Chandra, Vedant; Cargile, Phillip A.; Ji, Alexander P.; Conroy, Charlie; Rix, Hans-Walter; Cunningham, Emily; Dias, Bruno; Laporte, Chervin; Cerny, William; Limberg, Guilherme; Bandyopadhyay, Avrajit; Bonaca, Ana; Casey, Andrew R.; Donor, John; Fern谩ndez-Trincado, Jos茅 G.; Frinchaboy, Peter M.; Gupta, Pramod; Hawkins, Keith; Johnson, Jennifer A.; Kollmeier, Juna A.; Lucey, Madeline; Medan, Ilija; M茅sz谩ros, Szabolcs; Morrison, Sean; S谩nchez-Gallego, Jos茅; Saydjari, Andrew K.; Sayres, Conor; Schlaufman, Kevin C.; Stassun, Keivan G.; Tayar, Jamie; Way, Zachary (2026).听.听Astrophysical Journal, 1000(2), 283.听
The Sloan Digital Sky Survey V (SDSS-V) is carrying out the first full-sky survey of stars in the Milky Way鈥檚聽stellar halo(the extended, sparse region surrounding the galaxy) using low-resolution聽spectroscopy聽(analyzing starlight to learn about stars鈥� properties). This study describes the data-processing system used for this survey, which combines multiple types of observations鈥攕tellar spectra, brightness measurements (photometry), and distance information from聽parallax鈥攖o estimate key properties such as a star鈥檚 temperature, chemical composition (metallicity), abundance of certain elements (like聽alpha elements, which trace stellar history), and distance.
The resulting dataset, called the聽BOSS-MINESweeper catalog, was carefully tested by comparing its results with well-studied star clusters and more precise, high-resolution surveys. The catalog proves powerful for several types of research: it can identify unusual stars with rare chemical signatures, reveal previously unknown structures in the distant halo, and map how stars move across the galaxy on very large scales.
Overall, this work provides a major new resource for studying the formation and evolution of the Milky Way. The catalog is publicly available and will continue to grow with future data releases.
Figure 1.聽Top: distribution of SDSS-V halo stars observed up through 2024, in Galactic coordinates. This figure includes data observed from both APO and LCO, although only APO data are released in DR19. Bottom: stellar distribution in Gaia color鈥搈agnitude space, colored by median SNR (in the 4750鈭�5500 脜 region) of the co-added BOSS spectrum. Contours of target density are overlaid. The displayed color range corresponds to stellar temperatures from 鈮�3800 to 6500 K.