J/A+A/707/A30 Qasar pairs with Gaia astrometric data (Chen+, 2026)
Search for quasar pairs with Gaia astrometric data. I. Method and candidates.
Chen Q., Jing L., Zhu X., Fang Y., He Z., Deng Z., Xiang C., Wu J.
<Astron. Astrophys. 707, A30 (2026)>
=2026A&A...707A..30C 2026A&A...707A..30C (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Redshifts ; Photometry ; Optical
Keywords: methods: data analysis - methods: statistical - catalogs -
astrometry - quasars: general
Abstract:
Quasar pairs, a special subclass of galaxy pairs, are valuable in the
investigation of quasar interaction and clustering, the coevolution
between the two quasars' host galaxies, and the growth of supermassive
black holes, as well as the formation and evolution of galaxies
overall. However, quasar pairs on kiloparsec 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 100kpc to known quasars in
the Million Quasar Catalog. These candidates are Gaia sources with
proper motions and parallaxes that are consistent with zero. A visual
inspection of the sample was performed to remove the contamination of
crowded stellar fields and nearby galaxies. A total of 4112 quasar
pair candidates were isolated, with a median member separation of
8.81", a median Gaia G-band magnitude of 20.52, and a median redshift
of 1.61. Following a comparison of our catalog with three major
candidate quasar pair catalogs, we identified 3984 new quasar pair
candidates that had previously been overlooked in the three catalogs.
Several interesting quasar pair candidates are highlighted and
discussed in this work. We also offer a brief discussion of our quasar
selection and several techniques for improving the success rate of
quasar pair selection. Extensive spectroscopic follow-up campaigns are
currently underway to validate their astrophysical nature.
Description:
The MGQPC (Quasar Pair Candidates derived from the cross-match of MQC
and Gaia) catalog contains 4112 plausible quasar pair candidates. It
is based on the Million Quasars catalogue (MQC) version 8 and Gaia
DR3. Each row of the catalog contains data for two sources: A and B.
Source A is a known quasar from the MQC with a redshift greater than
0.5, while source B is an astrometrically selected quasar
candidate.These quasar candidates are Gaia sources with proper motions
and parallaxes that are consistent with zero.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
mgqpc.dat 370 4112 Quasar Pair Candidates derived from the
cross-match of Million Quasars catalogue (MQC)
and Gaia
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
VII/294 : The Million Quasars (Milliquas) catalogue, version 8 (Flesch, 2023)
Byte-by-byte Description of file: mgqpc.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- System Pair name designated by the center coordinates
at J2000 (ICRS), JHHMMSSsss+DDMMSSsss
(SystemName)
25- 49 A25 --- NameA The name of pair member A retrieved from the
Million Quasars catalogue (NAME)
51- 54 A4 --- TypeA The object type of pair member A retrieved
from the MQCv8 (TYPE)
56- 63 F8.6 --- zA Redshift of pair member A, updated with the
MQCv8 and SIMBAD (Z_A)
65- 75 F11.8 arcsec seplim Cross-matching radius calculated with Z_A and
100 kpc (ec seplim)
77- 84 A8 --- --- [Gaia DR3]
86-104 I19 --- GaiaDR3A Unique Gaia DR3 identifier (source_id) of
pair member A (DR3Name_A)
106-118 F13.9 deg RAAdeg Gaia (ICRS) at Ep=2000 right ascension of
pair member A (RA_A)
120-132 F13.9 deg DEAdeg Gaia (ICRS) at Ep=2000 declination of pair
member A (DEC_A)
134-142 F9.6 --- GmagA Gaia G-band magnitude pair member A (Gmag_A)
144-153 F10.6 --- BPmagA ? Gaia BP-band magnitude pair member A
(BPmag_A)
155-163 F9.6 --- RPmagA ? Gaia RP-band magnitude pair member A
(RPmag_A)
165-175 E11.9 --- f0plxA ? Probability density of zero parallax
calculated for pair member A (f0plxA)
177-198 E22.16 --- f0pmA ? Probability density of zero proper motion
calculated for pair member A (f0pmA)
200-207 A8 --- --- [Gaia DR3]
209-227 I19 --- GaiaDR3B Unique Gaia DR3 identifier (source_id) of
pair member B (DR3Name_B)
229-241 F13.9 deg RABdeg Gaia (ICRS) at Ep=2000 right ascension of
pair member B (RA_B)
243-255 F13.9 deg DEBdeg Gaia (ICRS) at Ep=2000 declination of
pair member B (DEC_B)
257-265 F9.6 --- GmagB Gaia G-band magnitude pair member B (Gmag_B)
267-276 F10.6 --- BPmagB ? Gaia BP-band magnitude pair member B
(BPmag_B)
278-287 F10.6 --- RPmagB ? Gaia RP-band magnitude pair member B
(RPmag_B)
289-300 E12.9 --- f0plxB Probability density of zero parallax
calculated for pair member B (f0plxB)
302-313 F12.9 --- f0pmB Probability density of zero proper motion
calculated for pair member B (f0pmB)
315-323 F9.6 arcsec sepAB Angular separation between the two members in
the pair (sep_AB)
325-337 F13.9 deg GLONB Galactic longitude of pair member B (l_B)
339-350 F12.8 deg GLATB Galactic latitude of pair member B (b_B)
352-357 A6 --- SkyLab Label of the sky region where pair member B
is located (SkyLab) (1)
359-364 A6 --- MTypeB Morphological type of pair member B retrieved
from DESI-LS DR10 (MorphoType_B)
366-370 A5 --- VIClass Pair classification assigned by visual
Inspection (VIClass) (2)
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Note (1): e.g., "Gb2030" represents the sky region of 20 deg ≤ |b| < 30 deg.
Note (2): Pair classification as follows:
QPC = quasar pair candidate
LQC = lensed quasar candidate
WSLQC = wide-separation lensed quasar candidate
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Acknowledgements:
From Qihang Chen, chenqihang(at)bnu.edu.cn
The authors thank the anonymous referee for the valuable comments that
improved the quality and clarity of the manuscript. The authors thank
Qirong Yuan, Heng Yu, He Gao, Yiping Shu, Xikai Shan, Yuming Fu, and
Yuanzhen Han for their suggestions and guidance on several details.
This work has been supported by the Chinese National Natural Science
Foundation grant No. 12333001 and by the National Key R&D Program of
China (2021YFA0718500 and 2025YFA1614101).
We acknowledge the use of public data from the following facilities:
Gaia, SDSS, LAMOST, DESI, DESI Legacy Survey, and Pan-STARRS. This
research made use of the following software packages: Astropy (Astropy
Collaboration et al. 2013, 2018, 2022), Matplotlib (Hunter 2007),
NumPy (van der Walt et al. 2011; Harris et al. 2020), Pandas (Wes
McKinney 2010; pandas development team 2022), TOPCAT (Taylor 2005),
HumVI (Marshall et al. 2015, 2016).
(End) Patricia Vannier [CDS] 26-Jan-2026