Central galaxy growth and feedback in the most massive nearby cool core cluster

TL;DR

This study investigates the central galaxy and cooling processes in the nearby cool core galaxy cluster RXCJ1504.1-0248, revealing star formation, filamentary structures, and feedback mechanisms affecting intracluster gas dynamics.

Contribution

It provides detailed multi-wavelength observations of the most luminous nearby cool core cluster, highlighting the role of AGN feedback and filamentary nebulae in galaxy growth.

Findings

Approximately 80 Msun/yr of gas cools below X-ray temperatures.

Star formation rate in the BCG is about 140 Msun/yr.

The nebula's turbulent velocity is around 325 km/s.

Abstract

We present multi-wavelength observations of the centre of RXCJ1504.1-0248 - the galaxy cluster with the most luminous and relatively nearby cool core at z~0.2. Although there are several galaxies within 100 kpc of the cluster core, only the brightest cluster galaxy (BCG), which lies at the peak of the X-ray emission, has blue colours and strong line-emission. Approximately 80 Msun/yr of intracluster gas is cooling below X-ray emitting temperatures, similar to the observed UV star formation rate of ~140 Msun/yr. Most star formation occurs in the core of the BCG and in a 42 kpc long filament of blue continuum, line emission, and X-ray emission, that extends southwest of the galaxy. The surrounding filamentary nebula is the most luminous around any observed BCG. The number of ionizing stars in the BCG is barely sufficient to ionize and heat the nebula, and the line ratios indicate an additional heat source is needed. This heat source can contribute to the H\alpha-deduced star formation rates (SFRs) in BCGs and therefore the derived SFRs should only be considered upper limits. AGN feedback can slow down the cooling flow to the observed mass deposition rate if the black hole accretion rate is of the order of 0.5 Msun/yr at 10% energy output efficiency. The average turbulent velocity of the nebula is vturb ~325 km/s which, if shared by the hot gas, limits the ratio of turbulent to thermal energy of the intracluster medium to less than 6%.