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

Alexander, David M.; Davis, Tamara M.; Chaussidon, E.; Fawcett, V.A.; X. Gonzalez-Morales, Alma; Lan, Ting-Wen; Yèche, Christophe; Ahlen, S.; Aguilar, J.N.; Armengaud, E.; Bailey, S.; Brooks, D.; Cai, Z.; Canning, R.; Carr, A.; Chabanier, S.; Cousinou, Marie-Claude; Dawson, K.; de la Macorra, A.; Dey, A.; Dey, Biprateep; Dhungana, G.; Edge, A.C.; Eftekharzadeh, S.; Fanning, K.; Farr, James; Font-Ribera, A.; Garcia-Bellido, J.; Garrison, Lehman; Gaztañaga, E.; A Gontcho, Satya Gontcho; Gordon, C.; Medellin Gonzalez, Stefany Guadalupe; Guy, J.; Herrera-Alcantar, Hiram K.; Jiang, L.; Juneau, S.; Karaçaylı, N.G.; Kehoe, R.; Kisner, T.; Kovács, A.; Landriau, M.; Levi, Michael E.; Magneville, C.; Martini, P.; Meisner, Aaron M.; Mezcua, M.; Miquel, R.; Camacho, P. Montero; Moustakas, J.; Muñoz-Gutiérrez, Andrea; Myers, Adam D.; Nadathur, S.; Napolitano, L.; Nie, J.D.; Palanque-Delabrouille, N.; Pan, Z.; Percival, W.J.; Pérez-Ràfols, I.; Poppett, C.; Prada, F.; Ramírez-Pérez, César; Ravoux, C....

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Tamara M. Davis

E. Chaussidon

V.A. Fawcett

Alma X. Gonzalez-Morales

Ting-Wen Lan

Christophe Yèche

S. Ahlen

J.N. Aguilar

E. Armengaud

S. Bailey

D. Brooks

Z. Cai

R. Canning

A. Carr

S. Chabanier

Marie-Claude Cousinou

K. Dawson

A. de la Macorra

A. Dey

Biprateep Dey

G. Dhungana

S. Eftekharzadeh

K. Fanning

James Farr

A. Font-Ribera

J. Garcia-Bellido

Lehman Garrison

E. Gaztañaga

Satya Gontcho A Gontcho

C. Gordon

Stefany Guadalupe Medellin Gonzalez

J. Guy

Hiram K. Herrera-Alcantar

L. Jiang

S. Juneau

N.G. Karaçaylı

R. Kehoe

T. Kisner

A. Kovács

M. Landriau

Michael E. Levi

C. Magneville

P. Martini

Aaron M. Meisner

M. Mezcua

R. Miquel

P. Montero Camacho

J. Moustakas

Andrea Muñoz-Gutiérrez

Adam D. Myers

S. Nadathur

L. Napolitano

J.D. Nie

N. Palanque-Delabrouille

Z. Pan

W.J. Percival

I. Pérez-Ràfols

C. Poppett

F. Prada

César Ramírez-Pérez

C. Ravoux

D.J. Rosario

M. Schubnell

Gregory Tarlé

M. Walther

B. Weiner

S. Youles

Zhimin Zhou

H. Zou

Siwei Zou


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 nonnegligible 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 increase 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−1) 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 a median redshift precision and accuracy of ≈100 km s−1 and ≈70 km s−1, respectively. We constructed composite spectra to investigate why some quasars are missed by the standard pipeline and find that they are more host-galaxy dominated (i.e., distant analogs of "Seyfert galaxies") and/or more 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.

Journal Article Type Article
Acceptance Date Nov 22, 2022
Online Publication Date Feb 22, 2023
Publication Date Mar 1, 2023
Deposit Date Jun 8, 2023
Publicly Available Date Jun 8, 2023
Journal The Astronomical Journal
Print ISSN 0004-6256
Electronic ISSN 1538-3881
Publisher IOP Publishing
Peer Reviewed Peer Reviewed
Volume 165
Issue 3
Article Number 124
Public URL


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Copyright Statement
Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.

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