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.
Pseudo-Continua for M Dwarf BOSS Spectra
Pseudo-continua of M dwarf’s in SDSS-V, which can be used to properly flux “standardize” BOSS spectra
Catalog Data
Abstract
M dwarfs have complex atmospheres, and their spectra contain many wide and densely overlapping molecular features, so determining accurate stellar parameters by fitting models has been difficult. To circumvent this, other surveys have employed machine learning methods to transfer measurements of stellar parameters from high-resolution spectra to their medium-resolution counterparts. These methods provide large catalogs of stellar parameters but, if not addressed properly, are plagued by biases which are, in part, due to the normalization of the spectra. In Medan al. (2025) we developed a "standardization" method, which defines a pseudo-continuum of BOSS M dwarf spectra. The goal of the method was to create standardized spectra that preserved the dynamic range of stellar parameters and spectral features, but removed flux calibration issues in the BOSS spectra. To accomplish this, we use the spectrum's alpha shape to find the points which lie between the absorption features and apply local polynomial regression to find this pseudocontinuum. To tune the hyperparameters of this method, we created BOSS-like spectra from BT-NextGen models to replicate instrumental, signal-to-noise ratio, and reddening effects. We found that in both this generated set and a validation set of SDSS-V data, our method performs better than alternative standardizations by producing spectra that are both more uniform for M dwarfs with similar stellar parameters and more easily distinguished compared to M dwarfs of differing parameters. The main product of the VAC is the HDF5 file. It consists of both the meta-data from astra’s mwmAllVisit for all M dwarf’s observed with BOSS in DR20, and also includes the flux, inverse variance and the pseudo-continua calculated with our method for their spectra.
Catalog last modified: 2026-07-30 12:12:10