COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Courbin, F.; Bonvin, V.; Buckley-Geer, E.; Fassnacht, C. D.; Frieman, J.; Lin, Huan; Marshall, Philip J.; Suyu, S. H.; Treu, Tommaso; Anguita, T.; Motta, V.; Meylan, G.; Paic, E.; Tewes, M.; Agnello, Adriano; Chao, D. C. Y.; Chijani, M.; Gilman, Daniel; Rojas, Karina; Williams, Peter; Hempel, A.; Kim, S.; Lachaume, R.; Rabus, M.; Abbott, T. M. C.; Allam, S.; Annis, J.; Banerji, M.; Bechtol, K.; Benoit-Lévy, A.; Brooks, D.; Burke, D. L.; Rosell, A. Carnero; Kind, M. Carrasco; Carretero, J.; D’Andrea, C. B.; Costa, L. N. da; Davis, C.; DePoy, D. L.; Desai, S.; Flaugher, B.; Fosalba, P.; García-Bellido, J.; Gaztañaga, E.; Goldstein, Daniel A.; Gruen, D.; Gruendl, R. A.; Gschwend, J.; Gutiérrez, G.; Honscheid, K.; James, D. J.; Kuêhn, K.; Kuhlmann, S.; Kuropatkin, N.; Lahav, O.; Lima, M.; Maia, M. A. G.; March, M.; Marshall, J. L.; McMahon, R. G.; Menanteau, F.; Miquel, R.; Nord, B.; Plazas, A. A.; Sánchez, E.; Scarpine, V.; Schindler, R. H.; Schubnell, M.; Sevilla-Noarbe, I.; Smith, M.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Tarlè, G.; Tucker, D. L.; Walker, A. R.; Wester, W.

doi:10.1051/0004-6361/201731461

Cited by 82 publications

(40 citation statements)

References 40 publications

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“…86, 17.26, 18.34 and 18.56), making it second only to PSJ0147+4630 (Berghea et al 2017) in terms of the brightest fourth image. This makes the system ideal for high-cadence, high signal-to-noise monitoring to determine time delays for cosmography (Courbin et al 2018). Our mass model (SIE+shear) is constrained exclusively by image positions and fluxes, as the lensing galaxy is not detected.…”

Section: J2145+6345mentioning

confidence: 99%

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Gravitationally lensed quasars in Gaia – II. Discovery of 24 lensed quasars

Lemon

Auger

McMahon

et al. 2018

Monthly Notices of the Royal Astronomical Society

106

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We report the discovery and spectroscopic confirmation of 22 new gravitationally lensed quasars found using Gaia data release 2. The selection was made using several techniques: multiple Gaia detections around objects in quasar candidate catalogues, modelling of unWISE coadd pixels using Gaia astrometry, and Gaia detections offset from photometric and spectroscopic galaxies. Spectra of 33 candidates were obtained with the William Herschel Telescope, 22 of which are lensed quasars, 2 highly probably lensed quasars, 5 nearly identical quasar pairs, 1 inconclusive system, and 3 contaminants. Of the 3 confirmed quadruply imaged systems, J2145+6345 is a 2.1 arcsecond separation quad with 4 bright images (G=16. 86, 17.26, 18.34, 18.56), making it ideal for time delay monitoring. Analysing this new sample alongside known lenses in the Pan-STARRS footprint, and comparing to expected numbers of lenses, we show that, as expected, we are biased towards systems with bright lensing galaxies and low source redshifts. We discuss possible techniques to remove this bias from future searches. A |b|>20 complete sample of lensed quasars detected by Gaia and with image separations above 1 arcsecond will provide a valuable statistical sample of around 350 systems. Currently only 96 known lenses satisfy these criteria, yet promisingly, our unWISE modelling technique is able to recover all of these with simple WISE-Gaia colour cuts that remove ∼80 per cent of previously followed-up contaminants. Finally, we provide an online database of known lenses, quasar pairs, and contaminant systems.

