Related papers: Identifying Lenses with Small-Scale Structure. I. …
When the source in a 4-image gravitational lens lies close to a "fold" caustic, two of the lensed images lie close together. If the lens potential is smooth on the scale of the separation between the two close images, then the difference…
Flux ratio `anomalies' in quadruply-imaged gravitational lenses can be explained with galactic substructure of the sort predicted by CDM, but the strength and uniqueness of that hypothesis needs to be further assessed. A good way to do that…
We develop a new approach for studying flux anomalies in quadruply-imaged fold lens systems. We show that in the absence of substructure, microlensing, or differential absorption, the expected flux ratios of a fold pair can be tightly…
We discuss whether one should expect that multiply imaged QSOs can be understood with `simple' lens models which contain a handful of parameters. Whereas for many lens systems such simple mass models yield a remarkably good description of…
Substructure in distant gravitational lens galaxies can be detected because it alters the brightnesses and shapes of the lensed images. The optical and radio flux ratios in the four-image lens B1422+231 imply that there is a \sim 10^4-10^7…
Gravitational lensing of a background source by a foreground galaxy lens occasionally produces four images of the source. The cusp and the fold relations impose conditions on the ratios of magnifications of these four-image lenses. In this…
The existence of flux-ratio anomalies between fold and cusp images in galaxy-scale strong-lens systems has led to an interpretation based on the presence of a high mass-fraction of cold-dark-matter (CDM) substructures around galaxies, as…
We study the anomalous flux ratio which is observed in some four-image lens systems, where the source lies close to a fold caustic. In this case two of the images are close to the critical curve and their flux ratio should be equal to…
Simple models for lensing potentials that successfully reproduce the positions of quadruple images to high accuracy fail abysmally in reproducing the flux ratios of the multiple images, suggesting the presence of small scale structure…
We review five often used quad lens models, each of which has analytical solutions and can produce four images at most. Each lens model has two parameters, including one that describes the intensity of non-dimensional mass density, and the…
We examine the ability of gravitational lens time delays to reveal complex structure in lens potentials. In Congdon, Keeton & Nordgren (2008), we predicted how the time delay between the bright pair of images in a "fold" lens scales with…
The observables in a strong gravitational lens are usually just the image positions and sometimes the flux ratios. We develop a new and simple algorithm which allows a set of models to be fitted exactly to the observations. Taking our cue…
We present the first resolved mid-IR (11 micron) observations of the four-image quasar lens H1413+117 using the Michelle camera on Gemini North. All previous observations (optical, near-IR, and radio) of this lens show a "flux anomaly,"…
We present a study of the lens properties of quadruply imaged systems, lensed by numerically simulated galaxies. We investigate a simulated elliptical and disc galaxy drawn from high resolution simulations of galaxy formation in a…
The gravitational lensing constraints on the small mass end of the LCDM mass function are discussed. Here a conservative approach is taken where only the most difficult to explain image flux anomalies in strong QSO lenses are emphasized.…
We investigate the statistics of flux anomalies in gravitationally lensed QSOs as a function of dark matter halo properties such as substructure content and halo ellipticity. We do this by creating a very large number of simulated lenses…
We explore the origin of flux ratio anomaly in quadruple lens systems. Using a semi-analytic method based on $N$-body simulations, we estimate the effect of possible magnification perturbation caused by subhaloes with a mass scale of <$\sim…
It has been argued that the flux anomalies detected in gravitationally lensed QSOs are evidence for substructures in the foreground lensing haloes. In this paper we investigate this issue in greater detail focusing on the Cusp relation…
This paper primarily addresses the question of whether recent lensing observations probing the small scale structure in the universe are consistent with the LCDM model. A conservative approach is taken where only the most difficult to…
In recent years, gravitational lensing has been used as a means to detect substructure in galaxy-sized halos, via anomalous flux ratios in quadruply-imaged lenses. In addition to causing anomalous flux ratios, substructure may also perturb…