scholarly journals The double quasar Q2138-431: detection of a lensing galaxy

2021 ◽  
Vol 503 (3) ◽  
pp. 3848-3855
Author(s):  
M R S Hawkins
Keyword(s):  
Time Lag ◽  
Hubble Constant ◽  
Light Curves ◽  
Gravitational Lens ◽  
Apparent Magnitude ◽  
Mass Model ◽  
Faint Galaxy ◽  
Consistent Picture ◽  
The Uk

ABSTRACT This paper reviews the question of whether the wide separation double quasar Q2138-431 is a gravitational lens. From early work, the two quasar images are known to have almost identical spectra and redshifts, but no lensing galaxy has so far been detected. In this paper, we used recent deep surveys in infrared and optical bands to search for the presence of a galaxy with the expected properties of a gravitational lens. The search revealed a 5σ detection of a faint galaxy between the two quasar images on a deep J-band frame from the VISTA Science Archive, with apparent magnitude J = 20.68. Non-detection in the I-band implied a redshift z > 0.6, and mass modelling of the quasar system gave a mass of $1.31 \times 10^{12} \, \mathrm{M}_\odot$ for the lensing galaxy, with mass-to-light ratio M⊙/L⊙ = 9.0. Archival photographic data from the UK 1.2m Schmidt telescope covering 25 yr were used to construct light curves for the two quasar images, which were then cross-correlated to measure any time lag. This showed image B to lead image A by around a year, consistent with 410 d from the mass model. Although the similarity of the spectra and the detection of the lensing galaxy are the most compelling arguments for the classification of Q2138-431 as a gravitational lens, the time delay and mass-to-light ratio provide a consistent picture to support this conclusion. The wide separation of the quasar images and the simplicity of the mass model make Q2138-431 an excellent system for the measurement of the Hubble constant.

scholarly journals A SHARP view of H0LiCOW: H0 from three time-delay gravitational lens systems with adaptive optics imaging

2019 ◽  
Vol 490 (2) ◽  
pp. 1743-1773 ◽  
Author(s):  
Geoff C-F Chen ◽  
Christopher D Fassnacht ◽  
Sherry H Suyu ◽  
Cristian E Rusu ◽  
James H H Chan ◽  
...  
Keyword(s):  
Time Delay ◽  
Adaptive Optics ◽  
Cold Dark Matter ◽  
Hubble Space Telescope ◽  
Hubble Constant ◽  
Companion Paper ◽  
Gravitational Lens ◽  
High Angular Resolution ◽  
Full Time ◽  
Mass Model

ABSTRACT We present the measurement of the Hubble constant, H0, with three strong gravitational lens systems. We describe a blind analysis of both PG 1115+080 and HE 0435−1223 as well as an extension of our previous analysis of RXJ 1131−1231. For each lens, we combine new adaptive optics (AO) imaging from the Keck Telescope, obtained as part of the SHARP (Strong-lensing High Angular Resolution Programme) AO effort, with Hubble Space Telescope (HST) imaging, velocity dispersion measurements, and a description of the line-of-sight mass distribution to build an accurate and precise lens mass model. This mass model is then combined with the COSMOGRAIL-measured time delays in these systems to determine H0. We do both an AO-only and an AO + HST analysis of the systems and find that AO and HST results are consistent. After unblinding, the AO-only analysis gives $H_{0}=82.8^{+9.4}_{-8.3}~\rm km\, s^{-1}\, Mpc^{-1}$ for PG 1115+080, $H_{0}=70.1^{+5.3}_{-4.5}~\rm km\, s^{-1}\, Mpc^{-1}$ for HE 0435−1223, and $H_{0}=77.0^{+4.0}_{-4.6}~\rm km\, s^{-1}\, Mpc^{-1}$ for RXJ 1131−1231. The joint AO-only result for the three lenses is $H_{0}=75.6^{+3.2}_{-3.3}~\rm km\, s^{-1}\, Mpc^{-1}$. The joint result of the AO + HST analysis for the three lenses is $H_{0}=76.8^{+2.6}_{-2.6}~\rm km\, s^{-1}\, Mpc^{-1}$. All of these results assume a flat Λ cold dark matter cosmology with a uniform prior on Ωm in [0.05, 0.5] and H0 in [0, 150] $\rm km\, s^{-1}\, Mpc^{-1}$. This work is a collaboration of the SHARP and H0LiCOW teams, and shows that AO data can be used as the high-resolution imaging component in lens-based measurements of H0. The full time-delay cosmography results from a total of six strongly lensed systems are presented in a companion paper.

scholarly journals Classification of multiwavelength transients with Machine Learning

2020 ◽  
Author(s):  
K Sooknunan ◽  
M Lochner ◽  
Bruce A Bassett ◽  
H V Peiris ◽  
R Fender ◽  
...  
Keyword(s):  
Machine Learning ◽  
Small Sample ◽  
Light Curves ◽  
Machine Learning Techniques ◽  
Optical Data ◽  
Test Time ◽  
Test Accuracy ◽  
Training Set ◽  
The Impact

