Publications by Marc Gentile | EPFL Graph Search

Shear measurement bias: I. Dependencies on methods, simulation parameters, and measured parameters

We present a study of the dependencies of shear bias on simulation (input) and measured (output) parameters, noise, point-spread function anisotropy, pixel size, and the model bias coming from two different and independent galaxy shape estimators. We used ...

EDP SCIENCES S A2020

The Pristine survey IV: approaching the Galactic metallicity floor with the discovery of an ultra-metal-poor star

Pascale Jablonka, Marc Gentile, Silvia Martin de Nicolas Agut, Carmela Lardo, Nicolas Lawrence Etienne Longeard

The early Universe presented a star formation environment that was almost devoid of heavy elements. The lowest metallicity stars thus provide a unique window into the earliest Galactic stages, but are exceedingly rare and difficult to find. Here, we presen ...

OXFORD UNIV PRESS2018

The Pristine survey - III. Spectroscopic confirmation of an efficient search for extremely metal-poor stars

Pascale Jablonka, Marc Gentile

The Pristine survey is a narrow-band, photometric survey focused around the wavelength region of the Ca II H&K absorption lines, designed to efficiently search for extremely metal-poor stars. In this work, we use the first results of amedium-resolution spe ...

Oxford Univ Press2017

GREAT3 results - I. Systematic errors in shear estimation and the impact of real galaxy morphology

Malte Tewes, Frédéric Courbin, Thibault Adrien Kuntzer, Marc Gentile, Guldariya Nurbaeva, Huanyuan Shan, Jean-Luc Starck, Jun Zhang

We present first results from the third GRavitational lEnsing Accuracy Testing (GREAT3) challenge, the third in a sequence of challenges for testing methods of inferring weak gravitational lensing shear distortions from simulated galaxy images. GREAT3 was ...

Oxford University Press2015

The Third Gravitational Lensing Accuracy Testing (Great3) Challenge Handbook

Frédéric Courbin, Marc Gentile, Richard Massey

The GRavitational lEnsing Accuracy Testing 3 (GREAT3) challenge is the third in a series of image analysis challenges, with a goal of testing and facilitating the development of methods for analyzing astronomical images that will be used to measure weak gr ...

University of Chicago Press2014

Weak Gravitational Lensing by Large-Scale Structures : A Tool for Constraining Cosmology

Marc Gentile

There is now very strong evidence that our Universe is undergoing an accelerated expansion period as if it were under the influence of a gravitationally repulsive “dark energy” component. Furthermore, most of the mass of the Universe seems to be in the for ...

EPFL2013

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

Image analysis for cosmology: results from the GREAT10 Galaxy Challenge

Nicolas Cantale, Malte Tewes, Frédéric Courbin, Marc Gentile, Guldariya Nurbaeva, Richard Massey

In this paper, we present results from the weak-lensing shape measurement GRavitational lEnsing Accuracy Testing 2010 (GREAT10) Galaxy Challenge. This marks an order of magnitude step change in the level of scrutiny employed in weak-lensing shape measureme ...

Blackwell Publishing Ltd, Oxford2012

Gravitational Lensing Accuracy Testing 2010 (Great10) Challenge Handbook

Frédéric Courbin, Marc Gentile, Guldariya Nurbaeva, Anaïs Marie Rassat, Richard Massey, Michael Hirsch, Matthias Bethge

GRavitational lEnsing Accuracy Testing 2010 (GREAT10) is a public image analysis challenge aimed at the development of algorithms to analyze astronomical images. Specifically, the challenge is to measure varying image distortions in the presence of a varia ...

2011

On the effect of image denoising on galaxy shape measurements

Georges Meylan, Frédéric Courbin, Marc Gentile, Guldariya Nurbaeva

Weak gravitational lensing is a very sensitive way of measuring cosmological parameters, including dark energy, and of testing current theories of gravitation. In practice, this requires exquisite measurement of the shapes of billions of galaxies over larg ...

2011

Results of the GREAT08 Challenge: an image analysis competition for cosmological lensing

Frédéric Courbin, Marc Gentile, Anaïs Marie Rassat, Richard Massey, Michael Hirsch, Matthias Bethge

We present the results of the Gravitational LEnsing Accuracy Testing 2008 (GREAT08) Challenge, a blind analysis challenge to infer weak gravitational lensing shear distortions from images. The primary goal was to stimulate new ideas by presenting the probl ...

Blackwell Publishing Ltd, Oxford2010