A Massive, Cooling-Flow-Induced Starburst in the Core of a Highly Luminous Galaxy Cluster

TL;DR

This study reports a galaxy cluster with an exceptionally strong cooling flow and a massive starburst in its central galaxy, challenging existing feedback models that prevent runaway cooling in cool core clusters.

Contribution

It presents the first detailed observation of a galaxy cluster with a massive cooling flow and starburst, indicating feedback mechanisms may be less effective or delayed.

Findings

Unusually high cooling flow rate of 3820 solar masses per year.

Central galaxy experiencing a star formation rate of 740 solar masses per year.

Implication that star formation may occur directly from intracluster medium accretion.

Abstract

In the cores of some galaxy clusters the hot intracluster plasma is dense enough that it should cool radiatively in the cluster's lifetime, leading to continuous "cooling flows" of gas sinking towards the cluster center, yet no such cooling flow has been observed. The low observed star formation rates and cool gas masses for these "cool core" clusters suggest that much of the cooling must be offset by astrophysical feedback to prevent the formation of a runaway cooling flow. Here we report X-ray, optical, and infrared observations of the galaxy cluster SPT-CLJ2344-4243 at z = 0.596. These observations reveal an exceptionally luminous (L_2-10 keV = 8.2 x 10^45 erg/s) galaxy cluster which hosts an extremely strong cooling flow (dM/dt = 3820 +/- 530 Msun/yr). Further, the central galaxy in this cluster appears to be experiencing a massive starburst (740 +/- 160 Msun/yr), which suggests that the feedback source responsible for preventing runaway cooling in nearby cool core clusters may not yet be fully established in SPT-CLJ2344-4243. This large star formation rate implies that a significant fraction of the stars in the central galaxy of this cluster may form via accretion of the intracluster medium, rather than the current picture of central galaxies assembling entirely via mergers.