3:30–4:30 pm ERC 401
Host: Alex Drlica-Wagner
Anirudh Chiti (KICP) "Uncovering ancient stars in the Large Magellanic Cloud"
The Large Magellanic Cloud (LMC; M_star ~ 10^9 M_sun) is the largest Milky Way satellite and is nearly a major galaxy in its own right, having its own ecosystem of satellite galaxies and showing evidence of hierarchical assembly. Intriguingly, the LMC is on first infall (~2 Gyr ago), meaning that its lowest metallicity stars ought to sample the signatures of the first stars and early chemical and galactic evolution in a formerly distant, extra-galactic environment. First, I will present the detection of 10 stars between -4.1 < [Fe/H] < -2.5 in the LMC- the first detection of any stars in the system below [Fe/H] = -2.5, opening a window to direct studies of the very early evolution of this formerly extragalactic ecosystem. These stars confirm previous suggestions that the early environment of the Large Magellanic Cloud was markedly different from the Milky Way, either having extremely inefficient star formation or experiencing strong inflows of pristine gas. There is also a notable difference in the carbon abundances of these stars from the Milky Way’s lowest metallicity stars, suggesting a deviation in their early chemical evolution. The most metal-poor star in this sample ([Fe/H] = -4.1) is also plausibly a second-generation star, reflecting the nucleosynthetic yields of Pop III supernovae that occurred in the early LMC ecosystem. I will conclude by discussing a proposed survey of the southern sky using a newly installed, metallicity-sensitive Calcium H+K filter on DECam. This survey would enable such low metallicity star searches in most southern dwarf galaxies and streams, providing a comprehensive sample for insights on environmental variations in early stellar, chemical, and galactic evolution.
