Properties of stellar populations and white dwarfs in a semi-analytic Milky Way disk model based on Gaia DR3
CMD produced by JJ model
This thesis presents the extension of the semi-analytic chemo-dynamic model of the Milky Way disc, known as the JJ model, first presented by Just and Jahreiß (2010), to include white dwarfs (WD). Initially, we test the calibrated JJ model and found minor inconsistencies (about 0.2 % and 2.2 % in 25 pc and 60 pc volume) in total star counts based on Gaia EDR3 data, implying excellent data-to-model consistency. Subsequently, this work incorporated WD synthesis into the model using BaSTI DA and DB (carbon-oxygen core) isochrones and an initial-final mass relation. This work also modeled stellar lifetimes and derived an analytical fit for the DA/DB ratio as a function of effective temperature. Additionally, we established a volume-complete sample of Gaia DR3 WDs within 60 pc and found that the updated JJ model over-predicts WDs by 52%, potentially attributed to assumptions regarding the initial mass function (IMF) and star formation rate (SFR). Exploring this dependency on the IMF, we derived a test IMF; however, a thorough MCMC-based model calibration is warranted. This extended JJ model serves as a valuable tool for studying Milky Way evolution, IMF, SFR, and WD kinematics.
