Astronomers have discovered strange clouds of electrons surrounding distant galaxies using CSIRO’s Australian Square Kilometer Array Pathfinder (ASKAP) telescope, a radio telescope situated about 800 kilometers north of Perth, in the Murchison region of Western Australia. The clouds, which are about a billion light-years away and never been seen before, resemble ghostly apparitions.
Evolutionary Map of the Universe
The discovery of the clouds is one of the initial results from the first pilot survey of the Evolutionary Map of the Universe (EMU), observed at 944 MHz with the ASKAP radio telescope. “We are getting used to surprises as we scan the skies as part of the EMU project, and probe deeper into the Universe than any previous telescope,” said Professor Ray Norris, an astronomer at Western Sydney University and CSIRO.
Shown above is the image of the two galaxies Norris and colleagues think are responsible for the streams of electrons (shown as curved arrows) that form the ‘dancing ghosts’, but the authors don’t understand what is causing the filament labelled as 3. The radio telescope is sensitive to emission from accelerating electrons, but astronomers also expect protons, neutral atoms, and possibly dark matter to also be in the vicinity.
“We had no idea what they were”
“When you boldly go where no telescope has gone before, you are likely to make new discoveries”, said Norris. “When we first saw the ‘dancing ghosts’ we had no idea what they were,” Norris added. “After weeks of work, we figured out we were seeing two ‘host’ galaxies, about a billion light-years away. In their centers are two supermassive black holes, squirting out jets of electrons that are then bent into grotesque shapes by an intergalactic wind.”
“New discoveries however always raise new questions and this one is no different,” Norris noted. “We still don’t know where the wind is coming from? Why is it so tangled? And what is causing the streams of radio emission? It will probably take many more observations and modelling before we understand any of these things.” The pair of distant galaxies are likely in the process of merging, producing complex tidal tails and dynamical interactions with the surrounding intergalactic medium.
Shaped by Intergalactic Magnetic Fields
When asked about the source of the stream of electrons that shape the ghostly clouds, Norris wrote in an email to The Daily Galaxy: “These radio waves are produced by electrons ejected from near the supermassive black hole, and then pulled off track by the intergalactic magnetic fields. This bending of the electron’s path causes the electron to release energy that we see as radio waves. We understand that process, but we don’t understand how these jets of electrons get bent into weird shapes. I think they are probably being blown sideways by intergalactic winds, caused by the motion of galaxies as they fall into a nearby cluster. But it is really hard to understand that process in details – its a bit like interpreting patterns of clouds in a weather map.”
Other objects and phenomena uncovered so far as part of the EMU project include the discovery of the Odd Radio Circles. “We are even finding surprises in places we thought we understood,” Norris said.
A Surprise Discovery
“Next door to the well-studied galaxy IC5063, we found a giant radio galaxy, one of the largest known, whose existence had never even been suspected. Its supermassive black hole is generating jets of electrons nearly 5 million light-years long.”
The first results of the EMU survey were published in the Publications of the Astronomical Society of Australia.
Image credit: Jayanne English & Ray Norris / EMU Project / Dark Energy Survey.