Discovery of two bright high-redshift gravitationally lensed quasars revealed by Gaia

Christopher Desira, Yiping Shu, Matthew W. Auger, Richard G. McMahon, Cameron A. Lemon, Timo Anguita, Favio Neira

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

We present the discovery and preliminary characterisation of two high-redshift gravitationally lensed quasar systems in Gaia Data Release 2 (DR2). Candidates with ltiple close-separation Gaia detections and quasar-like colours in WISE, Pan-STARRS, and DES are selected for follow-up spectroscopy with the New Technology Telescope. We confi DES J215028.71-465251.3 as a $z$ = 4.130 ± 0.006 asymmetric, doubly imaged lensed quasar system and model the lensing mass distribution as a singular isotheal sphere. The system has an Einstein radius of 1.202 ± 0.005 arcsec and a predicted time delay of 122.0 d between the quasar images, assuming a lensing galaxy redshift of $z$ = 0.5, making this a priority system for future optical monitoring. We confi PS J042913.17+142840.9 as a $z$ = 3.866 ± 0.003 four-image quasar system in a cusp configuration, lensed by two foreground galaxies. The system is well modelled using a singular isotheal ellipsoid for the primary lens and a singular isotheal sphere for the secondary lens with Einstein radii 0.704 ± 0.006 and 0.241 ± 0.030 arcsec, respectively. A maxim predicted time delay of 9.6 d is calculated, assuming lensing galaxy redshifts of $z$ = 1.0. Furtheore, PS J042913.17+142840.9 exhibits a large flux ratio anomaly, up to a factor of 2.66 ± 0.37 in i band, that varies across optical and near-infrared wavelengths. We discuss LSST and its implications for future high-redshift lens searches and outline an extension to the search using supervised machine learning techniques.

Original languageEnglish
Pages (from-to)738-747
Number of pages10
JournalMonthly Notices of the Royal Astronomical Society
Volume509
Issue number1
DOIs
Publication statusPublished - 1 Jan 2022

Keywords

  • general
  • gravitational lensing
  • methods
  • observational
  • quasars
  • strong

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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