A Data-Driven Model of Nucleosynthesis Reveals Dilution Signature in Milky Way Stellar Abundances

Abstract

The Galactic stellar abundance patterns are dominantly produced by prompt core-collapse supernovae and delayed Type-Ia supernovae. Though nucleosynthesis is complex, the observed abundance structure is largely two-dimensional. We fit the abundances of 15 elements for a large sample of stars in APOGEE DR17 using a flexible, data-driven K-process model (KPM). With K=2, this model describes each abundance in each star as the sum of a prompt and a delayed process contribution. We find that a K=2 model can explain the observed abundances well, and can predict the abundances in the Galactic disk to accuracies of 0.02 to 0.05 dex. The remaining abundance residuals show complex structures with respect to age, guiding radius, and vertical action, tracing kinematic structures in the Milky Way. We find that some, but not all, of the effects in the low-α disk can be explained by dilution with fresh gas.