A recent study using the Atacama Large Millimeter/submillimeter Array (ALMA) Telescope has revealed significant findings about the Southern Pinwheel Galaxy M83. The research, led by Jin Koda from Stony Brook University, along with collaborators Maki Nagata and Fumi Egusa from the University of Tokyo, has identified 10 high-velocity clouds of molecular gas moving at velocities distinct from the galaxy's rotation. This suggests that these gases, which contribute to star formation, originate from outside the galaxy.
The team's findings have been published in The Astrophysical Journal. Their research provides insights into how galaxies evolve by converting gas into stars. Without external gas sources, a galaxy's existing gas would be depleted in approximately one billion years, halting star formation.
Professor Koda's team is conducting an extensive study of molecular gas in M83 using ALMA data. "This galaxy resembles our own Milky Way," Koda noted, suggesting that their findings might offer clues about star formation and evolution in our galaxy as well.
Nagata explained that their analysis involved high-sensitivity molecular gas emission line data obtained by ALMA, leading to the discovery of these unusual high-velocity clouds. "Most of these clouds do not correspond to any known supernova remnants in M83," added Koda.
Egusa proposed two main scenarios for these molecular gas clouds: they could be accreted directly from outside or ejected by supernova explosions within the galaxy and later returned due to gravity. However, Koda pointed out that even if accelerated by supernova explosions, their kinetic energies are too high to be attributed to a single event.
Nagata emphasized that "many of the observed high-velocity clouds must be flowing into M83 from external sources." This study represents the first systematic investigation of such clouds in nearby galaxies.
The researchers plan to continue exploring how molecular gas forms outside galaxies. Their work is supported partly by the National Science Foundation under grant numbers 2006600 and 2406608.