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

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.

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

Astronomy and Astrophysics ◽

10.1051/0004-6361/201732240 ◽

2018 ◽

Vol 617 ◽

pp. A140 ◽

Cited By ~ 11

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.

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

Symposium - International Astronomical Union ◽

10.1017/s0074180900080244 ◽

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).

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VLBI Observations of the 0957+561 Gravitational Lens System

Symposium - International Astronomical Union ◽

10.1017/s0074180900134473 ◽

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.

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Can We Measure H0 with VLBI Observations of Gravitational Images?

Symposium - International Astronomical Union ◽

10.1017/s0074180900134485 ◽

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.

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The presence of interstellar scintillation in the 15 GHz interday variability of 1158 OVRO-monitored blazars

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz2488 ◽

2019 ◽

Vol 489 (4) ◽

pp. 5365-5380 ◽

Cited By ~ 1

Author(s):

J Y Koay ◽

D L Jauncey ◽

T Hovatta ◽

S Kiehlmann ◽

H E Bignall ◽

...

Keyword(s):

Flux Density ◽

High Energy ◽

Short Term ◽

Owens Valley ◽

Hot Stars ◽

Radio Observatory ◽

Interstellar Scintillation ◽

The Galaxy ◽

Rare Class

ABSTRACT We have conducted the first systematic search for interday variability in a large sample of extragalactic radio sources at 15 GHz. From the sample of 1158 radio-selected blazars monitored over an ∼10 yr span by the Owens Valley Radio Observatory 40-m telescope, we identified 20 sources exhibiting significant flux density variations on 4-d time-scales. The sky distribution of the variable sources is strongly dependent on the line-of-sight Galactic H α intensities from the Wisconsin H α Mapper Survey, demonstrating the contribution of interstellar scintillation (ISS) to their interday variability. 21 per cent of sources observed through sightlines with H α intensities larger than 10 rayleighs exhibit significant ISS persistent over the ∼10 yr period. The fraction of scintillators is potentially larger when considering less significant variables missed by our selection criteria, due to ISS intermittency. This study demonstrates that ISS is still important at 15 GHz, particularly through strongly scattered sightlines of the Galaxy. Of the 20 most significant variables, 11 are observed through the Orion–Eridanus superbubble, photoionized by hot stars of the Orion OB1 association. The high-energy neutrino source TXS 0506+056 is observed through this region, so ISS must be considered in any interpretation of its short-term radio variability. J0616−1041 appears to exhibit large ∼20 per cent interday flux density variations, comparable in magnitude to that of the very rare class of extreme, intrahour scintillators that includes PKS0405−385, J1819+3845, and PKS1257−326; this needs to be confirmed by higher cadence follow-up observations.

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Search for Radio Recombination Lines towards the Gravitational Lens PKS1830-211

Symposium - International Astronomical Union ◽

10.1017/s0074180900168676 ◽

2002 ◽

Vol 199 ◽

pp. 116-117

Author(s):

N.R. Mohan ◽

K.R. Anantharamaiah ◽

W.M. Goss

Keyword(s):

Flux Density ◽

Emission Measure ◽

Gravitational Lens ◽

Lens System ◽

Frequency Range ◽

Ionized Gas ◽

Density Measurements ◽

Radio Recombination Lines ◽

Upper Limits ◽

Single Epoch

A search for radio recombination lines near 20 cm at z=0.193 and z=0.886 towards the gravitational lens system PKS1830-211 has yielded upper limits of |τL| ≤ 5 × 10−5 and ≤ 5 × 10−4 at the two redshifts respectively. Based on the non-detections, we derive upper limits to the emission measure of the ionized gas in the absorbing systems. We also present continuum flux density measurements over the frequency range 0.3—45 GHz made at a single epoch.

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

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa828 ◽

2020 ◽

Vol 494 (4) ◽

pp. 6072-6102 ◽

Cited By ~ 27

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.

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Strongly lensed SNe Ia in the era of LSST: observing cadence for lens discoveries and time-delay measurements

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935370 ◽

2019 ◽

Vol 631 ◽

pp. A161 ◽

Cited By ~ 7

Author(s):

S. Huber ◽

S. H. Suyu ◽

U. M. Noebauer ◽

V. Bonvin ◽

D. Rothchild ◽

...

Keyword(s):

Time Delay ◽

Percent Level ◽

Hubble Constant ◽

Sampling Frequency ◽

Season Length ◽

Delay Measurement ◽

Type Ia ◽

Local Distance ◽

Ia Supernovae

The upcoming Large Synoptic Survey Telescope (LSST) will detect many strongly lensed Type Ia supernovae (LSNe Ia) for time-delay cosmography. This will provide an independent and direct way for measuring the Hubble constant H0, which is necessary to address the current 4.4σ tension in H0 between the local distance ladder and the early Universe measurements. We present a detailed analysis of different observing strategies (also referred to as cadence strategy) for the LSST, and quantify their impact on time-delay measurement between multiple images of LSNe Ia. For this, we simulated observations by using mock LSNe Ia for which we produced mock-LSST light curves that account for microlensing. Furthermore, we used the free-knot splines estimator from the software PyCS to measure the time delay from the simulated observations. We find that using only LSST data for time-delay cosmography is not ideal. Instead, we advocate using LSST as a discovery machine for LSNe Ia, enabling time delay measurements from follow-up observations from other instruments in order to increase the number of systems by a factor of 2–16 depending on the observing strategy. Furthermore, we find that LSST observing strategies, which provide a good sampling frequency (the mean inter-night gap is around two days) and high cumulative season length (ten seasons with a season length of around 170 days per season), are favored. Rolling cadences subdivide the survey and focus on different parts in different years; these observing strategies trade the number of seasons for better sampling frequency. In our investigation, this leads to half the number of systems in comparison to the best observing strategy. Therefore rolling cadences are disfavored because the gain from the increased sampling frequency cannot compensate for the shortened cumulative season length. We anticipate that the sample of lensed SNe Ia from our preferred LSST cadence strategies with rapid follow-up observations would yield an independent percent-level constraint on H0.

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