Abstract
Stars are important tracers of and contributors to Milky Way (MW) chemical evolution. Because stars largely retain the chemical compositions of their birth clouds throughout their life, we can use their chemical abundances to trace the composition of the interstellar medium (ISM) at the time and location of their birth. In addition, we can use highly evolved stars and their byproducts to study the contributions of stars to enriching the ISM. I have worked on two projects in the last two years that explore these topics.
My first project examines the nebular parameters, chemical abundances, and kinematic properties of eight highly-extincted planetary nebulae (PNe) with the Low Resolution Spectrograph 2 on the Hobby-Eberly Telescope. PNe are valuable tools in the study of chemical evolution because they allow access to elements undetectable in stellar spectra and also present the full nucleosynthetic history of their progenitor asymptotic giant branch star, prominent sources of MW neutron-capture elements. These targets all lack high-quality optical data in the literature, something that is crucial for constraining important nebular parameters that act as inputs to abundance calculations. Additionally, some of these objects show signs of neutron-capture element enrichment in their infrared spectra. I present our preliminary results and compare the chemical and kinematic membership signatures of each PN to assess each object's membership probability to the thin disk, thick disk, and halo of the MW.
My second project explores the chemical and dynamical evolution of our local Solar neighborhood through the lens of twelve newfound, elongated stellar groups (called ‘strings’) discovered kinematically in Gaia DR3. We use the chemical data from GALAH DR3 to study the chemical distributions, homogeneities, and ages of each structure. We find that 1) all but three structures in our sample are generally more homogeneous in [X/H] than their local fields, 2) several structures are as chemically homogeneous as open clusters, and 3) chemical indicators, which include Li and chemical clock abundance ratios, support the isochronal ages of these structures. I use these results to present possible formation mechanisms for these structures and reflect on the advantages that chemistry brings to age analyses.
