In addition to the primary SDSS photometry and spectroscopy, there are a few extra catalogs created by our collaborators that are distributed through the SAS. These Value-Added Catalogs (VACs) are listed below, and include catalogs that were released in earlier data releases.
Stellar Parameters from BOSS Spectra with The CLAM
Stellar parameters (Teff, logg, [Fe/H] and [alpha/M]) derived from DR20 BOSS spectra using the BOSS-CLAM method
Catalog Data
Abstract
This value added catalog presents BOSS-CLAM, a generative, forward modeling pipeline for inferring effective temperature (Teff), surface gravity (logg), metallicity ([Fe/H]), and alpha-abundance ([alpha/M]) from continuum-normalized BOSS spectra. BOSS-CLAM (Medan et al., submitted) maps stellar labels to Non-negative 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 sigma_[Fe/H] = 0.15 dex and sigma_[alpha/M] = 0.06 dex at signal-to-noise SNR = 10. Finally, the BOSS-CLAM catalog can be used to recover known chemical structure of the Milky Way disk and is well-suited for Galactic archaeology, chemical tagging, and stellar population modeling. The VAC contains both a nominal HDF5 file and a “lite” version of the catalog. The nominal version contains all meta-data from astra’s mwmAllStar file, the BOSS-CLAM stellar parameters and full covariance matrices, forward modeled spectra and detailed flags on the parameters. The lite version contains a subset of the meta-data from astra’s mwmAllStar file, the BOSS-CLAM stellar parameters and full covariance matrices, and detailed flags on the parameters. The lite version is available in both HDF5 and FITS file formats. There is a Python notebook tutorial available for this VAC, which you can find on GitHub here.
Catalog last modified: 2026-07-30 12:12:10