Cycling of the powerful AGN in MS 0735.6+7421 and the duty cycle of radio AGN in Clusters

TL;DR

This study analyzes deep X-ray observations of galaxy cluster MS 0735.6+7421, revealing energetic AGN activity, cavities, shocks, and a duty cycle indicating AGN outbursts occur roughly every third of the cooling time, impacting cluster heating.

Contribution

It provides detailed measurements of cavities, shocks, and AGN power decline, and quantifies the duty cycle of AGN activity in galaxy clusters with multiple cavity generations.

Findings

Cavities with diameters of 200-240 kpc and enthalpy of 9×10^61 erg.

Shock front with Mach number 1.26 injecting 4×10^61 erg.

AGN power has declined by a factor of 30 over 100 Myr.

Abstract

We present an analysis of deep Chandra X-ray observations of the galaxy cluster MS 0735.6+7421, which hosts the most energetic radio AGN known. Our analysis has revealed two cavities in its hot atmosphere with diameters of 200-240 kpc. The total cavity enthalpy, mean age, and mean jet power are $9\times 10^{61}$ erg, $1.6\times 10^{8}$ yr, and $1.7\times 10^{46}$ erg/s, respectively. The cavities are surrounded by nearly continuous temperature and surface brightness discontinuities associated with an elliptical shock front of Mach number 1.26 (1.17-1.30) and age of $1.1\times 10^{8}$ yr. The shock has injected at least $4\times 10^{61}$ erg into the hot atmosphere at a rate of $1.1\times 10^{46}$ erg/s. A second pair of cavities and possibly a second shock front are located along the radio jets, indicating that the AGN power has declined by a factor of 30 over the past 100 Myr. The multiphase atmosphere surrounding the central galaxy is cooling at a rate of 36 Msun/yr, but does not fuel star formation at an appreciable rate. In addition to heating, entrainment in the radio jet may be depleting the nucleus of fuel and preventing gas from condensing out of the intracluster medium. Finally, we examine the mean time intervals between AGN outbursts in systems with multiple generations of X-ray cavities. We find that, like MS0735, their AGN rejuvenate on a timescale that is approximately 1/3 of their mean central cooling timescales, indicating that jet heating is outpacing cooling in these systems.