Can a black hole fire up a cold heart?

Radio astronomers have detected jets of hot gas blasted out by a black hole 5.9 billion light-years away in the constellation Phoenix.

It’s an important result, they suggest, for helping explain the co-evolution of galaxies, gas and black holes in galaxy clusters.

The work was led by Takaya Akahori from the National Astronomical Observatory of Japan and is described in a paper in the journal Publications of the Astronomical Society of Japan.

Galaxies gather in clusters through mutual gravitational attraction, and between them is very dilute gas that can be detected by X-ray observations. If this gas cooled, it would condense under its own gravity to form stars at the centre of the cluster.

However, cooled gas and stars are not usually observed in the hearts of nearby clusters, the researchers say, indicating that some mechanism must be heating the intra-cluster gas and preventing star formation.

One potential candidate for the heat source is jets of high-speed gas accelerated by a supermassive black hole in the central galaxy.

The Phoenix Cluster is unusual in that it does show signs of dense cooled gas and massive star formation around the central galaxy. This led Akahori and colleagues to ask whether the central galaxy has black hole jets as well.

To find out, they used the Australia Telescope Compact Array (ATCA) to search for black holes and detected matching structures extending out from opposite sides of the central galaxy.

Comparison with observations of the region taken from the Chandra X-ray Observatory archive data revealed that the structures detected by ATCA correspond to cavities of less dense gas, indicating that they are a pair of bipolar jets emitted by a black hole in the galaxy.

It is, therefore, the researchers say, the first example of intra-cluster gas cooling and black hole jets co-existing in the distant Universe.