J/ApJ/925/162 VODKA: HST discovers double SDSS-Gaia quasars (Chen+, 2022)
Varstrometry for Off-nucleus and Dual subKiloparsec AGN (VODKA): Hubble Space
Telescope discovers double quasars.
Chen Y.-C., Hwang H.-C., Shen Y., Liu X., Zakamska N.L., Yang Q., Li J.I.
<Astrophys. J., 925, 162-162 (2022)>
=2022ApJ...925..162C 2022ApJ...925..162C (SIMBAD/NED BibCode)
ADC_Keywords: QSOs; Redshifts; Optical; Surveys; Photometry, HST; Ultraviolet;
Active gal. nuclei
Keywords: Black hole physics; Active galaxies; Quasars; Double quasars; Surveys
Abstract:
Dual supermassive black holes (SMBHs) at ∼kiloparsec scales are the
progenitor population of SMBH mergers and play an important role in
understanding the pairing and dynamical evolution of massive black
holes in galaxy mergers. Because of the stringent resolution
requirement and the apparent rareness of these small-separation pairs,
there are scarce observational constraints on this population, with
few confirmed dual SMBHs at <10 kpc separations at z>1. Here we
present results from a pilot search for kiloparsec-scale dual quasars
selected with Gaia Data release 2 (DR2) astrometry and followed up
with Hubble Space Telescope (HST) Wide Field Camera 3 dual-band (F475W
and F814W) snapshot imaging. Our targets are quasars primarily
selected with the varstrometry technique, i.e., light centroid jitter
caused by asynchronous variability from both members in an unresolved
quasar pair, supplemented by subarcsecond pairs already resolved by
Gaia DR2. We find an overall high fraction of HST-resolved pairs among
the varstrometry-selected quasars (unresolved in Gaia DR2), ∼30%-50%,
increasing toward high redshift (∼60%-80% at z>1.5). We discuss the
nature of the 45 resolved subarcsecond pairs based on HST and
supplementary data. A substantial fraction (∼40%) of these pairs are
likely physical quasar pairs or gravitationally lensed quasars. We
also discover a triple quasar candidate and a quadruply lensed quasar,
which is among the smallest-separation quadruple lenses. These results
provide important guidelines to improve varstrometry selection and
follow-up confirmation of ∼kiloparsec-scale dual SMBHs at high redshift.
Description:
We observed 84 out of the 150 SDSS/Gaia DR2 targets with the Wide
Field Camera 3 (WFC3) on board the HST in Cycle 27 and 28 from 2019
October 9 UT to 2021 September 23 UT (Program ID: SNAP-15900;
PI: Hwang). Each target was imaged in the UVIS/F475W (with pivot
wavelength λp=4773Å and effective width of 1344Å) and
UVIS/F814W (with λp=8024Å and effective width of 1536Å)
filters. The typical net exposure times are 360s in the F475W filter
and 400s in the F814W filter for each target.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 100 84 *Target properties and log of the HST observations
table3.dat 119 45 *Properties of the 45 HST targets with multiple cores
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Note on table2.dat and table3.dat: Magnitudes are reported in ST magnitude
(mST=-2.5log(Fλ)-21.1), where Fλ is in units
of erg/s/cm2/Å.
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
VIII/65 : 1.4GHz NRAO VLA Sky Survey (NVSS) (Condon+ 1998)
II/311 : WISE All-Sky Data Release (Cutri+ 2012)
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
VII/286 : SDSS quasar catalog, fourteenth data release (Paris+, 2018)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
II/357 : The Dark Energy Survey (DES): Data Release 1 (Abbott+, 2018)
I/350 : Gaia EDR3 (Gaia Collaboration, 2020)
J/A+AS/116/95 : Magellanic Clouds PNe line intensities (Leisy+, 1996)
J/PASP/110/863 : A Stellar Spectral Flux Library: 1150 - 25000 A (Pickles 1998)
J/AJ/131/1 : Binary quasars in the SDSS (Hennawi+, 2006)
J/ApJ/640/579 : Near-infrared spectra of 27 SDSS quasars (Glikman+, 2006)
J/AJ/131/2766 : Quasar luminosity function from SDSS-DR3 (Richards+, 2006)
J/AJ/135/496 : SDSS quasar lens search. II. (Inada+, 2008)
J/ApJ/705/L76 : AGNs with double-peaked [OIII] lines (Wang+, 2009)
J/ApJ/708/427 : Type 2 AGNs with double-peaked [OIII] lines (Liu+, 2010)
J/ApJ/716/866 : SDSS search for binary AGN (Smith+, 2010)
J/ApJ/719/1672 : SDSS binary quasars at high redshift. I. (Hennawi+, 2010)
J/ApJS/194/45 : QSO properties from SDSS-DR7 (Shen+, 2011)
J/ApJ/737/101 : AGN pairs from SDSS-DR7. I. (Liu+, 2011)
J/ApJ/746/L22 : Dual AGNs in the nearby Universe (Koss+, 2012)
J/AJ/143/119 : SDSS Quasar Lens Search. V. Final catalog (Inada+, 2012)
J/ApJ/753/156 : T/Y brown dwarfs with WISE photometry (Kirkpatrick+, 2012)
J/ApJS/201/23 : Spectroscopy of 88 z<0.7 SDSS QSOs (Eracleous+, 2012)
J/AJ/144/125 : Photometry & spectroscopy of Markarian 266 (Mazzarella+, 2012)
