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, C and Auger, M W and Desai, Shantanu and et al, . (2020) The STRong lensing Insights into the dark energy survey (STRIDES) 2017/2018 follow-up campaign: Discovery of 10 lensed quasars and 10 quasar pairs. Monthly Notices of the Royal Astronomical Society, 494 (3). pp. 1-21. ISSN 0035-8711

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Abstract

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 onKeck, confirming 10 newlensed 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 samemagnitude, 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. © 2020 The Author(s).

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IITH Creators:

IITH Creators	ORCiD
Desai, Shantanu	http://orcid.org/0000-0002-0466-3288

Item Type:

Article

Additional Information:

This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, ht tps://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

Uncontrolled Keywords:

Gravitational lensing: strong; Methods: observational; Quasars: general

Subjects:

Physics

Divisions:

Department of Physics

Depositing User:

. LibTrainee 2021

Date Deposited:

23 Nov 2022 10:46

Last Modified:

23 Nov 2022 10:46