papers

Publications (400)

astro-ph.CO2024

Euclid preparation: XLVIII. The pre-launch Science Ground Segment simulation framework

Euclid Collaboration, S. Serrano, P. Hudelot +274

The European Space Agency's Euclid mission is one of the upcoming generation of large-scale cosmology surveys, which will map the large-scale structure in the Universe with unprece…

astro-ph2006

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses II. SDSS J0924+0219: the redshift of the lensing galaxy, the quasar spectral variability and the Einstein rings

A. Eigenbrod, F. Courbin, S. Dye +6

(Abridged) We present our VLT/FORS1 deep spectroscopic observations of the gravitationally lensed quasar SDSS J0924+0219, as well as archival HST/NICMOS and ACS images of the same…

astro-ph2001

The FALCON concept: multi-object spectroscopy combined with MCAO in near-IR

F. Hammer, F. Sayède, E. Gendron +16

A large fraction of the present-day stellar mass was formed between z=0.5 and z~3 and our understanding of the formation mechanisms at work at these epochs requires both high spati…

astro-ph.GA2026

Euclid: Scaled-up little red dots and other sources with v-shaped spectral energy distributions at z>4

Euclid Collaboration, A. A. Tumborang, K. I. Caputi +169

Little Red Dots (LRDs) are some the most intriguing galaxy populations recently identified at z>~4 with JWST. They constitute the most extreme class of a more abundant population o…

astro-ph.GA2025

Euclid preparation. Estimating galaxy physical properties using CatBoost chained regressors with attention

Euclid Collaboration, A. Humphrey, P. A. C. Cunha +232

Euclid will image ~14000 deg^2 of the extragalactic sky at visible and NIR wavelengths, providing a dataset of unprecedented size and richness that will facilitate a multitude of s…

astro-ph2005

Photometric monitoring of the doubly imaged quasar UM673: possible evidence for chromatic microlensing

Th. Nakos, F. Courbin, J. Poels +12

We present the results of two-band CCD photometric monitoring of the gravitationally lensed quasar Q 0142-100 (UM 673).The data, obtained at ESO-La Silla with the 1.54 m Danish tel…

astro-ph.CO2011

On the effect of image denoising on galaxy shape measurements

G. Nurbaeva, F. Courbin, M. Gentile +1

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 re…

astro-ph.CO2026

Euclid preparation. Three-dimensional galaxy clustering in configuration space: Three-point correlation function estimation

Euclid Collaboration, A. Veropalumbo, M. Moresco +303

Higher-order correlation functions are firmly established as a fundamental tool for the statistical analysis of clustering in modern galaxy surveys. It was demonstrated that they g…

astro-ph2005

ZEN and the search for high-redshift galaxies

J. P. Willis, F. Courbin, J-P. Kneib +1

We present the ZEN (z equals nine) survey: a deep, narrow J-band search for proto-galactic Lya emission at redshifts z=9. In the first phase of the survey, dubbed ZEN1, we combine…

astro-ph.CO2020

TDCOSMO IV: Hierarchical time-delay cosmography -- joint inference of the Hubble constant and galaxy density profiles

S. Birrer, A. J. Shajib, A. Galan +24

The H0LiCOW collaboration inferred via gravitational lensing time delays a Hubble constant km s, describing deflector mass density pro…

astro-ph.GA2024

Euclid: Early Release Observations -- Deep anatomy of nearby galaxies

L. K. Hunt, F. Annibali, J. -C. Cuillandre +196

Euclid is poised to make significant advances in the study of nearby galaxies in the local Universe. Here we present a first look at 6 galaxies observed for the Nearby Galaxy Showc…

astro-ph.CO2022

Euclid preparation: XIX. Impact of magnification on photometric galaxy clustering

F. Lepori, I. Tutusaus, C. Viglione +183

We investigate the importance of lensing magnification for estimates of galaxy clustering and its cross-correlation with shear for the photometric sample of Euclid. Using updated s…

astro-ph.CO2017

H0LiCOW V. New COSMOGRAIL time delays of HE0435-1223: to 3.8% precision from strong lensing in a flat CDM model

