Publications de Christoph Ernst René Schäfer

Measurement of the inclusive and differential t(t)over-bar gamma cross sections in the dilepton channel and effective field theory interpretation in proton-proton collisions at root s=13 TeV

Matthias Finger, Varun Sharma, Olivier Martin, Ian Smith, Jean-François Carlin, Arvind Shah, Rakesh Chawla, Thomas Mountford, Chao Wang, João Miguel das Neves Duarte

The production cross section of a top quark pair in association with a photon is measured in proton-proton collisions in the decay channel with two oppositely charged leptons (e(+/-)mu(-/+), e(+)e(-), or mu(+)mu(-)). The measurement is performed using 138 ...

Springer Nature2022

Galaxy cluster cores as seen with VLT/MUSE: New strong-lensing analyses of RX J2129.4+0009, MS 0451.6-0305, and MACS J2129.4-0741

Jean-Paul Richard Kneib, Markus Rexroth, Christoph Ernst René Schäfer

We present strong-lensing analyses of three galaxy clusters, RX J2129.4 + 0009 (z = 0.235), MS 0451.6 - 0305 (z = 0.55), and MACS J2129.4 - 0741 (z = 0.589), using the powerful combination of Hubble Space Telescope (HSI) multiband observations, and Multi-U ...

OXFORD UNIV PRESS2021

Methods for strong gravitational lens detection and analysis using machine learning and high performance computing

Christoph Ernst René Schäfer

The study of strong gravitational lenses is a relatively new scientific field in astronomy with many applications in cosmology. Its unique observables allow astronomers to trace dark matter, determine the expansion of the universe and study galaxy evolutio ...

EPFL2020

Lenstool-HPC: A High Performance Computing based mass modelling tool for cluster-scale gravitational lenses

Jean-Paul Richard Kneib, Christoph Ernst René Schäfer

With the upcoming generation of telescopes, cluster scale strong gravitational lenses will act as an increasingly relevant probe of cosmology and dark matter. The better resolved data produced by current and future facilities requires faster and more effic ...

ELSEVIER2020

High Performance Computing for gravitational lens modeling: Single vs double precision on GPUs and CPUs

Jean-Paul Richard Kneib, Markus Rexroth, Christoph Ernst René Schäfer

Strong gravitational lensing is a powerful probe of cosmology and the dark matter distribution. Efficient lensing software is already a necessity to fully use its potential and the performance demands will only increase with the upcoming generation of tele ...

ELSEVIER2020

Machine-learning Classifiers for Intermediate Redshift Emission-line Galaxies

Jean-Paul Richard Kneib, Johan Comparat, Christoph Ernst René Schäfer, David Schlegel

Classification of intermediate redshift (z = 0.3-0.8) emission line galaxies as star-forming galaxies, composite galaxies, active galactic nuclei (AGNs), or low-ionization nuclear emission regions (LINERs) using optical spectra alone was impossible because ...

IOP PUBLISHING LTD2019

Target-based fiber assignment for large survey spectrographs

Jean-Paul Richard Kneib, Laleh Makarem, Christoph Ernst René Schäfer

Next generation massive spectroscopic survey projects have to process a massive amount of targets. The preparation of subsequent observations should be feasible in a reasonable amount of time. We present a fast algorithm for target assignment that scales a ...

Spie-Int Soc Optical Engineering2016

The PCA Lens-Finder: application to CFHTLS

Jean-Paul Richard Kneib, Frédéric Courbin, Rémy Elie Joseph, Danuta Janina Paraficz, Christoph Ernst René Schäfer

We present the results of a new search for galaxy-scale strong lensing systems in CFHTLS Wide. Our lens-finding technique involves a preselection of potential lens galaxies, applying simple cuts in size and magnitude. We then perform a Principal Component ...

Edp Sciences S A2016