Publications by Frédéric Courbin

Euclid preparation: LXVII. Deep learning true galaxy morphologies for weak lensing shear bias calibration

To date, galaxy image simulations for weak lensing surveys usually approximate the light profiles of all galaxies as a single or double Sérsic profile, neglecting the influence of galaxy substructures and morphologies deviating from such a simplified param ...

2025

Euclid: A complete Einstein ring in NGC 6505

Georges Meylan, Frédéric Courbin, Benjamin Yvan Alexandre Clement

We report the discovery of a complete Einstein ring around the elliptical galaxy NGC 6505, at z = 0.042. This is the first strong gravitational lens discovered in Euclid and the first in an NGC object from any survey. The combination of the low redshift of ...

2025

Euclid preparation: LIV. Sensitivity to neutrino parameters

Georges Meylan, Frédéric Courbin

Context. The Euclid mission of the European Space Agency will deliver weak gravitational lensing and galaxy clustering surveys that can be used to constrain the standard cosmological model and extensions thereof. Aims. We present forecasts from the combina ...

2025

Euclid II. The VIS instrument

Georges Meylan, Frédéric Courbin

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

Euclid preparation: LIX. Angular power spectra from discrete observations

Georges Meylan, Frédéric Courbin

In this paper we present the framework for measuring angular power spectra in the Euclid mission. The observables in galaxy surveys, such as galaxy clustering and cosmic shear, are not continuous fields, but discrete sets of data, obtained only at the posi ...

2025

Euclid: Early Release Observations – Unveiling the morphology of two Milky Way globular clusters out to their periphery

Georges Meylan, Frédéric Courbin

As part of the Euclid Early Release Observations (ERO) programme, we analysed deep, wide-field imaging from the VIS and NISP instruments of two Milky Way globular clusters (GCs), namely NGC 6254 (M10) and NGC 6397, to look for observational evidence of the ...

2025

Euclid preparation: LXII. Simulations and non-linearities beyond Lambda cold dark matter. 1. Numerical methods and validation

Georges Meylan, Frédéric Courbin

To constrain cosmological models beyond ACDM, the development of the Euclid analysis pipeline requires simulations that capture the non-linear phenomenology of such models. We present an overview of numerical methods and N-body simulation codes developed t ...

2025

Euclid preparation: LVIII. Detecting extragalactic globular clusters in the Euclid survey

Georges Meylan, Frédéric Courbin

Extragalactic globular clusters (EGCs) are an abundant and powerful tracer of galaxy dynamics and formation, and their own formation and evolution is also a matter of extensive debate. The compact nature of globular clusters means that they are hard to spa ...

2025

Euclid and KiDS-1000: Quantifying the impact of source-lens clustering on cosmic shear analyses

Georges Meylan, Frédéric Courbin

Cosmic shear is a powerful probe of cosmological models and the transition from current Stage-III surveys such as the Kilo-Degree Survey (KiDS) to the increased area and redshift range of Stage IV surveys such as Euclid will significantly increase the prec ...

2025

Euclid preparation: LVI. Sensitivity to non-standard particle dark matter models

Georges Meylan, Frédéric Courbin

The Euclid mission of the European Space Agency will provide weak gravitational lensing and galaxy clustering surveys that can be used to constrain the standard cosmological model and its extensions, with an opportunity to test the properties of dark matte ...

2025

LXXI. Simulations and nonlinearities beyond ΛCDM. 3. Constraints on f(R) models from the photometric primary probes

Georges Meylan, Frédéric Courbin

We study the constraint on f(R) gravity that can be obtained by photometric primary probes of the Euclid mission. Our focus is the dependence of the constraint on the theoretical modelling of the nonlinear matter power spectrum. In the Hu–Sawicki f(R) grav ...

2025

Euclid: Early Release Observations – Deep anatomy of nearby galaxies

Georges Meylan, Frédéric Courbin, Pascale Jablonka

Euclid is poised to make significant advances in the study of nearby galaxies in the Local Universe. Here we present a first look at six galaxies observed for the Nearby Galaxy Showcase as part of the Euclid Early Release Observations acquired between Augu ...

2025

Euclid preparation: LXV. Determining the weak lensing mass accuracy and precision for galaxy clusters

Georges Meylan, Frédéric Courbin

The ability to measure unbiased weak-lensing (WL) masses is a key ingredient to exploit galaxy clusters as a competitive cosmological probe with the ESA Euclid survey or future missions. We investigate the level of accuracy and precision of cluster masses ...

2025

Euclid: III. The NISP Instrument

Georges Meylan, Frédéric Courbin

The Near-Infrared Spectrometer and Photometer (NISP) on board the Euclid satellite provides multiband photometry and R âÂ ³ 450 slitless grism spectroscopy in the 950- 2020 nm wavelength range. In this reference article, we illuminate the background of NIS ...

2025

Euclid: The Early Release Observations Lens Search Experiment

Georges Meylan, Frédéric Courbin, Georgios Vernardos, Lucie Anemone Scharré

We investigated the ability of the Euclid telescope to detect galaxy-scale gravitational lenses. To do so, we performed a systematic visual inspection of the 0.7 deg2 Euclid Early Release Observations data towards the Perseus cluster using both the high-re ...

2025

Euclid: Early Release Observations – Globular clusters in the Fornax galaxy cluster, from dwarf galaxies to the intracluster field

Georges Meylan, Frédéric Courbin

We present an analysis of Euclid observations of a 0.6 deg2 field in the central region of the Fornax galaxy cluster that were acquired during the performance verification phase. With these data, we investigated the potential of Euclid to identify globular ...

2025

Euclid preparation: LVII. Observational expectations for redshift z < 7 active galactic nuclei in the Euclid Wide and Deep surveys

Georges Meylan, Frédéric Courbin

We forecast the expected population of active galactic nuclei (AGN) observable in the Euclid Wide Survey (EWS) and Euclid Deep Survey (EDS). Starting from an X-ray luminosity function (XLF), we generated volume-limited samples of the AGN expected in the Eu ...

2025

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

Georges Meylan, Frédéric Courbin, 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: LXVI. Impact of line-of-sight projections on the covariance between galaxy cluster multi-wavelength observable properties: Insights from hydrodynamic simulations

Georges Meylan, Frédéric Courbin

Context. Cluster cosmology can benefit from combining multi-wavelength studies. In turn, these studies benefit from a characterisation of the correlation coefficients among different mass-observable relations. Aims. In this work, we aim to provide informat ...

2025

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

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

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