Detecting Sound-Wave-Like Surface Brightness Ripples in Cluster Cores

TL;DR

This paper examines how to detect sound-wave-like ripples in galaxy cluster cores, analyzing projection effects and estimating observation times needed for detection with current X-ray telescopes.

Contribution

It provides a detailed analysis of projection effects on ripple amplitude and estimates detection times for ripples in various galaxy clusters using Chandra.

Findings

Projection reduces observed ripple amplitude, especially for smaller wavelengths.

Detection time depends strongly on cluster flux and ripple amplitude.

Several galaxy clusters could have detectable ripples with ~1Ms Chandra observations.

Abstract

We investigate the observational requirements for the detection of sound-wave-like features in galaxy cluster cores. We calculate the effect of projection on the observed wave amplitude, and find that the projection factor depends only weakly on the underlying cluster properties but strongly on the wavelength of the sound waves, with the observed amplitude being reduced by a factor ~5 for 5 kpc waves but only by a factor ~ 2 for 25 kpc waves. We go on to estimate the time needed to detect ripples similar to those previously detected in the Perseus cluster in other clusters. We find that the detection time scales most strongly with the flux of the cluster and the amplitude of the ripples. By connecting the ripple amplitude to the heating power in the system, we estimate detection times for a selection of local clusters and find that several may have ripples detected with ~1Ms Chandra time.