Cusp-core transformations induced by AGN feedback in the progenitors of cluster galaxies

TL;DR

This study demonstrates that AGN feedback-driven gas outflows in galaxy cluster progenitors can cause irreversible dark matter core formation through repeated potential fluctuations, as shown in idealized simulations.

Contribution

It provides controlled simulation evidence that AGN feedback can generate dark matter cores by expelling baryons and dark matter from cluster centers, clarifying the physical mechanism.

Findings

AGN feedback causes gas expulsion and potential fluctuations.

Repeated cycles lead to irreversible dark matter profile modifications.

Outflows are the primary mechanism for core creation in clusters.

Abstract

In a recent study (Martizzi et al. 2012), we used cosmological simulations to show that active galactic nuclei (AGN) feedback on the gas distribution in clusters of galaxies can be important in determining the spatial distribution of stars and dark matter in the central regions of these systems. The hierarchical assembly of dark matter, baryons and black holes obscures the physical mechanism behind the restructuring process. Here we use idealized simulations to follow the response of a massive dark matter halo as we feed the central black hole with a controlled supply of cold gas. This removes most of the complexity taking place in the cosmological simulations that may have biased our previous study. We confirm our previous results: gas heated and expelled from the central regions of the halo by AGN feedback can return after cooling; repeated cycles generate gravitational potential fluctuations responsible for irreversible modifications of the dark matter mass profile. The main result is the expulsion of large amounts of baryons and dark matter from the central regions of the halo. According to the work presented here, outflow induced fluctuations represent the only mechanism able to efficiently create dark matter cores in clusters of galaxies.