Semi-analytic chemo-dynamic model of the Milky Way disk

• Applicant: Dr. Kseniia Sysoliatina
• Subject Area: Astrophysics and Astronomy
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 523499018

In this project, we plan to construct a comprehensive chemo-dynamic model of the Milky Way (MW) disk based on the two python codes: jjmodel code, a realisation of the semi-analytic Just-Jahreiß (JJ) model, and the Chempy code, a leaky-box multi-zone chemical evolution model. The JJ model describes the Galaxy as an axisymmetric system that includes the thin and thick disk, molecular and atomic gas, as well as stellar and dark matter halo components. It iteratively solves the Poisson equation and predicts a self-consistent pair of vertical potential and density; the latter is turned into star counts with a stellar evolution library. The JJ model has been calibrated against different datasets in the solar neighbourhood (such as Hipparcos, SDSS, Gaia, and APOGEE) and is now generalised for the whole Galactic disk. During the next three years, we plan to achieve three main goals. First, we will develop an analytic treatment for the in-plane stellar motion which will complement the vertical stellar kinematics already included in the JJ model. Second, using bright tracers, such as A, F, Red Clump stars, or Cepheids type I from Gaia DR3, we will calibrate the updated JJ model within 4-5 kpc from the Sun. We will use the Markov Chain Monte Carlo (MCMC) routine for the efficient exploration of the parameter space. The reconstructed radial variation of the star formation history will give us an insight into the MW formation process (e.g. inside-out disk growth scenario can be tested). Thirdly, we will combine the JJ model with the Chempy code and will explore abundance patterns of 10-20 s- and r-process chemical elements across the MW disk and compare them to the data from high-resolution spectroscopic surveys, such as APOGEE, GALAH, Gaia-ESO, or the upcoming surveys SDSS-V and 4MOST. By optimising model parameters with the MCMC, we will reconstruct the MW gas infall history, estimate relative contributions of the asymptotic giant branch and supernovae enrichment processes, and analyse the role of radial mixing. Our secondary goals include improvements in the stellar population synthesis process: we plan to add a population of white dwarfs and take into account binary evolution to reproduce a more realistic colour-magnitude diagram. We also plan to use the updated JJ model calibrated across the disk, to study non-axisymmetric disk features, such as the spiral arms and warp, and compare their revealed structure to the existing models. The chemo-dynamic MW model based on the JJ model and Chempy will be a flexible open-source tool suitable for testing different MW evolutionary scenarios and performing stellar population synthesis across the Galactic disk.

• DFG Programme: Research Grants
• International Connection: Ukraine
• Co-Investigator: Professor Dr. Andreas Just
• Cooperation Partner: Dr. Oleksiy Golubov