Spiral arms and bars in early galaxies may have been the key to their high star formation rates, according to new research. This challenges the long-held belief that early galaxies were chaotic and messy, and instead suggests that these structures played a crucial role in driving gas transport and star formation.
The study, published in Astronomy and Astrophysics and arXiv.org, analyzed the movements of cold gas in star-forming galaxies during the Cosmic Noon, a period around two to three billion years after the Big Bang. The researchers used the NOEMA3D survey, which examined massive main-sequence galaxies with the JWST and NOEMA, to generate high-resolution studies of molecular gas kinematics.
The findings revealed that massive disk galaxies with bars and spiral arms efficiently moved cold gas around, leading to high star formation rates. This contradicts the previous understanding that early galaxies were irregular and dynamically unstable. Instead, the study found that these galaxies had well-ordered structures, with 4 out of 10 showing clear spiral arms and central bars.
By measuring gas velocities and subtracting the velocities due to rotation, the researchers determined that spiral arms and bars move star-forming gas around in the galaxies. This means that these structures are actively redistributing gas, channeling it into the inner regions where stars form. The rate of inflow is comparable to the galaxies' star formation rates, suggesting that the gas is fueling star formation and may also be contributing to supermassive black holes.
The study's lead author, Dr. Juan Manuel Espejo Salcedo, notes that the results provide compelling evidence that spiral arms and bars were already driving gas transport when the universe was at its peak of star-forming activity. This challenges the previous understanding that early galaxies were clumpy and messy, and instead suggests that these structures played a crucial role in the evolution of galaxies.
The findings also have implications for our understanding of the Milky Way. The study suggests that ancient galaxies were very similar to our modern Milky Way, with clear spiral arms and a bar. However, the speed at which gas moved through them was much higher than in local galaxies.
In conclusion, the research highlights the importance of spiral arms and bars in the evolution of galaxies, and challenges the long-held belief that early galaxies were chaotic and messy. The findings provide a new perspective on the role of these structures in driving gas transport and star formation, and offer valuable insights into the formation and evolution of galaxies.
