Mapping the Distant and Metal-poor Milky Way with SDSS-V

Abstract The fifth-generation Sloan Digital Sky Survey (SDSS-V) is conducting the first all-sky low-resolution spectroscopic survey of the Milky Way’s (MW) stellar halo. We describe the stellar parameter pipeline for the SDSS-V halo survey, which simultaneously models spectra, broadband photometry, and parallaxes to derive stellar parameters, metallicities, alpha abundances, and distances. The resulting Baryon Oscillation Spectroscopic Survey (BOSS)- MINESweeper catalog is validated across a wide range of stellar parameters and metallicities using star clusters and a comparison to high-resolution spectroscopic surveys. We demonstrate several scientific capabilities of this dataset: identifying the most chemically peculiar stars in our Galaxy, discovering and mapping distant halo substructures, and measuring the all-sky dynamics of the MW on the largest scales. The BOSS- MINESweeper catalog for SDSS DR19 is publicly available and will be updated for future data releases.