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

Abstract

We report the results of the STRong lensing Insights from the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed quasar candidates either with EFOSC2 on the NTT or ESI on Keck, which confirm 10 new gravitationally lensed quasars and 10 quasar pairs with similar spectra, but which do not show a lensing galaxy in DES images. Eight lensed quasars are doubly imaged with source redshifts between 0.99 and 2.90, one is triply imaged by a group (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 SOAR or NIRC2 on Keck, give total magnifications between 3.2 and 5.6, and Einstein radii between 0.49 and 1.97 arcseconds. After spectroscopic follow-up, we extract multi-epoch $grizY$ photometry of confirmed lensed quasars and contaminant quasar+star pairs from the first 4 years of DES data using parametric multi-band modelling, and compare variability in each system's components. By measuring the reduced ${\chi }^2$ 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 with stellar components. Based on our spectroscopic follow-up, this variability information can improve selection of lensed quasars and quasar pairs from 34-45 per cent to 51-70 per cent, with the majority of remaining contaminants being compact star-forming galaxies. Using mock lensed quasar lightcurves 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 (excluding microlensing differences), explained by the magnification bias and hence lower luminosity (more variable) sources in quads.

arXiv comment22 pages, 16 figures, submitted to MNRAS

References in corpus (78)

• emcee: The MCMC Hammer
• The Wide-field Infrared Survey Explorer (WISE): Mission Description and Initial On-orbit Performance
• The Gaia mission
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• The Hyper Suprime-Cam SSP Survey: Overview and Survey Design
• The Dark Energy Camera
• SUMSS: A Wide-Field Radio Imaging Survey of the Southern Sky. II. The Source Catalogue
• The Pan-STARRS1 Surveys
• Modeling the Time Variability of SDSS Stripe 82 Quasars as a Damped Random Walk
• Gaia Data Release 2: Catalogue validation
• Gaia Data Release 1: Astrometry - one billion positions, two million proper motions and parallaxes
• The Dark Energy Survey Data Release 1
• NEOWISE Observations of Near-Earth Objects: Preliminary Results
• Gravitationally lensed quasars and supernovae in future wide-field optical imaging surveys
• Gaia Data Release 1: Catalogue validation
• ESI, a new Keck Observatory echellette spectrograph and imager
• The population of galaxy-galaxy strong lenses in forthcoming optical imaging surveys
• Quasar Microlensing at High Magnification and the Role of Dark Matter: Enhanced Fluctuations and Suppressed Saddlepoints
• STRIDES: a 3.9 per cent measurement of the Hubble constant from the strong lens system DES J0408-5354
• Time Delay Cosmography
• Cosmology from gravitational lens time delays and Planck data
• The Dark Energy Survey Image Processing Pipeline
• Sizes and Temperature Profiles of Quasar Accretion Disks from Chromatic Microlensing
• Dark Energy Survey Year 1 Results: Redshift distributions of the weak lensing source galaxies
• The internal structure of the lens PG1115+080: breaking degeneracies in the value of the Hubble Constant
• The Time Delays of Gravitational Lens HE0435-1223: An Early-Type Galaxy With a Rising Rotation Curve
• Selecting Quasars by their Intrinsic Variability
• Strong Lens Time Delay Challenge: II. Results of TDC1
• Revisiting Stochastic Variability of AGNs with Structure Functions
• COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XI. Techniques for time delay measurement in presence of microlensing
• Is every strong lens model unhappy in its own way? Uniform modelling of a sample of 13 quadruply+ imaged quasars
• Gaia Data Release 1, Pre-processing and source list creation
• COSMOGRAIL XVI: Time delays for the quadruply imaged quasar DES J0408-5354 with high-cadence photometric monitoring
• Gravitationally Lensed Quasars in Gaia: II. Discovery of 24 Lensed Quasars
• Forward Global Photometric Calibration of the Dark Energy Survey
• Gravitationally lensed quasars in Gaia: III. 22 new lensed quasars from Gaia Data Release 2
• Time delay and lens redshift for the doubly imaged BAL quasar SBS1520+530
• Variability selected high-redshift quasars on SDSS Stripe 82
• A microlensing study of the accretion disc in the quasar MG 0414+0534
• Characterization and correction of charge-induced pixel shifts in DECam
• Improving time-delay cosmography with spatially resolved kinematics
• VDES J2325-5229 a z=2.7 gravitationally lensed quasar discovered using morphology independent supervised machine learning
• COSMOGRAIL XVII: Time delays for the quadruply imaged quasar PG 1115+080
• The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2016 follow-up campaign. I. Overview and classification of candidates selected by two techniques
• DES meets Gaia: discovery of strongly lensed quasars from a multiplet search
• COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses V. The time delay in SDSS J1650+4251
• Data Mining for Gravitationally Lensed Quasars
• SHARP - III: First Use Of Adaptive Optics Imaging To Constrain Cosmology With Gravitational Lens Time Delays
• Strong Lens Time Delay Challenge: I. Experimental Design
• Observational selection biases in time-delay strong lensing and their impact on cosmography
• SOAR Adaptive Module (SAM): seeing improvement with a UV laser
• Subaru Telescope adaptive optics observations of gravitationally lensed quasars in the Sloan Digital Sky Survey
• A Simple Method To Find All Lensed Quasars
• A Two-Year Time Delay for the Lensed Quasar SDSS J1029+2623
• First lensed quasar systems from the VST-ATLAS survey: one quad, two doubles and two pairs of lensless twins
• The Discovery of a Five-Image Lensed Quasar at z = 3.34 using PanSTARRS1 and Gaia
• The ensemble photometric variability of over $10^5$ quasars in the Dark Energy Camera Legacy Survey and the Sloan Digital Sky Survey
• Time Delay and Accretion Disk Size Measurements in the Lensed Quasar SBS 0909+532 from Multiwavelength Microlensing Analysis
• Discovering Gravitational Lenses Through Measurements Of Their Time Delays
• New aperture photometry of QSO 0957+561; application to time delay and microlensing
• Firedec: a two-channel finite-resolution image deconvolution algorithm
• Mass models and environment of the new quadruply lensed quasar SDSS J1330+1810
• Time Delay Measurements for the Cluster-lensed Sextuple Quasar SDSS J2222+2745
• The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2016 follow-up campaign. II. New quasar lenses from double component fitting
• Quasar Lenses in the South: searches over the DES public footprint
• Time Delays in the Gravitationally Lensed Quasar H1413+117 (Cloverleaf)
• Quasar Lenses and Galactic Streams: Outlier Selection and GAIA Multiplet Detection
• COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses IV. Models of prospective time-delay lenses
• Doubly imaged quasar SDSS J1515+1511: time delay and lensing galaxies
• A Gravitationally Lensed Quasar Discovered in OGLE
• Polarization microlensing in the quadruply imaged broad absorption line quasar H1413+117
• Evidence for two spatially separated UV continuum emitting regions in the Cloverleaf broad absorption line quasar
• The Brighter-Fatter and other Sensor Effects in CCD Simulations for Precision Astronomy
• Difference Imaging of Lensed Quasar Candidates in the SDSS Supernova Survey Region
• MiNDSTEp differential photometry of the gravitationally lensed quasars WFI2033-4723 and HE0047-1756: Microlensing and a new time delay
• Lensed quasar search via time variability with the HSC transient survey
• Discovery of the optically bright, wide separation double quasar SDSS J1442+4055
• Spectroscopic follow-up of double quasar candidates