V. Bonvin, F. Courbin, S. H. Suyu +15

We present a new measurement of the Hubble Constant H0 and other cosmological parameters based on the joint analysis of three multiply-imaged quasar systems with measured gravitati…

astro-ph.GA2024

Euclid: Early Release Observations -- Overview of the Perseus cluster and analysis of its luminosity and stellar mass functions

J. -C. Cuillandre, M. Bolzonella, A. Boselli +199

The Euclid ERO programme targeted the Perseus cluster of galaxies, gathering deep data in the central region of the cluster over 0.7 square degree, corresponding to approximately 0…

astro-ph.CO2019

H0LiCOW - IX. Cosmographic analysis of the doubly imaged quasar SDSS 1206+4332 and a new measurement of the Hubble constant

S. Birrer, T. Treu, C. E. Rusu +15

We present a blind time-delay strong lensing (TDSL) cosmographic analysis of the doubly imaged quasar SDSS 1206+4332. We combine the relative time delay between the quasar images,…

astro-ph.GA2022

Euclid preparation. XXV. The Euclid Morphology Challenge -- Towards model-fitting photometry for billions of galaxies

Euclid Collaboration, E. Merlin, M. Castellano +218

The ESA Euclid mission will provide high-quality imaging for about 1.5 billion galaxies. A software pipeline to automatically process and analyse such a huge amount of data in real…

astro-ph.GA2025

Euclid Quick Data Release (Q1). A first view of the star-forming main sequence in the Euclid Deep Fields

Euclid Collaboration, A. Enia, L. Pozzetti +348

The star-forming main sequence (SFMS) is a tight relation observed between stellar masses and star formation rates (SFR) in a population of galaxies. This relation is observed at d…

astro-ph.GA2025

Euclid: A machine-learning search for dual and lensed AGN at sub-arcsec separations

L. Ulivi, F. Mannucci, M. Scialpi +189

Cosmological models of hierarchical structure formation predict the existence of a widespread population of dual accreting supermassive black holes (SMBHs) on kpc-scale separations…

astro-ph.CO2011

Zooming into the broad line region of the gravitationally lensed quasar Q2237+0305 = the Einstein Cross: III. Determination of the size and structure of the CIV and CIII] emitting regions using microlensing

D. Sluse, R. Schmidt, F. Courbin +6

We aim to use microlensing taking place in the lensed quasar Q2237+0305 to study the structure of the broad line region and measure the size of the region emitting the CIV and CIII…

astro-ph.GA2024

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

F. R. Marleau, J. -C. Cuillandre, M. Cantiello +193

We make use of the unprecedented depth, spatial resolution, and field of view of the Euclid Early Release Observations of the Perseus galaxy cluster to detect and characterise the…

astro-ph.CO2023

Euclid: Calibrating photometric redshifts with spectroscopic cross-correlations

K. Naidoo, H. Johnston, B. Joachimi +126

Cosmological constraints from key probes of the Euclid imaging survey rely critically on the accurate determination of the true redshift distributions, , of tomographic redsh…

astro-ph.GA2025

Euclid: Early Release Observations -- Interplay between dwarf galaxies and their globular clusters in the Perseus galaxy cluster

T. Saifollahi, A. Lançon, Michele Cantiello +183

We present an analysis of globular clusters (GCs) of dwarf galaxies in the Perseus galaxy cluster to explore the relationship between dwarf galaxy properties and their GCs. Our foc…

astro-ph.GA2019

The STRong lensing Insights into the Dark Energy Survey (STRIDES) 2017/2018 follow-up campaign: Discovery of 10 lensed quasars and 10 quasar pairs

C. Lemon, M. W. Auger, R. McMahon +65

We report the results of the STRong lensing Insights from the Dark Energy Survey (STRIDES) follow-up campaign of the late 2017/early 2018 season. We obtained spectra of 65 lensed q…

astro-ph.GA2026

Euclid: Quick Data Release (Q1) -- Dual AGN in low-mass galaxies

M. Mezcua, B. Laloux, M. Scialpi +164

Dual active galactic nuclei (AGNs) are expected in hierarchical galaxy evolution models, in which low-mass galaxies merge to build more massive ones. While observational evidence f…

astro-ph.CO2026

Euclid Quick Data Release (Q1). The role of cosmic connectivity in shaping galaxy clusters

