Analytic relations for magnifications and time delays in gravitational lenses with fold and cusp configurations

Congdon, Arthur B.; Keeton, Charles R.; Nordgren, C. Erik

doi:10.1111/j.1365-2966.2008.13604.x

Cited by 20 publications

(27 citation statements)

References 35 publications

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“…More particularly, four-image lenses in cusp configurations (where the source is close to the cusp of the astroid caustic) and fold configurations (resulting from the source being close to the caustic fold) give clear theoretical expectations for image flux ratios which must be obeyed by any smooth model. In cusp lenses, there are three close images and the middle image is expected to have the brightness of the sum of the outer two (Schneider & Weiss 1992); in fold lenses, the two close images are expected to have the same flux (Keeton, Gaudi & Petters 2003;Congdon, Keeton & Nordgren 2008). Because of optical microlensing, radio lens systems have traditionally been used for this work (Mao & Schneider 1998, Fassnacht et al 1999, Metcalf & Zhao 2002, Metcalf 2005, Kratzer et al 2011.…”

Section: Introductionmentioning

confidence: 99%

Observations of radio-quiet quasars at 10-mas resolution by use of gravitational lensing

Jackson

Tagore

Roberts

et al. 2015

Mon. Not. R. Astron. Soc.

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We present VLA detections of radio emission in four four-image gravitational lens systems with quasar sources: HS 0810+2554, RX J0911+0511, HE 0435−1223 and SDSS J0924+0219, and e-MERLIN observations of two of the systems. The first three are detected at a high level of significance, and SDSS J0924+0219 is detected. HS 0810+2554 is resolved, allowing us for the first time to achieve 10-mas resolution of the source frame in the structure of a radio quiet quasar. The others are unresolved or marginally resolved. All four objects are among the faintest radio sources yet detected, with intrinsic flux densities in the range 1-5µJy; such radio objects, if unlensed, will only be observable routinely with the Square Kilometre Array. The observations of HS 0810+2554, which is also detected with e-MERLIN, strongly suggest the presence of a mini-AGN, with a radio core and milliarcsecond scale jet. The flux densities of the lensed images in all but HE 0435−1223 are consistent with smooth galaxy lens models without the requirement for smaller-scale substructure in the model, although some interesting anomalies are seen between optical and radio flux densities. These are probably due to microlensing effects in the optical.

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Section: Introductionmentioning

confidence: 99%

Observations of radio-quiet quasars at 10-mas resolution by use of gravitational lensing

Jackson

Tagore

Roberts

et al. 2015

Mon. Not. R. Astron. Soc.

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“…Secondly, time‐variable sources allow us to measure time delays between multiple images; these time delays contain rich information on the lens potentials as well as cosmology (e.g. Witt, Mao & Keeton 2000; Kochanek 2002; Saha & Williams 2003; Schechter 2005; Oguri 2007a; Congdon, Keeton & Nordgren 2008; Keeton & Moustakas 2009; Congdon, Keeton & Nordgren 2010; Keeton 2010).…”

Section: Introductionmentioning

confidence: 99%

Gravitationally lensed quasars and supernovae in future wide-field optical imaging surveys

Oguri

Marshall

2010

Monthly Notices of the Royal Astronomical Society

362

303

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Cadenced optical imaging surveys in the next decade will be capable of detecting time‐varying galaxy‐scale strong gravitational lenses in large numbers, increasing the size of the statistically well‐defined samples of multiply imaged quasars by two orders of magnitude, and discovering the first strongly lensed supernovae. We carry out a detailed calculation of the likely yields of several planned surveys, using realistic distributions for the lens and source properties and taking magnification bias and image configuration detectability into account. We find that upcoming wide‐field synoptic surveys should detect several thousand lensed quasars. In particular, the Large Synoptic Survey Telescope (LSST) should find more than some 8000 lensed quasars, some 3000 of which will have well‐measured time delays. The LSST should also find some 130 lensed supernovae during the 10‐yr survey duration, which is compared with ∼15 lensed supernovae predicted to be found by a deep, space‐based supernova survey done by the Joint Dark Energy Mission. We compute the quad fraction in each survey, predicting it to be ∼15 per cent for the lensed quasars and ∼30 per cent for the lensed supernovae. Generating a mock catalogue of around 1500 well‐observed double‐image lenses, as could be derived from the LSST survey, we compute the available precision on the Hubble constant and the dark energy equation parameters for the time‐delay distance experiment (assuming priors from Planck): the predicted marginalized 68 per cent confidence intervals are σ(w0) = 0.15, σ(wa) = 0.41 and σ(h) = 0.017. While this is encouraging in the sense that these uncertainties are only 50 per cent larger than those predicted for a space‐based Type Ia supernova sample, we show how the dark energy figure of merit degrades with decreasing knowledge of the lens mass distribution.

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“…In this regard, gravitational lenses with two or three close images deserve special attention because, in these cases, the sources must be close to either a fold or a cusp of the caustic. It is well known for any smooth lensing potential that the close images follow asymptotic flux ratio relations: for a close pair, their flux ratio approaches unity when their separation goes to zero, while for a close triple, the ratio of the flux of the middle image to the sum of the fluxes of the two outer images asymptotically goes to unity (Mao 1992; Schneider & Weiss 1992; Keeton, Gaudi & Petters 2003; Congdon, Keeton & Nordgren 2008). However, the observed lensing systems often violate these asymptotic relations.…”

Section: Introductionmentioning

confidence: 99%

Effects of dark matter substructures on gravitational lensing: results from the Aquarius simulations

Mao

Wang

et al. 2009

Monthly Notices of the Royal Astronomical Society

108

112

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We use the high-resolution Aquarius simulations of the formation of Milky Way-sized haloes in the cold dark matter cosmology to study the effects of dark matter substructures on gravitational lensing. Each halo is resolved with ∼10 8 particles (at a mass resolution m p ∼ 10 3 to 10 4 h −1 M ) within its virial radius. Subhaloes with masses m sub 10 5 h −1 M are well resolved, an improvement of at least two orders of magnitude over previous lensing studies. We incorporate a baryonic component modelled as a Hernquist profile and account for the response of the dark matter via adiabatic contraction. We focus on the 'anomalous' flux ratio problem, in particular on the violation of the cusp-caustic relation due to substructures. We find that subhaloes with masses less than ∼10 8 h −1 M play an important role in causing flux anomalies; such low-mass subhaloes have been unresolved in previous studies. There is large scatter in the predicted flux ratios between different haloes and between different projections of the same halo. In some cases, the frequency of predicted anomalous flux ratios is comparable to that observed for the radio lenses, although in most cases it is not. The probability for the simulations to reproduce the observed violations of the cusp lenses is ≈10 −3 . We therefore conclude that the amount of substructure in the central regions of the Aquarius haloes is insufficient to explain the observed frequency of violations of the cusp-caustic relation. These conclusions are based purely on our dark matter simulations which ignore the effect of baryons on subhalo survivability.

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Analytic relations for magnifications and time delays in gravitational lenses with fold and cusp configurations

Cited by 20 publications

References 35 publications

Observations of radio-quiet quasars at 10-mas resolution by use of gravitational lensing

Observations of radio-quiet quasars at 10-mas resolution by use of gravitational lensing

Gravitationally lensed quasars and supernovae in future wide-field optical imaging surveys

Effects of dark matter substructures on gravitational lensing: results from the Aquarius simulations

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