Abstract With the advent of powerful telescopes such as the Square Kilometer Array and the Vera C. Rubin Observatory, we are entering an era of multiwavelength transient astronomy that will lead to a dramatic increase in data volume. Machine learning techniques are well suited to address this data challenge and rapidly classify newly detected transients. We present a multiwavelength classification algorithm consisting of three steps: (1) interpolation and augmentation of the data using Gaussian processes; (2) feature extraction using wavelets; (3) classification with random forests. Augmentation provides improved performance at test time by balancing the classes and adding diversity into the training set. In the first application of machine learning to the classification of real radio transient data, we apply our technique to the Green Bank Interferometer and other radio light curves. We find we are able to accurately classify most of the eleven classes of radio variables and transients after just eight hours of observations, achieving an overall test accuracy of 78%. We fully investigate the impact of the small sample size of 82 publicly available light curves and use data augmentation techniques to mitigate the effect. We also show that on a significantly larger simulated representative training set that the algorithm achieves an overall accuracy of 97%, illustrating that the method is likely to provide excellent performance on future surveys. Finally, we demonstrate the effectiveness of simultaneous multiwavelength observations by showing how incorporating just one optical data point into the analysis improves the accuracy of the worst performing class by 19%.

scholarly journals Towards a hydrological classification of European soils: preliminary test of its predictive power for the base flow index using river discharge data

2007 ◽  
Vol 11 (4) ◽  
pp. 1501-1513 ◽  
Author(s):  
M. K. Schneider ◽  
F. Brunner ◽  
J. M. Hollis ◽  
C. Stamm
Keyword(s):  
Water Movement ◽  
Base Flow ◽  
Regression Coefficients ◽  
Northern Europe ◽  
Flow Index ◽  
Discharge Data ◽  
Base Flow Index ◽  
The Uk

Abstract. Predicting discharge in ungauged catchments or contaminant movement through soil requires knowledge of the distribution and spatial heterogeneity of hydrological soil properties. Because hydrological soil information is not available at a European scale, we reclassified the Soil Geographical Database of Europe (SGDBE) at 1:1 million in a hydrological manner by adopting the Hydrology Of Soil Types (HOST) system developed in the UK. The HOST classification describes dominant pathways of water movement through soil and was related to the base flow index (BFI) of a catchment (the long-term proportion of base flow on total stream flow). In the original UK study, a linear regression of the coverage of HOST classes in a catchment explained 79% of BFI variability. We found that a hydrological soil classification can be built based on the information present in the SGDBE. The reclassified SGDBE and the regression coefficients from the original UK study were used to predict BFIs for 103 catchments spread throughout Europe. The predicted BFI explained around 65% of the variability in measured BFI in catchments in Northern Europe, but the explained variance decreased from North to South. We therefore estimated new regression coefficients from the European discharge data and found that these were qualitatively similar to the original estimates from the UK. This suggests little variation across Europe in the hydrological effect of particular HOST classes, but decreasing influence of soil on BFI towards Southern Europe. Our preliminary study showed that pedological information is useful for characterising soil hydrology within Europe and the long-term discharge regime of catchments in Northern Europe. Based on these results, we draft a roadmap for a refined hydrological classification of European soils.

scholarly journals Authors' Response to: Alcohol imagery and branding, and age classification of films popular in the UK

2012 ◽  
Vol 41 (3) ◽  
pp. 887-888
Author(s):  
A. Lyons ◽  
A. McNeill ◽  
I. Gilmore ◽  
J. Britton
Keyword(s):  
The Uk

Phenotypic and Genotypic Associations Between Migraine and Lipoprotein Subtractions

Neurology ◽  
2021 ◽  
pp. 10.1212/WNL.0000000000012919
Author(s):  
Yanjun Guo ◽  
Iyas Daghlas ◽  
Padhraig Gormley ◽  
Franco Giulianini ◽  
Paul M Ridker ◽  
...  
Keyword(s):  
Genetic Correlation ◽  
Genetic Relationships ◽  
Meta Analysis ◽  
European Ancestry ◽  
Health Study ◽  
Lipoprotein Subfractions ◽  
Genetic Components ◽  
The Uk ◽  
Summary Data

