Speaker
Description
The chemical abundance patterns exhibited by stars in Ultra-Faint Dwarf (UFD) galaxies can provide a wealth of information about the evolutionary history of UFDs, including what dynamical history the stars in a UFD may have experienced. Of particular interest are stars in the outer regions of UFDs because they may hold evidence of tidal stripping, mergers, or other mechanisms; and because of the localized nature of enrichment events in UFDs, it is important to use every available star in analyses of UFD histories. I present detailed abundances from high-resolution spectroscopy with Gemini/GRACES for five new stars in three UFDs, Coma Berenices (Com Ber), Ursa Major I (UMaI), and Boötes I (BooI), where four of our five stars are at distances greater than two half-light radii. The chemistries for all three galaxies are consistent with the outermost stars forming in the central regions, then moving to their current locations through dynamical mechanisms. In BooI, the lower metallicity and lack of strong carbon enrichment of its outermost stars could also be evidence of a dwarf galaxy merger. The abundance ratios and chemical patterns of the stars in Com Ber are consistent with contributions from SN Ia (including an unusually high Ni value), which is unexpected for its star formation history and in conflict with previous suggestions that this system evolved chemically from a single core collapse supernova event. We look forward to the new GHOST (Gemini High-resolution Optical SpecTrograph), which will make these types of chemical abundance-quality observations possible for many more stars in UFDs.
| Do you plan to attend the symposium in-person or virtually? | in-person |
|---|
