J/ApJ/964/69 Quaia, the Gaia-unWISE Quasar catalog (Storey-Fisher+, 2024)
Quaia, the Gaia-unWISE Quasar catalog: an all-sky spectroscopic quasar sample.
Storey-Fisher K., Hogg D.W., Rix H.-W., Eilers A.-C., Fabbian G.,
Blanton M.R., Alonso D.
<Astrophys. J., 964, 69 (2024)>
=2024ApJ...964...69S 2024ApJ...964...69S
ADC_Keywords: QSOs; Spectra, optical; Photometry, infrared; Surveys; Redshifts;
Proper motions
Keywords: Quasars ; Catalogs ; Large-scale structure of the universe ; Gaia ;
Active galactic nuclei
Abstract:
We present a new, all-sky quasar catalog, Quaia, that samples the
largest comoving volume of any existing spectroscopic quasar sample.
The catalog draws on the 6,649,162 quasar candidates identified by the
Gaia mission that have redshift estimates from the space observatory's
low-resolution blue photometer/red photometer spectra. This initial
sample is highly homogeneous and complete, but has low purity, and 18%
of even the bright (G<20.0) confirmed quasars have discrepant redshift
estimates (|Δz/(1+z)|>0.2) compared to those from the Sloan
Digital Sky Survey (SDSS). In this work, we combine the Gaia
candidates with unWISE infrared data (based on the Wide-field Infrared
Survey Explorer survey) to construct a catalog useful for cosmological
and astrophysical quasar studies. We apply cuts based on proper
motions and colors, reducing the number of contaminants by
approximately four times. We improve the redshifts by training a
k-Nearest Neighbor model on SDSS redshifts, and achieve estimates on
the G<20.0 sample with only 6% (10%) catastrophic errors with
|Δz/(1+z)|>0.2 (0.1), a reduction of approximately three times
(approximately two times) compared to the Gaia redshifts. The final
catalog has 1,295,502 quasars with G<20.5, and 755,850 candidates in
an even cleaner G<20.0 sample, with accompanying rigorous selection
function models. We compare Quaia to existing quasar catalogs, showing
that its large effective volume makes it a highly competitive sample
for cosmological large-scale structure analyses.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
quaiag200.dat 195 755850 *Quaia, the Gaia-unWISE G<20.0 Quasar catalog
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Note on quaiag200.dat: The G<20.0 version is cleaner and has overall better
redshift estimates than the G<20.5 version which contains 1,295,502 sources.
It is just a subset of the G<20.5 catalog with an additional magnitude
cut, but the associated selection function and random catalog are
different.
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Description of file:
quaia_G20.0.fits is the original catalog in FITS format as available at:
10.5281/zenodo.10403370
The FTP also contains the quaia_G20.5.fits (G<20.5) version in FITS format.
See also:
II/363 : The band-merged unWISE Catalog (Schlafly+, 2019)
VII/285 : Gaia DR2 quasar and galaxy classification (Bailer-Jones+, 2019)
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)
I/356 : Gaia DR3 Part 2. Extra-galactic (Gaia Collaboration, 2022)
I/357 : Gaia DR3 Part 3. Non-single stars (Gaia Collaboration, 2022)
J/ApJ/778/98 : Cross-correlation of SDSS QSOs and BOSS galaxies (Shen+, 2013)
J/ApJ/815/33 : A Hubble diagram for quasars (Risaliti+, 2015)
J/AJ/154/269 : A new photo-z method for quasars in Stripe 82 (Yang+, 2017)
J/A+A/644/A17 : Astrometrically-selected QSO candidates (Heintz+, 2020)
J/A+A/642/A150 : Quasars as standard candles. III. (Lusso+, 2020)
J/A+A/668/A99 : Gaia DR3 quasar and galaxy classification (Hughes+, 2022)
J/A+A/674/A41 : Composite quasar spectra from Gaia DR3 (Gaia Coll., 2023)
J/ApJS/264/9 : Southern phot. QSOs from DES DR2 & NIR surveys (Yang+, 2023)
Byte-by-byte Description of file: quaiag200.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 source identifier (source_id)
21- 36 A16 --- objID unWISE DR1 objID identifier (unwise_objid)
38- 46 F9.7 --- zQuaia [0.086/4.63] Spectroscopic redshift estimate
(redshift_quaia)
48- 56 F9.7 --- e_zQuaia [0.016/1.9] zQuaia uncertainty
(redshiftquaiaerr)
58- 68 F11.7 deg RAdeg Right ascension (ICRS) at Ep=2016.0 (ra)
70- 80 F11.7 deg DEdeg Declination (ICRS) at Ep=2016.0 (dec)
82- 92 F11.7 deg GLON Galactic longitude (l)
94-104 F11.7 deg GLAT Galactic latitude (b)
106-112 F7.4 mag Gmag [13.88/20] Gaia G-band mean magnitude
(photgmean_mag)
114-120 F7.4 mag BPmag [13.99/21.25] Gaia BP-band mean magnitude
(photbpmean_mag)
122-128 F7.4 mag RPmag [13.46/20.24] Gaia RP-band mean magnitude
(photrpmean_mag)
130-138 F9.6 mag W1mag [8/17.9] WISE W1 (3.4um) band magnitude
(magw1vg)
140-148 F9.6 mag W2mag [7.4/16.8] WISE W2 (4.6um) band magnitude
(magw2vg)
150-157 F8.6 mas/yr pm [0.0005/4.9] Total proper motion (pm)
159-167 F9.6 mas/yr pmRA [-3.9/4.6] Proper motion in right ascension
direction (pmRA*cosDE) (pmra)
169-177 F9.6 mas/yr pmDE [-4.1/3.7] Proper motion in declination
direction (pmdec)
179-186 F8.6 mas/yr e_pmRA [0.014/2.2] pmRA uncertainty (pmra_error)
188-195 F8.6 mas/yr e_pmDE [0.016/2] pmDE uncertainty (pmdec_error)
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History:
Downloaded at: http://zenodo.org/records/10403370
(DOI: 10.5281/zenodo.8060754)
Licence: Creative Commons Attribution 4.0 International
(End) Emmanuelle Perret [CDS] 05-Nov-2025