J/MNRAS/486/4987 Gravitationally lensed quasars in Pan-STARRS1 (Rusu+, 2019)
A search for gravitationally lensed quasars and quasar pairs in Pan-STARRS1:
spectroscopy and sources of shear in the diamond 2M1134-2103.
Rusu C.E., Berghea C.T., Fassnacht C.D., More A., Seman E., Nelson G.J.,
Chen G.C.-F.
<Mon. Not. R. Astron. Soc., 486, 4987-5007 (2019)>
=2019MNRAS.486.4987R 2019MNRAS.486.4987R (SIMBAD/NED BibCode)
ADC_Keywords: Gravitational lensing ; QSOs ; Optical
Keywords: gravitational lensing: strong - quasars: individual: 2M1134-2103
Abstract:
We present results of a systematic search for gravitationally lensed
quasars in Pan-STARRS1. Our final sample of candidates comprises of 91
systems, not including 25 rediscovered lensed quasars and quasar
pairs. In the absence of spectroscopy to verify the lensing nature of
the candidates, the main sources of contaminants are likely to be
quasar pairs, which we consider to be a byproduct of our work, and a
smaller number of quasar + star associations. Among the independently
discovered quads is 2M1134-2103, for which we obtained spectroscopy
for the first time, finding a redshift of 2.77 for the quasar. There
is evidence for microlensing in at least one image. We perform
detailed mass modelling of this system using archival imaging data,
and find that the unusually large shear responsible for the
diamond-like configuration can be attributed mainly to a faint
companion ∼4arcsec away, and to a galaxy group/cluster ∼30arcsec away.
We also set limits of z∼0.5-1.5 on the redshift of the lensing galaxy,
based on its brightness, the image separation of the lensed images,
and an analysis of the observed photometric flux ratios.
Description:
PS1 is a wide-field imaging system with a 1.8m telescope and 7.7deg2
field of view, located on the summit of Haleakala in the Hawaiian
island of Maui. The 1.4 Gpixel camera consists of 60 CCDs with pixel
size of 0.256arcsec (Onaka & al. 2008SPIE.7014E..0DO; Tonry & Onaka
2009amos.confE..40T).
We start our search with the AGN candidates catalogue of Secrest et
al. (2015ApJS..221...12S 2015ApJS..221...12S, Cat. J/ApJS/221/12), based on two
mid-infrared colours measured with the Wide-field Infrared Survey
Explorer (WISE; Wright et al. 2010AJ....140.1868W 2010AJ....140.1868W). We cross-correlate
this catalogue with the PS1 catalogue (Chambers et al.
2016arXiv161205560C 2016arXiv161205560C, Cat. II/349) using a 3arcsec radius cone search
and keep 79951 candidates which have at least two counterparts. We
then impose a faint magnitude cut of i=19.5 on the closest
counterpart, in order to eliminate spurious candidates. Finally, we
impose that the two brightest sources in each system should be similar
in colour, removing the ones with g-i differences larger than 1.5mag
and i-y differences larger than 1.0mag. The final sample contains
18015 candidates.
We downloaded 30x30arcsec2 postage stamp colour JPEG images of the
candidates using the PS1 cut-out service
(http://hla.stsci.edu/fitscutcgi_interface.html), which were inspected
visually. The sample of 448 was then graded using the following
grading system: 0: unlikely to be a lens; 1: possibly a lens candidate
(satisfies only some criteria); 2: probably a lens candidate
(satisfies most criteria); 3: almost certainly a lens. We find 312
systems with an average grade ≥1, and discard the rest.
