COSMOGRAIL: the COSmological MOnitoring  
 of GRAvItational Lenses

Vuissoz, C.; Courbin, F.; Sluse, Dominique; Meylan, G.; Ibrahimov, M.; Asfandiyarov, I. M.; Stoops, E.; Eigenbrod, A.; Guillou, L. Le; Winckel, H. Van; Magain, Pierre

doi:10.1051/0004-6361:20065823

Cited by 63 publications

(75 citation statements)

References 16 publications

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“…Nevertheless, the expected substructure and line-of-sight inhomogeneities mentioned above will put a lower limit to the positional accuracy at which lens systems can be modeled with smooth matter distributions. In any case, since the SPT is more general than the MST, it will limit the accuracy of some applications of strong gravitational lensing such as the detection of substructures via the time-delay method (Keeton & Moustakas 2009), the estimate of H 0 for systems where only one time delay is measured (Vuissoz et al 2007;Suyu 2012), or the determination of the profile of the dark matter distribution based only on strong lensing (e.g. Cohn et al 2001;Eichner et al 2012).…”

Section: Discussionmentioning

confidence: 99%

Source-position transformation: an approximate invariance in strong gravitational lensing

Schneider

Sluse

2014

A&A

149

146

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The main obstacle that gravitational lensing has in determining accurate masses of deflectors, or in determining precise estimates for the Hubble constant, is the degeneracy of lensing observables with respect to the mass-sheet transformation (MST). The MST is a global modification of the mass distribution which leaves all image positions, shapes, and flux ratios invariant, but which changes the time delay. Here we show that another global transformation of lensing mass distributions exists which leaves image positions and flux ratios almost invariant, and of which the MST is a special case. As is the case for the MST, this new transformation only applies if one considers only those source components that are at the same distance from us. Whereas for axi-symmetric lenses this source position transformation exactly reproduces all strong lensing observables, it does so only approximately for more general lens situations. We provide crude estimates for the accuracy with which the transformed mass distribution can reproduce the same image positions as the original lens model, and present an illustrative example of its performance. This new invariance transformation is most likely the reason why the same strong lensing information can be accounted for with rather different mass models.

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Section: Discussionmentioning

confidence: 99%

Source-position transformation: an approximate invariance in strong gravitational lensing

Schneider

Sluse

2014

A&A

149

146

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“…The algorithm has been implemented in various analysis of quasars (Burud et al 2000(Burud et al , 2002aHjorth et al 2002;Jakobsson et al 2005;Vuissoz et al 2007;Eigenbrod et al 2006a).…”

Section: Photometrymentioning

confidence: 99%

Results of optical monitoring of 5 SDSS double QSOs with the Nordic Optical Telescope

Paraficz¹,

Hjorth²,

Elíasdóttir

2009

A&A

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We present optical R-band light curves of five SDSS double QSOs (SDSS J0903+5028, SDSS J1001+5027, SDSS J1206+4332, SDSS J1353+1138, SDSS J1335+0118) obtained from monitoring at the Nordic Optical Telescope (NOT) between September 2005 and September 2007. We also present analytical and pixelated modeling of the observed systems. For SDSS J1206+4332, we measured the time delay to be Δτ = 116 +4 −5 days, which, for a singular isothermal ellipsoid model, corresponds to a Hubble constant of 73 +3 −4 km s −1 Mpc −1 . Simultaneous pixelated modeling of five other systems for which a time delay has now been previously measured at the NOT leads to H 0 = 61.5 +8 −4 km s −1 Mpc −1 . Finally, by comparing light curves of the two images of each system, suitably shifted by the predicted or observed time-delays, we found no evidence of microlensing variability over the course of the monitoring period.

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“…The COSMOGRAIL project, i.e. the COSmological MOnitoring of GRAvItational Lenses, aims to provide the community with A&A 538, A99 (2012) exquisite lightcurves and accurate time-delay measurements for a sample of more than 20 lensed quasars (Eigenbrod et al 2005;Vuissoz et al 2007Vuissoz et al , 2008Courbin et al 2011). To understand degeneracies affecting lens models, we started to model all systems monitored by COSMOGRAIL as well as those monitored by earlier campaigns in a uniform way.…”

Section: Introductionmentioning

confidence: 99%

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Sluse

Chantry

Magain

et al. 2012

A&A

Self Cite

121

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Gravitationally lensed quasars can be used as powerful cosmological and astrophysical probes. We can (i) infer the Hubble constant H 0 based on the so-called time-delay technique, (ii) unveil substructures along the line-of-sight toward distant galaxies, and (iii) compare the shape and the slope of baryons and dark matter distributions in the inner regions of galaxies. To reach these goals, we need highaccuracy astrometry of the quasar images relative to the lensing galaxy and morphology measurements of the lens. In this work, we first present new astrometry for 11 lenses with measured time delays, namely, JVAS B0218+357, SBS 0909+532, RX J0911.4+0551, FBQS J0951+2635, HE 1104-1805, PG 1115+080, JVAS B1422+231, SBS 1520+530, CLASS B1600+434, CLASS B1608+656, and HE 2149-2745. These measurements proceed from the use of the Magain-Courbin-Sohy (MCS) deconvolution algorithm applied in an iterative way (ISMCS) to near-IR HST images. We obtain a typical astrometric accuracy of about 1-2.5 mas and an accurate shape measurement of the lens galaxy. Second, we combined these measurements with those of 14 other lensing systems, mostly from the COSMOGRAIL set of targets, to present new mass models of these lenses. The modeling of these 25 gravitational lenses led to the following results: 1) in four double-image quasars (HE0047-1746, J1226-006, SBS 1520+530, and HE 2149-2745), we show that the influence of the lens environment on the time delay can easily be quantified and modeled, hence putting these lenses with high priority for time-delay determination; 2) for quadruple-image quasars, the difficulty often encountered in reproducing the image positions to milli-arcsec accuracy (astrometric anomaly problem) is overcome by explicitly including the nearest visible galaxy/satellite in the lens model. However, one anomalous system (RXS J1131-1231) does not show any luminous perturber in its vicinity, and three others (WFI 2026-4536, WFI 2033, and B2045+265) have problematic modeling. These four systems are the best candidates for a pertubation by a dark matter substructure along the line-of-sight; 3) we revisit the correlation between the position angle (PA) and ellipticity of the light and of the mass distribution in lensing galaxies. As in previous studies, we find a significant correlation between the PA of the light and of the mass distributions. However, in contrast with these same studies, we find that the ellipticity of the light and of the mass also correlate well, suggesting that the overall spatial distribution of matter is not very different from the baryon distribution in the inner ∼5 kpc of lensing galaxies. This offers a new test for high-resolution hydrodynamical simulations.

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COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Cited by 63 publications

References 16 publications

Source-position transformation: an approximate invariance in strong gravitational lensing

Source-position transformation: an approximate invariance in strong gravitational lensing

Results of optical monitoring of 5 SDSS double QSOs with the Nordic Optical Telescope

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

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