Performance of the Quasar Spectral Templates for the Dark Energy Spectroscopic Instrument

Millions of quasar spectra will be collected by the Dark Energy Spectroscopic Instrument (DESI), leading to a fourfold increase in the number of known quasars. High-accuracy quasar classification is essential to tighten constraints on cosmological parameters measured at the highest redshifts DESI observes (z > 2.0). We present spectral templates for identification and redshift estimation of quasars in the DESI Year 1 data release. The quasar templates are comprised of two quasar eigenspectra sets, trained on spectra from the Sloan Digital Sky Survey. The sets are specialized to reconstruct quasar spectral variation observed over separate yet overlapping redshift ranges and, together, are capable of identifying DESI quasars from 0.05 < z < 7.0. The new quasar templates show significant improvement over the previous DESI quasar templates regarding catastrophic failure rates, redshift precision and accuracy, quasar completeness, and the contamination fraction in the final quasar sample.

Automated summary

The Dark Energy Spectroscopic Instrument (DESI) will collect millions of quasar spectra, increasing the known number of quasars fourfold. Accurate classification is important for examining cosmological parameters at high redshifts observed by DESI. Spectral templates have been developed for identifying and estimating redshifts of quasars in DESI Year 1 data release. These templates, trained on Sloan Digital Sky Survey spectra, can identify DESI quasars within the range of 0.05 < z < 7.0, and show significant improvements in failure rates, precision and accuracy of redshifts, completeness, and contamination fraction compared to previous DESI quasar templates.