scholarly journals Multi-frequency VLBI Observations of the Gravitational Lens B0218+357

1996 ◽  
Vol 175 ◽  
pp. 115-117
Author(s):  
R. W. Porcas ◽  
A. R. Patnaik
Keyword(s):  
Time Delay ◽  
Mass Distribution ◽  
Hubble Constant ◽  
Gravitational Lens ◽  
Radio Sources ◽  
Constant Independent ◽  
Lens System ◽  
Vlbi Observations ◽  
Spectrum Radio ◽  
Simple Mass

The gravitational lens system B0218+357 comprises 2 image components (A and B) and a radio ‘Einstein Ring’ (Patnaik et al, 1993). The redshift of the lens galaxy is 0.6847 (Browne et al, 1994) and that of the imaged source 0.96 (preliminary result; Lawrence et al, 1995). The separation of A and B, which are both flat-spectrum radio sources, is only 0.335 arcsec, leading to the hope that the lens is a single galaxy with a relatively simple mass distribution. Refsdal pointed out (1964) that a model of such a distribution, and a measurement of the time difference along the two image paths, leads to an estimate of the Hubble constant, independent of the usual steps in the distance ladder. B0218+357 is one of only a few lensed systems well suited for such measurements. A preliminary value of 12 days has been measured for the A-B time delay, derived from a comparison of the percentage polarisation variations of the images at 15GHz, using the VLA (Corbett et al, 1995).

scholarly journals Can We Measure H0 with VLBI Observations of Gravitational Images?

1988 ◽  
Vol 129 ◽  
pp. 207-208
Author(s):  
E. E. Falco ◽  
M. V. Gorenstein ◽  
I. I. Shapiro
Keyword(s):  
Time Delay ◽  
Mass Distribution ◽  
Velocity Dispersion ◽  
Gravitational Lens ◽  
Lens System ◽  
Relative Time ◽  
Surface Mass ◽  
A Value ◽  
Vlbi Observations ◽  
The Difference

We have used the relative positions and magnifications of the A and B images in the gravitational lens system 0957+561, obtained from VLBI observations, to constrain a model for the surface mass distribution of the lens. With measurements of the difference ΔτBA in propagation times associated with A and B (the “relative time delay”) and of the velocity dispersion of the main lensing galaxy, both to be obtained, our model will yield a value for H0 with an uncertainty of ∼ 20% due mainly to uncertainties in our assumptions.

scholarly journals VLBI Observations of the Gravitational-Lens Images of Q0957+561

1984 ◽  
Vol 110 ◽  
pp. 243-246
Author(s):  
M. V. Gorenstein ◽  
I. I. Shapiro ◽  
N. L. Cohen ◽  
R. J. Bonometti ◽  
E. E. Falco ◽  
...  
Keyword(s):  
Time Delay ◽  
Data Acquisition ◽  
Mass Distribution ◽  
Data Acquisition System ◽  
Gravitational Lens ◽  
Acquisition System ◽  
Vlbi Observations ◽  
Vlbi Data ◽  
Cosmological Constants

We have conducted a series of VLBI observations of the gravitational-lens images of the quasar Q0957+561 (Walsh et al., 1979), utilizing the Mark III VLBI data acquisition system (Rogers et al., 1983). The goals of our observations are to (1) map the milliarcsecond structure of the A and B images, (2) detect the predicted third image of the quasar, and (3) determine the time delay between the images. We will use these results to constrain the mass distribution of the lens and, possibly, cosmological constants.

scholarly journals Multi-Frequency VLBI Observations Of B0218+357

1996 ◽  
Vol 173 ◽  
pp. 311-316
Author(s):  
Richard W. Porcas ◽  
Alok R. Patnaik
Keyword(s):  
Mass Distribution ◽  
Gravitational Lens ◽  
Lens System ◽  
Double Structure ◽  
Vlbi Observations ◽  
The Matrix ◽  
5 Ghz

We present the results from VLBI observations at three frequencies of the gravitational lens system B0218+357. From the source double structure, seen in both the A and B images at 15 GHz, we have derived a relative magnification matrix, and we show that the lens mass distribution must be non-spherical. We investigate how far the matrix parameters derived from 15 GHz observations can be used to relate the A and B images at 1.7 and 5 GHz, where the image sizes are much larger.

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 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 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 The Milliarcsecond Core of 3C147 at 6 cm

1984 ◽  
Vol 110 ◽  
pp. 29-30 ◽  
Author(s):  
E. Preuss ◽  
W. Alef ◽  
N. Whyborn ◽  
P.N. Wilkinson ◽  
K.I. Kellermann
Keyword(s):  
Radio Source ◽  
Radio Sources ◽  
Radio Structure ◽  
Extragalactic Radio Sources ◽  
North East ◽  
The North ◽  
Vlbi Observations ◽  
Spectrum Radio ◽  
The One

3C147 is a compact (≲1″), steep spectrum radio source identified with a quasar at z = 0.545 (0″.001 = 7.4 pc; c/Ho = 6000 Mpc and qo = 0.5). The radio structure shown by VLBI observations at 18 cm (Readhead & Wilkinson, 1980; Simon et al., this volume), at 50 cm (Wilkinson et al., 1977), and at 90 cm (Simon et al., 1980 and 1983) shows a bright ‘core’ (60 pc at one end of a ‘jet’ ~0″.2 (1.5 kpc) in length oriented in p.a. ~ −130°. In this sense 3C147 is typical of the one-sided ‘core-jet’ structures commonly found in the centres of other extragalactic radio sources. However, MERLIN observations at 6 cm (Wilkinson, this vol.) and VLA observations at 2 cm (Crane & Kellermann, unpubl.; Readhead et al., 1980) show a larger elongated feature extending ~0″.5 (3.7 kpc) to the North East of the bright core in p.a. ~25° or on the opposite side to the 0″.2 jet.

