J/A+A/655/A114 HSC Variables in i-band (Chao+, 2021)
Strongly lensed candidates from the HSC transient survey.
Chao D.C.-Y., Chan J.H.-H., Suyu S.H., Yasuda N., Morokuma T.,
Jaelani A.T., Nagao T., Rusu C.E.
<Astron. Astrophys. 655, A114 (2021)>
=2021A&A...655A.114C 2021A&A...655A.114C (SIMBAD/NED BibCode)
ADC_Keywords: Active gal. nuclei ; Gravitational lensing ; Stars, variable ;
Surveys
Keywords: gravitational lensing: strong - methods: data analysis -
techniques: image processing
Abstract:
We present a lensed quasar search based on the variability of lens
systems in the Hyper Suprime-Cam (HSC) transient survey. Starting from
101353 variable objects with i-band photometry in the HSC transient
survey, we used a variability-based lens search method measuring the
spatial extent in difference images to select potential lensed quasar
candidates. We adopted conservative constraints in this variability
selection and obtained 83657 variable objects as possible lens
candidates. We then ran Chitah, a lens search algorithm based on the
image configuration, on those 83657 variable objects, and 2130
variable objects were identified as potential lensed objects. We
visually inspected the 2,130 variable objects, and seven of them are
our final lensed quasar candidates. Additionally, we found one lensed
galaxy candidate as a serendipitous discovery. Among the eight final
lensed candidates, one is the only known quadruply lensed quasar in
the survey field, HSCJ095921+020638. None of the other seven lensed
candidates have been previously classified as a lens nor a lensed
candidate. Three of the five final candidates with available Hubble
Space Telescope (HST) images, including HSCJ095921+020638, show clues
of a lensed feature in the HST images. We show that a tightening of
our variability selection criteria might result in the loss of
possible lensed quasar candidates, especially the lensed quasars with
faint brightness or narrow separation, without efficiently eliminating
the non-lensed objects; Chitah is therefore important as an advanced
examination to improve the lens search efficiency through the object
configuration. The recovery of HSCJ095921+020638 proves the
effectiveness of the variability-based lens search method, and this
lens search method can be used in other cadenced imaging surveys, such
as the upcoming Rubin Observatory Legacy Survey of Space and Time.
Description:
The catalog including the effective region areas of the variable
objects in the COSMOS field that get detected twice in the HSC
transient survey. The effective region areas in the catalog are from
i-band difference images at the epochs of 2016 Nov. 25, 2016 Nov. 29,
2016 Dec. 25, 2017 Jan. 2, 2017 Jan. 23, 2017 Jan. 30, 2017 Feb. 2,
2017 Feb. 25, 2017 Mar. 4, 2017 Mar. 23, 2017 Mar. 30, 2017 Apr. 26,
and 2017 Apr. 27. For more details, please refer to the paper.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
catalog.dat 120 101353 HSC Variables in i-band
--------------------------------------------------------------------------------
Byte-by-byte Description of file: catalog.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 I7 --- VID Variable ID
9- 20 F12.8 deg RAdeg Right ascension (J2000)
22- 31 F10.8 deg DEdeg Declination (J2000)
33- 36 I4 --- A1 ?=-99 Effective region area at 2016 Nov. 25
38- 41 I4 --- A2 ?=-99 Effective region area at 2016 Nov. 29
43- 46 I4 --- A3 ?=-99 Effective region area at 2016 Dec. 25
48- 51 I4 --- A4 ?=-99 Effective region area at 2017 Jan. 02
53- 56 I4 --- A5 ?=-99 Effective region area at 2017 Jan. 23
58- 61 I4 --- A6 ?=-99 Effective region area at 2017 Jan. 30
63- 66 I4 --- A7 ?=-99 Effective region area at 2017 Feb. 02
68- 71 I4 --- A8 ?=-99 Effective region area at 2017 Feb. 25
73- 76 I4 --- A9 ?=-99 Effective region area at 2017 Mar. 04
78- 81 I4 --- A10 ?=-99 Effective region area at 2017 Mar. 23
83- 86 I4 --- A11 ?=-99 Effective region area at 2017 Mar. 30
88- 91 I4 --- A12 ?=-99 Effective region area at 2017 Apr. 26
93- 96 I4 --- A13 ?=-99 Effective region area at 2017 Apr. 27
98-108 F11.6 --- chi2r ?=-99 CHITAH chi2res values (1)
110-120 F11.6 --- chi2 ?=-99 CHITAH chi2 values (1)
--------------------------------------------------------------------------------
Note (1): See Sec. 3.2 in the paper for the detail).
-99. or -99.000000 means that this object did not qualify the variability
selection criteria in the paper, or that the CHITAH-related values are
temporarily not available for this object.
--------------------------------------------------------------------------------
Acknowledgements:
Dani Chao, danichao(at)gapp.nthu.edu.tw
(End) Dani Chao [MPA, Germany/RBI, Croatia], Patricia Vannier [CDS] 15-Sep-2021