Time Delays in the Gravitational Lens CLASS B1608+656: Results from Second and Third Seasons of VLA Monitoring

2005 ◽  
Vol 201 ◽  
pp. 455-456
Author(s):  
Christopher. Fassnacht ◽  
Emily. Xanthopoulos ◽  
David. Rusin ◽  
Leon. Koopmans
Keyword(s):  
Time Delay ◽  
Flux Density ◽  
Time Delays ◽  
Optical Emission ◽  
Gravitational Lens ◽  
Delay Analysis ◽  
Constrained Model

The gravitational lens CLASS B1608+656 is one of the most promising lens systems for the measurement of H0 on cosmological scales. The three independent time delays between the four lensed images have been measured, and the extended lensed optical emission holds the promise for a very well-constrained model. The published time delay measurements are based on the first season of VLA monitoring, in which the background source varied by only 5% in flux density. The small level of variation leads to relatively large uncertainties in the determination of the time delays (10-20%). Two more seasons of monitoring have now been completed and the source flux density has changed by ˜25% during that time. We present the results of the continued VLA monitoring and the resulting time-delay analysis. The new data have significantly reduced the uncertainties on the time delays and, hence, reduced the uncertainties on the resulting determination of H0 from this system.

scholarly journals Accurate cosmology from gravitational-lens time delays

2012 ◽  
Vol 8 (S289) ◽  
pp. 331-338
Author(s):  
S. H. Suyu
Keyword(s):  
Time Delay ◽  
Time Delays ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Gravitational Lens ◽  
Current Status ◽  
Gravitational Lenses ◽  
Distance Measurements ◽  
One Step

AbstractThe time delays between the multiple images of a strong gravitational-lens system, together with a model of the lens-mass distribution, provide a one-step determination of the time-delay distance, and thus a measure of cosmological parameters, particularly the Hubble constant, H0. I review the recent advances in measuring time-delay distances, and present the current status of cosmological constraints based on gravitational-lens time delays. In particular, I report the time-delay distance measurements of two gravitational lenses and their implication for cosmology from a recent study by Suyuet al.

scholarly journals Ambiguities in gravitational lens models: impact on time delays of the source position transformation

2018 ◽  
Vol 617 ◽  
pp. A140 ◽  
Author(s):  
Olivier Wertz ◽  
Bastian Orthen ◽  
Peter Schneider
Keyword(s):  
Time Delay ◽  
Time Delays ◽  
Hubble Constant ◽  
Companion Paper ◽  
Gravitational Lens ◽  
Source Position ◽  
Double Image ◽  
Validity Criterion ◽  
Mass Profile ◽  
Image Pairs

The central ambition of the modern time delay cosmography consists in determining the Hubble constant H0 with a competitive precision. However, the tension with H0 obtained from the Planck satellite for a spatially flat ΛCDM cosmology suggests that systematic errors may have been underestimated. The most critical of these errors probably comes from the degeneracy existing between lens models that was first formalized by the well-known mass-sheet transformation (MST). In this paper, we assess to what extent the source position transformation (SPT), a more general invariance transformation which contains the MST as a special case, may affect the time delays predicted by a model. To this aim, we have used pySPT, a new open-source python package fully dedicated to the SPT that we present in a companion paper. For axisymmetric lenses, we find that the time delay ratios between a model and its SPT-modified counterpart simply scale like the corresponding source position ratios, Δtˆ/Δt ≈ βˆ/β, regardless of the mass profile and the isotropic SPT. Similar behavior (almost) holds for nonaxisymmetric lenses in the double image regime and for opposite image pairs in the quadruple image regime. In the latter regime, we also confirm that the time delay ratios are not conserved. In addition to the MST effects, the SPT-modified time delays deviate in general no more than a few percent for particular image pairs, suggesting that its impact on time delay cosmography seems not be as crucial as initially suspected. We also reflected upon the relevance of the SPT validity criterion and present arguments suggesting that it should be reconsidered. Even though a new validity criterion would affect the time delays in a different way, we expect from numerical simulations that our conclusions will remain unchanged.

