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Georges Meylan

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Publications associées (182)

Discovery of the Lensed Quasar System DES J0408-5354

Eduardo Sanchez, Georges Meylan, Frédéric Courbin, Hung-Hsu Chan, Adriano Agnello

We report the discovery and spectroscopic confirmation of the quad-like lensed quasar system DES J0408-5354 found in the Dark Energy Survey (DES) Year 1 (Y1) data. This system was discovered during a search for DES Y1 strong lensing systems using a method ...

Iop Publishing Ltd2017

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XV. Assessing the achievability and precision of time-delay measurements

Malte Tewes, Georges Meylan, Frédéric Courbin, Thibault Adrien Kuntzer, Vivien François Bonvin

COSMOGRAIL is a long-term photometric monitoring of gravitationally lensed quasars aimed at implementing Refsdal's time-delay method to measure cosmological parameters, in particular H-0. Given the long and well sampled light curves of strongly lensed quas ...

Edp Sciences S A2016

Firedec: a two-channel finite-resolution image deconvolution algorithm

Nicolas Cantale, Malte Tewes, Georges Meylan, Frédéric Courbin, Pascale Jablonka

We present a two-channel deconvolution method that decomposes images into a parametric point-source channel and a pixelized extended-source channel. Based on the central idea of the deconvolution algorithm proposed by Magain et al. (1998, ApJ, 494, 472), t ...

Edp Sciences S A2016

Evaluating the effect of stellar multiplicity on the point spread function of space-based weak lensing surveys

Georges Meylan, Frédéric Courbin, Thibault Adrien Kuntzer

The next generation of space-based telescopes used for weak lensing surveys will require exquisite point spread function (PSF) determination. Previously negligible effects may become important in the reconstruction of the PSF, in part because of the improv ...

Edp Sciences S A2016

Disc colours in field and cluster spiral galaxies at 0.5 less than or similar to z less than or similar to 0.8

Nicolas Cantale, Georges Meylan, Frédéric Courbin, Pascale Jablonka

We present a detailed study of the colours of late-type galaxy discs for ten of the EDisCS galaxy clusters with 0.5 less than or similar to z less than or similar to 0.8. Our cluster sample contains 172 spiral galaxies, and our control sample is composed o ...

Edp Sciences S A2016

Strong Lens Time Delay Challenge. Ii. Results Of Tdc1

Malte Tewes, Georges Meylan, Frédéric Courbin, Vivien François Bonvin

We present the results of the first strong lens time delay challenge. The motivation, experimental design, and entry level challenge are described in a companion paper. This paper presents the main challenge, TDC1, which consisted of analyzing thousands of ...

American Astronomical Society2015

A Consistent Picture Emerges: A Compact X-Ray Continuum Emission Region In The Gravitationally Lensed Quasar Sdss J0924+0219

Malte Tewes, Georges Meylan, Frédéric Courbin

We analyze the optical, UV, and X-ray microlensing variability of the lensed quasar SDSS J0924+ 0219 using six epochs of Chandra data in two energy bands (spanning 0.4-8.0 keV, or 1-20 keV in the quasar rest frame), 10 epochs of F275W (rest-frame 1089 angs ...

American Astronomical Society2015

Discovery of two gravitationally lensed quasars in the Dark Energy Survey

Eduardo Sanchez, Georges Meylan, Frédéric Courbin, Yi Zhang, Adriano Agnello

We present spectroscopic confirmation of two new gravitationally lensed quasars, discovered in the Dark Energy Survey (DES) and Wide-field Infrared Survey Explorer (WISE) based on their multiband photometry and extended morphology in DES images. Images of ...

Oxford Univ Press2015

Hopfield neural network deconvolution for weak lensing measurement

Malte Tewes, Georges Meylan, Frédéric Courbin, Guldariya Nurbaeva

Weak gravitational lensing has the potential to place tight constraints on the equation of the state of dark energy. However, this will only be possible if shear measurement methods can reach the required level of accuracy. We present a new method for meas ...

EDP Sciences2015

A 7 deg(2) survey for galaxy-scale gravitational lenses with the HST imaging archive(star)

Georges Meylan, Frédéric Courbin, Ravindra Pawase

We present the results of a visual search for galaxy-scale gravitational lenses in similar to 7 deg(2) of Hubble Space Telescope (HST) images. The data set comprises the whole imaging data ever taken with the Advanced Camera for Surveys (ACS) in the filter ...

