The Quasar Candidates Catalogs of DESI Legacy Imaging Survey Data Release 9

Abstract

Quasars can be used to measure baryon acoustic oscillations at high redshift, which are considered as direct tracers of the most distant large-scale structures in the Universe. It is fundamental to select quasars from observations before implementing the above research. This work focuses on creating a catalog of quasar candidates based on photometric data to provide primary priors for further object classification with spectroscopic data in the future, such as The Dark Energy Spectroscopic Instrument (DESI) Survey. We adopt a machine learning algorithm (Random Forest, RF) for quasar identification. The training set includes $651,073$ positives and $1,227,172$ negatives, in which the photometric information are from DESI Legacy Imaging Surveys (DESI-LIS) \& Wide-field Infrared Survey Explore (WISE), and the labels are from a database of spectroscopically confirmed quasars based on Sloan Digital Sky Survey (SDSS) and the Set of Identifications \& Measurements and Bibliography for Astronomical Data (SIMBAD). The trained RF model is applied to point-like sources in DESI-LIS Data Release 9. To quantify the classifier's performance, we also inject a testing set into the to-be-applied data. Eventually, we obtained $1,953,932$ Grade-A quasar candidates and $22,486,884$ Grade-B quasar candidates out of $425,540,269$ sources ($\sim 5.7\%$). The catalog covers $\sim 99\%$ of quasars in the to-be-applied data by evaluating the completeness of the classification on the testing set. The statistical properties of the candidates agree with that given by the method of color-cut selection. Our catalog can intensely decrease the workload for confirming quasars with the upcoming DESI data by eliminating enormous non-quasars but remaining high completeness. All data in this paper is publicly available online.

11 figures, 13 pages, 3 tables; accepted by RAA, comments welcome!

References in corpus (20)

• A Catalog of Quasar Properties from SDSS DR7
• The Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological Implications from two Decades of Spectroscopic Surveys at the Apache Point observatory
• Baryon Acoustic Oscillations in the Lyα forest of BOSS DR11 quasars
• The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release
• Sizes and Temperature Profiles of Quasar Accretion Disks from Chromatic Microlensing
• Quasar Accretion Disks Are Strongly Inhomogeneous
• Evolution of the Cool Gas in the Circumgalactic Medium (CGM) of Massive Halos -- A Keck Cosmic Web Imager (KCWI) Survey of Ly$\alpha$ Emission around QSOs at $z\approx 2$
• Preliminary Target Selection for the DESI Luminous Red Galaxy (LRG) Sample
• The Minimum Testable Abundance of Primordial Black Holes at Future Gravitational-Wave Detectors
• MusE GAs FLOw and Wind (MEGAFLOW) VIII. Discovery of a MgII emission halo probed by a quasar sightline
• Preliminary Target Selection for the DESI Quasar (QSO) Sample
• The Sizes of Quasar Host Galaxies with the Hyper Suprime-Cam Subaru Strategic Program
• Measuring Quasar Variability with Pan-STARRS1 and SDSS
• Host galaxies of high-redshift quasars: supermassive black hole growth and feedback
• Statistical strong lensing. I. Constraints on the inner structure of galaxies from samples of a thousand lenses
• Finding Quasars behind the Galactic Plane. I. Candidate Selections with Transfer Learning
• The Probabilistic Random Forest applied to the selection of quasar candidates in the QUBRICS Survey
• Probing the Inner Circumgalactic Medium and Quasar Illumination around the Reddest `Extremely Red Quasar' (ERQ)
• Absorption-line Environments of High-redshift BOSS Quasars
• A Search for Blazar Activity in Broad-Absorption-Line Quasars