Dr Jacinta Delhaize, a Research Fellow at the University of Cape Town and lead author of the work, said “Many hundreds of thousands of radio galaxies have already been discovered. However, only around 800 of these have radio jets exceeding 700 kilo-parsecs in size, or around 22 times the size of the Milky Way. These truly enormous systems are called ‘giant radio galaxies’.”
Despite the scarcity of giant radio galaxies, the authors found two of these cosmic beasts in a remarkably small patch of sky.
Dr Delhaize said, “We found these giant radio galaxies in a region of sky which is only about 4 times the area of the full moon, though the galaxies are much further away and much larger than the moon. Based on our current knowledge of the density of giant radio galaxies in the sky, the probability of finding two of them in this region is extremely small.”
“This means that giant radio galaxies are probably far more common than we thought!”
Dr Matthew Prescott, a Research Fellow at the University of the Western Cape and co-author of the work, said, “These two galaxies are special because they are much bigger than most other radio galaxies. They are more than 2 Mega-parsecs across, which is around 6.5 million light years or about 62 times the size of the Milky Way. Yet they are fainter than others of the same size.”
“We suspect that many more galaxies like these should exist, because of the way we think galaxies should grow and change over their lifetimes.”
The giant radio galaxies were spotted in new radio maps of the sky created by the MEERKAT International Gigahertz Tiered Extragalactic Exploration (MIGHTEE) survey. It is one of the large survey projects underway with South Africa’s impressive MeerKAT radio telescope and involves a team of astronomers from around the world.