An international team led by a young South African researcher has announced a comprehensive overview paper for the MeerKAT Galaxy Cluster Legacy Survey (MGCLS).
In a statement, the South African Radio Astronomy Observatory (SARAO) says the paper, to be published in the Astronomy & Astrophysics journal, presents some exciting, novel results.
It is accompanied by the public release of a huge trove of curated data now available for astronomers worldwide to address a variety of challenging questions, such as those relating to the formation and evolution of galaxies throughout the universe, it notes.
Launched in 2018, the South African MeerKAT radio telescope is a precursor to the Square Kilometre Array, which aims to answer fundamental astrophysical questions about the nature of objects in the universe.
Using SA’s MeerKAT telescope, located in the Karoo region of the Northern Cape, this first observatory-led survey demonstrates MeerKAT’s exceptional strengths by producing highly-detailed and sensitive images of the radio emission from 115 clusters of galaxies, says SARAO.
The observations, amounting to approximately 1 000 hours of telescope time, were done in the year following the inauguration of MeerKAT in 2018, it adds.
“In those days we were still characterising our new telescope, while developing further capabilities required by numerous scientists,” says Dr Sharmila Goedhart, SARAO head of commissioning and science operations.
“But we knew that MeerKAT was already very capable for studies of this sort, and we observed galaxy clusters as needed to fill gaps in the observing schedule.”
According to SARAO, this was only the start. It notes that more than two years of work followed to convert the raw data into radio images, using powerful computers, and to perform scientific analysis addressing a variety of topics.
This was done by a large team of South African and international experts led by Dr Kenda Knowles of Rhodes University and SARAO.
SARAO explains that the force of gravity has filled the expanding universe with objects extending over an astounding range of sizes, from comets that are 10km (one thirty-thousandth of a light-second) across, to clusters of galaxies that can span 10 million light-years.
These galaxy clusters are complex environments, host to thousands of galaxies, magnetic fields and large regions – millions of light-years across – of extremely hot (millions of degrees) gas, electrons and protons moving close to the speed of light, and dark matter.
It adds those “relativistic” electrons, spiralling around the magnetic fields, produce the radio emission that MeerKAT can “see” with unprecedented sensitivity, opening new horizons for deeper understanding of these structures.
Thus MeerKAT, particularly when adding information from optical and infrared and X-ray telescopes, is exceptionally well-suited to study the interplay between the components that determine the evolution of galaxy clusters, the largest structures in the universe held together by gravity, SARAO notes.
“We live in an ocean of air, but we can’t see it directly. However, if it’s filled with smoke or dust or water droplets, then suddenly we can see the gusts and swirls, whether they’re a gentle breeze or an approaching tornado. Similarly, the motions of the X-ray-glowing plasma in galaxy clusters are usually hidden from us,” the organisation says.
“Radio emission from the sprinkling of relativistic electrons in this plasma can uncover the dramatic storms in clusters, stirred up when clusters collide with each other, or when jets of material spew out of supermassive black holes in the centres of galaxies.”
The MGCLS has produced detailed images of the extremely faint radio sky, while surveying a very large volume of space.
“That’s what’s already enabled us to serendipitously discover rare kinds of galaxies, interactions and diffuse features of radio emission, many of them quite beautiful,” explains Knowles.
SARAO says a number of additional studies delving more deeply into some of the initial discoveries are already under way by members of the MGCLS team.
Beyond that, it says, the richness of the science resulting from the MGCLS is expected to grow over the coming years, as astronomers from around the world download the data from the SARAO MeerKAT archive, and probe it to answer their own questions.
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