Skip to main content

Research Repository

Advanced Search

Target Selection and Validation of DESI Quasars

Chaussidon, Edmond; Yèche, Christophe; Palanque-Delabrouille, Nathalie; Alexander, David M.; Yang, Jinyi; Ahlen, Steven; Bailey, Stephen; Brooks, David; Cai, Zheng; Chabanier, Solène; Davis, Tamara M.; Dawson, Kyle; de laMacorra, Axel; Dey, Arjun; Dey, Biprateep; Eftekharzadeh, Sarah; Eisenstein, Daniel J.; Fanning, Kevin; Font-Ribera, Andreu; Gaztañaga, Enrique; A Gontcho, Satya Gontcho; Gonzalez-Morales, Alma X.; Guy, Julien; Herrera-Alcantar, Hiram K.; Honscheid, Klaus; Ishak, Mustapha; Jiang, Linhua; Juneau, Stephanie; Kehoe, Robert; Kisner, Theodore; Kovács, Andras; Kremin, Anthony; Lan, Ting-Wen; Landriau, Martin; Le Guillou, Laurent; Levi, Michael E.; Magneville, Christophe; Martini, Paul; Meisner, Aaron M.; Moustakas, John; Muñoz-Gutiérrez, Andrea; Myers, Adam D.; Newman, Jeffrey A.; Nie, Jundan; Percival, Will J.; Poppett, Claire; Prada, Francisco; Raichoor, Anand; Ravoux, Corentin; Ross, Ashley J.; Schlafly, Edward; Schlegel, David; Tan, Ting; Tarlé, Gregory; Zhou, Rongpu; Zh...

Target Selection and Validation of DESI Quasars Thumbnail


Edmond Chaussidon

Christophe Yèche

Nathalie Palanque-Delabrouille

Jinyi Yang

Steven Ahlen

Stephen Bailey

David Brooks

Zheng Cai

Solène Chabanier

Tamara M. Davis

Kyle Dawson

Axel de laMacorra

Arjun Dey

Biprateep Dey

Sarah Eftekharzadeh

Daniel J. Eisenstein

Kevin Fanning

Andreu Font-Ribera

Enrique Gaztañaga

Satya Gontcho A Gontcho

Alma X. Gonzalez-Morales

Julien Guy

Hiram K. Herrera-Alcantar

Klaus Honscheid

Mustapha Ishak

Linhua Jiang

Stephanie Juneau

Robert Kehoe

Theodore Kisner

Andras Kovács

Anthony Kremin

Ting-Wen Lan

Martin Landriau

Laurent Le Guillou

Michael E. Levi

Christophe Magneville

Paul Martini

Aaron M. Meisner

John Moustakas

Andrea Muñoz-Gutiérrez

Adam D. Myers

Jeffrey A. Newman

Jundan Nie

Will J. Percival

Claire Poppett

Francisco Prada

Anand Raichoor

Corentin Ravoux

Ashley J. Ross

Edward Schlafly

David Schlegel

Ting Tan

Gregory Tarlé

Rongpu Zhou

Zhimin Zhou

Hu Zou


The Dark Energy Spectroscopic Instrument (DESI) survey will measure large-scale structures using quasars as direct tracers of dark matter in the redshift range 0.9 < z < 2.1 and using Lyα forests in quasar spectra at z > 2.1. We present several methods to select candidate quasars for DESI, using input photometric imaging in three optical bands (g, r, z) from the DESI Legacy Imaging Surveys and two infrared bands (W1, W2) from the Wide-field Infrared Survey Explorer. These methods were extensively tested during the Survey Validation of DESI. In this paper, we report on the results obtained with the different methods and present the selection we optimized for the DESI main survey. The final quasar target selection is based on a random forest algorithm and selects quasars in the magnitude range of 16.5 < r < 23. Visual selection of ultra-deep observations indicates that the main selection consists of 71% quasars, 16% galaxies, 6% stars, and 7% inconclusive spectra. Using the spectra based on this selection, we build an automated quasar catalog that achieves a fraction of true QSOs higher than 99% for a nominal effective exposure time of ∼1000 s. With a 310 deg−2 target density, the main selection allows DESI to select more than 200 deg−2 quasars (including 60 deg−2 quasars with z > 2.1), exceeding the project requirements by 20%. The redshift distribution of the selected quasars is in excellent agreement with quasar luminosity function predictions.

Journal Article Type Article
Acceptance Date Dec 3, 2022
Online Publication Date Feb 28, 2023
Publication Date Feb 10, 2023
Deposit Date Jun 21, 2023
Publicly Available Date Jun 21, 2023
Journal Astrophysical Journal
Print ISSN 0004-637X
Electronic ISSN 1538-4357
Publisher American Astronomical Society
Peer Reviewed Peer Reviewed
Volume 944
Issue 1
Article Number 107
Public URL


Published Journal Article (5.8 Mb)

Publisher Licence URL

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.

You might also like

Downloadable Citations