scholarly journals Photometric Monitoring Of The Lensed QSO 0957+561

1996 ◽  
Vol 173 ◽  
pp. 53-54
Author(s):  
D. Sinachopoulos ◽  
M. Burger ◽  
E. van Dessel ◽  
M. Geffert ◽  
M. Thibor ◽  
...  
Keyword(s):  
Time Delay ◽  
Gravitational Lens ◽  
Large Field ◽  
Photometric Study ◽  
First Results ◽  
Photometric Monitoring

We present our first results of a photometric monitoring project of the twin quasar 0957+561. This project aims mainly at the improvement of the determination of the time delay ΔT(A,B) for this gravitational lens, since the “time delay controversy on QSO 0957+561 (is) not yet decided” (Pelt et al. 1994). In addition, the quite large field of the CCD used allows also a long-term astrometric and photometric study of stars and galaxies in the field within a radius of about 10 arcminutes around the lens.

scholarly journals Determination of the time scale of photoemission from the measurement of spin polarization

2018 ◽  
Vol 5 (6) ◽  
Author(s):  
Mauro Fanciulli ◽  
Hugo Dil
Keyword(s):  
Experimental Data ◽  
Time Delay ◽  
Matrix Element ◽  
Spin Polarization ◽  
Time Delays ◽  
Upper And Lower Bounds ◽  
Recent Experimental Data ◽  
The Matrix ◽  
Phase Term

The Eisenbud-Wigner-Smith (EWS) time delay of photoemission depends on the phase term of the matrix element describing the transition. Because of an interference process between partial channels, the photoelectrons acquire a spin polarization which is also related to the phase term. The analytical model for estimating the time delay by measuring the spin polarization is reviewed in this manuscript. In particular, the distinction between scattering EWS and interfering EWS time delay will be introduced, providing an insight in the chronoscopy of photoemission. The method is applied to the recent experimental data for Cu(111) presented in M. Fanciulli et al., PRL 118, 067402 (2017), allowing to give better upper and lower bounds and estimates for the EWS time delays.

scholarly journals Limits between the Cosmological Parameters from Strong Lensing Observations for Generalized Isothermal Models

2009 ◽  
Vol 6 (2) ◽  
pp. 394-400
Author(s):  
Baghdad Science Journal
Keyword(s):  
Time Delay ◽  
Time Delays ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Gravitational Lens ◽  
Angular Structure ◽  
Density Distributions ◽  
General Family ◽  
Strong Lensing ◽  
Elegant Form

This paper including a gravitational lens time delays study for a general family of lensing potentials, the popular singular isothermal elliptical potential (SIEP), and singular isothermal elliptical density distribution (SIED) but allows general angular structure. At first section there is an introduction for the selected observations from the gravitationally lensed systems. Then section two shows that the time delays for singular isothermal elliptical potential (SIEP) and singular isothermal elliptical density distributions (SIED) have a remarkably simple and elegant form, and that the result for Hubble constant estimations actually holds for a general family of potentials by combining the analytic results with data for the time delay and by using the models of distances.

scholarly journals VLBI Observations of the 0957+561 Gravitational Lens System

1988 ◽  
Vol 129 ◽  
pp. 201-206
Author(s):  
M. V. Gorenstein ◽  
R. J. Bonometti ◽  
N. L. Cohen ◽  
E. E. Falco ◽  
I. I. Shapiro ◽  
...  
Keyword(s):  
Time Delay ◽  
Flux Density ◽  
Gravitational Lens ◽  
Time Variability ◽  
Lens System ◽  
Relative Time ◽  
Vlbi Observations ◽  
New Information ◽  
Superluminal Motion ◽  
Upper Limits

A series of VLBI observations of the gravitational lens system 0957+561 at λ13 cm has yielded the positions of the A and B images, the relative magnification of their largest discernible radio structures, and the time variability of their smallest discernible radio structures. These observations have also allowed upper limits to be placed on the flux density of an expected third image. The positions and relative magnification of the A and B images provide new information with which to constrain models of the lens that forms the images. The detection of variations in the flux densities of the cores of A and B suggests that observations at shorter wavelengths may reveal superluminal motion, which may in turn provide a means to measure the relative time delay.

