scholarly journals MIFAL: fully automated Multiple-Image Finder ALgorithm for strong-lens modelling – proof of concept

2019 ◽  
Vol 491 (3) ◽  
pp. 3778-3792 ◽  
Author(s):  
Mauricio Carrasco ◽  
Adi Zitrin ◽  
Gregor Seidel
Keyword(s):  
Simple Procedure ◽  
Lens Model ◽  
Proof Of Concept ◽  
Photometric Redshifts ◽  
Multiple Images ◽  
Mass Distributions ◽  
Photometric Redshift ◽  
Multiple Image ◽  
Strong Lensing ◽  
Blind Manner

ABSTRACT We outline a simple procedure designed for automatically finding sets of multiple images in strong lensing (SL) clusters. We show that by combining (a) an arc-finding (or source extracting) program, (b) photometric redshift measurements, and (c) a preliminary light-traces-mass lens model, multiple-image systems can be identified in a fully automated (‘blind’) manner. The presented procedure yields an assessment of the likelihood of each arc to belong to one of the multiple-image systems, as well as the preferred redshift for the different systems. These could be then used to automatically constrain and refine the initial lens model for an accurate mass distribution. We apply this procedure to Cluster Lensing And Supernova with Hubble observations of three galaxy clusters, MACS J0329.6-0211, MACS J1720.2 + 3536, and MACS J1931.8-2635, comparing the results to published SL analyses where multiple images were verified by eye on a particular basis. In the first cluster all originally identified systems are recovered by the automated procedure, and in the second and third clusters about half are recovered. Other known systems are not picked up, in part due to a crude choice of parameters, ambiguous photometric redshifts, or inaccuracy of the initial lens model. On top of real systems recovered, some false images are also mistakenly identified by the procedure, depending on the thresholds used. While further improvements to the procedure and a more thorough scrutinization of its performance are warranted, the work constitutes another important step toward fully automatizing SL analyses for studying mass distributions of large cluster samples.

scholarly journals Revisiting Abell 2744: a powerful synergy of GLASS spectroscopy and HFF photometry

2015 ◽  
Vol 11 (A29B) ◽  
pp. 776-778
Author(s):  
Xin Wang ◽  
Keyword(s):  
Mass Distribution ◽  
Galaxy Cluster ◽  
Adaptive Mesh ◽  
Field Of View ◽  
Relative Distribution ◽  
Lens Model ◽  
Photometric Redshifts ◽  
Screening Process ◽  
Photometric Redshift ◽  
Extensive Analysis

AbstractWe present new emission line identifications and improve the lensing reconstruction of the mass distribution of galaxy cluster Abell 2744 using the Grism Lens-Amplified Survey from Space (GLASS) spectroscopy and the Hubble Frontier Fields (HFF) imaging. We performed blind and targeted searches for faint line emitters on all objects, including the arc sample, within the field of view (FoV) of GLASS prime pointings. We report 55 high quality spectroscopic redshifts, 5 of which are for arc images. We also present an extensive analysis based on the HFF photometry, measuring the colors and photometric redshifts of all objects within the FoV, and comparing the spectroscopic and photometric redshift estimates. In order to improve the lens model of Abell 2744, we develop a rigorous algorithm to screen arc images, based on their colors and morphology, and selecting the most reliable ones to use. As a result, 25 systems (corresponding to 72 images) pass the screening process and are used to reconstruct the gravitational potential of the cluster pixellated on an adaptive mesh. The resulting total mass distribution is compared with a stellar mass map obtained from the Spitzer Frontier Fields data in order to study the relative distribution of stars and dark matter in the cluster.

scholarly journals Close galaxy pairs with accurate photometric redshifts

2020 ◽  
Vol 634 ◽  
pp. A123 ◽  
Author(s):  
Facundo Rodriguez ◽  
Elizabeth Johana Gonzalez ◽  
Ana Laura O’Mill ◽  
Enrique Gaztañaga ◽  
Pablo Fosalba ◽  
...  
Keyword(s):  
Test Sample ◽  
Dark Matter Halo ◽  
Accelerating Universe ◽  
Identification Algorithm ◽  
Photometric Redshifts ◽  
Galaxy Groups ◽  
Mass Distributions ◽  
Photometric Redshift ◽  
Formation And Evolution ◽  
Isolated Systems

