Publications de Malte Tewes | EPFL Graph Search

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

Slobodan Ilic, Malte Tewes, Georges Meylan, Frédéric Courbin, Fabio Finelli, Richard Massey, Maurizio Martinelli, Alessandro Pezzotta, Gianluca Castignani, Marcello Farina, Yi Wang

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: Improving the efficiency of weak lensing shear bias calibration

Malte Tewes, Georges Meylan, Frédéric Courbin, Richard Massey, Marcello Farina, Yi Wang

To obtain an accurate cosmological inference from upcoming weak lensing surveys such as the one conducted by Euclid, the shear measurement requires calibration using galaxy image simulations. As it typically requires millions of simulated galaxy images and ...

Edp Sciences S A2024

Strong gravitational lensing by AGNs as a probe of the quasar-host relations in the distant Universe

Malte Tewes, Frédéric Courbin, Martin Raoul Robert Millon, Aymeric Alexandre Galan

A rare case of a quasar acting as a gravitational lens allows a precise determination of the mass of the quasar's host galaxy and offers a new path to studying the connections between supermassive black holes and their host galaxies. ...

NATURE PORTFOLIO2023

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

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

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

COSMOGRAIL XVIII. time delays of the quadruply lensed quasar WFI2033-4723

Malte Tewes, Georges Meylan, Frédéric Courbin, Sun Hee Kim, Vivien François Bonvin, Martin Raoul Robert Millon, Hung-Hsu Chan, Karina Alexandra Rojas Olate

We present new measurements of the time delays of WFI2033-4723. The data sets used in this work include 14 years of data taken at the 1.2 m Leonhard Euler Swiss telescope, 13 years of data from the SMARTS 1.3 m telescope at Las Campanas Observatory and a s ...

2019

Weak-lensing shear measurement with machine learning Teaching artificial neural networks about feature noise

Malte Tewes, Frédéric Courbin, Thibault Adrien Kuntzer, Nicolai Hildebrandt

Cosmic shear, that is weak gravitational lensing by the large-scale matter structure of the Universe, is a primary cosmological probe for several present and upcoming surveys investigating dark matter and dark energy, such as Euclid or WFIRST. The probe re ...

EDP SCIENCES S A2019

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses

Eduardo Sanchez, Malte Tewes, Georges Meylan, Frédéric Courbin, Sun Hee Kim, Vivien François Bonvin, Eric Gérard Guy Paic, Karina Alexandra Rojas Olate, Adriano Agnello

2018

COSMOGRAIL XVII. Time delays for the quadruply imaged quasar PG 1115+080

Malte Tewes, Georges Meylan, Frédéric Courbin, Sun Hee Kim, Vivien François Bonvin, Martin Raoul Robert Millon, Eric Gérard Guy Paic, Hung-Hsu Chan, Karina Alexandra Rojas Olate

We present time-delay estimates for the quadruply imaged quasar PG 1115+080. Our results are based on almost daily observations for seven months at the ESO MPIA 2.2m telescope at La Silla Observatory, reaching a signal-to-noise ratio of about 1000 per quas ...

EDP SCIENCES S A2018

H0LiCOW-I. H-0 Lenses in COSMOGRAIL's Wellspring: program overview

Malte Tewes, Georges Meylan, Frédéric Courbin, Vivien François Bonvin, Olga Tihhonova, Adriano Agnello

Strong gravitational lens systems with time delays between the multiple images allow measurements of time-delay distances, which are primarily sensitive to the Hubble constant that is key to probing dark energy, neutrino physics and the spatial curvature o ...

Oxford Univ Press2017

H0LiCOW-V. New COSMOGRAIL time delays of HE 0435-1223: H-0 to 3.8 per cent precision from strong lensing in a flat Lambda CDM model

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

We present a new measurement of the Hubble Constant H-0 and other cosmological parameters based on the joint analysis of three multiply imaged quasar systems with measured gravitational time delays. First, we measure the time delay of HE 0435-1223 from 13- ...

Oxford Univ Press2017

H0LiCOW-II. Spectroscopic survey and galaxy-group identification of the strong gravitational lens system HE 0435-1223

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

Galaxies located in the environment or along the line of sight towards gravitational lenses can significantly affect lensing observables, and can lead to systematic errors on the measurement of H-0 from the time-delay technique. We present the results of a ...

Oxford Univ Press2017

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

Stellar classification from single-band imaging using machine learning

Malte Tewes, Frédéric Courbin, Thibault Adrien Kuntzer

Information on the spectral types of stars is of great interest in view of the exploitation of space-based imaging surveys. In this article, we investigate the classification of stars into spectral types using only the shape of their diffraction pattern in ...

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

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

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

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

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

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