Cool Core Clusters from Cosmological Simulations

TL;DR

This study uses advanced cosmological hydrodynamic simulations including AGN feedback and thermal diffusion to reproduce the observed diversity of cool-core and non-cool-core galaxy clusters, matching their entropy and iron profiles.

Contribution

The paper demonstrates that incorporating AGN feedback and artificial thermal diffusion in simulations produces realistic cool-core cluster structures consistent with observations.

Findings

Simulated clusters show entropy profiles similar to observed CC and NCC clusters.

Cool-core clusters in simulations have steeper iron abundance profiles than NCC clusters.

The combination of AGN feedback and thermal diffusion is key to realistic cluster core modeling.

Abstract

We present results obtained from a set of cosmological hydrodynamic simulations of galaxy clusters, aimed at comparing predictions with observational data on the diversity between cool-core (CC) and non-cool-core (NCC) clusters. Our simulations include the effects of stellar and AGN feedback and are based on an improved version of the smoothed particle hydrodynamics code GADGET-3, which ameliorates gas mixing and better captures gas-dynamical instabilities by including a suitable artificial thermal diffusion. In this Letter, we focus our analysis on the entropy profiles, the primary diagnostic we used to classify the degree of cool-coreness of clusters, and on the iron profiles. In keeping with observations, our simulated clusters display a variety of behaviors in entropy profiles: they range from steadily decreasing profiles at small radii, characteristic of cool-core systems, to nearly flat core isentropic profiles, characteristic of non-cool-core systems. Using observational criteria to distinguish between the two classes of objects, we find that they occur in similar proportions in both simulations and in observations. Furthermore, we also find that simulated cool-core clusters have profiles of iron abundance that are steeper than those of NCC clusters, which is also in agreement with observational results. We show that the capability of our simulations to generate a realistic cool-core structure in the cluster population is due to AGN feedback and artificial thermal diffusion: their combined action allows us to naturally distribute the energy extracted from super-massive black holes and to compensate for the radiative losses of low-entropy gas with short cooling time residing in the cluster core.