Scientists at The University of Western Australia’s node of the International Centre for Radio Astronomy Research (ICRAR) have made a remarkable discovery: a large structure stretching about 185,000 light-years between two galaxies, NGC 4532 and DDO 137, positioned some 53 million light-years from Earth.
In line with a study published within the Monthly Notices of the Royal Astronomical Society, the team also detected an enormous tail of gas extending one other 1.6 million light-years beyond the bridge, making it the most important feature of its kind ever recorded.
Lead researcher Professor Lister Staveley-Smith from ICRAR UWA explained that the finding provides a very important recent insight into how galaxies influence one another.
“Our modeling showed that the tidal forces acting between these galaxies, alongside their proximity to the large Virgo cluster of galaxies, played a vital role within the gas dynamics we observed,” Professor Staveley-Smith said.
He added that because the galaxies orbited each other and moved toward the superheated gas cloud surrounding the Virgo cluster, which reaches temperatures about 200 times hotter than the Sun’s surface, they experienced “ram pressure.” This effect stripped gas from the galaxies and heated it as they passed through the dense environment.
“The method is akin to atmospheric burn-up when a satellite re-enters the Earth’s upper atmosphere, but has prolonged over a period of a billion years,” he said.
“The density of electrons and the speed at which galaxies are falling into the new gas cloud are enough to clarify why a lot gas has been pulled away from the galaxies and into the bridge and surrounding areas.”
The invention was made as a part of the Widefield ASKAP L-band Legacy All-sky Survey (WALLABY), a large-scale project that maps hydrogen gas throughout the Universe using the ASKAP radio telescope, owned and operated by CSIRO, Australia’s national science agency.
Co-author Professor Kenji Bekki of ICRAR UWA said the team identified the large gas structures through high-resolution observations of neutral hydrogen, a key ingredient in star formation.
“Neutral hydrogen plays a vital role within the formation of stars, making this finding fundamental to understanding how galaxies interact and evolve, particularly in dense environments,” Professor Bekki said.
Professor Staveley-Smith said the system had strong similarities with our own Milky Way and Magellanic System, providing a novel opportunity to review such interactions intimately.
“Understanding these gas bridges and their dynamics provides critical insights into how galaxies evolve over time, how galactic gas is redistributed, and the various conditions under which galaxies may or may not form stars,” he said.
“This contributes to our broader understanding of probably the most massive structures within the Universe and their life cycles, which helps us grasp more about their vast complexities and history of star formation.”