Scientists at the University of Western Australia's ICRAR node have discovered a massive bridge of neutral hydrogen gas connecting the dwarf galaxies NGC 4532 and DDO 137. This structure spans 185,000 light-years and is located 53 million light-years from Earth. The finding, part of the WALLABY survey, reveals how interactions with the Virgo cluster strip gas from galaxies.
Researchers using the ASKAP radio telescope, operated by Australia's CSIRO, identified the colossal bridge during the Widefield ASKAP L-band Legacy All-sky Survey (WALLABY). The bridge links NGC 4532 and DDO 137, two dwarf galaxies influenced by tidal forces and their proximity to the Virgo cluster. A study detailing the discovery was published in the Monthly Notices of the Royal Astronomical Society.
The team also detected a tail of gas extending 1.6 million light-years beyond the bridge, marking the largest such feature recorded. Lead researcher Professor Lister Staveley-Smith from ICRAR UWA explained the dynamics: "Our modeling showed that the tidal forces acting between these galaxies, alongside their proximity to the massive Virgo cluster of galaxies, played a crucial role in the gas dynamics we observed."
As the galaxies orbit each other and approach the Virgo cluster's superheated gas cloud—reaching temperatures 200 times hotter than the Sun's surface—they experience ram pressure. This strips gas from the galaxies, heating it over about a billion years. Professor Staveley-Smith compared it to "atmospheric burn-up when a satellite re-enters the Earth's upper atmosphere, but has extended over a period of a billion years."
Co-author Professor Kenji Bekki highlighted the implications for star formation: "Neutral hydrogen plays a crucial role in the formation of stars, making this finding fundamental to understanding how galaxies interact and evolve, particularly in dense environments."
The system resembles the Milky Way and Magellanic System, offering insights into galactic evolution, gas redistribution, and star formation in massive cosmic structures. The electron density and galactic infall speed into the hot cloud account for the extensive gas stripping observed.