A deeper X-ray study of the core of the Perseus galaxy cluster: the power of sound waves and the distribution of metals and cosmic rays

TL;DR

This study uses deep Chandra X-ray observations to analyze sound waves, metal distribution, and nonthermal components in the Perseus galaxy cluster's core, revealing energy dissipation, activity history, and complex gas properties.

Contribution

It provides detailed insights into the energy flux from sound waves, metal and temperature distributions, and nonthermal electron pressure in the Perseus cluster core, advancing understanding of cluster heating mechanisms.

Findings

Sound waves contribute significantly to energy balance within 75-100 kpc.

Metal distribution peaks at 40 kpc and is highly clumpy.

Nonthermal electron pressure is high within 40 kpc and affects sound wave power.

Abstract

We make a further study of the very deep Chandra observation of the X-ray brightest galaxy cluster, A426 in Perseus. We examine the radial distribution of energy flux inferred by the quasi-concentric ripples in surface brightness, assuming they are due to sound waves, and show that it is a significant fraction of the energy lost by radiative cooling within the inner 75-100 kpc, where the cooling time is 4-5 Gyr, respectively. The wave flux decreases outward with radius, consistent with energy being dissipated. Some newly discovered large ripples beyond 100 kpc, and a possible intact bubble at 170 kpc radius, may indicate a larger level of activity by the nucleus a few 100 Myr ago. The distribution of metals in the intracluster gas peaks at a radius of about 40 kpc and is significantly clumpy on scales of 5 kpc. The temperature distribution of the soft X-ray filaments and the hard X-ray emission component found within the inner 50 kpc are analysed in detail. The pressure due to the nonthermal electrons, responsible for a spectral component interpreted as inverse Compton emission, is high within 40 kpc of the centre and boosts the power in sound waves there; it drops steeply beyond 40 kpc. We find no thermal emission from the radio bubbles; in order for any thermal gas to have a filling factor within the bubbles exceeding 50 per cent, the temperature of that gas has to exceed 50 keV.