scholarly journals VLBI Observations of Gravitational Lens Systems

1988 ◽  
Vol 129 ◽  
pp. 191-199
Author(s):  
Edwin L. Turner
Keyword(s):  
Gravitational Lens ◽  
Lens System ◽  
Additional Test ◽  
System A ◽  
Vlbi Observations ◽  
Vlbi Data ◽  
Cosmological Tests ◽  
Superluminal Expansion ◽  
Additional Constraints

Four specific and particularly powerful types of possible VLBI lens studies are discussed. First, comparison of mas scale structure in putative pairs of images separated by arc seconds can provide a powerful additional test of the lens hypothesis in specific candidate systems. Second, VLBI searches for lens systems with image separations too small for resolution by optical or VLA searches will limit (or even determine!) the cosmological density of condensed objects with individual masses ∼ 106M⊙. Third, study of multiply imaged superluminal expansion events will allow a determination of the light travel time delay between different images in a lens system, a quantity which is quite difficult to measure by other means but which would allow profound cosmological tests. Fourth, VLBI data can be used to determine relative image parities and even the full magnification matrix of various images in a lens system, thus providing powerful additional constraints on detailed lens models. Finally, the speculative possibility of detecting Galactic stellar lensing events using VLBI techniques is discussed.

scholarly journals STRIDES: a 3.9 per cent measurement of the Hubble constant from the strong lens system DES J0408−5354

2020 ◽  
Vol 494 (4) ◽  
pp. 6072-6102 ◽  
Author(s):  
A J Shajib ◽  
S Birrer ◽  
T Treu ◽  
A Agnello ◽  
E J Buckley-Geer ◽  
...  
Keyword(s):  
Time Delay ◽  
Hubble Space Telescope ◽  
Hubble Constant ◽  
Lens System ◽  
Microwave Background ◽  
Angular Diameter Distance ◽  
Measured Time ◽  
Local Distance ◽  
Previous Sample ◽  
The Cost

ABSTRACT We present a blind time-delay cosmographic analysis for the lens system DES J0408−5354. This system is extraordinary for the presence of two sets of multiple images at different redshifts, which provide the opportunity to obtain more information at the cost of increased modelling complexity with respect to previously analysed systems. We perform detailed modelling of the mass distribution for this lens system using three band Hubble Space Telescope imaging. We combine the measured time delays, line-of-sight central velocity dispersion of the deflector, and statistically constrained external convergence with our lens models to estimate two cosmological distances. We measure the ‘effective’ time-delay distance corresponding to the redshifts of the deflector and the lensed quasar $D_{\Delta t}^{\rm eff}=$$3382_{-115}^{+146}$ Mpc and the angular diameter distance to the deflector Dd = $1711_{-280}^{+376}$ Mpc, with covariance between the two distances. From these constraints on the cosmological distances, we infer the Hubble constant H0= $74.2_{-3.0}^{+2.7}$ km s−1 Mpc−1 assuming a flat ΛCDM cosmology and a uniform prior for Ωm as $\Omega _{\rm m} \sim \mathcal {U}(0.05, 0.5)$. This measurement gives the most precise constraint on H0 to date from a single lens. Our measurement is consistent with that obtained from the previous sample of six lenses analysed by the H0 Lenses in COSMOGRAIL’s Wellspring (H0LiCOW) collaboration. It is also consistent with measurements of H0 based on the local distance ladder, reinforcing the tension with the inference from early Universe probes, for example, with 2.2σ discrepancy from the cosmic microwave background measurement.

scholarly journals A VLA/Merlin/VLBA For Intermediate Scale Lenses and the Discovery of a New Lens System?

1996 ◽  
Vol 173 ◽  
pp. 399-400
Author(s):  
P. Augusto ◽  
P.N. Wilkinson ◽  
I.W.A. Browne
Keyword(s):  
Dwarf Galaxies ◽  
Mass Range ◽  
Compact Objects ◽  
Radio Sources ◽  
Early Type ◽  
Lens System ◽  
Spectrum Radio ◽  
Deep Survey ◽  
First Time ◽  
Better Than

We are searching for small lens systems (50-250 mas or 108–109M⊙) in a sample of ∼ 1800 flat spectrum radio sources. This is the first time a systematic search has been made “between” the VLA and VLBI resolutions. Finding any would indicate the existence of other than the “conventional” spiral/elliptical lenses (only ∼ 0.01% chance - Turner et al. (1984)). For example, faint galaxies are numerous (∼ 106 gal/deg2 - Lilly (1993), Glazebrook et al. 1995), compact (HST Medium Deep Survey (MDS) - Griffiths et al. 1994) and ideally placed for lensing (< z >∼ 0.6 - MDS, Smail et al. (1994); c.f. Turner et al. 1984). Early-type dwarf galaxies (dE,N and cE), if extant at intermediate-z as favored by MDS are also obvious lens candidates. If no lenses are found, a limit 400 times better than the current one (Surdej et al. 1993), ΩL < 0.001, will be placed on the cosmological density of compact objects (e.g. black holes) for the above mass range.

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