Multiply imaged quasars in the Gaia DR1

Ducourant, C.; Delchambre, L.; Finet, F.; Krone-Martins, A.; Campion, J.-F. Le; Mignard, F.; Slezak, E.; Surdej, Jean; Teixeira, R.; Wertz, O.

doi:10.1017/s1743921317006445

Cited by 3 publications

(2 citation statements)

References 9 publications

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“…The first Gaia data release, on 14 September 2016, catalogued known lensed quasars within its brightness threshold, but it rarely catalogued all images (Lemon et al 2017;Ducourant et al 2018b). The second Gaia data release (GDR2, Gaia Collaboration et al 2018), on 25 April 2018, has a marked improvement in detecting closely separated images, down to 0.4 arcseconds (Arenou et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Gravitationally lensed quasars in Gaia – II. Discovery of 24 lensed quasars

Lemon

Auger

McMahon

et al. 2018

Monthly Notices of the Royal Astronomical Society

106

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We report the discovery and spectroscopic confirmation of 22 new gravitationally lensed quasars found using Gaia data release 2. The selection was made using several techniques: multiple Gaia detections around objects in quasar candidate catalogues, modelling of unWISE coadd pixels using Gaia astrometry, and Gaia detections offset from photometric and spectroscopic galaxies. Spectra of 33 candidates were obtained with the William Herschel Telescope, 22 of which are lensed quasars, 2 highly probably lensed quasars, 5 nearly identical quasar pairs, 1 inconclusive system, and 3 contaminants. Of the 3 confirmed quadruply imaged systems, J2145+6345 is a 2.1 arcsecond separation quad with 4 bright images (G=16. 86, 17.26, 18.34, 18.56), making it ideal for time delay monitoring. Analysing this new sample alongside known lenses in the Pan-STARRS footprint, and comparing to expected numbers of lenses, we show that, as expected, we are biased towards systems with bright lensing galaxies and low source redshifts. We discuss possible techniques to remove this bias from future searches. A |b|>20 complete sample of lensed quasars detected by Gaia and with image separations above 1 arcsecond will provide a valuable statistical sample of around 350 systems. Currently only 96 known lenses satisfy these criteria, yet promisingly, our unWISE modelling technique is able to recover all of these with simple WISE-Gaia colour cuts that remove ∼80 per cent of previously followed-up contaminants. Finally, we provide an online database of known lenses, quasar pairs, and contaminant systems.

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Section: Introductionmentioning

confidence: 99%

Gravitationally lensed quasars in Gaia – II. Discovery of 24 lensed quasars

Lemon

Auger

McMahon

et al. 2018

Monthly Notices of the Royal Astronomical Society

106

View full text Add to dashboard Cite

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“…This selection method follows that of Lemon et al (2018), relying on multiple Gaia detections near WISE -selected candidate quasars, or single Gaia detections corresponding to extended DES objects. The latter technique was developed on account of Gaia DR1 often cataloguing only single components of lensed quasars (Ducourant et al 2018). The input catalogue for both searches is AllWISE detections with W1 −W2 >0.5, W1 <15.5, and catalogued uncertainties in W1 and W2.…”

Section: Methodsmentioning

confidence: 99%

The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: discovery of 10 lensed quasars and 10 quasar pairs

Lemon

Auger

McMahon

et al. 2020

Monthly Notices of the Royal Astronomical Society

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We report the results of the STRong lensing Insights into the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates with ESO Faint Object Spectrograph and Camera 2 on the NTT and Echellette Spectrograph and Imager on Keck, confirming 10 new lensed quasars and 10 quasar pairs. Eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged (DESJ0345−2545, z = 1.68), and one is quadruply imaged (quad: DESJ0053−2012, z = 3.8). Singular isothermal ellipsoid models for the doubles, based on high-resolution imaging from SAMI on Southern Astrophysical Research Telescope or Near InfraRed Camera 2 on Keck, give total magnifications between 3.2 and 5.6, and Einstein radii between 0.49 and 1.97 arcsec. After spectroscopic follow-up, we extract multi-epoch grizY photometry of confirmed lensed quasars and contaminant quasar + star pairs from DES data using parametric multiband modelling, and compare variability in each system’s components. By measuring the reduced χ2 associated with fitting all epochs to the same magnitude, we find a simple cut on the less variable component that retains all confirmed lensed quasars, while removing 94 per cent of contaminant systems. Based on our spectroscopic follow-up, this variability information improves selection of lensed quasars and quasar pairs from 34-45 per cent to 51–70 per cent, with most remaining contaminants being star-forming galaxies. Using mock lensed quasar light curves we demonstrate that selection based only on variability will over-represent the quad fraction by 10 per cent over a complete DES magnitude-limited sample, explained by the magnification bias and hence lower luminosity/more variable sources in quads.

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Survey of gravitationally lensed objects in HSC imaging (SuGOHI) – IX. Discovery of strongly lensed quasar candidates

Chan,

Wong,

Ding

et al. 2023

Monthly Notices of the Royal Astronomical Society

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We report the discovery of new lensed quasar candidates in the imaging data of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) DR4, covering $1\, 310\deg ^2$ of the sky with median seeing in the i-band of ≈0.6″. In addition to two catalogs of MILLIQUAS and AllWISEAGN, containing confirmed and candidate quasars, we preselect quasar sources using color cuts from the HSC (grizy) and unWISE (W1 + W2) photometric data based on SDSS spectroscopic catalogs. We search for the presence of multiple point sources with similar color through the convolution of the Laplacian of the preselected quasar image cutouts with the Laplacian of the point spread function, resulting in a reduction of lens candidates from 1 652 329 to 121 511 (7.4%). After visual binary classification, we grade 6 199 (0.4%) potential lenses on a scale of 0 to 3, with 3 indicating a lens and 0 indicating a non-lens. Finally we obtain 162 lens candidates with an average grade of ≥2, and among them, we successfully recover 18 known lenses. By fitting the light distribution and removing the known contaminants, we discover that 57 new systems contain at least two point sources and a galaxy in between, including 10 possible quadruply lensed quasars. This new sample exhibits a median separation of 1.26″ and a magnitude limit of i ≈ 22. Spectroscopic or high-resolution imaging follow up on these newly discovered lensed quasar candidates will further allow their natures to be confirmed.

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Multiply imaged quasars in the Gaia DR1

Cited by 3 publications

References 9 publications

Gravitationally lensed quasars in Gaia – II. Discovery of 24 lensed quasars

Gravitationally lensed quasars in Gaia – II. Discovery of 24 lensed quasars

The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: discovery of 10 lensed quasars and 10 quasar pairs

Survey of gravitationally lensed objects in HSC imaging (SuGOHI) – IX. Discovery of strongly lensed quasar candidates

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