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.

scholarly journals Blending and obscuration in weak lensing magnification

2021 ◽  
Author(s):  
E Gaztanaga ◽  
S J Schmidt ◽  
M D Schneider ◽  
J A Tyson
Keyword(s):  
Systematic Errors ◽  
Weak Lensing ◽  
Wide Field ◽  
Photometric Redshifts ◽  
Field Surveys ◽  
Systematic Effects ◽  
The Impact ◽  
Close Pairs ◽  
Mass Profiles

Abstract We test the impact of some systematic errors in weak lensing magnification measurements with the COSMOS 30-band photo-z Survey flux limited to Iauto < 25.0 using correlations of both source galaxy counts and magnitudes. Systematic obscuration effects are measured by comparing counts and magnification correlations. We use the ACS-HST catalogs to identify potential blending objects (close pairs) and perform the magnification analyses with and without blended objects. We find that blending effects start to be important (∼ 0.04 mag obscuration) at angular scales smaller than 0.1 arcmin. Extinction and other systematic obscuration effects can be as large as 0.10 mag (U-band) but are typically smaller than 0.02 mag depending on the band. After applying these corrections, we measure a 3.9σ magnification signal that is consistent for both counts and magnitudes. The corresponding projected mass profiles of galaxies at redshift z ≃ 0.6 (MI ≃ −21) is Σ = 25 ± 6M⊙h3/pc2 at 0.1 Mpc/h, consistent with NFW type profile with M200 ≃ 2 × 1012M⊙h/pc2. Tangential shear and flux-size magnification over the same lenses show similar mass profiles. We conclude that magnification from counts and fluxes using photometric redshifts has the potential to provide complementary weak lensing information in future wide field surveys once we carefully take into account systematic effects, such as obscuration and blending.

scholarly journals Out of sight, out of mind? The impact of correlated clustering in substructure lensing

2021 ◽  
Author(s):  
Alexandres Lazar ◽  
James S Bullock ◽  
Michael Boylan-Kolchin ◽  
Robert Feldmann ◽  
Onur Çatmabacak ◽  
...  
Keyword(s):  
Dark Matter ◽  
Principal Axis ◽  
Major Axis ◽  
Line Of Sight ◽  
Gravitational Lenses ◽  
Local Clustering ◽  
Analytic Expression ◽  
Halo Masses ◽  
The Impact

Abstract A promising route for revealing the existence of dark matter structures on mass scales smaller than the faintest galaxies is through their effect on strong gravitational lenses. We examine the role of local, lens-proximate clustering in boosting the lensing probability relative to contributions from substructure and unclustered line-of-sight (LOS) haloes. Using two cosmological simulations that can resolve halo masses of Mhalo ≃ 109 M⊙ (in a simulation box of length Lbox ∼ 100 Mpc) and 107 M⊙ (Lbox ∼ 20 Mpc), we demonstrate that clustering in the vicinity of the lens host produces a clear enhancement relative to an assumption of unclustered haloes that persists to >20 Rvir. This enhancement exceeds estimates that use a two-halo term to account for clustering, particularly within 2 − 5 Rvir. We provide an analytic expression for this excess, clustered contribution. We find that local clustering boosts the expected count of 109 M⊙ perturbing haloes by ${\sim }35{{\ \rm per\ cent}}$ compared to substructure alone, a result that will significantly enhance expected signals for low-redshift (zl ≃ 0.2) lenses, where substructure contributes substantially compared to LOS haloes. We also find that the orientation of the lens with respect to the line of sight (e.g. whether the line of sight passes through the major axis of the lens) can also have a significant effect on the lensing signal, boosting counts by an additional $\sim 50{{\ \rm per\ cent}}$ compared to a random orientations. This could be important if discovered lenses are biased to be oriented along their principal axis.