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/468/77 : Sample of confirmed quasar pairs (Eftekharzadeh+, 2017)
J/AJ/154/269 : A new photo-z method for quasars in Stripe 82 (Yang+, 2017)
J/ApJ/888/73 : Varstrometry of SDSS quasars with Gaia DR2 data (Hwang+, 2020)
J/ApJS/264/4 : Cand. Double AGNs from Gaia & WISE (CDAGN) (Makarov+, 2023)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 19 A19 --- Name Name of the source (JHHMMSS.ss+DDMMSS.s) (G1)
21 A1 --- f_Name [m] m: multiple sources in HST
23- 27 F5.3 --- z [0.1/3.1] Spectroscopic redshift
(except flagged)
28 A1 --- f_z [d] d: photometric redshift
30- 34 F5.2 mag rmag [17.17/20.1]? SDSS r-band PSF magnitude
36- 40 F5.2 mag Gmag1 [16.3/21.1] Gaia G-band magnitude, first value
42- 46 F5.2 mag Gmag2 [17.79/20.83]? Gaia G-band magnitude, second
value
48 A1 --- f_Gmag Flag on Gmag (1)
50- 55 F6.3 mas epsi1 [0/14.3] Gaia astrometricexcessnoise, first
value
57- 62 F6.3 mas epsi2 [0/12]? Gaia astrometricexcessnoise, second
value
64 A1 --- f_epsi Flag on epsi (1)
66- 70 F5.1 e/s Std1 [12.6/225.1] Standard deviation of Gaia
G-band flux, first value (2)
72- 76 F5.1 e/s Std2 [12.8/120.5]? Standard deviation of Gaia
G-band flux, second value (2)
78 A1 --- f_Std Flag on Std (1)
80- 89 A10 "Y/M/D" Date HST observation date (UT)
91- 94 I4 s Exp1 [40/1320] HST exposure time in F475W filter
96- 98 I3 s Exp2 [40/600] HST exposure time in F814W filter
100 I1 --- Cat [1/6] Target category (G2)
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Note (1): Flag as follows:
a = Though Gaia DR2 detects two sources in J0322-5515, the HST observations
only reveal one source. Recent Gaia EDR3 (Gaia Col. 2021, I/350) only
shows one source in J0322-5515, which suggests that the second source
in Gaia DR2 is an artifact.
Note (2): Standard deviation of Gaia G-band flux
(=photgmeanfluxerror*(photgn_obs)1/2).
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 19 A19 --- Name Name of the source (JHHMMSS.ss+DDMMSS.s) (G1)
21- 25 F5.3 --- z [0.1/3.1] Spectroscopic redshift
(except flagged)
26 A1 --- f_z [d] d: photometric redshift
28- 31 F4.2 arcsec Sep [0.18/0.74]? Angular separation
33- 35 F3.1 kpc rp [1/6.2]? Projected physical separation based
on the redshift, rp
37- 41 F5.1 deg PA [1.9/333.3]? Position angle between the two
brightest sources, east of north
43- 47 F5.2 mag F475W1 [17.58/21.29] HST F475W ST magnitude, source 1
49- 53 F5.2 mag F475W2 [18.58/23.87] HST F475W ST magnitude, source 2
55- 59 F5.2 mag F475W3 [21.89/24.87]? HST F475W ST magnitude, source 3
61- 65 F5.2 mag F475W4 [22.73]? HST F475W ST magnitude, source 4
67- 71 F5.2 mag F814W1 [17.55/22.34] HST F814W ST magnitude, source 1
73- 77 F5.2 mag F814W2 [18.86/22.44] HST F814W ST magnitude, source 2
79- 83 F5.2 mag F814W3 [21.77/24]? HST F814W ST magnitude, source 3
85- 89 F5.2 mag F814W4 [22.68]? HST F814W ST magnitude, source 4
91 I1 --- Cat [1/6] Target category (G1)
93- 115 A23 --- Class Best-effort classification (1)
117- 119 A3 --- f_Class Flag(s) on Class (2)
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Note (1): The term "stars" in classification means more than one PSF component
with star-like color, instead of an extended source.
Note (2): Flag as follows:
s = Targets that are confirmed spectroscopically
a = See detailed discussion in Shen et al. (2021NatAs...5..569S 2021NatAs...5..569S).
b = The classifications are based on the spatially resolved optical spectra
from Gemini.
c = The classification is based on the unresolved SDSS spectra.
d = The targets reveal irregular merger features.
e = Using a fiducial redshift of 2.0 for the quadruply lensed quasar. The
photo-z is biased due to the contamination of the foreground galaxy.
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Global notes:
Note (G1): Target names are based on Gaia DR2 coordinates; the coordinates of
the brightest source are used if multiple sources are detected in Gaia.
Note (G2): Target category as follows:
1 = SDSS DR7+DR14 quasars with a single Gaia match within 3"
(17+9 occurrences in Tables 2+3)
2 = WISE+PS1 quasars with a single Gaia match within 3" (26+7 occurrences)
3 = WISE-only quasars without SDSS and Pan-STARRS1 information and with
a single Gaia match within 3" (13+2 occurrences)
4 = SDSS quasars with multiple Gaia matches (7+7 occurrences)
5 = WISE+PS1 quasars with multiple Gaia matches (15+15 occurrences)
6 = WISE-only quasars with multiple Gaia matches (6+5 occurrences)
See Section 2.1.
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History:
From electronic version of the journal
References:
Hwang et al. Paper I. 2020ApJ...888...73H 2020ApJ...888...73H Cat. J/ApJ/888/73
(End) Emmanuelle Perret [CDS] 07-Sep-2023