Search for Quasar Pairs with $Gaia$ Astrometric Data. I. Method and Candidates

Abstract

Quasar pairs, a special subclass of galaxy pairs, are valuable in the investigation of quasar interaction, clustering, co-evolution between the two quasars' host galaxies, the growth of supermassive black holes, as well as the formation and evolution of galaxies. However, quasar pairs on kpc scales are observationally rare. The scarcity of available samples hindered the deeper exploration and statistics of these objects. In this work, we apply an astrometric method to systematically search for quasar candidates within a transverse distance of 100 kpc to known quasars in the Million Quasar Catalog. These candidates are \textit{Gaia} sources with proper motions and parallaxes that are consistent with zero. Visual inspection of the sample was performed to remove the contamination of crowded stellar fields and nearby galaxies. A total of 4\,112 quasar pair candidates were isolated, with a median member separation of 8.81{\arcsec}, a median \textit{Gaia} $G$-band magnitude of 20.52, and a median redshift of 1.61. Our catalog was compared with three major candidate quasar pair catalogs and identified 3\,984 new quasar pair candidates previously uncataloged in the three catalogs. Several interesting quasar pair candidates are highlighted and discussed. We also briefly discussed our quasar selection and several techniques for improving the success rate of quasar pair selection. Extensive spectroscopic follow-up campaigns are being carried out to validate their astrophysical nature.

16 pages, 14 figures, 3 tables. Published in Astronomy & Astrophysics, 707, A30 (2026). DOI: 10.1051/0004-6361/202555435

References in corpus (55)

• Array Programming with NumPy
• The NumPy array: a structure for efficient numerical computation
• The Gaia mission
• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• Gaia Data Release 3: Summary of the content and survey properties
• The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release
• A possible close supermassive black-hole binary in a quasar with optical periodicity
• The Eighteenth Data Release of the Sloan Digital Sky Surveys: Targeting and First Spectra from SDSS-V
• A Candidate Sub-Parsec Supermassive Binary Black Hole System
• The Half Million Quasars (HMQ) Catalogue
• Active Galactic Nucleus Pairs from the Sloan Digital Sky Survey. I. The Frequency on ~ 5-100 kpc Scales
• Quasar Clustering at $25\kpch$ from a Complete Sample of Binaries
• The Million Quasars (Milliquas) Catalogue, v8
• Gravitationally lensed quasars in Gaia -- IV. 150 new lenses, quasar pairs, and projected quasars
• Quaia, the Gaia-unWISE Quasar Catalog: An All-Sky Spectroscopic Quasar Sample
• Varstrometry for Off-nucleus and Dual sub-Kpc AGN (VODKA): Hubble Space Telescope Discovers Double Quasars
• Unveiling the population of dual- and lensed- AGNs at sub-arcsec separations
• Dual supermassive black holes at close separation revealed by the Hyper Suprime-Cam Subaru Strategic Program
• Dynamical evolution of cosmic supermassive binary black holes and their gravitational wave radiation
• A hidden population of high-redshift double quasars unveiled by astrometry
• Observations of a Magellanic Corona
• A close quasar pair in a disk-disk galaxy merger at z = 2.17
• Finding Quasars behind the Galactic Plane. I. Candidate Selections with Transfer Learning
• New multiple AGN systems with sub-arcsec separation: confirmation of candidates selected via the novel GMP method
• Statistics of Galactic-Scale Quasar Pairs at Cosmic Noon
• Quasars with Proper Motions and the Link to Double and Multiple AGNs
• A Survey for High-redshift Gravitationally Lensed Quasars and Close Quasars Pairs. I. the Discoveries of an Intermediately-lensed Quasar and a Kpc-scale Quasar Pair at $z\sim 5$
• CatNorth: An Improved Gaia DR3 Quasar Candidate Catalog with Pan-STARRS1 and CatWISE
• Dual AGN candidates with double-peaked [O III] lines matching that of confirmed dual AGNs
• MUSE adaptive-optics spectroscopy confirms dual active galactic nuclei and strongly lensed systems at sub-arcsec separation
• A study of purely astrometric selection of extragalactic point sources with Gaia
• Reliable Identification of Binary Supermassive Black Holes from Rubin Observatory Time-Domain Monitoring
• COOL-LAMPS III: Discovery of a 25".9 Separation Quasar Lensed by a Merging Galaxy Cluster
• Discovering strongly lensed quasar candidates with catalogue-based methods from DESI Legacy Surveys
• Finding Multiply-Lensed and Binary Quasars in the DESI Legacy Imaging Surveys
• The environment of low redshift quasar pairs
• Spiral Arms in Broad-line Regions of Active Galactic Nuclei. II. Loosely Wound Cases: Reverberation Properties
• VLBI imaging of the pre-coalescence SMBHB candidate SDSS J143016.05+230344.4
• The CatSouth Quasar Candidate Catalog for the Southern Sky and a Unified All-Sky Catalog Based on Gaia DR3
• Final stage of merging binaries of supermassive black holes: observational signatures
• Gemini Multi-Object Spectrograph Integral Field Unit Spectroscopy of the Double-peaked Broad Emission Line of a Red Active Galactic Nucleus
• A catalog of candidate double and lensed quasars from Gaia and WISE data
• Varstrometry Selected Radio-Loud Candidates of Dual and Off-Nucleus Quasars at Sub-kpc Scales
• SDSS J222428.53+261423.2: unique emission lines properties unveil a sub-kiloparsec dual AGN candidate
• Overdensity of galaxies in the environment of quasar pairs
• SQUAB I: The first release of Strange QUasar candidates with ABnormal astrometric characteristics from Gaia EDR3 and SDSS
• Astrometric Jitter as a Detection Diagnostic for Recoiling and Slingshot Supermassive Black Hole Candidates
• Finding binary active galactic nuclei candidates by the centroid shift in imaging surveys II. Testing the method with SDSS J233635.75-010733.7
• Gaia GraL: Gaia DR2 Gravitational Lens Systems. VII. XMM-Newton Observations of Lensed Quasars
• Discovery of 19 strongly-lensed quasars, dual and projected quasars in DESI-LS
• Velocity offset between emission and absorption lines might be an effective indicator of dual core system
• DULAG: A DUal and Lensed AGN candidate catalog with GMP method
• Strange Quasar Candidates with Abnormal Astrometric Characteristics from Gaia EDR3 and SDSS (SQUAB-II): Optical Identifications
• Quasar Pairs as Large--Scale Structure tracers
• Serendipitous discovery of a physical binary quasar at z=1.76