Background and Objective:To evaluate phenotypic and genetic relationships between migraine and lipoprotein subfractions.Methods:We evaluated phenotypic associations between migraine and 19 lipoprotein subfractions measures in the Women’s Genome Health Study (WGHS, N=22,788). We then investigated genetic relationships between these traits using summary statistics from the International Headache Genetics Consortium (IHGC) for migraine (Ncase=54,552, Ncontrol=297,970) and combined summary data for lipoprotein subfractions (N up to 47,713).Results:There was a significant phenotypic association (odds ratio=1.27 [95% confidence interval:1.12-1.44]) and a significant genetic correlation at 0.18 (P=0.001) between migraine and triglyceride-rich lipoproteins (TRLP) concentration but not for LDL or HDL subfractions. Mendelian randomization (MR) estimates were largely null implying that pleiotropy rather than causality underlies the genetic correlation between migraine and lipoprotein subfractions. Pleiotropy was further supported in cross-trait meta-analysis revealing significant shared signals at four loci (chr2p21 harboring THADA, chr5q13.3 harboring HMGCR, chr6q22.31 harboring HEY2, and chr7q11.23 harboring MLXIPL) between migraine and lipoprotein subfractions. Three of these loci were replicated for migraine (P<0.05) in a smaller sample from the UK Biobank. The shared signal at chr5q13.3 colocalized with expression of HMGCR, ANKDD1B, and COL4A3BP in multiple tissues.Conclusions:The current study supports the association between certain lipoprotein subfractions, especially for TRLP, and migraine in populations of European ancestry. The corresponding shared genetic components may be help identify potential targets for future migraine therapeutics.Classification of Evidence:This study provides Class I evidence that migraine is significantly associated with some lipoprotein subfractions.

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.

‘The NDNAD Has No Ability in Itself to be Discriminatory’: Ethnicity and the Governance of the UK National DNA Database

Sociology ◽  
2013 ◽  
Vol 47 (5) ◽  
pp. 976-992 ◽  
Author(s):  
David Skinner
Keyword(s):  
Black People ◽  
Crime Scene ◽  
Institutional Racism ◽  
Use Of Data ◽  
Dna Database ◽  
The Uk ◽  
Dna Profiles ◽  
Political Governance ◽  
Ethnic Appearance

This article explores the place of ‘ethnicity’ in the operation, management and contestation of the UK National DNA Database (NDNAD). In doing so, it examines the limitations of bioethics as a response to political questions raised by the new genetics. The UK police forensic database has been racialised in a number of distinct ways: in the over-representation of black people in the database population; in the classification of all DNA profiles according to ‘ethnic appearance’; in the use of data for experiments to determine the ethnicity of crime scene DNA; and in the focus on ethnicity in public debate about the database. This racialisation presented potential problems of legitimacy for the NDNAD but, as the article shows, these have been partly neutralised through systems of ethico-political governance. In these systems of governance discussion of institutional racism has been postponed or displaced by other ways of talking about ethnicity and identity.

Methodology for Automated Supervised Classification of Light Curves in the CoRoT Exoplanet Database

2008 ◽  
Author(s):  
J. Debosscher ◽  
L. M. Sarro ◽  
M. López ◽  
C. Aerts ◽  
Coryn A.L. Bailer-Jones
Keyword(s):  
Supervised Classification ◽  
Light Curves

scholarly journals Association of poor sleep burden in middle age and older adults with risk for delirium during hospitalization

2021 ◽  
Author(s):  
Ma Cherrysse Ulsa ◽  
Xi Zheng ◽  
Peng Li ◽  
Arlen Gaba ◽  
Patricia M Wong ◽  
...  
Keyword(s):  
Sleep Disturbances ◽  
Proportional Hazards ◽  
Time Lag ◽  
Cox Proportional Hazards ◽  
Poor Sleep ◽  
Cardiovascular Risks ◽  
Cox Proportional Hazards Models ◽  
Increased Risk ◽  
The Uk

Abstract Background Delirium is a distressing neurocognitive disorder recently linked to sleep disturbances. However, the longitudinal relationship between sleep and delirium remains unclear. This study assessed the associations of poor sleep burden, and its trajectory, with delirium risk during hospitalization. Methods 321,818 participants from the UK Biobank (mean age 58±8y[SD]; range 37-74y) reported (2006-2010) sleep traits (sleep duration, excessive daytime sleepiness, insomnia-type complaints, napping, and chronotype–a closely-related circadian measure for sleep timing), aggregated into a sleep burden score (0-9). New-onset delirium (n=4,775) was obtained from hospitalization records during 12y median follow-up. 42,291 (mean age 64±8; range 44-83y) had repeat sleep assessment on average 8y after their first. Results In the baseline cohort, Cox proportional hazards models showed that moderate (aggregate scores=4-5) and severe (scores=6-9) poor sleep burden groups were 18% (hazard ratio 1.18 [95% confidence interval 1.08-1.28], p&lt;0.001) and 57% (1.57 [1.38-1.80], p&lt;0.001), more likely to develop delirium respectively. The latter risk magnitude is equivalent to two additional cardiovascular risks. These findings appeared robust when restricted to postoperative delirium and after exclusion of underlying dementia. Higher sleep burden was also associated with delirium in the follow-up cohort. Worsening sleep burden (score increase ≥2 vs. no change) further increased the risk for delirium (1.79 [1.23-2.62], p=0.002) independent of their baseline sleep score and time-lag. The risk was highest in those under 65y at baseline (p for interaction &lt;0.001). Conclusion Poor sleep burden and worsening trajectory were associated with increased risk for delirium; promotion of sleep health may be important for those at higher risk.

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