scholarly journals The Hubble Constant from (CLASS) Gravitational Lenses

2001 ◽  
Vol 18 (2) ◽  
pp. 179-181 ◽  
Author(s):  
L. V. E. Koopmans ◽  
The CLASS Collaboration
Keyword(s):  
Time Delays ◽  
Hubble Constant ◽  
Gravitational Lens ◽  
Gravitational Lenses ◽  
Monitoring Programs ◽  
Systematic Uncertainties ◽  
Sky Survey ◽  
Image Pairs ◽  
Near Future

AbstractOne of the main objectives of the Cosmic Lens All-Sky Survey (CLASS) collaboration has been to find gravitational lens (GL) systems at radio wavelengths that are suitable for the determination of time delays between image pairs. The survey is now near completion and at least 18 GL systems have been found. Here, I will discuss our efforts to measure time delays from several of these systems with the ultimate aim of constraining the Hubble Constant (H0). Thus far three CLASS GL systems (B0218+357, B1600+434 and B1608+656) have yielded measurements of time delays, from which values of H0 ≈ 60–70 km s−1 Mpc−1 have been estimated. Although most GL systems give similar values of H0, statistical and systematic uncertainties are still considerable. To reduce these uncertainties, I will mention two monitoring programs that we are undertaking to (re)measure time delays in 14 CLASS GL systems and address several important issues for the near future.

scholarly journals The Gravitational Lens System B1030+074. Discovery and Follow-up

1999 ◽  
Vol 194 ◽  
pp. 373-378
Author(s):  
E. Xanthopoulos ◽  
I. W. A. Browne ◽  
L. J. King ◽  
N. J. Jackson ◽  
D. R. Marlow ◽  
...  
Keyword(s):  
Time Delay ◽  
Flux Density ◽  
Density Ratio ◽  
Hubble Constant ◽  
Time Variable ◽  
Gravitational Lens ◽  
Lens System ◽  
Double Image ◽  
The Galaxy

We report the discovery of a new double image gravitational lens system B1030+074 which was found during the Jodrell Bank - VLA Astrometric Survey (JVAS). We have collected extensive radio data on the system using the VLA, MERLIN, the EVN and the VLBA as well as HST WFPC2 and NICMOS observations. The lensed images are separated by 1.56 arcseconds and their flux density ratio at centimetric wavelengths is approximately 14:1 although the ratio is slightly frequency dependent and the images appear to be time variable. The HST pictures show both the lensed images and the lensing galaxy close to the weaker image. The lensing galaxy has substructure which could be either part of the galaxy or a companion object. We have modeled B1030+074 using a Singular Isothermal Ellipsoid that yielded a time delay of 156/h50 days. This lens is likely to be suitable for the measurement of the Hubble constant.

scholarly journals Effects Of Large-Scale Structure Upon The Determination Of Ho From Time Delays

1996 ◽  
Vol 173 ◽  
pp. 91-92
Author(s):  
G.C. Surpi ◽  
D.D. Harari ◽  
J.A. Frieman
Keyword(s):  
Hubble Parameter ◽  
Time Delays ◽  
Large Scale ◽  
Angular Position ◽  
Order Effect ◽  
Gravitational Lens ◽  
Leading Order ◽  
Lens System ◽  
The Relationship

We have analyzed the effects of both large-scale inhomogeneities in the mass distribution and cosmological gravitational waves upon the time delay between two images in a gravitational lens system. We have shown that their leading order effect, which could potentially bias the determination of the Hubble parameter, is indistinguishable from a change in the relative angle between the source and the lens axis. Since the absolute angular position of the source is not directly measurable, nor does it enter the relationship between the Hubble parameter and the lens observables, the determination of Ho from gravitational lens time delays follows in the usual way, as if the metric perturbations were absent.

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