), independently of the much larger range of subgrid models employed in that reference. This may point towards additional physics missing from these simulations.…”

Turbulence in the ICM from mergers, cool-core sloshing, and jets: results from a new multi-scale filtering approach

“…Only recently fully cosmological grid simulations have reached a sufficient dynamical range to model the evolution and feedback of AGN outflows in detail, studying the interplay between AGNs and the ICM (e.g. Xu et al 2009;Teyssier et al 2011;Dubois et al 2011;Kim et al 2011). Recently, the outflows from AGNs in the multiphase ICM has been simulated in detail with FLASH simulations by Gaspari et al (2012a,b).…”

On the Road to More Realistic Galaxy Cluster Simulations: The Effects of Radiative Cooling and Thermal Feedback Prescriptions on the Observational Properties of Simulated Galaxy Clusters

“…Numerical simulations have demonstrated that AGNs may be important sources of feedback energy and significantly impact the energy balance in clusters. Simulations show that AGNs bring simulations closer to observations by preventing overcooling, which lowers cluster central densities (Sijacki et al 2007;Short & Thomas 2009;Teyssier et al 2011;Dubois et al 2012), improves the distribution of metals (Fabjan et al 2010;McCarthy et al 2010;Dubois et al 2011), and regulates star formation rates and triggers quenching (Di Matteo et al 2005;Sijacki & Springel 2006).…”