Author ORCID Identifier
Date of Award
Doctor of Philosophy (PhD)
Physics and Astronomy
High-dimensional datatsets of local stars are now available thanks to large surveys. These data are useful for Galactic archaeology, which seeks to understand the history of the Milky Way. These studies predominantly utilize more massive stars, but low-mass stars dominate in the Galaxy and would provide the highest-resolution view of the local chemo-dynamical- age structure. Here we construct the novel methodologies needed to accomplish this to better constrain Milky Way models. First, we construct our dataset by developing a Bayesian cross-matching method that we apply to ~6 million high proper motion Gaia sources. The resulting catalog has a marginally higher match rate than internal Gaia DR2 matches and a significant improvement for Pan-STARRS (~20.8% to ~99.8% within the survey footprint). With these data, we develop a photometric-metallicity relationship that has an average precision of ±0.12 dex for dwarfs with 3500 K and is largely free of systematic errors present in past studies due to the removal of unresolved binaries in this work. As a result, we devoted time to developing methods to detect binaries without using astrometry. Here we present this method, which would increase the number of local (d<200 >pc) low angular separation binaries by ~91%, and the results of a speckle imaging campaign. Finally, we combined the astrometric and photometric-metallicity data to get a detailed view of the chemo-dynamic-age structure of ~250,000 low-mass stars. Here we observe trends in metallicity and vertical velocity dispersion hypothesized to be due to differences in mean age. To test this, we develop a method to estimate the age distribution of sub-populations of stars using GALAH defined probability density functions of W vs. [M/H]. We estimate the probable age distribution for regions in the kinematic plane, where we see significant sub-structure; high angular momentum streams have higher concentrations of younger stars (Gyr), while the Hercules streams are dominated by older stars (8-10 Gyr). With these data, we preview a method for constraining test particle simulations to determine Galactic potential parameters. The methodologies presented here demonstrate the power of low-mass stars and how they can be used to better understand our Galaxy.
Medan, Ilija, "The Chemodynamic-Age Structure of the Local Population of Low-Mass Stars." Dissertation, Georgia State University, 2023.
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