Improved Redshifts for DESI EDR Quasars

TL;DR

This paper provides improved systemic redshift estimates for DESI EDR quasars using emission-line fits, significantly enhancing redshift accuracy especially at higher redshifts, which benefits various scientific analyses.

Contribution

The authors present a new method for estimating quasar redshifts that improves upon the DESI pipeline, particularly for high-redshift quasars, and make these redshifts publicly available.

Findings

19% of pipeline redshifts deviate by >500 km/s from new estimates

Redshift accuracy is notably improved at z>1

New redshifts are publicly accessible online

Abstract

The Dark Energy Spectroscopic Instrument (DESI) survey will provide optical spectra for $\sim 3$ million quasars. Accurate redshifts for these quasars will facilitate a broad range of science applications. Here we provide improved systemic redshift estimates for the $\sim 95$k quasars included in the DESI Early Data Release (EDR), based on emission-line fits to the quasar spectra. The majority of the DESI pipeline redshifts are reliable. However, $\sim 19\%$ of the EDR quasars have pipeline redshifts that deviate from our new redshifts by $>500\,{\rm km\,s^{-1}}$. We use composite quasar spectra to demonstrate the improvement of our redshift estimates, particularly at $z>1$. These new redshifts are available at \url{https://github.com/QiaoyaWu/DESI_EDR_qsofit/blob/main/DESI_EDR_Aug29_redshift_only.fits}.