Precision Spectroscopy for 1.9 Million Galaxies from SDSS-IV: Improved Spectral Measurements and Catalogs for eBOSS

TL;DR

This paper presents an improved spectral analysis pipeline for the eBOSS survey, producing a comprehensive catalog of galaxy spectral measurements that enhances the scientific utility of the dataset for galaxy evolution and cosmology research.

Contribution

Introduction of the eBOSS Data Analysis Pipeline (eBOSS-DAP) for uniform spectral measurements, enabling detailed analysis of 1.9 million galaxy spectra from SDSS-IV.

Findings

High-quality spectral measurements for nearly 1.9 million galaxies

Assessment of calibration and measurement reliability

Release of extensive data products for community use

Abstract

The Sloan Digital Sky Survey IV DR17 Extended Baryon Oscillation Spectroscopic Survey (eBOSS) consists of 2,233,939 high-quality optical galaxy spectra obtained through 2" fibers, providing a rich spectroscopic resource for studying galaxy evolution across a broad redshift range. eBOSS was designed primarily for large-scale structure and BAO measurements and, as such, focused on galaxy redshifts, leaving much of the information contained in the spectra unexplored. In addition to the trove of spectra, the large number of repeat observations (197,521 duplicate spectra) enables evaluation of the survey's spectrophotometric quality. To unlock this potential, we introduce the eBOSS Data Analysis Pipeline (eBOSS-DAP), adapted from the MaNGA-DAP, which delivers uniform measurements of emission-line fluxes and equivalent widths, stellar and gas kinematics, continuum spectral indices, and stellar population fits. Using the eBOSS-DAP, we successfully analyze 1,899,553 high-quality galaxy spectra below a redshift of $z < 1.12$ to produce an extensive spectroscopic catalog for the eBOSS galaxy sample. We characterize the calibration performance, quantify the reliability of the derived measurements, and release a suite of data products that fully exploit the power of the eBOSS dataset. These catalogs open the door to a new generation of studies in galaxy evolution and cosmology.