Discovering strongly lensed quasar candidates with catalogue-based methods from DESI Legacy Surveys

Abstract

The Hubble tension, revealed by a $\sim 5\sigma$ discrepancy between measurements of the Hubble-Lemaitre constant from early- and local-Universe observations, is one of the most significant problems in modern cosmology. In order to better understand the origin of this mismatch, independent techniques to measure $H_0$, such as strong lensing time delays, are required. Notably, the sample size of such systems is key to minimising statistical uncertainties and cosmic variance, which can be improved by exploring the datasets of large-scale sky surveys like DESI (Dark Energy Spectroscopic Instrument). We identify possible strong lensing time-delay systems within DESI by selecting candidate multiply imaged lensed quasars from a catalogue of 24,440,816 candidate QSOs contained in the 9th data release of the DESI Legacy Imaging Surveys (DESI-LS). Using a friend-of-friends-like algorithm on spatial co-ordinates, our method generates an initial list of compact quasar groups. This list is subsequently filtered using a measure of the similarity of colours of a group's members and the likelihood that they are quasars. A visual inspection finally selects candidate strong lensing systems based on the spatial configuration of the group members. We identify 620 new candidate multiply imaged lensed quasars (101 Grade-A, 214 Grade-B, 305 Grade-C). This number excludes 53 known spectroscopically confirmed systems and existing candidate systems identified in other similar catalogues. When available, these new candidates will be further checked by combining the spectroscopic and photometric data from DESI. The catalogues and images of the candidates in this work are available online (https://github.com/EigenHermit/lensed_qso_cand_catalogue_He-22/).

Accepted by A&A. 14 pages, 11 figures. Comments are welcome

References in corpus (16)

• Large Magellanic Cloud Cepheid Standards Provide a 1% Foundation for the Determination of the Hubble Constant and Stronger Evidence for Physics Beyond LambdaCDM
• A distance to the Large Magellanic Cloud that is precise to one per cent
• The Sloan Digital Sky Survey Quasar Catalog: Sixteenth Data Release
• The fourth data release of the Kilo-Degree Survey: ugri imaging and nine-band optical-IR photometry over 1000 square degrees
• lenstronomy II: A gravitational lensing software ecosystem
• Measuring the Hubble constant with Type Ia supernovae as near-infrared standard candles
• The multiple quasar Q2237+0305 under a microlensing caustic
• Data Mining for Gravitationally Lensed Quasars
• Hot New Early Dark Energy
• Deep Learning for Strong Lensing Search: Tests of the Convolutional Neural Networks and New Candidates from KiDS DR3
• CHITAH: Strong-gravitational-lens hunter in imaging surveys
• Microlensing of the broad-line region in the quadruply imaged quasar HE0435-1223
• Microlensing of the broad emission lines in 27 gravitationally lensed quasars. Broad line region structure and kinematics
• Revisiting the Lensed Fraction of High-Redshift Quasars
• The Hubble tension in the non-flat Super-$\Lambda \mathrm{CDM}$ model
• SQUAB I: The first release of Strange QUasar candidates with ABnormal astrometric characteristics from Gaia EDR3 and SDSS

Cited by in corpus (2)

• Streamlined Lensed Quasar Identification in Multiband Images via Ensemble Networks
• Discovery of the lensed quasar eRASS1 J050129.5-073309 with $\text{SRG}/$eROSITA and $Gaia$