Chronology of our Galaxy from Gaia colour--magnitude diagram fitting (ChronoGal). I. The formation and evolution of the thin disc from the Gaia Catalogue of Nearby Stars

Vol. 687
5. Galactic structure, stellar clusters and populations

Chronology of our Galaxy from Gaia colour--magnitude diagram fitting (ChronoGal). I. The formation and evolution of the thin disc from the Gaia Catalogue of Nearby Stars

Studying the star formation history (SFH) of the Milky Way on a star-to-star basis is still an expensive endeavor. To address this, the authors introduce a new tool for deriving this SFH by fitting color-magnitude diagrams (CMDs) based on Gaia data. After being used to obtain the metallicity and age distributions of the solar neighborhood, the new method was applied to the complete catalog of stars within 100 pc of the Sun, comprising mostly (but not only) thin-disk stars. As a result, the authors find that stars at the solar radius predominantly formed at solar metallicities early on (~11 Gyr ago) until a break occurred and three stellar populations emerged from ``some dramatic event’’ in the Milky Way’s life. This period was then followed by more significant star formation that occurred in a bursty manner. Intriguingly, thick-disk stars were also found in the sample. The results could be independently confirmed with high-precision spectroscopy: the presented CMD fitting technique achieved an accuracy and precision better than 10%, thereby providing an important proof-of-concept for detailed, future studies of the formation history of the Milky Way disk(s).