J/ApJS/280/23 Radio-loudness stat. of QSOs from Quaia-VLASS (Arsenov+, 2025)
Radio-loudness statistics of quasars from Quaia-VLASS.
Arsenov N., Frey S., Kovacs A., Slavcheva-Mihova L.
<Astrophys. J. Suppl. Ser., 280, 23 (2025)>
=2025ApJS..280...23A 2025ApJS..280...23A
ADC_Keywords: QSOs; Radio sources; Photometry, infrared; Optical; Redshifts;
Magnitudes, absolute; Reddening
Keywords: Catalogs ; Surveys ; Active galaxies ; Quasars ; Radio loud quasars ;
Large-scale structure of the universe
Abstract:
Quasars are objects of high interest in extragalactic astrophysics,
cosmology, and astrometry. One of their useful qualities is their
potential radio-loudness. However, the fraction of radio-loud versus
radio-quiet quasars is subject to ongoing investigations, where the
statistical power is limited by the low number of known quasars with
radio counterparts. In this analysis, we revisited the radio-loudness
statistics of quasars by significantly expanding the pool of known
sources. Our main goal was to create a new, value-added quasar catalog
with information about their extinction-corrected magnitudes, radio
flux density, possible contamination levels, and other flags, besides
their sky coordinates and photometric redshifts. We cross-matched the
optical Quaia catalog of about 1.3 million quasars (from the Gaia
data) with 1.9 million sources from the Very Large Array Sky Survey
(VLASS) radio catalog. We explored different thresholds for the
matching radius, balancing completeness and purity of the resulting
Quaia-VLASS catalog, and found 1.5" a sufficient choice. Our main
finding is that the quasar radio-loud fraction is in good agreement
with previous works (<10%), and there is no significant large-scale
sky pattern in radio-loudness. The exact estimate depends on the
G-band magnitude limit, and we observed weak trends with redshift and
absolute optical magnitude, possibly indicating remnant systematic
effects in our data.
Description:
The main goal of this work is to crossmatch a large sample of
optically detected quasars with a catalog of radio sources, mainly
following the steps in Ivezic+ (2002AJ....124.2364I 2002AJ....124.2364I), concentrating on
the radio-loudness statistics.
For the optical quasar catalog, we chose the recently compiled Quaia
(Storey-Fisher+ 2024, J/ApJ/964/69) because of its large sky coverage,
high completeness, and high astrometric accuracy.
The other data set that we used is based on the ongoing Very Large
Array Sky Survey (VLASS; Lacy+ 2020PASP..132c5001L 2020PASP..132c5001L) at 3GHz (S band),
conducted with the Very Large Array in New Mexico, in particular the
VLASS Epoch 2 Quick Look (VLASS2 QL) catalog. Unlike Quaia, the VLASS2
QL catalog does not cover the full sky, and its 3.0 million radio
sources are distributed at declinations of δ>-40°.
The crossmatched Quaia-VLASS catalog with 43,650 sources and
accompanying codes is available at doi:10.5281/zenodo.16035690
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 245 43650 Quaia-VLASS cross-matches catalog
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See also:
I/356 : Gaia DR3 Part 2. Extra-galactic (Gaia Collaboration, 2022)
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)
VII/294 : The Million Quasars (Milliquas) catalogue, version 8 (Flesch, 2023)
J/ApJ/430/467 : Superluminal motions for extragal. sources (Vermeulen+, 1994)
J/A+A/342/378 : 6 and 20cm flux densities of radio galaxies (Gurvits+ 1999)
