A recent study using the Atacama Large Millimeter/submillimeter Array (ALMA) Telescope has unveiled new insights into galaxy evolution. The research, led by Jin Koda from Stony Brook University in collaboration with Maki Nagata and Fumi Egusa of the University of Tokyo, along with an international team of astrophysicists, discovered 10 high-velocity clouds composed of molecular gas in the Southern Pinwheel Galaxy M83. These clouds are moving at velocities distinct from the galaxy’s overall rotation, suggesting they originate from outside the galaxy.
The findings, published in The Astrophysical Journal, shed light on how galaxies evolve over time through star formation. Gas serves as a crucial material for forming stars, and without external gas supply, a galaxy’s existing gas would be depleted within about one billion years, halting star formation. The study’s insights into M83’s molecular composition provide a deeper understanding of this evolutionary process.
Professor Koda highlighted the significance of studying M83 due to its resemblance to the Milky Way: “This galaxy resembles our own Milky Way, therefore findings there may also provide clues into star formation and galaxy evolution in the Milky Way.”
Maki Nagata explained their methodology: “We analyzed high-sensitivity molecular gas emission line data obtained by ALMA. This led to the discovery of the 10 high-velocity clouds composed, unusually, of molecular gas.” Koda added that most clouds do not match any known supernova remnants in M83.
Fumi Egusa proposed two scenarios for these clouds’ existence: direct accretion from outside or ejection by supernova explosions followed by gravitational fallback. However, Koda noted that even if accelerated by supernovae, their kinetic energies are too high for a single event explanation: “These features strongly suggest that many of the observed high-velocity clouds must be flowing into M83 from external sources,” Nagata concluded.
The authors assert this study as the first systematic investigation of such clouds in nearby galaxies and plan to continue researching how molecular gas forms outside galaxies.
This research received partial support from the National Science Foundation under grant numbers 2006600 and 2406608.
