Large MeerKAT data release reveals beautiful new cosmic puzzles

BY SARAO Astronomers worldwide now have access to a huge trove of curated data flowing from the MeerKAT Galaxy Cluster Legacy Survey (MGCLS).

The dataset was publicly released to accompany a comprehensive overview paper published in the Astronomy & Astrophysics journal. By delving into this, astronomers can get closer to answering a variety of challenging questions, such as those relating to the formation and evolution of galaxies throughout the Universe.

Using the South African Radio Astronomy Observatory’s (SARAO) MeerKAT telescope – an SKA precursor instrument – this first observatory-led survey demonstrated MeerKAT’s exceptional strengths. Observations amounting to approximately 1,000 hours of telescope time produced highly detailed and sensitive images of the radio emission from 115 clusters of galaxies. They were carried out in 2018.

“In those days we were still characterising our new telescope while developing further capabilities required by numerous scientists,” said the head of Commissioning and Science Operations at SARAO, Dr Sharmila Goedhart. “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.”

More than two years of work followed to convert the raw data into radio images, using powerful computers, and to perform scientific analysis. This was done by a large team of South African and international experts led by a young South African researcher from Rhodes University and SARAO, Dr Kenda Knowles.

The force of gravity has filled the expanding Universe with objects extending over an astounding range of sizes, from comets that are 10km 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 of extremely hot gas, electrons and protons moving close to the speed of light, and dark matter.

Such“relativistic” electrons, spiralling around the magnetic fields, produce the radio emission that MeerKAT can detect with unprecedented sensitivity, allowing for a deeper understanding of these structures. Thus radio telescopes such as MeerKAT and the future SKA are exceptionally well-suited to studying the evolution of galaxy clusters, the largest structures in the universe held together by gravity, particularly when adding information from optical and infrared and X-ray telescopes.

The MGCLS paper presents more than 50 newly discovered patches of emission. Some of them have been explained and others remain a mystery, awaiting advances in our understanding of the physical behaviour of galaxy cluster plasmas.

Access the dataset: https://archive-gw-1.kat.ac.za/public/repository/10.48479/7epd-w356/index.html

Read the paper: https://www.aanda.org/articles/aa/abs/2022/01/aa41488-21/aa41488-21.html

A few examples of the physical behaviour of galaxy cluster plasmas, some associated with the bright emission from so-called “radio galaxies”, powered by the jets of supermassive black holes.

Credit: SARAO