J/ApJ/888/73 Varstrometry of SDSS quasars with Gaia DR2 data (Hwang+, 2020)
Varstrometry for Off-nucleus and Dual subKiloparsec AGN (VODKA): methodology
and initial results with Gaia DR2.
Hwang H.-C., Shen Y., Zakamska N., Liu X.
<Astrophys. J., 888, 73 (2020)>
=2020ApJ...888...73H 2020ApJ...888...73H
ADC_Keywords: QSOs; Proper motions; Parallaxes, trigonometric; Spectra, optical
Keywords: Quasars ; Double quasars
Abstract:
Gaia's precision astrometry allows systematic identification of
optically selected subkiloparsec dual active galactic nuclei (AGNs),
off-nucleus AGNs, and small-scale lensed quasars by
"varstrometry"-where variability-induced astrometric jitter, i.e.,
temporal displacements of photocenter in unresolved sources, can be
reasonably well detected or constrained. This approach extends
systematic searches for small-scale (≥mas) dual and off-nucleus AGNs
to the poorly explored regime between ∼10pc and ∼1kpc, with Gaia's
full sky coverage and depth to G∼21. We outline the general principles
of this method and calculate the expected astrometric signals from the
full time series of photocenter measurements and light curves. We
demonstrate the feasibility of varstrometry by using Gaia DR2 data on
a sample of variable pre-main-sequence stars with known close
companions. We find that extended host galaxies have a significant
impact on the accuracy of astrometric and photometric variability in
Gaia DR2, a situation to be improved in future Gaia releases. Using
spectroscopically confirmed Sloan Digital Sky Survey quasars, we
present several examples of candidate subkiloparsec off-nucleus or
dual AGNs selected from Gaia DR2. We discuss the merits and
limitations of this method and a follow-up strategy for promising
candidates. We highlight Gaia's potential of systematically
discovering and characterizing the subkiloparsec off-nucleus and dual
AGN population in the entire optical sky.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 97 19 List of genuine quasars that have
significant non-zero parallaxes from Gaia DR2
table3.dat 100 30 List of genuine quasars that have
significant non-zero proper motions from Gaia DR2
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See also:
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
VIII/92 : The FIRST Survey Catalog, Version 2014Dec17 (Helfand+ 2015)
VII/289 : SDSS quasar catalog, sixteenth data release (DR16Q) (Lyke+, 2020)
J/AJ/126/1720 : ugriz and Hα of double-peaked AGN (Strateva+, 2003)
J/AJ/129/2542 : BL Lac from SDSS (Collinge+, 2005)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJS/201/23 : Spectroscopy of 88 z<0.7 SDSS QSOs (Eracleous+, 2012)
J/ApJ/745/119 : Close companions to young stars. I. ChaI & Tau (Nguyen+, 2012)
J/ApJ/789/112 : Offset AGN Candidates (Comerford+, 2014)
J/ApJ/789/140 : SDSS quasars balmer emission lines (Liu+, 2014)
J/ApJ/799/72 : Binary AGNs from the VLA Stripe 82 survey (Fu+, 2015)
J/MNRAS/453/1562 : CRTS close supermassive black hole binaries (Graham+, 2015)
J/ApJS/221/12 : AGNs in the MIR using AllWISE data (Secrest+, 2015)
J/MNRAS/446/2985 : Double-lobed radio sources catalog (van Velzen+, 2015)
J/ApJS/224/19 : The KepVIM catalog (Makarov+, 2016)
J/A+A/618/A56 : Gaia GraL. II. Known multiply imaged quasars (Ducourant+, 2018)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 18 A18 --- SDSS SDSS identifier (HHMMSS.ss+DDMMSS.s; J2000)
20- 38 F19.15 deg RAdeg [15.5/339] Gaia DR2 barycentric
right ascension (ICRS) at Ep=2015.5
40- 58 F19.16 deg DEdeg [-9.5/60.5] Gaia DR2 barycentric
declination (ICRS) at Ep=2015.5
60- 78 F19.16 mas plx [0.43/13.97]? Parallax
80- 97 F18.16 --- Errplx [0.8/9.2]? Parallax divided by the error
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 18 A18 --- SDSS SDSS Identifier (HHMMSS.ss+DDMMSS.s; J2000)
20- 38 F19.15 deg RAdeg [8.2/260.8] Gaia DR2 barycentric
right ascension (ICRS) at Ep=2015.5
40- 59 F20.16 deg DEdeg [-10.9/52.8] Gaia DR2 barycentric
declination (ICRS) at Ep=2015.5
61- 80 F20.17 mas/yr pm [0.13/43.52]? Total proper motion
82-100 F19.16 --- Errpm [0.49/47.8]? Total proper motion divided
by the error
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History:
From electronic version of the journal
References:
Chen et al. Paper II. 2022ApJ...925..162C 2022ApJ...925..162C Cat. J/ApJ/925/162
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 22-Oct-2021