The Oldest Fossil Radio Galaxy Discovered Yet Has Been Found Hiding in A Cluster

If we had been able to see into the heart of Abell 980 around 260 million years ago, we might have seen something really amazing.

The bright galaxy in the cluster erupted because of activity from its black hole, which caused huge bubbles to blow into space.

The bubbles are known as radio lobes and are the oldest of their kind.

There are two younger lobes found. The combined object is a rare example of a double pair of lobes and suggests that the black hole in the parent galaxy has erupted.

Radio lobes can extend millions of light-years, much larger than the galaxies from which they erupt, so they can affect the intergalactic medium. Studying these structures can help us understand the medium and the black holes that create them.

There are radio lobes in the universe. The universe has radio waves. When a black hole is active it slurps down matter from the space around it.

While most of the material falls onto the black hole, some of it is accelerated along the black hole's external magnetic field lines to its poles, where it is launched into space.

The jets expand into lobes that interact with the medium in the universe. Radio emissions can be produced by these lobes.

It's rare to find examples past 200 million years old, as we view them, because they fade away quickly. Valuable information can be recorded about the conditions in which they were formed.

Paul and his colleagues theorize that the hot, relaxed medium of a low-mass and quiet galaxy cluster is likely to prolong their lives.

They found a cluster in Abell 980, located around 2 billion light-years away, using the Giant Metre Wave Radio Telescope. They were able to detect faint radio structures that were 260 million years old.

The next step was to identify where the lobes came from.

Krishna and his colleagues were able to find it in a second paper. Krishna and his team showed that it wasn't always in the center of Abell 980. It moved 100,000 light-years from the position at which it emitted the first pair of lobes.

The second pair of lobes were produced when the galaxy erupted again. There are only a few dozen examples of double-double radio galaxies that have been found so far.

Krishna and his team have named the two pairs of lobes in Abell 980 the 'detached double-double radio galaxies'. Only two other candidates have been reported, making this discovery the most plausible so far.

Future, more sensitive radio observations could help shed light on the recurrent nature of black holes.

The two papers are in the press of two organizations. You can find them here and here.