Matter near a gravitational lens galaxy or projected along the line of sight (LOS) can affect strong lensing observables by more than contemporary measurement errors. We simulate lens fields with ...realistic three-dimensional mass configurations (self-consistently including voids), and then fit mock lensing observables with increasingly complex lens models to quantify biases and uncertainties associated with different ways of treating the lens environment (ENV) and LOS. We identify the combination of mass, projected offset, and redshift that determines the importance of a perturbing galaxy for lensing. Foreground structures have a stronger effect on the lens potential than background structures, due to nonlinear effects in the foreground and downweighting in the background. There is dramatic variation in the net strength of ENV/LOS effects across different lens fields; modeling fields individually yields stronger priors for H0 than ray tracing through N-body simulations. Models that ignore mass outside the lens yield poor fits and biased results. Adding external shear can account for tidal stretching from galaxies at redshifts , but it requires corrections for external convergence and cannot reproduce nonlinear effects from foreground galaxies. Using the tidal approximation is reasonable for most perturbers as long as nonlinear redshift effects are included. Even then, the scatter in H0 is limited by the lens profile degeneracy. Asymmetric image configurations produced by highly elliptical lens galaxies are less sensitive to the lens profile degeneracy, so they offer appealing targets for precision lensing analyses in future surveys like LSST and Euclid.
Strong gravitational lensing provides a powerful probe of the physical properties of quasars and their host galaxies. A high fraction of the most luminous high-redshift quasars was predicted to be ...lensed due to magnification bias. However, no multiple imaged quasar was found at z > 5 in previous surveys. We report the discovery of J043947.08+163415.7, a strongly lensed quasar at z = 6.51, the first such object detected at the epoch of reionization, and the brightest quasar yet known at z > 5. High-resolution Hubble Space Telescope imaging reveals a multiple imaged system with a maximum image separation θ ∼ 0 2, best explained by a model of three quasar images lensed by a low-luminosity galaxy at z ∼ 0.7, with a magnification factor of ∼50. The existence of this source suggests that a significant population of strongly lensed, high-redshift quasars could have been missed by previous surveys, as standard color selection techniques would fail when the quasar color is contaminated by the lensing galaxy.
In strong gravitational lens systems, the light bending is usually dominated by one main galaxy, but may be affected by other mass along the line of sight (LOS). Shear and convergence can be used to ...approximate the contributions from less significant perturbers (e.g. those that are projected far from the lens or have a small mass), but higher order effects need to be included for objects that are closer or more massive. We develop a framework for multiplane lensing that can handle an arbitrary combination of tidal planes treated with shear and convergence and planes treated exactly (i.e. including higher order terms). This framework addresses all of the traditional lensing observables including image positions, fluxes, and time delays to facilitate lens modelling that includes the non-linear effects due to mass along the LOS. It balances accuracy (accounting for higher order terms when necessary) with efficiency (compressing all other LOS effects into a set of matrices that can be calculated up front and cached for lens modelling). We identify a generalized multiplane mass sheet degeneracy, in which the effective shear and convergence are sums over the lensing planes with specific, redshift-dependent weighting factors.
ABSTRACT
The Hubble Frontier Fields data, along with multiple data sets obtained by other telescopes, have provided some of the most extensive constraints on cluster lenses to date. Multiple lens ...modelling teams analyzed the fields and made public a number of deliverables. By comparing these results, we can then undertake a unique and vital test of the state of cluster lens modelling. Specifically, we see how well the different teams can reproduce similar magnifications and mass profiles. We find that the circularly averaged mass profiles of the fields are remarkably constrained (scatter $\lt 5{{\ \rm per\ cent}}$) at distances of 1 arcmin from the cluster core, yet magnifications can vary significantly. Averaged across the six fields, we find a bias of −6 per cent (−17 per cent) and a scatter of ∼40 per cent (∼65 per cent) at a modest magnification of 3 (10). Statistical errors reported by individual teams are often significantly smaller than the differences among all the teams, indicating the importance of continued systematics studies in cluster lensing.
Gravitational lensing has emerged as a powerful probe of the matter distribution on subgalactic scales, which itself may contain important clues about the fundamental origins and properties of dark ...matter. Broadly speaking, two different approaches have been taken in the literature to map the small-scale structure of the Universe using strong lensing, with one focused on measuring the position and mass of a small number of discrete massive subhalos appearing close in projection to lensed images, and the other focused on detecting the collective effect of all the small-scale structures between the lensed source and the observer. In this paper, we follow the latter approach and perform a detailed study of the sensitivity of galaxy-scale gravitational lenses to the ensemble properties of small-scale structure. As in some previous studies, we adopt the language of the substructure power spectrum to characterize the statistical properties of the small-scale density field. We present a comprehensive theory that treats lenses with extended sources as well as those with time-dependent compact sources (such as quasars) in a unified framework for the first time. Our approach uses mode functions to provide both computational advantages and insights about couplings between the lens and source. The goal of this paper is to develop the theory and gain the intuition necessary to understand how the sensitivity to the substructure power spectrum depends on the source and lens properties, with the eventual aim of identifying the most promising targets for such studies.
