The Detectability of AGN Cavities in Cooling-Flow Clusters

TL;DR

This study investigates how active galactic nucleus (AGN) cavities influence cooling flows in galaxy clusters, suggesting that AGN outbursts are frequent and often undetected, with a duty cycle potentially near 100%.

Contribution

It provides the first comprehensive estimate of the AGN outburst duty cycle in cooling flow clusters using Chandra data.

Findings

At least 60% of cooling flow clusters have AGN outbursts with significant heating potential.

Many clusters may have undetected cavities, indicating a higher duty cycle.

Deeper observations are needed to better constrain the AGN activity frequency.

Abstract

Chandra X-ray Observatory has revealed X-ray cavities in many nearby cooling flow clusters. The cavities trace feedback from the central active galactic nulceus (AGN) on the intracluster medium (ICM), an important ingredient in stabilizing cooling flows and in the process of galaxy formation and evolution. But, the prevalence and duty cycle of such AGN outbursts is not well understood. To this end, we study how the cooling is balanced by the cavity heating for a complete sample of clusters (the Brightest 55 clusters of galaxies, hereafter B55). In the B55, we found 33 cooling flow clusters, 20 of which have detected X-ray bubbles in their ICM. Among the remaining 13, all except Ophiuchus could have significant cavity power yet remain undetected in existing images. This implies that the duty cycle of AGN outbursts with significant heating potential in cooling flow clusters is at least 60 % and could approach 100 %, but deeper data is required to constrain this further.