Astronomers studying 30 Ultra-Diffuse Galaxies (UDGs) in the Hydra galaxy cluster have found unexpected rotational motion in around half of them. These findings challenge previous theories on how these faint galaxies form and evolve.
The research team utilised the LEWIS observing programme, conducted with the MUSE integral field spectrograph on the Very Large Telescope in Chile. This allowed them to measure the movement of stars within these faint galaxies.
A detailed study of UDG32 revealed its position at the tail end of a gas filament linked to the spiral galaxy NGC 3314A. The data suggest that UDG32's location is not coincidental but instead connected to the galaxy’s tidal tail.
One theory suggests that UDGs may form when gas is pulled from larger galaxies due to gravitational interactions. If gas clouds remain in the filaments, they can collapse and create stars, forming UDGs. The findings from UDG32 support this theory.
UDG32 contains more elements heavier than hydrogen and helium compared to other UDGs in the Hydra cluster. Despite its stars being younger, their composition suggests they formed from metal-enriched gas shed by a larger, older galaxy.
The LEWIS project has doubled the number of spectroscopically analysed UDGs and provided a broader understanding of their properties within a forming galaxy cluster. The research has helped establish links between star motion, dark matter content, and galaxy formation.
The research team has published their findings in two papers in the journal Astronomy & Astrophysics. Their results contribute to an evolving understanding of how UDGs develop and interact within galaxy clusters.