Wiley-Blackwell2014

Cosmology From Gravitational Lens Time Delays And Planck Data

Malte Tewes, Georges Meylan, Frédéric Courbin

Under the assumption of a flat Lambda CDM cosmology, recent data from the Planck satellite point toward a Hubble constant that is in tension with that measured by gravitational lens time delays and by the local distance ladder. Prosaically, this difference ...

Iop Publishing Ltd2014

Weak lensing mass map and peak statistics in Canada-France-Hawaii Telescope Stripe 82 survey

Georges Meylan, Frédéric Courbin, Johan Comparat, Jean-Paul Richard Kneib, Huanyuan Shan

We present a weak lensing mass map covering similar to 124 deg(2) of the Canada-France-Hawaii Telescope Stripe 82 Survey (CS82). We study the statistics of rare peaks in the map, including peak abundance, the peak-peak correlation functions and the tangent ...

Wiley-Blackwell2014

A PCA-based automated finder for galaxy-scale strong lenses

Georges Meylan, Frédéric Courbin, Jean-Paul Richard Kneib, Rémy Elie Joseph

We present an algorithm using principal component analysis (PCA) to subtract galaxies from imaging data and also two algorithms to find strong, galaxy-scale gravitational lenses in the resulting residual image. The combined method is optimised to find full ...

EDP Sciences2014

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XIII. Time delays and 9-yr optical monitoring of the lensed quasar RX J1131-1231

Nicolas Cantale, Malte Tewes, Georges Meylan, Frédéric Courbin

We present the results from nine years of optically monitoring the gravitationally lensed z(QSO) = 0.658 quasar RX J1131-1231. The R-band light curves of the four individual images of the quasar were obtained using deconvolution photometry for a total of 7 ...

Edp Sciences S A2013

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XI. Techniques for time delay measurement in presence of microlensing

Malte Tewes, Georges Meylan, Frédéric Courbin

Measuring time delays between the multiple images of gravitationally lensed quasars is now recognized as a competitive way to constrain the cosmological parameters, and it is complementary with other cosmological probes. This requires long and well sampled ...

Edp Sciences S A2013

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XIV. Time delay of the doubly lensed quasar SDSS J1001+5027

Malte Tewes, Georges Meylan, Frédéric Courbin

This paper presents optical R-band light curves and the time delay of the doubly imaged gravitationally lensed quasar SDSS J1001+5027 at a redshift of 1.838. We have observed this target for more than six years, between March 2005 and July 2011, using the ...

Edp Sciences S A2013

Image Analysis For Cosmology: Results From The Great10 Star Challenge

Georges Meylan, Frédéric Courbin, Marc Gentile, Richard Massey

We present the results from the first public blind point-spread function (PSF) reconstruction challenge, the GRavitational lEnsing Accuracy Testing 2010 (GREAT10) Star Challenge. Reconstruction of a spatially varying PSF, sparsely sampled by stars, at non- ...

University of Chicago Press2013

Interpolating point spread function anisotropy

Georges Meylan, Frédéric Courbin, Marc Gentile

Planned wide-field weak lensing surveys are expected to reduce the statistical errors on the shear field to unprecedented levels. In contrast, systematic errors like those induced by the convolution with the point spread function (PSF) will not benefit fro ...

Edp Sciences S A2013

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XII. Time delays of the doubly lensed quasars SDSS J1206+4332 and HS 2209+1914

Malte Tewes, Georges Meylan, Frédéric Courbin

Aims. Within the framework of the COSMOGRAIL collaboration we present 7- and 8.5-year-long light curves and time-delay estimates for two gravitationally lensed quasars: SDSS J1206+4332 and HS 2209+1914. Methods. We monitored these doubly lensed quasars in ...

Edp Sciences S A2013

Two Accurate Time-Delay Distances From Strong Lensing: Implications For Cosmology

Malte Tewes, Georges Meylan, Frédéric Courbin

Strong gravitational lenses with measured time delays between the multiple images and models of the lens mass distribution allow a one-step determination of the time-delay distance, and thus a measure of cosmological parameters. We present a blind analysis ...

American Astronomical Society2013

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