We present IRAM NOrthern Extended Millimeter Array, James Clerk Maxwell Telescope/Submillimetre Common-User Bolometer Array-2 and Very Large Array (VLA) observations of the most distant known ...gravitationally lensed quasar, J0439+1634 at z = 6.5. We detect strong dust emission, C ii 158 m, C i 369 m, O i 146 m, CO(6-5), CO(7-6), CO(9-8), CO(10-9), H2O 31,2−22,1, and H2O 32,1−31,2 lines, as well as a weak radio continuum. The strong C ii line yields a systemic redshift of the host galaxy to be z = 6.5188 0.0002. The magnification makes J0439+1634 the far-infrared (FIR) brightest quasar at z > 6 known, with the brightest C ii line yet detected at this redshift. The FIR luminosity is (3.4 0.2) × 1013 −1 L , where ∼2.6-6.6 is the magnification of the host galaxy, estimated based on the lensing configuration from HST imaging. We estimate the dust mass to be (2.2 0.1) × 109 −1 . The CO spectral line energy distribution using four CO lines are best fit by a two-component model of the molecular gas excitation. The estimates of molecular gas mass derived from CO lines, and atomic carbon mass are consistent, in the range of (3.9-8.9) × 1010 −1 . The C ii/C i, C ii/CO, and O i/C ii line luminosity ratios suggest a photodissociation region model with more than one component. The ratio of H2O 32,1−31,2 line luminosity to LTIR is consistent with values in local and high-redshift ultra-/hyper-luminous infrared galaxies. The VLA observations reveal an unresolved radio continuum source, and indicate that J0439+1634 is a radio-quiet quasar with R = 0.05-0.17.
Substructure in the lens HE 0435−1223 Fadely, Ross; Keeton, Charles R
Monthly Notices of the Royal Astronomical Society,
January 2012, Letnik:
419, Številka:
2
Journal Article
Recenzirano
Odprti dostop
We investigate the properties of dark matter substructure in the gravitational lens HE 0435−1223 (z
l=0.455) via its effects on the positions and flux ratios of the quadruply imaged background quasar ...(z
s= 1.689). We start with a smooth mass model, add individual, truncated isothermal clumps near the lensed images and use the Bayesian evidence to compare the quality of different models. Compared with smooth models, models with at least one clump near image A are strongly favoured. The mass of this clump within its Einstein radius is log10(M
A
Ein) = 7.65+0.87
− 0.84 (in units of h
−1
70 M⊙). The Bayesian evidence provides weaker support for a second clump near image B, with log10(M
B
Ein) = 6.55+1.01
− 1.51. We also examine models with a full population of substructure, and find the mass fraction in substructure at the Einstein radius to be f
sub>rsim 0.000 77, assuming the total clump masses follow a mass function dN/dM∝M
−1.9 over the range M= 107-1010 M⊙. Few-clump and population models produce similar Bayesian evidence values, so neither type of model is objectively favoured.
Abstract
The arrival times, positions and fluxes of multiple images in strong lens systems can be used to infer the presence of dark subhaloes in the deflector, and thus test predictions of cold dark ...matter models. However, gravitational lensing does not distinguish between perturbations to a smooth gravitational potential arising from baryonic and non-baryonic mass. In this work, we quantify the extent to which the stellar mass distribution of a deflector can reproduce flux ratio and astrometric anomalies typically associated with the presence of a dark matter subhalo. Using Hubble Space Telescope images of nearby galaxies, we simulate strong lens systems with real distributions of stellar mass as they would be observed at redshift zd = 0.5. We add a dark matter halo and external shear to account for the smooth dark matter field, omitting dark substructure, and use a Monte Carlo procedure to characterize the distributions of image positions, time delays and flux ratios for a compact background source of diameter 5 pc. By convolving high-resolution images of real galaxies with a Gaussian point spread function, we simulate the most detailed smooth potential one could construct given high-quality data, and find scatter in flux ratios of ≈10 per cent, which we interpret as a typical deviation from a smooth potential caused by large- and small-scale structure in the lensing galaxy. We demonstrate that the flux ratio anomalies arising from galaxy-scale baryonic structure can be minimized by selecting the most massive and round deflectors and by simultaneously modelling flux ratio and astrometric data.
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