Sound waves in the intracluster medium of the Centaurus cluster

TL;DR

This paper reports the discovery of ripple-like X-ray surface brightness oscillations in the Centaurus cluster, interpreted as sound waves generated by radio bubbles, which could significantly contribute to heating the cluster core.

Contribution

It provides the first detection of sound waves in the intracluster medium of the Centaurus cluster and estimates their power and potential role in balancing radiative cooling.

Findings

Detected 3-5% surface brightness oscillations with 9 kpc wavelength

Estimated sound wave power of 5x10^42 erg/s at 30 kpc

Sound wave power could offset a significant portion of cooling in the cluster core

Abstract

We report the discovery of ripple-like X-ray surface brightness oscillations in the core of the Centaurus cluster of galaxies, found with 200 ks of Chandra observations. The features are between 3 to 5 per cent variations in surface brightness with a wavelength of around 9 kpc. If, as has been conjectured for the Perseus cluster, these are sound waves generated by the repetitive inflation of central radio bubbles, they represent around 5x10^42 erg/s of spherical sound-wave power at a radius of 30 kpc. The period of the waves would be 10^7 yr. If their power is dissipated in the core of the cluster, it would balance much of the radiative cooling by X-ray emission, which is around 1.3x10^43 erg/s within the inner 30 kpc. The power of the sound waves would be a factor of four smaller that the heating power of the central radio bubbles, which means that energy is converted into sound waves efficiently.