scholarly journals A dedicated source-position transformation package: pySPT

2018 ◽  
Vol 619 ◽  
pp. A117 ◽  
Author(s):  
Olivier Wertz ◽  
Bastian Orthen
Keyword(s):  
Time Delays ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Companion Paper ◽  
Source Position ◽  
Development Platform ◽  
Lens Modeling ◽  
A Minor ◽  
Modeling Code ◽  
The Impact

Modern time-delay cosmography aims to infer the cosmological parameters with a competitive precision from observing a multiply imaged quasar. The success of this technique relies upon a robust modeling of the lens mass distribution. Unfortunately strong degeneracies between density profiles that lead to almost the same lensing observables may bias precise estimates of the Hubble constant. The source position transformation (SPT), which covers the well-known mass-sheet transformation (MST) as a special case, defines a new framework to investigate these degeneracies. In this paper, we present pySPT, a python package dedicated to the SPT. We describe how it can be used to evaluate the impact of the SPT on lensing observables. We review most of its capabilities and elaborate on key features that we used in a companion paper regarding SPT and time delays. The pySPT program also comes with a subpackage dedicated to simple lens modeling. This can be used to generate lensing related quantities for a wide variety of lens models independent of any SPT analysis. As a first practical application, we present a correction to the first estimate of the impact on time delays of the SPT, which has been experimentally found in a previous work between a softened power law and composite (baryons + dark matter) lenses. We find that the large deviations previously predicted have been overestimated because of a minor bug in the public lens modeling code lensmodel (v1.99), which is now fixed. We conclude that the predictions for the Hubble constant deviate by ∼7%, first and foremost as a consequence of an MST. The latest version of pySPT is available on Github, a software development platform, along with some tutorials to describe in detail how making the best use of pySPT.

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 TDCOSMO

2020 ◽  
Vol 642 ◽  
pp. A194 ◽  
Author(s):  
D. Gilman ◽  
S. Birrer ◽  
T. Treu
Keyword(s):  
Dark Matter ◽  
Time Delay ◽  
Time Delays ◽  
Arrival Time ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Line Of Sight ◽  
Gravitational Lenses ◽  
Additional Source ◽  
Precision Limit

Time delay cosmography uses the arrival time delays between images in strong gravitational lenses to measure cosmological parameters, in particular the Hubble constant H0. The lens models used in time delay cosmography omit dark matter subhalos and line-of-sight halos because their effects are assumed to be negligible. We explicitly quantify this assumption by analyzing mock lens systems that include full populations of dark matter subhalos and line-of-sight halos, applying the same modeling assumptions used in the literature to infer H0. We base the mock lenses on six quadruply imaged quasars that have delivered measurements of the Hubble constant, and quantify the additional uncertainties and/or bias on a lens-by-lens basis. We show that omitting dark substructure does not bias inferences of H0. However, perturbations from substructure contribute an additional source of random uncertainty in the inferred value of H0 that scales as the square root of the lensing volume divided by the longest time delay. This additional source of uncertainty, for which we provide a fitting function, ranges from 0.7 − 2.4%. It may need to be incorporated in the error budget as the precision of cosmographic inferences from single lenses improves, and it sets a precision limit on inferences from single lenses.

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 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 Astrometric requirements for strong lensing time-delay cosmography

2019 ◽  
Vol 489 (2) ◽  
pp. 2097-2103 ◽  
Author(s):  
Simon Birrer ◽  
Tommaso Treu
Keyword(s):  
Time Delay ◽  
Time Delays ◽  
Cosmological Parameters ◽  
Hubble Constant ◽  
Direct Estimate ◽  
Strong Lensing ◽  
Image Separation ◽  
Modelling Techniques ◽  
Precision Time ◽  
Image Position

ABSTRACT The time-delay between the arrival of photons of multiple images of time-variable sources can be used to constrain absolute distances in the Universe, and in turn obtain a direct estimate of the Hubble constant and other cosmological parameters. To convert the time-delay into distances, it is well known that the gravitational potential of the main deflector and the contribution of the matter along the line of sight need to be known to a sufficient level of precision. In this paper, we discuss a new astrometric requirement that is becoming important, as time-delay cosmography improves in precision and accuracy with larger samples, and better data and modelling techniques. We derive an analytic expression for the propagation of astrometric uncertainties on the multiple image positions into the inference of the Hubble constant and derive requirements depending on image separation and relative time-delay. We note that this requirement applies equally to the image position measurements and to the accuracy of the model in reproducing them. To illustrate the requirement, we discuss some example lensing configurations and highlight that, especially for time-delays of order 10 d or shorter, the relative astrometric requirement is of order milliarcseconds, setting a tight requirement on both measurements and models. With current optical infrared technology, astrometric uncertainties may be the dominant limitation for strong lensing cosmography in the small image-separation regime when high-precision time-delays become accessible.

