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.
Spectral subtypes, morphology, and H-alpha emission for late-K and M dwarfs observed with BOSS
Spectral classifications of low-mass stars using a set of empirical spectral templates, along with 3-D Galactic space velocities
Catalog Data
Abstract
This value added catalog compares optical BOSS spectra of low-mass stars to a set of 536 empirical spectral templates assembled from earlier SDSS optical spectra (Galligan & Lépine 2026), which span a broad range of effective temperatures and metallicities. The BOSS spectra are matched to their best-fit templates to assign: (1) a spectral subtype, which range from K5.0 to M8.5 with half-subtype resolution, (2) a “morphology class”, which ranges from 0.5 to 12.5 in half-integer steps, (3) H-alpha equivalent widths, and (4) calculated UVW velocities relative to the Sun. The templates are adapted from Zhong et al. (2015) , which use spectra of K/M dwarfs classified according to the spectral indices from Lépine et al. (2003) to determine spectral sub-type and the morphology class ('MC"), which is correlated with metallicity in M dwarfs. The MC parameter presented here is an updated and interpolated version of the four metallicity classes (d/sd/esd/usd) defined in Lépine et al. (2007) , which describe the relative strengths of the TiO and CaH absorption features that dominate M-dwarf spectra in the optical regime. Stars with MC=0.5 are consistent with super-metal-rich abundances, while stars with MC=12.5 appear to be the most metal-poor, with solar metallicity (thin disk) objects near MC=2.0. We also calculate H-alpha equivalent widths, which help identify very active and potentially young M dwarfs. The UVW velocity components of motion are most useful at validating the MC parameter by associating the stars with their most likely parent population (disk, old disk, halo). This catalog is described in further detail in Galligan & Lépine (2026).
Catalog last modified: 2026-07-30 12:12:10