Context. Studies of galaxy pairs can provide valuable information to jointly understand the formation and evolution of galaxies and galaxy groups. Consequently, taking the new high-precision photo-z surveys into account, it is important to have reliable and tested methods that allow us to properly identify these systems and estimate their total masses and other properties. Aims. In view of the forthcoming Physics of the Accelerating Universe Survey (PAUS), we propose and evaluate the performance of an identification algorithm of projected close isolated galaxy pairs. We expect that the photometrically selected systems can adequately reproduce the observational properties and the inferred lensing mass–luminosity relation of a pair of truly bound galaxies that are hosted by the same dark matter halo. Methods. We developed an identification algorithm that considers the projected distance between the galaxies, the projected velocity difference, and an isolation criterion in order to restrict the sample to isolated systems. We applied our identification algorithm using a mock galaxy catalog that mimics the features of PAUS. To evaluate the feasibility of our pair finder, we compared the identified photometric samples with a test sample that considers that both members are included in the same halo. Taking advantage of the lensing properties provided by the mock catalog, we also applied a weak-lensing analysis to determine the mass of the selected systems. Results. Photometrically selected samples tend to show high purity values, but tend to misidentify truly bounded pairs as the photometric redshift errors increase. Nevertheless, overall properties such as the luminosity and mass distributions are successfully reproduced. We also accurately reproduce the lensing mass–luminosity relation as expected for galaxy pairs located in the same halo.

scholarly journals Strong lensing models of eight CLASH clusters from extensive spectroscopy: Accurate total mass reconstructions in the cores

2019 ◽  
Vol 632 ◽  
pp. A36 ◽  
Author(s):  
G. B. Caminha ◽  
P. Rosati ◽  
C. Grillo ◽  
G. Rosani ◽  
K. I. Caputi ◽  
...  
Keyword(s):  
Total Mass ◽  
High Efficiency ◽  
Mass Density ◽  
Mean Value ◽  
Parametric Models ◽  
Large Field ◽  
Redshift Range ◽  
Multiple Images ◽  
Mass Distributions ◽  
Strong Lensing

We carried out a detailed strong lensing analysis of a sub-sample of eight galaxy clusters of the Cluster Lensing And Supernova survey with Hubble (CLASH) in the redshift range of zcluster = [0.23 − 0.59] using extensive spectroscopic information, primarily from the Multi Unit Spectroscopic Explorer (MUSE) archival data and complemented with CLASH-VLT redshift measurements. The observed positions of the multiple images of strongly lensed background sources were used to constrain parametric models describing the cluster total mass distributions. Different models were tested in each cluster depending on the complexity of its mass distribution and on the number of detected multiple images. Four clusters show more than five spectroscopically confirmed multiple image families. In this sample, we did not make use of families that are only photometrically identified in order to reduce model degeneracies between the values of the total mass of a cluster source redshifts, in addition to systematics due to the potential misidentifications of multiple images. For the remaining four clusters, we used additional families without any spectroscopic confirmation to increase the number of strong lensing constraints up to the number of free parameters in our parametric models. We present spectroscopic confirmation of 27 multiply lensed sources, with no previous spectroscopic measurements, spanning over the redshift range of zsrc = [0.7 − 6.1]. Moreover, we confirm an average of 48 galaxy members in the core of each cluster thanks to the high efficiency and large field of view of MUSE. We used this information to derive precise strong lensing models, projected total mass distributions, and magnification maps. We show that, despite having different properties (i.e. number of mass components, total mass, redshift, etc.), the projected total mass and mass density profiles of all clusters have very similar shapes when rescaled by independent measurements of M200c and R200c. Specifically, we measured the mean value of the projected total mass of our cluster sample within 10 (20)% of R200c to be 0.13 (0.32) of M200c, with a remarkably small scatter of 5 (6)%. Furthermore, the large number of high-z sources and the precise magnification maps derived in this work for four clusters add up to the sample of high-quality gravitational telescopes to be used to study the faint and distant Universe.

scholarly journals Model-independent and model-based local lensing properties of CL0024+1654 from multiply imaged galaxies

