Abundances of low-metallicity stars in Sgr dwarf galaxy

By studying the chemical abundances of stars in the Sgr core and tidal streams, we can gain insights into the assembly history of this galaxy and its early heavy element nucleosynthesis processes. We efficiently selected extremely metal-poor candidates in the core and streams for high-resolution spectroscopic analysis using metallicity-sensitive photometry from SkyMapper DR2 and Gaia DR3 XP spectra, and proper motions.

We present a sample of 37 Sgr stars with detailed chemical abundances, of which we identify 10 extremely metal-poor ([Fe/H]<=-3.0) stars, 25 very metal-poor ([Fe/H]<=-2.0) stars, and two metal-poor ([Fe/H]<=-1.0) stars. This sample increases the number of extremely metal-poor Sgr stars analyzed with high-resolution spectroscopy by a factor of 5. Of these stars, 15 are identified as members of the Sgr tidal stream, while the remaining 22 are associated with the core.