Our final classification of the 312 candidates is: 91 surviving
candidates yet unconfirmed (see Table 1), 25 confirmed systems, and
196 rejected candidates (see Table B1).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 238 91 Sample of gravitationally lensed quasar
candidates and quasar pair candidates identified
systematically from PS1
tableb1.dat 205 221 Previously confirmed candidates, and those ruled
out by Gaia data or existing spectroscopy
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See also:
II/349 : The Pan-STARRS release 1 (PS1) Survey - DR1 (Chambers+, 2016)
I/345 : Gaia DR2 (Gaia Collaboration 2018)
J/ApJS/221/12 : AGNs in the MIR using AllWISE data (Secrest+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Quasar candidate name (HHMMSS+DDMMSS)
15- 24 F10.6 deg RAdeg Right ascension (J2000)
26- 35 F10.6 deg DEdeg Declination (J2000)
37 I1 --- Comp Number of components (G1)
39- 43 F5.2 mag imag i-band magnitude in the AB system of the
brightest resolved component
45- 47 F3.1 arcsec Sep Separation between the lens candidate point
sources or, in case of a quad, the maximum
separation between any of the point sources
49 A1 --- Rank [ABC] Alphabetic ranking as gravitationally
lensed quasars (1)
51- 55 F5.2 mag Gmag1 ? G-band magnitude of the first component (2)
57- 61 F5.2 mag Gmag2 ? G-band magnitude of the second component (2)
63- 67 F5.2 mag Gmag3 ? G-band magnitude of the third component (2)
69-236 A168 --- Notes Remarks (G2)
238 A1 --- f_Name Flag on name (3)
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Note (1): Ranking as follows:
A = average grade >2.5 (1/91)
B = average grade >1.5 (4/91)
C = average grade ≥1 (86/91)
Note (2): We give the Gaia DR2 (Gaia Collaboration 2018A&A...616A...1G 2018A&A...616A...1G,
Cat. I/345) G-band magnitudes for each system, in the order of
increasing separation from the WISE source coordinates
Note (3): Flag as follows:
a = After the first draft of this work (arXiv:1803.07175v1), this system
was independently announced by Delchambre et al. (2019A&A...622A.165D 2019A&A...622A.165D,
Cat. J/A+A/622/A165) as a candidate. Our glafic modelling of the
observed configuration with an SIE+γ mass profile results in a
perfect fit, but the model is underconstrained because the lensing
galaxy is not detected.
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Name Quasar candidate name (HHMMSS+DDMMSS)
15- 24 F10.6 deg RAdeg Right ascension (J2000)
26- 35 F10.6 deg DEdeg Declination (J2000)
37 I1 --- Comp Number of components (G1)
39- 43 F5.2 mag imag i-band magnitude in the AB system of the
brightest resolved component
45- 47 F3.1 arcsec Sep Separation between the lens candidate point
sources or, in case of a quad, the maximum
separation between any of the point sources
49 A1 --- Rank [ABC] Alphabetic ranking as gravitationally
lensed quasars (1)
51 I1 --- f_Name Flag on Name (2)
53-205 A153 --- Notes Remarks (G2)
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Note (1): Ranking as follows:
A = average grade >2.5
B = average grade >1.5
C = average grade ≥1
Note (2): Flag as follows:
1 = 25 confirmed systems (6 quads, 9 doubles, 10 quasar pairs)
2 = 196 rejected candidates either due to their Gaia-based properties, or
due to spectroscopic results from the literature
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Global Notes:
Note (G1): We use the number of PS1 sources inside 3arcsec radius, but revise it
based on visual inspection, removing spurious sources and counting
additional objects which appear to be part of the system
Note (G2): Here 'p-l' stands for 'point-like', whereas 'AEN' (astrometric excess
noise), 'p' (parallax), and 'pm' (proper motion) are Gaia-based
measurements.
SQLS refers to the SDSS Quasar Lens Search (Inada et al.
2012AJ....143..119I 2012AJ....143..119I, Cat. J/AJ/143/119). SDSS spectra were searched
inside Data Release 14 (Abolfathi et al. 2018ApJS..235...42A 2018ApJS..235...42A).
'NIQ' stands for nearly identical quasars.
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History:
From electronic version of the journal
(End) Ana Fiallos [CDS] 28-Oct-2022