2018 ◽  
Vol 612 ◽  
pp. A17 ◽  
Author(s):  
Jenny Wagner ◽  
Jori Liesenborgs ◽  
Nicolas Tessore
Keyword(s):  
Gravitational Lensing ◽  
Cosmological Parameters ◽  
Linear Mapping ◽  
Small Scale ◽  
Parametric Modelling ◽  
Lens Model ◽  
Confidence Bounds ◽  
Multiple Images ◽  
Multiple Image ◽  
Model Independent

Context. Local gravitational lensing properties, such as convergence and shear, determined at the positions of multiply imaged background objects, yield valuable information on the smaller-scale lensing matter distribution in the central part of galaxy clusters. Highly distorted multiple images with resolved brightness features like the ones observed in CL0024 allow us to study these local lensing properties and to tighten the constraints on the properties of dark matter on sub-cluster scale. Aim. We investigate to what precision local magnification ratios, $\mathcal{J}$, ratios of convergences, f, and reduced shears, g = (g1, g2), can be determined independently of a lens model for the five resolved multiple images of the source at zs = 1.675 in CL0024. We also determine if a comparison to the respective results obtained by the parametric modelling tool Lenstool and by the non-parametric modelling tool Grale can detect biases in the models. For these lens models, we analyse the influence of the number and location of the constraints from multiple images on the lens properties at the positions of the five multiple images of the source at zs = 1.675. Methods. Our model-independent approach uses a linear mapping between the five resolved multiple images to determine the magnification ratios, ratios of convergences, and reduced shears at their positions. With constraints from up to six multiple image systems, we generate Lenstool and Grale models using the same image positions, cosmological parameters, and number of generated convergence and shear maps to determine the local values of $\mathcal{J}$, f, and g at the same positions across all methods. Results. All approaches show strong agreement on the local values of $\mathcal{J}$, f, and g. We find that Lenstool obtains the tightest confidence bounds even for convergences around one using constraints from six multiple-image systems, while the best Grale model is generated only using constraints from all multiple images with resolved brightness features and adding limited small-scale mass corrections. Yet, confidence bounds as large as the values themselves can occur for convergences close to one in all approaches. Conclusions. Our results agree with previous findings, support the light-traces-mass assumption, and the merger hypothesis for CL0024. Comparing the different approaches can detect model biases. The model-independent approach determines the local lens properties to a comparable precision in less than one second.

scholarly journals Strong Lensing Cosmography in the Frontier Fields

2015 ◽  
Vol 11 (A29B) ◽  
pp. 801-803
Author(s):  
Eric Jullo ◽  
Ana Acebron ◽  
Marceau Limousin ◽  
Carlo Giocoli ◽  
Giulia Despali ◽  
...  
Keyword(s):  
Dark Energy ◽  
Cosmological Parameters ◽  
Simulated Data ◽  
Systematic Errors ◽  
Matter Density ◽  
Model Parameters ◽  
Lens Model ◽  
Multiple Images ◽  
Strong Lensing ◽  
Energy Equations

AbstractThe wealth of strong lensing features observed in the Frontier Fields clusters offers insights on the nature of dark energy. The large number of multiple-images systems with redshifts allows to simultaneously estimate the lens model parameters and the cosmological parameters involved in the distances calculations. In particular for the ΛCDM model, it is possible to estimate the matter density Ωm and the dark energy equations parameters wX. In this talk, I will present recent analyses of systematic errors based on Frontier Fields observed and simulated data.

scholarly journals Hierarchical Matching and Regression with Application to Photometric Redshift Estimation

2016 ◽  
Vol 12 (S325) ◽  
pp. 145-155
Author(s):  
Fionn Murtagh
Keyword(s):  
Information Structure ◽  
Data Analytics ◽  
A Priori ◽  
Sloan Digital Sky Survey ◽  
Photometric Redshifts ◽  
Merging Galaxies ◽  
Photometric Redshift ◽  
Sky Survey ◽  
Wide Range ◽  
Regression Problems

AbstractThis work emphasizes that heterogeneity, diversity, discontinuity, and discreteness in data is to be exploited in classification and regression problems. A global a priori model may not be desirable. For data analytics in cosmology, this is motivated by the variety of cosmological objects such as elliptical, spiral, active, and merging galaxies at a wide range of redshifts. Our aim is matching and similarity-based analytics that takes account of discrete relationships in the data. The information structure of the data is represented by a hierarchy or tree where the branch structure, rather than just the proximity, is important. The representation is related to p-adic number theory. The clustering or binning of the data values, related to the precision of the measurements, has a central role in this methodology. If used for regression, our approach is a method of cluster-wise regression, generalizing nearest neighbour regression. Both to exemplify this analytics approach, and to demonstrate computational benefits, we address the well-known photometric redshift or ‘photo-z’ problem, seeking to match Sloan Digital Sky Survey (SDSS) spectroscopic and photometric redshifts.

