New Insights into Milky Way's Chemical Evolution from Gaia-ESO Data
Recent research has highlighted the presence of a metal-poor, young stellar population in the chemical thin disk of the Milky Way. This study, conducted by Marco Palla and colleagues, focuses on the evolution of abundance gradients within the galaxy using data from the Gaia-ESO survey. The researchers analyzed a large sample of open clusters, which serve as effective tracers for understanding the chemical evolution of the Milky Way.
The study employed a careful selection process to exclude stars that might be biased in spectral analysis. The resulting sample was compared against detailed chemical evolution models of the Milky Way, testing various scenarios of galactic evolution. The findings indicate a notable decrease in metallicity between intermediate-age (1 to 3 billion years) and young (less than 1 billion years) open clusters. This decrease challenges the previously accepted two-infall model of gas accretion, suggesting instead that a three-infall model may better explain the observed data.
The three-infall model posits that the chemical thin disk was formed through one or two subsequent gas accretion episodes, with the latest occurring within the last three billion years. This late gas accretion is proposed to have triggered a dilution of metals, which accounts for the low metallic content found in the young clusters. The study extends the framework of the three-infall model to encompass the entire Galactic disk for the first time.
These findings contribute to our understanding of the Milky Way's formation and evolution, particularly regarding how recent gas accretion events have influenced the chemical composition of its stellar populations. The implications of this research are significant for astrophysics, as they provide insights into the processes that shape the structure and evolution of galaxies.
The full paper can be cited as: Palla, M., Magrini, L., Spitoni, E., Matteucci, F., Viscasillas Vázquez, C., Franchini, M., Molero, M., & Randich, S. (2024). Mapping radial abundance gradients with Gaia-ESO open clusters: Evidence of recent gas accretion in the Milky Way disk. arXiv:2408.17395.