Abell 3266 Astronomers discover a physics-defying shockwave in a distant galaxy
Fossil remains of the black hole-eating frenzy of the past have been found deep within one of the largest galaxy clusters in our sky.
Astronomers also saw physics-defying plasma shockwaves, and loops of radio energy within the same galaxy cluster.
Key points:
- Astronomers have discovered a trio of rare objects in a distant galaxy cluster known as Abell 3266
- One of the mysterious objects is a shockwave relic dubbed the “wrong way”.
- The objects were discovered using radio telescopes in Western Australia and New South Wales
The cluster – Abell 3266 – is located 800 million light-years away and spans the sky 300 million light-years in the southern constellation Reticulum.
An international team of astronomers, led by Christopher Riseley of the University of Bologna in Italy, studied the cluster in detail using the powerful Australian Square Kilometer Array Pathfinder radio telescope in outback Western Australia, and the smaller Australia Telescope Compact Array in Narrabri, New South Wales.
The team reported their findings today in the Royal Astronomical Society’s Monthly Notices.
Clusters of galaxies are some of the largest and most dynamic objects in the universe, said astrophysicist and co-author Tessa Vernstrom of the University of Western Australia.
“That’s where you get the interaction of dark matter and galaxies and a lot of different physics going on,” said Dr Vernstrom.
“There are galaxies merging, active galaxies with huge black holes [blasting jets of energy into space]shockwaves and turbulence.”
The Abell 3266 has all of that — and more that has left scientists baffled.
The team combined their findings from the radio telescope (in red, orange and yellow), with images taken in X-rays and visible light (blue and white) to produce the stunning image above.
So let’s dive in and take a closer look at this cluster.
active galaxy
The cluster contains a number of active galaxies, with a supermassive black hole at its heart that sends out enormous beams of energy.
One galaxy in the lower right corner stands out. Instead of having large jets coming out of their center, they bend.
The warped jets are caused by the movement of galaxies in the cluster.
“So it’s like wind pressure pushing the jet back,” said Dr Vernstrom.
“It can tell you about the dynamics that are going on and how things move with each other.”
party fossil
Not all galaxies are active. At the top right of the image is the fossilized remains (red) of a supermassive black hole that has stopped feeding in its galaxy (a small white blob towards the bottom of the red area in the insert image).
“Sometimes a jet [coming out of supermassive black holes] just turn it off,” said Dr Vernstrom.
“And because black holes aren’t given new material, the stuff they’ve ejected just ages and starts to fade.”
Relic shockwave
In the lower left corner is what appears to be the remnant of the shockwave created when several parts of the cluster pass over each other.
But instead of facing inward, the relic, dubbed the “wrong way”, faces away from the center of the cluster.
“If it was a shock wave, you might think it would bend like an arc around the edge, but this one is upside down,” says Dr Vernstrom.
Sometimes it’s hard to tell if the effect is real or a product of the way it’s been imaged, but Dr Vernstrom says the team thinks it’s real.
This relic is also much brighter in the radio spectrum than would be expected in any model.
“So we didn’t really understand what he was telling us,” he said.
“Maybe there’s some kind of new physics going on there that we don’t fully understand when our models don’t match the observations.”
hello middle
Lying in the center of the cluster is a faint blob of radio emission known as a halo.
“We actually can’t really see it because it’s basically very dim and spread out over this large area,” said Dr Vernstrom.
The enlarged image below shows the halo’s borders in blue dashed lines.
Dr Vernstrom said halos appear in groups where there have been recent mergers, but are rare.
“We only know about 100 of these objects, and we’ve never seen one in this cluster before,” he said.
Emissions are produced by electrons that have been swayed by the turbulence created by the interaction of galaxies, gas, and particles packed into the center of the cluster.
“It’s like if you had two storm fronts colliding and merging – the structure in the clouds and the weather getting mixed up.”
The electrons are propelled as they travel around the magnetic field lines between galaxies.
New telescope power
Despite thousands of clusters, Dr Vernstrom said we have found “very few” objects like the one in Abell 3266.
“They are inherently difficult to detect.”
He said it was only possible to see this cluster in great detail using the new telescope.
“We’ll never see this [without] ASKAP.”
The telescope uses a series of 36 antennas to detect the source of radio emission – the longest energy wavelength – in the sky.
“By looking at the radio, you see a different kind of physics than when you look at other wavelengths,” said Dr Vernstrom.
Using multiple antennas spread over 6 kilometers, it is also much more sensitive and can see more detail than smaller radio telescopes.
Dr Vernstrom said the discovery in this cluster is just the beginning of what scientists will discover with ASKAP.
Over the next five years, the telescope will survey the entire southern sky.
“We’ll see more of this sort of thing.”
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