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 Encryption Algorithm of Multiple-Image Using Mixed Image Elements and Two Dimensional Chaotic Economic Map

Entropy ◽  
2018 ◽  
Vol 20 (10) ◽  
pp. 801 ◽  
Author(s):  
A. Karawia
Keyword(s):  
Logistic Map ◽  
Experimental Results ◽  
Encryption Algorithm ◽  
Current Work ◽  
Two Dimensional ◽  
Huge Number ◽  
Multiple Images ◽  
Encrypted Image ◽  
Multiple Image

To enhance the encryption proficiency and encourage the protected transmission of multiple images, the current work introduces an encryption algorithm for multiple images using the combination of mixed image elements (MIES) and a two-dimensional economic map. Firstly, the original images are grouped into one big image that is split into many pure image elements (PIES); secondly, the logistic map is used to shuffle the PIES; thirdly, it is confused with the sequence produced by the two-dimensional economic map to get MIES; finally, the MIES are gathered into a big encrypted image that is split into many images of the same size as the original images. The proposed algorithm includes a huge number key size space, and this makes the algorithm secure against hackers. Even more, the encryption results obtained by the proposed algorithm outperform existing algorithms in the literature. A comparison between the proposed algorithm and similar algorithms is made. The analysis of the experimental results and the proposed algorithm shows that the proposed algorithm is efficient and secure.

Fractal-Based Secured Multiple-Image Compression and Distribution

2011 ◽  
pp. 515-532
Author(s):  
Hsuan T. Chang ◽  
Chih-Chung Hsu
Keyword(s):  
Image Compression ◽  
Image Similarity ◽  
Multiple Images ◽  
Image Distribution ◽  
Coding Scheme ◽  
Multiple Image ◽  
Image Compression And Encryption ◽  
Novel Design

This chapter introduces a pioneer concept in which multiple images are simultaneously considered in the compression and secured distribution frameworks. We have proposed the so-called fractal mating coding scheme to successfully implement the joint image compression and encryption concept through a novel design in the domain pool construction. With the exploration of the intra- and inter-image similarity among multiple images, not only the coding performance can be improved, but also the secured image distribution purpose can be achieved. The authors hope that the revealed fractal-based ideas in this chapter will provide a different perspective for the image compression and distribution framework.

scholarly journals Template-Assisted Electrochemical Synthesis of CdSe Quantum Dots—Polypyrrole Composite Nanorods

2020 ◽  
Vol 10 (17) ◽  
pp. 5966
Author(s):  
Won-Seok Kang ◽  
Taegon Oh ◽  
Gwang-Hyeon Nam ◽  
Hyo-Sop Kim ◽  
Ki-Suk Kim ◽  
...  
Keyword(s):  
Simple Procedure ◽  
Hybrid Structure ◽  
Proof Of Concept ◽  
Interface Area ◽  
Anodic Aluminum ◽  
Enhanced Photoluminescence ◽  
Polypyrrole Composite ◽  
High Level ◽  
Oxide Membranes ◽  
Composite Nanorods

Luminescent nanoparticles have reached a high level of maturity in materials and spectral tunability for optics and optoelectronics. However, the lack of facile methodology for heterojunction formation of the nanoparticles provides many challenges for scalability. In this paper we demonstrate a simple procedure to synthesize a nanoparticle-embedded polymer nanorod hybrid structure via a template-based electrochemical method using anodic aluminum oxide membranes. This method enables the formation of interactive nanostructures wherein the interface area between the two components is maximized. As a proof of concept, semiconducting CdSe nanoparticles were embedded in polypyrrole nanorods with dimensions that can be finely tuned. We observed enhanced photoluminescence of the hybrid structures compared with bare polypyrrole nanorods.

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