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• STRIDES: a 3.9 per cent measurement of the Hubble constant from the strong lens system DES J0408-5354
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• Gaia GraL: Gaia DR2 Gravitational Lens Systems. VI. Spectroscopic Confirmation and Modeling of Quadruply-Imaged Lensed Quasars
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• A Survey for High-redshift Gravitationally Lensed Quasars and Close Quasars Pairs. I. the Discoveries of an Intermediately-lensed Quasar and a Kpc-scale Quasar Pair at $z\sim 5$
• A machine learning based approach to gravitational lens identification with the International LOFAR Telescope
• Testing the Evolution of the Correlations between Supermassive Black Holes and their Host Galaxies using Eight Strongly Lensed Quasars
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• COOL-LAMPS III: Discovery of a 25".9 Separation Quasar Lensed by a Merging Galaxy Cluster
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• TDCOSMO XVII. New time delays in 22 lensed quasars from optical monitoring with the ESO-VST 2.6m and MPG 2.2m telescopes
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• Anisotropic strong lensing as a probe of dark matter self-interactions
• Strong Lensed QSOs with Variability Detectable by LSST: How many are there?
• When Spectral Modeling Meets Convolutional Networks: A Method for Discovering Reionization-era Lensed Quasars in Multi-band Imaging Data
• High-resolution imaging follow-up of doubly imaged quasars
• Gaia GraL: Gaia DR2 Gravitational Lens Systems. VII. XMM-Newton Observations of Lensed Quasars
• Galaxy Spectra neural Networks (GaSNets). I. Searching for strong lens candidates in eBOSS spectra using Deep Learning
• DULAG: A DUal and Lensed AGN candidate catalog with GMP method
• TDCOSMO. XXIII. Measurement of the Hubble constant from the doubly lensed quasar HE1104-1805
• Simulation-guided galaxy evolution inference: A case study with strong lensing galaxies
• A Targeted Search for Variable Gravitationally Lensed Quasars
• Accelerating lensed quasar discovery and modeling with physics-informed variational autoencoders
• Finding Lensed Radio Sources with the VLA Sky Survey
• Lenses In VoicE (LIVE): Searching for strong gravitational lenses in the VOICE@VST survey using Convolutional Neural Networks
• Milky-Way-like stars in a galaxy core 8 billion years ago revealed by gravitational lensing
• SRG/eROSITA-SDSS view on the relation between X-ray and UV emission for quasars