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Georges Meylan

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Related publications (177)

Page 3 of 9

Euclid preparation XLIII. Measuring detailed galaxy morphologies for Euclid with machine learning

Frédéric Courbin, Georges Meylan, Austin Chandler Peel

The Euclid mission is expected to image millions of galaxies at high resolution, providing an extensive dataset with which to study galaxy evolution. Because galaxy morphology is both a fundamental parameter and one that is hard to determine for large samp ...

2024

Euclid preparation: VII. Forecast validation for Euclid cosmological probes

Yi Wang, Maurizio Martinelli, Georges Meylan, Murat Kunt, Slobodan Ilic

Aims. The Euclid space telescope will measure the shapes and redshifts of galaxies to reconstruct the expansion history of the Universe and the growth of cosmic structures. The estimation of the expected performance of the experiment, in terms of predicted ...

EDP SCIENCES SA2020

COSMOGRAIL: the COSmological MOnitoring of GRAvItational lenses - VII. Time delays and the Hubble constant from WFI J2033-4723

Frédéric Courbin, Georges Meylan, Christel Vuissoz

Gravitationally lensed quasars can be used to map the mass distribution in lensing galaxies and to estimate the Hubble constant H-0 by measuring the time delays between the quasar images. Here we report the measurement of two independent time delays in the ...

2008

Euclid preparation XXX. Performance assessment of the NISP red grism through spectroscopic simulations for the wide and deep surveys

Maurizio Martinelli, Frédéric Courbin, Georges Meylan, Michaela Hirschmann, Gianluca Castignani

This work focusses on the pilot run of a simulation campaign aimed at investigating the spectroscopic capabilities of the Euclid NearInfrared Spectrometer and Photometer (NISP), in terms of continuum and emission line detection in the context of galaxy evo ...

EDP SCIENCES S A2023

Euclid preparation: LXVIII. Extracting physical parameters from galaxies with machine learning

Frédéric Courbin, Georges Meylan, Olivia Mueller

The Euclid mission is generating a vast amount of imaging data in four broadband filters at a high angular resolution. This data will allow for the detailed study of mass, metallicity, and stellar populations across galaxies that will constrain their forma ...

2025

COSMOGRAIL: XIX. Time delays in 18 strongly lensed quasars from 15 years of optical monitoring star

Frédéric Courbin, Georges Meylan, Hung-Hsu Chan, Vivien François Bonvin, Malte Tewes, Martin Raoul Robert Millon, Aymeric Alexandre Galan, Rémy Elie Joseph, Eric Gérard Guy Paic, Cameron Alexander Campbell Lemon, Olga Tihhonova

We present the results of 15 years of monitoring lensed quasars, which was conducted by the COSMOGRAIL programme at the Leonhard Euler 1.2 m Swiss Telescope. The decade-long light curves of 23 lensed systems are presented for the first time. We complement ...

EDP SCIENCES S A2020

Euclid: Early Release Observations – Programme overview and pipeline for compact- and diffuse-emission photometry

Jean-Paul Richard Kneib, Frédéric Courbin, Georges Meylan, Pascale Jablonka

The Euclid Early Release Observations (ERO) showcase Euclid’s capabilities in advance of its main mission by targeting 17 astronomical objects, including galaxy clusters, nearby galaxies, globular clusters, and star-forming regions. A total of 24 hours of ...

2025

Hopfield neural network deconvolution for weak lensing measurement

Frédéric Courbin, Georges Meylan, Malte Tewes, 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

XXXIV. The effect of linear redshift-space distortions in photometric galaxy clustering and its cross-correlation with cosmic shear

Maurizio Martinelli, Frédéric Courbin, Georges Meylan, Malte Tewes, Slobodan Ilic, Gianluca Castignani, Alessandro Pezzotta

Context. The cosmological surveys that are planned for the current decade will provide us with unparalleled observations of the distribution of galaxies on cosmic scales, by means of which we can probe the underlying large-scale structure (LSS) of the Univ ...

Edp Sciences S A2024

Euclid preparation: XXXIX. The effect of baryons on the halo mass function

Frédéric Courbin, Georges Meylan

Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved.The Euclid photometric survey of galaxy clusters stands as a powerful cosmological tool, with the capacity to significantly propel our understand ...

2024

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

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

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

Euclid: Early Release Observations – Dwarf galaxies in the Perseus galaxy cluster

Frédéric Courbin, Georges Meylan, Pascale Jablonka

We make use of the unprecedented depth, spatial resolution, and field of view of the Euclid Early Release Observations (EROs) of the Perseus galaxy cluster to detect and characterise the dwarf galaxy population in this massive system. Using a dedicated ann ...

2025

Euclid preparation XLVI. The near-infrared background dipole experiment with Euclid

Frédéric Courbin, Georges Meylan

Verifying the fully kinematic nature of the long-known cosmic microwave background (CMB) dipole is of fundamental importance in cosmology. In the standard cosmological model with the Friedman–Lemaitre–Robertson–Walker (FLRW) metric from the inflationary ex ...

2024

Euclid preparation: X. The Euclid photometric-redshift challenge

Georges Meylan, Gianluca Castignani

Forthcoming large photometric surveys for cosmology require precise and accurate photometric redshift (photo-z) measurements for the success of their main science objectives. However, to date, no method has been able to produce photo-zs at the required acc ...

EDP SCIENCES S A2020

H0LiCOW-XIII. A 2.4 per cent measurement of H-0 from lensed quasars: 5.3 sigma tension between early- and late-Universe probes

Frédéric Courbin, Georges Meylan, Hung-Hsu Chan, Vivien François Bonvin, Martin Raoul Robert Millon, Olga Tihhonova

We present a measurement of the Hubble constant (H-0) and other cosmological parameters from a joint analysis of six gravitationally lensed quasars with measured time delays. All lenses except the first are analysed blindly with respect to the cosmological ...

OXFORD UNIV PRESS2020

Euclid: Searching for pair-instability supernovae with the Deep Survey

Yi Wang, Frédéric Courbin, Georges Meylan, Giovanni Longo

Pair-instability supernovae are theorized supernovae that have not yet been observationally confirmed. They are predicted to exist in low-metallicity environments. Because overall metallicity becomes lower at higher redshifts, deep near-infrared transient ...

EDP SCIENCES S A2022

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

Frédéric Courbin, Georges Meylan, Pascale Jablonka, Nicolas Jacques Joseph Marie Cantale

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

Euclid II. The VIS instrument

Frédéric Courbin, Georges Meylan

This paper presents the specification, design, and development of the Visible Camera (VIS) on the European Space Agency’s Euclid mission. VIS is a large optical-band imager with a field of view of 0.54 deg2 sampled at 000 . 1 with an array of 609 Megapixel ...

2025

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

Frédéric Courbin, Georges Meylan, Malte Tewes

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

Three quasi-stellar objects acting as strong gravitational lenses

Frédéric Courbin, Georges Meylan, Malte Tewes, François Henri Ambroise Rérat

We report the discovery of three new cases of quasi-stellar objects (QSOs) acting as strong gravitational lenses on background emission line galaxies: SDSS J0827+5224 (z(QSO) = 0.293, z(s) = 0.412), SDSS J0919+2720 (z(QSO) = 0.209, z(s) = 0.558), SDSS J100 ...

2012