The DESI Survey Validation: Results from Visual Inspection of the Quasar Survey Spectra

Abstract

A key component of the Dark Energy Spectroscopic Instrument (DESI) survey validation (SV) is a detailed visual inspection (VI) of the optical spectroscopic data to quantify key survey metrics. In this paper we present results from VI of the quasar survey using deep coadded SV spectra. We show that the majority (~70%) of the main-survey targets are spectroscopically confirmed as quasars, with ~16% galaxies, ~6% stars, and ~8% low-quality spectra lacking reliable features. A non-negligible fraction of the quasars are misidentified by the standard spectroscopic pipeline but we show that the majority can be recovered using post-pipeline "afterburner" quasar-identification approaches. We combine these "afterburners" with our standard pipeline to create a modified pipeline to improve the overall quasar yield. At the depth of the main DESI survey both pipelines achieve a good-redshift purity (reliable redshifts measured within 3000 km/s) of ~99%; however, the modified pipeline recovers ~94% of the visually inspected quasars, as compared to ~86% from the standard pipeline. We demonstrate that both pipelines achieve an median redshift precision and accuracy of ~100 km/s and ~70 km/s, respectively. We constructed composite spectra to investigate why some quasars are missed by the standard spectroscopic pipeline and find that they are more host-galaxy dominated (i.e., distant analogs of "Seyfert galaxies") and/or dust reddened than the standard-pipeline quasars. We also show example spectra to demonstrate the overall diversity of the DESI quasar sample and provide strong-lensing candidates where two targets contribute to a single spectrum.

Astronomical journal (in press). 26 pages, 15 figures, 9 tables, one of a suite of 8 papers detailing targeting for DESI. Figure data available from Zenodo (see paper for details)

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Cited by in corpus (36)

• DESI 2024 VI: Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations
• The Early Data Release of the Dark Energy Spectroscopic Instrument
• DESI Bright Galaxy Survey: Final Target Selection, Design, and Validation
• DESI 2024 IV: Baryon Acoustic Oscillations from the Lyman Alpha Forest
• DESI 2024 II: Sample Definitions, Characteristics, and Two-point Clustering Statistics
• Performance of the Quasar Spectral Templates for the Dark Energy Spectroscopic Instrument
• Testing AGN outflow and accretion models with CIV and HeII emission line demographics in z=2 quasars
• The Dark Energy Spectroscopic Instrument: One-dimensional power spectrum from first Lyman-$\alpha$ forest samples with Fast Fourier Transform
• Modified Gravity Constraints from the Full Shape Modeling of Clustering Measurements from DESI 2024
• A review of unsupervised learning in astronomy
• DESI z >~ 5 Quasar Survey. I. A First Sample of 400 New Quasars at z ~ 4.7-6.6
• Constraining primordial non-Gaussianity from DESI quasar targets and Planck CMB lensing
• Value Added Catalog of physical properties of more than 1.3 million galaxies from the DESI Survey
• Detecting and Characterizing Mg II absorption in DESI Survey Validation Quasar Spectra
• Host Dark Matter Halos of WISE-selected Obscured & Unobscured Quasars: Evidence for Evolution
• ELG Spectroscopic Systematics Analysis of the DESI Data Release 1
• The most distant HI galaxies discovered by the 500 m dish FAST
• Wide Area VISTA Extra-galactic Survey (WAVES): Unsupervised star-galaxy separation on the WAVES-Wide photometric input catalogue using UMAP and $\mathrm{HDBSCAN}$
• High redshift LBGs from deep broadband imaging for future spectroscopic surveys
• Galaxy Spectra neural Network (GaSNet). II. Using Deep Learning for Spectral Classification and Redshift Predictions
• The DESI One-Percent Survey: Modelling the clustering and halo occupation of all four DESI tracers with Uchuu
• PICZL: Image-based Photometric Redshifts for AGN
• Emission Line Predictions for Mock Galaxy Catalogues: a New Differentiable and Empirical Mapping from DESI
• The Compilation and Validation of the Spectroscopic Redshift Catalogs for the DESI-COSMOS and DESI-XMMLSS Fields
• DESI Mock Challenge: Constructing DESI galaxy catalogues based on FastPM simulations
• AstroInspect: a web-based system to organize, assess, and visually inspect astronomical objects
• Constraining primordial non-Gaussianity from the large scale structure two-point and three-point correlation functions
• A Morphological Model to Separate Resolved-Unresolved Sources in the DESI Legacy Surveys: Application in the LS4 Alert Stream
• The miniJPAS survey quasar selection V: combined algorithm
• DESI Mg II Absorbers: Extinction Characteristics & Quasar Redshift Accuracy
• The Impact of Spectroscopic Redshift Errors on Cosmological Measurements
• The Lyman-$\alpha$ Forest from LBGs: First 3D Correlation Measurement with DESI and Prospects for Cosmology
• Quiescent Host Galaxies of Extended Quasars Revealed by Spectrophotometric Decomposition
• Measurements of quasar proximity zones with the Ly$\alpha$ forest of DESI Y1 quasars
• Identifying Anomalous DESI Galaxy Spectra with a Variational Autoencoder
• Seeing through the dust: Unraveling near-infrared variability in type 2 active galactic nuclei