3:30–4:00 pm ERC 517
Host: Alexander Ji
Akshara Viswanathan (Groningen/Flatiron) "Tracing the Milky Way's ancient footsteps: Insights from chemodynamical investigations of bright and distant metal-poor stars"
Galaxy formation and evolution is a complex process. The chemodynamical study of metal-poor stars in the Milky Way provides a unique and powerful way of unlocking the secrets of star formation, and the growth of galactic structures. Leveraging large datasets including Gaia's precision astrometry, the Pristine survey's metallicity estimates for low-metallicity stars and our own spectroscopic follow-up observations, we conduct comprehensive chemodynamical analyses of some of the most metal-poor stars in the Galaxy. Here I present the first spectroscopic follow-up of ~250 stars with predicted [Fe/H] < -2.5 (extremely metal-poor, EMP) in the Milky Way from this new dataset. We find that 75% of the stars have indeed [Fe/H] < -2.5, while all of them are very metal-poor ([Fe/H] < -2). This means a large improvement over the existing methods that search for EMP stars. Additionally, we probe further out into the outer galactic halo, going beyond 30 kpc. This resulted in the confirmation of three brightest members of the most metal-poor structure known in the universe, the C-19 stellar stream, one of which is 50 degrees away from the detected main body of the stream. Some of the EMP stars we discovered are on prograde disk-like orbits, which needs further investigation. We also unveil an invaluable catalog of over 1,000 very metal-poor (VMP) stars from archival Gaia RVS spectra, with a significant portion lacking any literature parameters. This catalog serves as a treasure trove for high-resolution spectroscopic research, shedding light on VMP star characteristics across diverse Galactic regions. ( https://ui.adsabs.harvard.edu/abs/2023arXiv230906137V/abstract) Together, these works offer a fresh and comprehensive perspective on the Milky Way's assembly and growth from a chemodynamical standpoint, utilizing bright and distant metal-poor stars as invaluable guides to the early universe.
