The formation of the brightest cluster galaxies in cosmological simulations: the case for AGN feedback

TL;DR

This study uses high-resolution cosmological simulations to investigate how AGN feedback influences the formation and properties of brightest cluster galaxies, aligning simulated results with observed galaxy features.

Contribution

It demonstrates that including AGN feedback in simulations produces BCGs with realistic properties, unlike models with only supernovae feedback.

Findings

AGN feedback creates cores in luminous elliptical galaxies.

Simulated BCGs with AGN feedback match observed rotation and density profiles.

Supernovae-only models fail to reproduce observed galaxy characteristics.

Abstract

We use 500 pc resolution cosmological simulations of a Virgo-like galaxy cluster to study the properties of the brightest cluster galaxy (BCG) that forms at the center of the halo. We compared two simulations; one incorporating only supernovae feedback and a second that also includes prescriptions for black hole growth and the resulting AGN feedback from gas accretion. As previous work has shown, with supernovae feedback alone we are unable to reproduce any of the observed properties of massive cluster ellipticals. The resulting BCG is rotating quickly, has a high Sersic index, a strong mass excess in the center and a total central density profile falling more steeply than isothermal. Furthermore, it is far too efficient at converting most of the available baryons into stars which is strongly constrained by abundance matching. With a treatment of black hole dynamics and AGN feedback the BCG properties are in good agreement with data: they rotate slowly, have a cored surface density profile, a flat or rising velocity dispersion profile and a low stellar mass fraction. The AGN provides a new mechanism to create cores in luminous elliptical galaxies; the core expands due to the combined effects of heating from dynamical friction of sinking massive black holes and AGN feedback that ejects gaseous material from the central regions.