J/ApJ/873/132 ICRF3 radio-loud quasars with Gaia DR2 data (Makarov+, 2019)
The precious set of radio-optical Reference Frame objects in the light of Gaia
DR2 data.
Makarov V.V., Berghea C.T., Frouard J., Fey A., Schmitt H.R.
<Astrophys. J., 873, 132 (2019)>
=2019ApJ...873..132M 2019ApJ...873..132M
ADC_Keywords: Radio sources; Positional data; Photometry; Optical; Redshifts;
QSOs
Keywords: astrometry ; galaxies: nuclei ; quasars: general ; reference systems
Abstract:
We investigate a sample of 3413 International Celestial Reference
Frame (ICRF3) extragalactic radio-loud sources with accurate positions
determined by very long baseline interferometry in the S/X band,
mostly active galactic nuclei and quasars, which are cross-matched
with optical sources in the second Gaia data release (Gaia DR2). The
main goal of this study is to determine a core sample of astrometric
objects that define the mutual orientation of the two fundamental
reference frames, the Gaia (optical) and the ICRF3 (radio) frames. The
distribution of normalized offsets between the VLBI sources and their
optical counterparts is non-Rayleigh, with a deficit around the modal
value and a tail extending beyond the 3σ confidence level. A few
filters are applied to the sample in order to discard double
cross-matches, confusion sources, and Gaia astrometric solutions of
doubtful quality. Panoramic Survey Telescope and Rapid Response System
and Dark Energy Survey stacked multicolor images are used to further
deselect objects that are less suitable for precision astrometry, such
as extended galaxies, double and multiple sources, and obvious
misidentifications. After this cleaning, 2643 quasars remain, of which
20% still have normalized offset magnitudes exceeding 3, or a 99%
confidence level. We publish a list of 2119 radio-loud quasars of
prime astrometric quality. The observed dependence of binned median
offset on redshift shows the expected decline at small redshifts, but
also an unexpected rise at z∼1.6, which may be attributed to the
emergence of the CIV emission line in the Gaia's G band. The Gaia DR2
parallax zero-point is found to be color-dependent, suggesting an
uncorrected instrumental calibration effect.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 118 2119 Best quality radio-optical reference frame objects
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See also:
VII/241 : The 2dF QSO Redshift Survey (Croom+ 2004)
I/313 : LQRF: Large Quasar Reference Frame (Andrei+, 2009)
I/323 : International Celestial Reference Frame 2, ICRF2 (Ma+, 2009)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/MNRAS/263/425 : Low-z BQS Quasars (Miller+, 1993)
J/A+A/506/1477 : Radio source distribution (Titov+, 2009)
J/AJ/139/1713 : Celestial Reference Frame at 24 & 43GHz. II (Charlot+, 2010)
J/A+A/525/A37 : Variability of QSOs in SDSS Stripe 82 (Meusinger+, 2011)
J/ApJ/750/99 : The Pan-STARRS1 photometric system (Tonry+, 2012)
J/AJ/150/58 : VLBI ICRF2 (Fey+, 2015)
J/ApJS/221/12 : AGNs in the MIR using AllWISE data (Secrest+, 2015)
J/ApJS/224/19 : The KepVIM catalog (Makarov+, 2016)
J/ApJ/835/L30 : Dislodged AGNs (Makarov+, 2017)
J/MNRAS/467/L71 : Significance of VLBI/Gaia position offsets (Petrov+, 2017)
J/A+A/614/A140 : Large Quasar Astrometric Catalog 4, LQAC-4 (Gattano+, 2018)
http://hpiers.obspm.fr/webiers/newwww/icrf/ : IERS ICRS Center home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- IERS IERS designation (HHMM+DDd; B1950)
10- 22 F13.9 deg RAdeg ICRF3 right ascension
24- 36 F13.9 deg DEdeg [-85.6/88.2] ICRF3 declination
38- 56 I19 --- Gaia Gaia DR2 unique source identifier
58- 63 F6.3 mas Plx [-7.858/4.369]? Gaia DR2 parallax
65- 69 F5.3 mas e_Plx [0.019/2.617]? Uncertainty in Gaia parallax
71- 76 F6.3 mag Gmag [13.26/21.2] Gaia DR2 G magnitude
78- 83 F6.3 mag BPmag [13.59/21.8]? Gaia DR2 BP magnitude
85- 90 F6.3 mag RPmag [12.6/20.9]? Gaia DR2 RP magnitude
92- 96 F5.3 --- z [0.018/4.72]? Redshift (1)
98-104 F7.3 mas d1 [-32.4/19.5] Gaia-ICRF3 difference in RA
(times cos(DE))
106-112 F7.3 mas d2 [-11.8/27.6] Gaia-ICRF3 difference in DEC
114-118 F5.3 --- u [0.026/3] Normalized position difference (2)
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Note (1): Redshifts are from Optical Characteristics of Astrometric Radio
Sources (OCARS) compilation, August 2018 version --
Malkin (2013IzGla.220..507M 2013IzGla.220..507M); Titov & Malkin (2009, J/A+A/506/1477);
Malkin (2016AZh....93..968M 2016AZh....93..968M)
Note (2): u is defined in Equation 1, Section 2 as:
u=Δ/σΔ=(d12+d22)0.5/σΔ
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 14-Aug-2020