A recent study using the Atacama Large Millimeter/submillimeter Array (ALMA) Telescope has revealed new insights into the evolution of galaxies. The research, led by Jin Koda from Stony Brook University, focused on the Southern Pinwheel Galaxy M83 and uncovered 10 high-velocity clouds composed of molecular gas. These clouds are moving at velocities distinct from M83’s overall rotation, suggesting that they originate from outside the galaxy.
Koda collaborated with Maki Nagata and Fumi Egusa from the University of Tokyo, along with an international team of astrophysicists. Their findings were published in The Astrophysical Journal.
Galaxies evolve by converting gas into stars, and without external gas sources, star formation would cease within a billion years. The discovery provides insight into how galaxies like M83 may evolve over millions and billions of years.
“This galaxy resembles our own Milky Way, therefore findings there may also provide clues into star formation and galaxy evolution in the Milky Way,” Koda stated.
Nagata explained that they analyzed 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 scenarios for these molecular gas clouds: direct accretion from outside the galaxy or ejection by supernova explosions within the galaxy followed by gravitational fallback. However, Koda noted that their kinetic energies are too high to be explained by a single supernova event.
“These features strongly suggest that many of the observed high-velocity clouds must be flowing into M83 from external sources,” Nagata explained.
This study marks the first systematic investigation of high-velocity molecular clouds in nearby galaxies. The researchers plan to continue exploring how molecular gas forms outside galaxies.
The research received support from the National Science Foundation (NSF), under grant numbers 2006600 and 2406608.
