Powering of cool filaments in cluster cores by buoyant bubbles. I. Qualitative model

TL;DR

This paper presents a qualitative model where magnetic reconnection in the wakes of buoyant bubbles, inflated by AGN activity, powers the bright gaseous filaments observed in cool-core galaxy clusters.

Contribution

It introduces a novel qualitative model linking buoyant bubbles and magnetic reconnection to filament heating in galaxy clusters.

Findings

Magnetic reconnection explains filament luminosity and dissipation.

Buoyant bubbles' potential energy powers filament heating.

Model draws analogy to solar and Earth's magneto-tail phenomena.

Abstract

Cool-core clusters (e.g., Perseus or M87) often possess a network of bright gaseous filaments, observed in radio, infrared, optical and X-ray bands. We propose that these filaments are powered by the reconnection of the magnetic field in the wakes of buoyant bubbles. AGN-inflated bubbles of relativistic plasma rise buoyantly in the cluster atmosphere, stretching and amplifying the field in the wake to values of $\displaystyle \beta =8\pi P_{gas}/B^2\sim 1$. The field lines in the wake have opposite directions and are forced together as the bubble motion stretches the filament. This setup bears strong similarity to the coronal loops on the Sun or to the Earth's magneto-tail. The reconnection process naturally explains both the required level of local dissipation rate in filaments and the overall luminosity of filaments. The original source of power for the filaments is the potential energy of buoyant bubbles, inflated by the central AGN.