scholarly journals When Darwin Met Einstein: Gravitational Lens Inversion with Genetic Algorithms

2005 ◽  
Vol 22 (2) ◽  
pp. 128-135 ◽  
Author(s):  
Brendon J. Brewer ◽  
Geraint F. Lewis
Keyword(s):  
Genetic Algorithms ◽  
Gravitational Lensing ◽  
Surface Brightness ◽  
Initial Study ◽  
Brightness Distribution ◽  
Gravitational Lens ◽  
Atmospheric Effects ◽  
Lens Model ◽  
New Approach ◽  
Genetic Algorithm Approach

AbstractGravitational lensing can magnify a distant source, revealing structural detail which is normally unresolvable. Recovering this detail through an inversion of the influence of gravitational lensing, however, requires optimisation of not only lens parameters, but also of the surface brightness distribution of the source. This paper outlines a new approach to this inversion, utilising genetic algorithms to reconstruct the source profile. In this initial study, the effects of image degradation due to instrumental and atmospheric effects are neglected and it is assumed that the lens model is accurately known, but the genetic algorithm approach can be incorporated into more general optimisation techniques, allowing the optimisation of both the parameters for a lensing model and the surface brightness of the source.

scholarly journals Systematic errors in strong gravitational lensing reconstructions, a numerical simulation perspective

2020 ◽  
Vol 496 (2) ◽  
pp. 1718-1729 ◽  
Author(s):  
Wolfgang Enzi ◽  
Simona Vegetti ◽  
Giulia Despali ◽  
Jen-Wei Hsueh ◽  
R Benton Metcalf
Keyword(s):  
Gravitational Lensing ◽  
Time Delays ◽  
Surface Brightness ◽  
Mass Density ◽  
Control Sample ◽  
Brightness Distribution ◽  
Gravitational Lens ◽  
Galactic Potentials ◽  
Fractional Error ◽  
Approximate Bayesian

ABSTRACT We present the analysis of a sample of 24 SLACS-like galaxy–galaxy strong gravitational lens systems with a background source and deflectors from the Illustris-1 simulation. We study the degeneracy between the complex mass distribution of the lenses, substructures, the surface brightness distribution of the sources, and the time delays. Using a novel inference framework based on Approximate Bayesian Computation, we find that for all the considered lens systems, an elliptical and cored power-law mass density distribution provides a good fit to the data. However, the presence of cores in the simulated lenses affects most reconstructions in the form of a Source Position Transformation. The latter leads to a systematic underestimation of the source sizes by 50 per cent on average, and a fractional error in H0 of around $25_{-19}^{+37}$ per cent. The analysis of a control sample of 24 lens systems, for which we have perfect knowledge about the shape of the lensing potential, leads to a fractional error on H0 of $12_{-3}^{+6}$ per cent. We find no degeneracy between complexity in the lensing potential and the inferred amount of substructures. We recover an average total projected mass fraction in substructures of fsub < 1.7–2.0 × 10−3 at the 68 per cent confidence level in agreement with zero and the fact that all substructures had been removed from the simulation. Our work highlights the need for higher resolution simulations to quantify the lensing effect of more realistic galactic potentials better, and that additional observational constraint may be required to break existing degeneracies.

The CLASS Gravitational Lens Search

2005 ◽  
Vol 201 ◽  
pp. 443-444
Author(s):  
I. W. A. Browne ◽  
S. T. Myers
Keyword(s):  
High Resolution ◽  
Gravitational Lensing ◽  
Surface Brightness ◽  
Gravitational Lens ◽  
Radio Sources ◽  
Complete Sample ◽  
Spectrum Radio ◽  
Sky Survey ◽  
Morphological Criteria ◽  
Density Ratios

To exploit gravitational lensing for cosmology large, reliable and statistically complete surveys are required. With the Cosmic Lens All-Sky Survey (CLASS) we have set out to achieve these goals. We pre-select targets to be flat spectrum radio sources and map every source with the VLA at 200mas resolution. Candidates having multiple compact components with flux density ratios ≤10:1 and separation in the range 0.3 to 15 arcsec are followed up with high resolution MERLIN and VLBA observations, eliminating those candidates which do not match strictly defined surface brightness and morphological criteria. A complete sample of 11685 sources have been surveyed and nineteen lens systems have been found.

