Gravitational heating, clumps, overheating

TL;DR

This paper proposes that cold baryonic clumps accreted into galaxy clusters can effectively transfer gravitational energy to heat the core, addressing the overcooling problem through hydrodynamic interactions.

Contribution

It introduces a novel mechanism where cold baryonic clumps deliver gravitational energy to cluster cores via hydrodynamic drag, with simulation support.

Findings

Clumps carry sufficient energy to heat cluster cores.

Hydrodynamic drag allows clumps to penetrate and heat the center.

Simulations produce realistic entropy profiles.

Abstract

There is no shortage of energy around to solve the overcooling problem of cooling flow clusters. AGNs, as well as gravitational energy are both energetic enough to balance the cooling of cores of clusters. The challenge is to couple this energy to the baryons efficiently enough, and to distribute the energy in a manner that will not contradict observational constraints of metalicity and entropy profiles. Here we propose that if a small fraction of the baryons that are accreted to the cluster halo are in the form of cold clumps, they would interact with the hot gas component via hydrodynamic drag. We show that such clumps carry enough energy, penetrate to the center, and heat the core significantly. We then study the dynamic response of the cluster to this kind of heating using a 1D hydrodynamic simulation with sub-grid clump heating, and produce reasonable entropy profile in a dynamic self-consistent way.