BOSS-CLAM: Utilizing a Constrained Linear Absorption Model to Infer Stellar Parameters from BOSS Spectra
Year: 2026
Type: article
Abstract: Large spectroscopic surveys require robust pipelines capable of inferring stellar parameters over a wide range of the Hertzsprung–Russell (H-R) diagram from data of varying quality. SDSS-V is one such survey, where the data from the lower-resolution, optical BOSS spectrograph will provide a large dataset covering a wide range of Galactic stellar populations. To better analyze these data, we present BOSS-CLAM, a generative, forward-modeling pipeline for inferring effective temperature ( T eff ), surface gravity ( log g ), metallicity ([Fe/H]), and α -abundance ([ α /M]) from continuum-normalized BOSS spectra. BOSS-CLAM maps stellar labels to nonnegative matrix factorization (NMF) basis vector weights via a polynomial mapping jointly optimized with the spectral decomposition, which provides a more flexible framework for working with the lower-resolution BOSS data. Additionally, training labels are drawn from four complementary sources (ASPCAP, BOSS-MINESweeper , wide binaries, and a hot star validation sample), which enables coverage from cool M dwarfs through hot OB stars, and across a wide range of metallicity. We infer parameters for 1,708,214 BOSS spectra, with a recommended clean catalog of 915,514 sources. Validation against open and globular clusters demonstrates homogeneous, accurate abundances across a wide range of metallicity. Wide binary tests yield abundance uncertainties of σ [Fe/H] ≈ 0.15 dex and σ [ α /M] ≈ 0.06 dex at signal-to-noise ratio (SNR) = 10. Finally, we demonstrate that the BOSS-CLAM catalog recovers known chemical structure of the Milky Way disk and is well suited for Galactic archaeology, chemical tagging, and stellar population modeling. The pipeline, trained model, and catalog are publicly released as part of SDSS-V DR20.
Institutions: University of Toronto, Vanderbilt University, Flatiron Institute, Monash University, University of Chicago, NSF-Simons AI Institute for the Sky, Texas Christian University, Georgia State University, Carnegie Institution for Science, Johns Hopkins University, Heidelberg University, Max Planck Institute for Astronomy, Center for Astrophysics Harvard & Smithsonian, New York University, University of Colorado Boulder, University of Illinois Urbana-Champaign
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funders: National Science Foundation, Alfred P. Sloan Foundation, Yale University, Carnegie Institution of Washington, Ohio State University, California Institute of Technology, Harvard University, Johns Hopkins University, New Mexico State University, Space Telescope Science Institute, Flatiron Health, École Polytechnique Fédérale de Lausanne, Belgian Federal Science Policy Office, University of Toronto, KU Leuven, Universidad Nacional Autónoma de México, Yunnan University, Nanjing University, China National Textile and Apparel Council, Vlaamse regering, Leibniz-Institut für Astrophysik Potsdam, Max-Planck-Institut für Astronomie, University of Illinois at Urbana-Champaign, University of Colorado Boulder, Smithsonian Astrophysical Observatory, Leibniz-Gemeinschaft, National Astronomical Observatories, Chinese Academy of Sciences
Awards: Collaborative Research: Galactic Archaeology from Careful Modeling of Old Stars, G2593991423, G3002814323, SOUL: Stellar evOlution in fUll gLory: rotation, magnetism, oscillations, outflows, tides, and binarity, Metallicity Distributions of the Faintest Dwarf Galaxies, G5075890216, Collaborative Research: Chemical History of the Milky Way as Seen Through Open Clusters using SDSS and Gaia
OpenAlex ID: W7171569183