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 DESIGN DIRECTED ENGINEERING EDUCATION

2011 ◽  
Author(s):  
Ian Yellowley ◽  
Peihua Gu
Keyword(s):  
Engineering Education ◽  
Student Learning ◽  
Communication Skills ◽  
Educational Environment ◽  
Engineering Science ◽  
Engineering Curriculum ◽  
Turn On ◽  
New Material ◽  
Direct Student ◽  
The Impact

The authors examine the changes and opportunities in the educational environment that will occur as packaged courseware and virtual access to laboratories are assimilated into the engineering curriculum worldwide. The impact on Universities and in turn on Canadian industry will be major unless there is a coordinated effort that can turn the challenge into an opportunity. The opportunity, the authors believe, is to use this new material to allow innovative approaches to education that use Design to direct student learning. The major benefits would be a greater appreciation of technology and practice and significantly improved communication skills, (both of which are regarded as essential by industrial employers). The authors believe that the engineering science background would be enhanced rather than weakened by the approach suggested.

scholarly journals Impact of accelerometer based in physical layer wireless networks

2018 ◽  
Vol 7 (2.5) ◽  
pp. 15
Author(s):  
Zuhanis Mansor ◽  
Muhammad Khairulanwar bin Zulkafli
Keyword(s):  
Wireless Communication ◽  
Landscape Position ◽  
Line Of Sight ◽  
Noise Power ◽  
Signal Power ◽  
Propagation Channel ◽  
Signal To Noise ◽  
Downlink Throughput ◽  
The Impact ◽  
Non Line Of Sight

The initial deployments of antenna in the handset consist of fixed non-rotated antenna for transmitting and receiving the signal in the wireless communication scenario. However, link correlation at the UE shows very bad performance when the handset rotates in landscape position. This paper evaluates the impact of accelerometer on the downlink propagation channel of 3G smartphone for non-line-of-sight links. The performance average received signal power is studied for user equipment. Results show that the exploitation of an accelerometer provide better performance in terms of received signal power when the handset rotated from portrait to landscape position. It can be concluded that the deployment of accelerometer can be used to improve existing 3G smartphone received signal. Results also indicate that accelerometer can be used to improve downlink throughput since the signal-to-noise-power is increased by approximately 16%.

scholarly journals Effect of unfavourable population structure on estimates of heritability, systematic effects and breeding values

2008 ◽  
Vol 51 (6) ◽  
pp. 601-610
Author(s):  
A. P. Kominakis
Keyword(s):  
Population Structure ◽  
Mean Squared Error ◽  
Heritability Estimate ◽  
Breeding Values ◽  
Parameter Estimations ◽  
Squared Error ◽  
Heritability Estimation ◽  
Population Structures ◽  
Systematic Effects ◽  
The Impact

Abstract. Empirical estimations of heritability, systematic effects and predictions of sires’ breeding values (BVs) were obtained under various population structures for simulated populations consisted of n = 400 animals in 5 herds for a trait of medium heritability (h2 = 0.30). An infinitesimal additive genetic animal model was assumed while simulating data. Population structure was varied to allow for good and poor connectedness across herds and (non)random association between the genetic and the environmental effects. The impact of the various population structures on the parameter estimation(s) was assessed using Mean Squared Error (MSE) and Pearson’s correlations. Allowing sires to have progenies in more than one herd (good herd connectedness) and random use of sires across herds generally resulted in good parameter estimations. Poor connectedness significantly affected herd effects estimation and BV prediction but not heritability estimation as long as random usage of sires across environments was guaranteed. Selective use of the best sires in the best herds along with poor connectedness resulted in poorest estimations of all parameters examined. In the latter case, heritability was seriously underestimated (h2 = 0.06) while highest error, lowest accuracies for the BVs and a remarkable underestimation of the genetic gain were observed. Use of reference sires on a natural mating basis to create genetic links between herds has served a good solution for both heritability and BVs estimation under unfavorable structure. Mating 0.25 of the herd ewes with reference sires resulted in a heritability estimate close to the simulated one. Significantly better estimates of systematic effects and BVs were, however, obtained when 0.5 of the herd ewes were mated by reference sires.

scholarly journals Spatial Diffusion of Digital Innovations: Trends, Problems and Prospects of Empirical Research

2021 ◽  
Vol 17 (4) ◽  
pp. 118-142
Author(s):  
Viktor Blanutsa ◽  
Keyword(s):  
Empirical Research ◽  
Diffusion Processes ◽  
Search Algorithm ◽  
Moving Average ◽  
Bibliographic Databases ◽  
Annual Number ◽  
Spatial Diffusion ◽  
Significant Discrepancy ◽  
Regional Economic Policy ◽  
The Impact