scholarly journals The Impact of Metabolic Scion–Rootstock Interactions in Different Grapevine Tissues and Phloem Exudates

Metabolites ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 349
Author(s):  
Sara Tedesco ◽  
Alexander Erban ◽  
Saurabh Gupta ◽  
Joachim Kopka ◽  
Pedro Fevereiro ◽  
...  
Keyword(s):  
Agronomic Traits ◽  
Phloem Exudate ◽  
Graft Union ◽  
Reciprocal Effect ◽  
Metabolic Markers ◽  
Interaction Studies ◽  
Metabolic Interactions ◽  
A Minor ◽  
The Impact ◽  
Related Compounds

In viticulture, grafting is used to propagate Phylloxera-susceptible European grapevines, thereby using resistant American rootstocks. Although scion–rootstock reciprocal signaling is essential for the formation of a proper vascular union and for coordinated growth, our knowledge of graft partner interactions is very limited. In order to elucidate the scale and the content of scion–rootstock metabolic interactions, we profiled the metabolome of eleven graft combination in leaves, stems, and phloem exudate from both above and below the graft union 5–6 months after grafting. We compared the metabolome of scions vs. rootstocks of homografts vs. heterografts and investigated the reciprocal effect of the rootstock on the scion metabolome. This approach revealed that (1) grafting has a minor impact on the metabolome of grafted grapevines when tissues and genotypes were compared, (2) heterografting affects rootstocks more than scions, (3) the presence of a heterologous grafting partner increases defense-related compounds in both scion and rootstocks in shorter and longer distances from the graft, and (4) leaves were revealed as the best tissue to search for grafting-related metabolic markers. These results will provide a valuable metabolomics resource for scion–rootstock interaction studies and will facilitate future efforts on the identification of metabolic markers for important agronomic traits in grafted grapevines.

scholarly journals Optimality of index policies for stochastic scheduling with switching penalties

1992 ◽  
Vol 29 (04) ◽  
pp. 957-966 ◽  
Author(s):  
Mark P. Van Oyen ◽  
Dimitrios G. Pandelis ◽  
Demosthenis Teneketzis
Keyword(s):  
Optimal Policy ◽  
Time Delays ◽  
Stochastic Scheduling ◽  
Optimal Scheduling ◽  
Scheduling Policies ◽  
Parallel Queues ◽  
Lump Sum ◽  
Index Policies ◽  
Service Policy ◽  
The Impact

We investigate the impact of switching penalties on the nature of optimal scheduling policies for systems of parallel queues without arrivals. We study two types of switching penalties incurred when switching between queues: lump sum costs and time delays. Under the assumption that the service periods of jobs in a given queue possess the same distribution, we derive an index rule that defines an optimal policy. For switching penalties that depend on the particular nodes involved in a switch, we show that although an index rule is not optimal in general, there is an exhaustive service policy that is optimal.

scholarly journals The impact of line-of-sight structures on measuring H0 with strong lensing time delays

2021 ◽  
Vol 504 (2) ◽  
pp. 2224-2234
Author(s):  
Nan Li ◽  
Christoph Becker ◽  
Simon Dye
Keyword(s):  
Time Delays ◽  
Line Of Sight ◽  
Lens Model ◽  
Local Universe ◽  
Significant Discrepancy ◽  
Turn On ◽  
Strong Lensing ◽  
Systematic Effects ◽  
The Impact ◽  
Realistic Line

ABSTRACT Measurements of the Hubble–Lemaitre constant from early- and local-Universe observations show a significant discrepancy. In an attempt to understand the origin of this mismatch, independent techniques to measure H0 are required. One such technique, strong lensing time delays, is set to become a leading contender amongst the myriad methods due to forthcoming large strong lens samples. It is therefore critical to understand the systematic effects inherent in this method. In this paper, we quantify the influence of additional structures along the line of sight by adopting realistic light-cones derived from the cosmoDC2 semi-analytical extragalactic catalogue. Using multiple-lens plane ray tracing to create a set of simulated strong lensing systems, we have investigated the impact of line-of-sight structures on time-delay measurements and in turn, on the inferred value of H0. We have also tested the reliability of existing procedures for correcting for line-of-sight effects. We find that if the integrated contribution of the line-of-sight structures is close to a uniform mass sheet, the bias in H0 can be adequately corrected by including a constant external convergence κext in the lens model. However, for realistic line-of-sight structures comprising many galaxies at different redshifts, this simple correction overestimates the bias by an amount that depends linearly on the median external convergence. We therefore conclude that lens modelling must incorporate multiple-lens planes to account for line-of-sight structures for accurate and precise inference of H0.

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