J/ApJ/831/168 : 6GHz JVLA obs. of low-z SDSS quasars (Kellermann+, 2016)
J/A+A/598/A104 : LOFAR Two-metre Sky Survey (Shimwell+, 2017)
J/A+A/622/A11 : LoTSS/HETDEX. Optical quasars. I. (Guerkan+, 2019)
J/ApJ/871/258 : ELQS in SDSS. III. Full ELQS quasar cat. (Schindler+, 2019)
J/A+A/644/A159 : The third realization of the ICRF, ICRF3 (Charlot+, 2020)
J/ApJS/255/30 : VLASS QL Ep.1 Catalog, CIRADA version (Gordon+, 2021)
J/ApJ/922/202 : Radio luminous QSOs in SDSS DR14Q (Rusinek-Abarca+, 2021)
J/A+A/674/A41 : Composite quasar spectra from Gaia DR3 (Gaia Coll., 2023)
J/A+A/690/A321 : 1.7GHz images of 9 faint radio quasars (Krezinger+, 2024)
J/ApJ/964/69 : Quaia, the Gaia-unWISE Quasar catalog (Storey-Fisher+, 2024)
http://cirada.ca/vlasscatalogueql0 : VLASS Quick Look catalog homepage
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 19 I19 --- GaiaDR3 Gaia DR3 source identifier from Quaia
(Storey-Fisher+ 2024, J/ApJ/964/69)
21- 36 A16 --- unWISE unWISE DR1 source identifier from Quaia
38- 43 F6.4 --- z [0.08/4.4] Spectrophotometric redshift
estimate from Quaia
45- 50 F6.4 --- e_z [0.02/1.7] Uncertainty in z from Quaia
52- 64 F13.9 deg RAdeg Barycentric right ascension from Quaia
(ICRS) at Ep=2016.0
66- 78 F13.9 deg DEdeg [-40/89] Barycentric declination from Quaia
(ICRS) at Ep=2016.0
80- 88 F9.6 mag Gmag [13.8/20.5] Apparent Gaia G-band mean
magnitude from Quaia, not extinction
corrected (G'; photgmean_mag)
90- 98 F9.6 mag BPmag [13.9/21.3] Apparent Gaia integrated BP mean
magnitude from Quaia
100- 108 F9.6 mag RPmag [13.4/20.7] Apparent Gaia integrated RP mean
magnitude from Quaia
110- 118 F9.6 mag W1mag [8.9/18.1] Apparent unWISE W1 magnitude from
Quaia
120- 128 F9.6 mag W2mag [7.9/17.2] Apparent unWISE W2 magnitude from
Quaia
130- 140 A11 --- --- [VLASS2QLCIR]
142- 160 A19 --- Name Unique VLASS name (JHHMMSS.ss+DDMMSS.s)
162- 173 F12.8 deg RAVdeg VLASS right ascension
175- 186 F12.8 deg DEVdeg [-40/89] VLASS declination
188- 195 F8.3 mJy Ftot [0.02/7379] Integrated radio flux density
from VLASS
197- 204 F8.6 mag r [0.002/0.97] Sky area's reddening (1)
206- 214 F9.6 mag tmag [6.7/20.6] Apparent radio magnitude from this
work; Equation 3 (t=-2.5log(Ftot/3631Jy))
216- 224 F9.6 mag Gmag0 [13.7/20.5] Apparent extinction corrected
G-band magnitude from this work; Eq. 2 (1)
226- 235 F10.6 mag GMag [-31.6/-19.8] Absolute extinction corrected
G-band magnitude from this work; Equation 5
(Gabs=G+5-5.log(dlm(z)))
237- 243 F7.5 arcsec Sep [0.0007/1.5] Angular separation between VLASS
and Quaia coordinates from this work
245 I1 --- Loud [0/1] Loudness flag from this work; Eq. 4
(1=radio-loud) (2)
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Note (1): As provided by Storey-Fisher+ (2024, J/ApJ/964/69), the G-band
magnitudes of the Quaia sources are not corrected for Galactic
extinction. We thus corrected the G-band data following the formula:
G = G'-r.<Rξ>
where G' (Gmag) is the uncorrected magnitude, G (Gmag0) is the
extinction-corrected magnitude, and r is the reddening in the given region
of the sky as provided by Schlegel+ (1998ApJ...500..525S 1998ApJ...500..525S).
Further, <Rξ≳2.74 is the extinction coefficient for the Gaia
G band as provided by Casagrande & VandenBerg (2018MNRAS.479L.102C 2018MNRAS.479L.102C).
See Section 2.4.
Note (2): Flag as:
1 = radio-loud (41,496 occurrences)
0 = radio-quiet (2,154 occurrences)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 27-Mar-2026