The colliding cluster Abell 3266 as seen across the electromagnetic spectrum, using data from ASKAP and the ATCA (red/orange/yellow colours), XMM-Newton (blue) and the Dark Energy Survey (background map). Credit: Christopher Riseley (Università di Bologna), Author provided
The universe is littered with galaxy clusters—huge structures piled up at the intersections of the cosmic web. A single cluster can span millions of light-years across and be made up of hundreds, or even thousands, of galaxies.
However, these galaxies represent only a few percent of a cluster’s total mass. About 80% of it is dark matter, and the rest is a hot plasma “soup”: gas heated to above 10,000,000℃ and interwoven with weak magnetic fields.
We and our international team of colleagues have identified a series of rarely observed radio objects—a radio relic, a radio halo and fossil radio emission—within a particularly dynamic galaxy cluster called Abell 3266. They defy existing theories about both the origins of such objects and their characteristics.
Relics, haloes and fossils
Galaxy clusters allow us to study a broad range of rich processes—including magnetism and plasma physics—in environments we can’t recreate in our labs.
When clusters collide with each other, huge amounts of energy are put into the particles of the hot plasma, generating radio emission. And this emission comes in a variety of shapes and sizes.
“Radio relics” are one example. They are arc-shaped and sit towards a cluster’s outskirts, powered by shockwaves traveling through the plasma, which cause a jump in density or pressure, and energize the particles. An example of a shockwave on Earth is the sonic boom that happens when an aircraft breaks the sound barrier.
“Radio haloes” are irregular sources that lie towards the cluster’s center. They’re powered by turbulence in the hot plasma, which gives energy to the particles. We know both haloes and relics are generated by collisions between galaxy clusters—yet many of their gritty details remain elusive.
Then there are “fossil” radio sources. These are the radio leftovers from the death of a supermassive black hole at the center of a radio galaxy.
When they’re in action, black holes shoot huge jets of plasma far out beyond the galaxy itself. As they run out of fuel and shut off, the jets begin to dissipate. The remnants are what we detect as radio fossils.
Abell 3266
Our new paper, published in the Monthly Notices of the Royal Astronomical Society, presents a highly detailed study of a galaxy cluster called Abell 3266.
This is a particularly dynamic and messy colliding system around 800 million light-years away. It has all the hallmarks of a system that should be host to relics and haloes—yet none had been detected until recently.
Our data paint a complex picture. You can see this in the lead image: yellow colors show features where energy input is active. The blue haze represents the hot plasma, captured at X-ray wavelengths.
Redder colors show features that are only visible at lower frequencies. This means these objects are older and have less energy. Either they have lost a lot of energy over time, or they never had much to begin with.
The radio relic is visible in red near the bottom of the image (see below for a zoom). And our data here reveal particular features that have never been seen before in a relic.
The ‘wrong-way’ relic in Abell 3266 is shown here with yellow/orange/red colours representing the radio brightness. Credit: Christopher Riseley, using data from ASKAP, ATCA, XMM-Newton and the Dark Energy Survey
Its concave shape is also unusual, earning it the catchy moniker of a “wrong-way” relic. Overall, our data break our understanding of how relics are generated, and we’re still working to decipher the complex physics behind these radio objects.
Ancient remnants of a supermassive black hole
The radio fossil, seen towards the upper right of the lead image (and also below), is very faint and red, indicating it is ancient. We believe this radio emission originally came from the galaxy at the lower left, with a central black hole that has long been switched off.
The radio fossil in Abell 3266 is shown here with red colours and contours depicting the radio brightness measured by ASKAP, and blue colours showing the hot plasma. The cyan arrow points to the galaxy we think once powered the fossil. Credit: Christopher Riseley, using data from ASKAP, XMM-Newton and the Dark Energy Survey
Our best physical models simply can’t fit the data. This reveals gaps in our understanding of how these sources evolve—gaps that we’re working to fill.
Finally, using a clever algorithm, we de-focused the lead image to look for very faint emission that’s invisible at high resolution, unearthing the first detection of a radio halo in Abell 3266 (see below).
The radio halo in Abell 3266 is shown here with red colours and contours depicting the radio brightness measured by ASKAP, and blue colours showing the hot plasma. The dashed cyan curve marks the outer limits of the radio halo. Credit: Christopher Riseley, using data from ASKAP, XMM-Newton and the Dark Energy Survey
Toward the future
This is the beginning of the road towards understanding Abell 3266. We have uncovered a wealth of new and detailed information, but our study has raised yet more questions.
The telescopes we used are laying the foundations for revolutionary science from the Square Kilometer Array project. Studies like ours allow astronomers to figure out what we don’t know—but you can be sure we’re going to find out.
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We found some strange radio sources in a distant galaxy cluster. They’re making us rethink what we thought we knew (2022, August 1)
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NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