The aim of the study was to generalize the world experience of studying the spatial diffusion of digital innovations in order to determine trends in changing priorities, existing problems and possible prospects for empirical research. With the help of the author’s semantic search algorithm, approximately eighty journal articles published in the last twenty years were found in eight bibliographic databases. The use of a moving average and biproportional indices for quantitative analysis of the array of articles revealed four upward trends: an increase in the average annual number of publications on the subject under consideration, increased attention to the deployment of broadband communications, the impact of spatial diffusion on economic growth and the use of regions as territorial units for studying diffusion processes. An informal analysis of the articles led to the identification of five key problems of modern research: a significant discrepancy between the year of publication and the last year of the process under study, analysis of a limited number of digital innovations, lack of a comprehensive understanding of the joint spatial diffusion of several innovations, the dominance of the idea of the homogeneity for the initial territorial units and the unexplored system of factors contributing to or hindering the spread of digital innovations. Comparing the existing experience of studying the spatial diffusion of digital innovations with similar studies of other types of innovations allowed identifying five promising areas for further research: the use of big data; expanding the set of models used with the subsequent creation of a system of methods; the study of hierarchical, network and other methods of spatial diffusion; the definition of spatial innovation waves with an explanation of the reasons for the formation of territorial barriers and filters; creation of a theory of the spatiotemporal spread of digital innovations based on the generalization of empirical research. The necessity of determining the scope of application of the results obtained in diffusion studies outside of regional economic policy is noted

scholarly journals Short-term surface ice motion variations measured with a ground-based portable real aperture radar interferometer

2011 ◽  
Vol 57 (201) ◽  
pp. 53-60 ◽  
Author(s):  
Patrick Riesen ◽  
Tazio Strozzi ◽  
Andreas Bauder ◽  
Andreas Wiesmann ◽  
Martin Funk
Keyword(s):  
Line Of Sight ◽  
Interferometric Imaging ◽  
Short Term ◽  
Glacier Surface ◽  
Fast Acquisition ◽  
Surface Ice ◽  
The Impact ◽  
Real Aperture Radar ◽  
Aperture Radar

AbstractWe report measurements using a portable real aperture radar (Gamma Portable Radar Interferometer (GPRI)) for interferometric imaging of the surface ice motion on Gornergletscher, Switzerland, during the drainage of the adjacent ice-marginal lake Gornersee. The GPRI tracked the surface ice motion in line of sight over an area of ∼3 km2 down-glacier of Gornersee almost continuously during the drainage event. The displacement maps derived from the acquired interferograms capture the spatial distribution of the surface ice motion. Due to fast acquisition times of the microwave images, the GPRI was able to record sub-daily variations of the ice displacements, most likely caused by the impact of the Gornersee drainage on the ice motion of Gornergletscher. In situ point measurements of the ice displacement agree reasonably well with the results obtained by the GPRI and highlight the use of the GPRI for high-resolution measurements of glacier surface ice motion.

scholarly journals The Impact of CN Line Profile Measurements on the Cosmic Microwave Background Temperature

1990 ◽  
Vol 139 ◽  
pp. 390-391
Author(s):  
M. E. Kaiser ◽  
E. L. Wright
Keyword(s):  
Cosmic Microwave Background ◽  
Line Profile ◽  
Line Of Sight ◽  
High Signal ◽  
Microwave Background ◽  
A Value ◽  
Cosmic Microwave Background Temperature ◽  
Background Temperature ◽  
The Impact ◽  
Cmb Temperature

We present moderate to high signal-to-noise high-resolution (R ≈ 150,000–170,000) optical spectra toward ζ Oph. Gaussian fits to our data indicate a value of the line-width parameter b, of b = 1.4 ± 0.2 km s−1, along this line of sight. When CN is used as an indirect probe of the cosmic microwave background (CMB) temperature, the line profile is used to determine saturation corrections in the line. This affects column density calculations, which are reflected in the excitation temperature. Current measurements of the b-value along this line of sight range from 0.88 ± 0.02 km s−1 (Crane et al. 1986) to 1.3 ± 0.1 km s−1 (Hegyi, Traub, and Carleton 1972). The extreme range of these b-values yield saturation corrections to the CMB temperature that differ by 0.05 K, which is equal to the quoted precision of current measurements. Preliminary analysis of observations toward HD 29647 indicate that TCMB = 2.70 ± 0.14 K at 2.64 mm toward this line of sight.

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