scholarly journals Gravitational lensing by exotic objects

2017 ◽  
Vol 32 (34) ◽  
pp. 1730031 ◽  
Author(s):  
Hideki Asada
Keyword(s):  
Time Delay ◽  
Equation Of State ◽  
Gravitational Lensing ◽  
Modified Gravity ◽  
Standard Form ◽  
Phenomenological Approach ◽  
Gravity Theory ◽  
Gravitational Lens ◽  
Lens Model ◽  
Modified Gravity Theory

This paper reviews a phenomenological approach to the gravitational lensing by exotic objects such as the Ellis wormhole lens, where the exotic lens objects may follow a non-standard form of the equation of state or may obey a modified gravity theory. A gravitational lens model is proposed in the inverse powers of the distance, such that the Schwarzschild lens and exotic lenses can be described in a unified manner as a one parameter family. As observational implications, the magnification, shear, photo-centroid motion and time delay in this lens model are discussed.

New approach to constrained shape optimization using genetic algorithms

AIAA Journal ◽  
1998 ◽  
Vol 36 ◽  
pp. 51-61 ◽  
Author(s):  
M. C. Sharatchandra ◽  
Mihir Sen ◽  
Mohamed Gad-el-Hak
Keyword(s):  
Genetic Algorithms ◽  
Shape Optimization ◽  
New Approach

scholarly journals Quantifying the structure of strong gravitational lens potentials with uncertainty-aware deep neural networks

2020 ◽  
Vol 499 (4) ◽  
pp. 5641-5652
Author(s):  
Georgios Vernardos ◽  
Grigorios Tsagkatakis ◽  
Yannis Pantazis
Keyword(s):  
Confidence Intervals ◽  
Galaxy Evolution ◽  
Gravitational Lensing ◽  
Probability Distributions ◽  
Mass Density ◽  
Ground Truth ◽  
Gaussian Random Fields ◽  
Training Data ◽  
Gravitational Lens ◽  
Data Set

ABSTRACT Gravitational lensing is a powerful tool for constraining substructure in the mass distribution of galaxies, be it from the presence of dark matter sub-haloes or due to physical mechanisms affecting the baryons throughout galaxy evolution. Such substructure is hard to model and is either ignored by traditional, smooth modelling, approaches, or treated as well-localized massive perturbers. In this work, we propose a deep learning approach to quantify the statistical properties of such perturbations directly from images, where only the extended lensed source features within a mask are considered, without the need of any lens modelling. Our training data consist of mock lensed images assuming perturbing Gaussian Random Fields permeating the smooth overall lens potential, and, for the first time, using images of real galaxies as the lensed source. We employ a novel deep neural network that can handle arbitrary uncertainty intervals associated with the training data set labels as input, provides probability distributions as output, and adopts a composite loss function. The method succeeds not only in accurately estimating the actual parameter values, but also reduces the predicted confidence intervals by 10 per cent in an unsupervised manner, i.e. without having access to the actual ground truth values. Our results are invariant to the inherent degeneracy between mass perturbations in the lens and complex brightness profiles for the source. Hence, we can quantitatively and robustly quantify the smoothness of the mass density of thousands of lenses, including confidence intervals, and provide a consistent ranking for follow-up science.

Genetic Algorithms: A New Approach to the Timetable Problem

1992 ◽  
pp. 235-239 ◽  
Author(s):  
Alberto Colorni ◽  
Marco Dorigo ◽  
Vittorio Maniezzo
Keyword(s):  
Genetic Algorithms ◽  
New Approach ◽  
Timetable Problem

scholarly journals Inner dark matter distribution of the Cosmic Horseshoe (J1148+1930) with gravitational lensing and dynamics

2019 ◽  
Vol 631 ◽  
pp. A40 ◽  
Author(s):  
S. Schuldt ◽  
G. Chirivì ◽  
S. H. Suyu ◽  
A. Yıldırım ◽  
A. Sonnenfeld ◽  
...  
Keyword(s):  
Dark Matter ◽  
Gravitational Lensing ◽  
Gravitational Lens ◽  
Wide Field ◽  
Lens System ◽  
Matter Distribution ◽  
Mass Model ◽  
Luminous Matter ◽  
Dark Matter Distribution ◽  
Light Components