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Section: J2145+6345mentioning

confidence: 99%

“…The Pan-STARRS 3π survey (PS, Chambers et al 2016) is expected to have already imaged ∼2000 lensed quasars with images brighter than i = 22 and separated by more than 0.67 arcseconds (Oguri & Marshall 2010). Considering just the extragalactic (|b|>20) sky of PS (68 per cent of the sky), the number drops to ∼1350.…”

Section: Introductionmentioning

confidence: 99%

Gravitationally lensed quasars in Gaia – II. Discovery of 24 lensed quasars

Lemon

Auger

McMahon

et al. 2018

Monthly Notices of the Royal Astronomical Society

106

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“…There was a long delay before the discovery of the first lensed quasar (Walsh et al 1979) and then considerable controversy over the measurement of the first time delay (Schild (1990) versus Press et al (1992), resolved in favor of the former by Kundić et al (1997)). The measurement of delays is now routine (e.g., Bonvin et al 2019, Courbin et al 2018, Bonvin et al 2017 and the estimates are generally robust (e.g., Liao et al 2015). The challenge lies in their cosmological interpretation.…”

Section: Introductionmentioning

confidence: 99%

Overconstrained gravitational lens models and the Hubble constant

Kochanek

2020

Monthly Notices of the Royal Astronomical Society

104

106

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It is well known that measurements of H 0 from gravitational lens time delays scale as H 0 ∝ 1 − κ E where κ E is the mean convergence at the Einstein radius R E but that all available lens data other than the delays provide no direct constraints on κ E . The properties of the radial mass distribution constrained by lens data are R E and the dimensionless quantityis the second derivative of the deflection profile at R E . Lens models with too few degrees of freedom, like power law models with densities ρ ∝ r −n , have a one-to-one correspondence between ξ and κ E (for a power law model, ξ = 2(n − 2) and κ E = (3 − n)/2 = (2 − ξ)/4). This means that highly constrained lens models with few parameters quickly lead to very precise but inaccurate estimates of κ E and hence H 0 . Based on experiments with a broad range of plausible dark matter halo models, it is unlikely that any current estimates of H 0 from gravitational lens time delays are more accurate than ∼ 10%, regardless of the reported precision.

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“…The function predicts that a change of ∼ 0.3 − 0.5 mag, similar to what we observe for the D component, is expected only if the two epochs are separated by several years 7 . We caution the reader, however, that delay among different lightcurves might cause a large flux variation, as shown in Courbin et al (2018) for the lens D0408. Flux ratio variations among lightcurves also have implications for claims of substructure detection, as was shown explicitly by Agnello et al (2017) on the same lens.…”

Section: Variability Evidence For Wg0214mentioning

confidence: 94%

Spectroscopic confirmation and modelling of two lensed quadruple quasars in the Dark Energy Survey public footprint

Spiniello

Sergeyev

Marchetti

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Quadruply lensed quasars are extremely rare objects, but incredibly powerful cosmological tools. Only few dozen are known in the whole sky. Here we present the spectroscopic confirmation of two new quadruplets WG0214-2105 and WG2100-4452 discovered by within the Dark Energy Survey (DES) public footprints. We have conducted spectroscopic follow-up of these systems with the Southern African Large Telescope as part of a program that aims at confirming the largest possible number of optically selected strong gravitational lensing systems in the Equatorial and Southern Hemisphere. For both systems, we present the spectra for the sources and deflectors that allowed us to estimate the source redshifts and unambiguously confirm their lensing nature. For the brighter deflector (WG2100-4452), we measure the stellar velocity dispersion from the spectrum. We also obtain photometry for both lenses, directly from DES multi-band images, isolating the lens galaxies from the quasar images. One of the quadruplets, WG0214-2105, was also observed by Pan-STARRS, allowing us to estimate the apparent brightness of each quasar image at two different epochs, and thus to find evidence for flux variability. This result could suggest a microlensing event for the faintest components, although intrinsic variability cannot be excluded with only two epochs. Finally, we present simple lens models for both quadruplets, obtaining Einstein radii, SIE velocity dispersions, ellipticities, and position angles of the lens systems, as well as time delay predictions assuming a concordance cosmological model.

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COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Cited by 82 publications

References 40 publications

Gravitationally lensed quasars in Gaia – II. Discovery of 24 lensed quasars

Gravitationally lensed quasars in Gaia – II. Discovery of 24 lensed quasars

Overconstrained gravitational lens models and the Hubble constant

Spectroscopic confirmation and modelling of two lensed quadruple quasars in the Dark Energy Survey public footprint

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