Astronomers have recently uncovered fascinating details about a rare kind of galaxy known as Ultra-Diffuse Galaxies (UDGs). These faint and small galaxies have been a mystery since their discovery in 2015. A research team focused on 30 UDGs in the Hydra galaxy cluster, which is over 160 million light-years away, and they found something surprising. About half of these galaxies showed unexpected signs of motion, particularly a strange rotation of stars inside them.
Chiara Buttitta, a researcher at the National Institute for Astrophysics, expressed excitement about the findings. “We were not only able to measure stellar motions in these faint galaxies, but we also observed something we didn’t expect,” she said. This discovery challenges existing theories about how UDGs form and evolve.
The study was part of the LEWIS program, which uses advanced observations from the MUSE spectrograph on the Very Large Telescope (VLT) in Chile. This powerful instrument allows scientists to analyze faint galaxies in ways that were not possible before.
UDGs are intriguing because their formation is not fully understood. One theory suggests that they may form when gas is pulled from larger galaxies through gravitational interactions. If these gas clouds become dense enough, they can collapse to form stars, leading to the creation of a UDG. The team discovered that one of the galaxies they studied, named UDG32, is not just randomly located. It’s actually at the tip of a gas filament connected to a larger galaxy called NGC 3314A.
Interestingly, UDG32 has a higher concentration of heavier elements, or “metals,” than many of its peers in the Hydra cluster. These metals originate from the lifecycles of stars, and their presence indicates UDG32 likely formed from enriched material expelled by a nearby, older galaxy. This suggests a complex history for UDG32, reinforcing the idea that it has been influenced by its larger neighbor.
The LEWIS project has successfully doubled the number of UDGs analyzed so far and provided valuable insights into these faint galaxies within a forming galaxy cluster. Enrichetta Iodice, the scientific director of the LEWIS team, praised the project for revealing a wealth of data that helps piece together the formation history of these galaxies. The ability to study individual galaxies in detail allows researchers to learn more about their star populations and relationships to dark matter.
The team’s research has been published in two papers in the journal Astronomy & Astrophysics, contributing significantly to our understanding of these elusive galaxies. Astronomers hope that ongoing studies will continue to unravel the mysteries of UDGs and their role in the universe.
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