We present a detailed analysis of the inner mass structure of the Cosmic Horseshoe (J1148+1930) strong gravitational lens system observed with the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3). In addition to the spectacular Einstein ring, this systems shows a radial arc. We obtained the redshift of the radial arc counterimage zs, r = 1.961 ± 0.001 from Gemini observations. To disentangle the dark and luminous matter, we considered three different profiles for the dark matter (DM) distribution: a power law profile, the Navarro, Frenk, and White (NFW) profile, and a generalized version of the NFW profile. For the luminous matter distribution, we based the model on the observed light distribution that is fitted with three components: a point mass for the central light component resembling an active galactic nucleus, and the remaining two extended light components scaled by a constant mass-to-light ratio (M/L). To constrain the model further, we included published velocity dispersion measurements of the lens galaxy and performed a self-consistent lensing and axisymmetric Jeans dynamical modeling. Our model fits well to the observations including the radial arc, independent of the DM profile. Depending on the DM profile, we get a DM fraction between 60% and 70%. With our composite mass model we find that the radial arc helps to constrain the inner DM distribution of the Cosmic Horseshoe independently of the DM profile.

scholarly journals CO line and radio continuum study of elephant trunks: the Pillars of Creation in M16

2020 ◽  
Vol 492 (4) ◽  
pp. 5966-5979 ◽  
Author(s):  
Yoshiaki Sofue
Keyword(s):  
Surface Brightness ◽  
Galactic Plane ◽  
Brightness Distribution ◽  
Radio Continuum ◽  
Very Large Array ◽  
Heating Source ◽  
Velocity Gradients ◽  
Magnetic Oscillation ◽  
H Ii Region ◽  
Line Survey

ABSTRACT Molecular line and radio continuum properties of the elephant trunks (ET, Pillars of Creation) in M16 are investigated by analysing 12CO(J = 1−0) , 13CO(J = 1−0) and C18O(J = 1−0) line survey data from the Nobeyama 45-m telescope and the Galactic plane radio survey at 20 and 90 cm with the Very Large Array. The head clump of Pillar West I is found to be the brightest radio source in M16, showing a thermal spectrum and the properties of a compact H ii region, with the nearest O5 star in NGC 6611 being the heating source. The radio pillars have a cometary structure concave to the molecular trunk head, and the surface brightness distribution obeys a simple illumination law from a remote excitation source. The molecular density in the pillar head is estimated to be several 104 H2 cm−3 and the molecular mass is $\sim 13\!-\!40 \, \mathrm{M}_\odot$. CO-line kinematics reveals random rotation of the clumps in the pillar tail at ∼1–2 km s−1, comparable with the velocity dispersion and estimated Alfvén velocity. It is suggested that the random directions of the velocity gradients would manifest as torsional magnetic oscillation of the clumps around the pillar axis.

Optical Satellite Multiobjective Genetic Algorithms for Investigation of MH370 Debris

2020 ◽  
pp. 166-207
Keyword(s):  
Genetic Algorithm ◽  
Genetic Algorithms ◽  
Cloud Cover ◽  
Optical Remote Sensing ◽  
New Approach ◽  
Precise Method ◽  
Spectral Signatures ◽  
Remote Sensing Technique ◽  
Multiobjective Genetic Algorithms ◽  
Strength Constraints

At present, there is no precise method that can inform where the lost flight MH370 is. This chapter proposes a new approach to search for the missing flight MH370. To this end, multiobjective genetic algorithms are implemented. In this regard, a genetic algorithm is taken into consideration to optimize the MH370 debris that is notably based on the geometrical shapes and spectral signatures. Currently, there may be three limitations to optical remote sensing technique: (1) strength constraints of the spacecraft permit about two hours of scanning consistently within the day, (2) cloud cover prevents unique observations, and (3) moderate information from close to the ocean surface is sensed through the scanner. Needless to say that the objects that are spotted by different satellite data do not scientifically belong to the MH370 debris and could be just man-made without accurate identifications.

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