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20 April 2024

» arxiv » 1912.8977

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Gaia GraL: Gaia DR2 Gravitational Lens Systems. V. Doubly-imaged QSOs discovered from entropy and wavelets
A. Krone-Martins ; M.J. Graham ; D. Stern ; S.G. Djorgovski ; L. Delchambre ; C. Ducourant ; R. Teixeira ; A.J. Drake ; S. Scarano Jr. ; J. Surdej ; L. Galluccio ; P. Jalan ; O. Wertz ; J. Klüter ; F. Mignard ; C. Spindola-Duarte ; D. Dobie ; E. Slezak ; D. Sluse ; T. Murphy ; C. Boehm ; A. M. Nierenberg ; U. Bastian ; J. Wambsganss ; J.-F. LeCampion ;
Date:	19 Dec 2019
Abstract:	The discovery of multiply-imaged gravitationally lensed QSOs is fundamental to many astronomical and cosmological studies. However, these objects are rare and challenging to discover due to requirements of high-angular resolution astrometric, multiwavelength photometric and spectroscopic data. This has limited the number of known systems to a few hundred objects. We aim to reduce the constraints on angular resolution and discover multiply-imaged QSO candidates by using new candidate selection principles based on unresolved photometric time-series and ground-based images from public surveys. We selected candidates for multiply-imaged QSOs based on low levels of entropy computed from Catalina unresolved photometric time-series or Euclidean similarity to known lenses in a space defined by the wavelet power spectra of Pan-STARSS DR2 or DECaLS DR7 images, combined with multiple {it Gaia} DR2 sources or large astrometric errors and supervised and unsupervised learning methods. We then confirmed spectroscopically some candidates with the Palomar Hale, Keck-I, and ESO/NTT telescopes. Here we report the discovery and confirmation of seven doubly-imaged QSOs and one likely double quasar. This demonstrates the potential of combining space-astrometry, even if unresolved, with low spatial-resolution photometric time-series and/or low-spatial resolution multi-band imaging to discover multiply-imaged lensed QSOs.
Source:	arXiv, 1912.8977
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