Highly-luminous cool core clusters of galaxies: mechanically-driven or radiatively-driven AGN?

TL;DR

This study investigates highly luminous cool core galaxy clusters with active AGNs that lack detectable X-ray point sources, exploring how they sustain high luminosity and cooling without prominent X-ray nuclei, impacting understanding of jet feedback.

Contribution

The paper presents detailed Chandra observations of luminous cool core clusters revealing active nuclei without X-ray point sources, challenging existing models of AGN feedback mechanisms.

Findings

Clusters have high X-ray luminosity and short cooling times.

Active nuclei are present without detectable X-ray point sources.

Kinetic feedback may dominate over radiative processes in these clusters.

Abstract

Cool core clusters of galaxies require strong feedback from their central AGN to offset cooling. We present a study of strong cool core, highly-luminous (most with L_x > 10^(45) erg/s), clusters of galaxies in which the mean central AGN jet power must be very high yet no central point X-ray source is detected. Using the unique spatial resolution of Chandra, a sample of 13 clusters is analysed, including A1835, A2204, and one of the most massive cool core clusters, RXCJ1504.1-0248. All of the central galaxies host a radio source, indicating an active nucleus, and no obvious X-ray point source. For all clusters in the sample, the nucleus has an X-ray bolometric luminosity below 2 per cent of that of the entire cluster. We investigate how these clusters can have such strong X-ray luminosities, short radiative cooling-times of the inner intracluster gas requiring strong energy feedback to counterbalance that cooling, and yet have such radiatively-inefficient cores with, on average, Lkin/Lnuc exceeding 200. Explanations of this puzzle carry significant implications for the origin and operation of jets, as well as on establishing the importance of kinetic feedback for the evolution of galaxies and their surrounding medium.