Euclid Collaboration, C. Gouin, C. Laigle +337

The matter distribution around galaxy clusters is distributed over several filaments, reflecting their positions as nodes in the large-scale cosmic web. The number of filaments con…

astro-ph.GA2025

Euclid: Early Release Observations -- The Intracluster Light of Abell 2390

A. Ellien, M. Montes, S. L. Ahad +183

Intracluster light (ICL) provides a record of the dynamical interactions undergone by clusters, giving clues on cluster formation and evolution. Here, we analyse the properties of…

astro-ph.CO2024

Euclid preparation. Modelling spectroscopic clustering on mildly nonlinear scales in beyond-CDM models

Euclid Collaboration, B. Bose, P. Carrilho +229

We investigate the approximations needed to efficiently predict the large-scale clustering of matter and dark matter halos in beyond-CDM scenarios. We examine the normal branch…

astro-ph.GA2026

Euclid Quick Data Release (Q1). The Strong Lensing Discovery Engine F -- Bright and low-redshift strong lenses

Euclid Collaboration, L. R. Ecker, M. Fabricius +346

We present 72 additional galaxy-galaxy strong lenses that complement the sample discovered in the Euclid Quick Release 1 data (63.1 deg^2) of the Strong Lens Discovery Engine (SLDE…

astro-ph.GA2024

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

T. Saifollahi, K. Voggel, A. Lançon +196

We present an analysis of Euclid observations of a 0.5 deg field in the central region of the Fornax galaxy cluster that were acquired during the performance verification phase…

astro-ph1996

Sub-arcsecond imaging and spectroscopy of the radio-loud highly polarized quasar PKS 1610-771

F. Courbin, D. Hutsemekers, G. Meylan +2

We report on imaging and spectroscopic observations of the radio-loud, highly polarized quasar PKS 1610-771 (z = 1.71). Our long-slit spectroscopy of the companion 4.55 arcseconds…

astro-ph.GA2025

Euclid Quick Data Release (Q1): Hunting for luminous z > 6 galaxies in the Euclid Deep Fields -- forecasts and first bright detections

Euclid Collaboration, N. Allen, P. A. Oesch +309

The evolution of the rest-frame ultraviolet luminosity function (UV LF) is a powerful probe of early star formation and stellar mass build-up. At z > 6, its bright end (MUV < -21)…

astro-ph.GA2024

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

Euclid Collaboration, K. Voggel, A. Lançon +270

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 deb…

astro-ph1997

The LMC transition star R84 and the core of the LH 39 OB association

M. Heydari-Malayeri, F. Courbin, G. Rauw +3

On the basis of sub-arcsecond optical imaging we resolve and study the core components of the LMC OB association LH 39. The central star of the association, the rare transition obj…

astro-ph.GA2026

Euclid preparation. Probing galaxy evolution within cosmic voids in Euclid-like simulations

Euclid Collaboration, G. Papini, O. Cucciati +294

The evolution of galaxies is profoundly influenced by the environment in which they reside. Cosmic voids serve as pristine laboratories for studying galaxy evolution in the relativ…

astro-ph.GA2026

Euclid Quick Data Release (Q1): The geometry of dark matter halos from extragalactic streams

Euclid Collaboration, N. Starkman, J. Nibauer +295

Wide-field surveys like Euclid mark a new era of extragalactic stellar stream studies. With a large number of streams, it is now possible to constrain the dark matter halos of gala…

astro-ph.GA2025

Euclid Quick Data Release (Q1): The Strong Lensing Discovery Engine A -- System overview and lens catalogue

Euclid Collaboration, M. Walmsley, P. Holloway +372

We present a catalogue of 497 galaxy-galaxy strong lenses in the Euclid Quick Release 1 data (63 deg). In the initial 0.45\% of Euclid's surveys, we double the total number of…

astro-ph.GA2024

Euclid: ERO -- NISP-only sources and the search for luminous galaxies

J. R. Weaver, S. Taamoli, C. J. R. McPartland +185

This paper presents a search for high redshift galaxies from the Euclid Early Release Observations program "Magnifying Lens." The 1.5 deg area covered by the twin Abell lensing…

astro-ph.CO2022

Euclid: Forecast constraints on consistency tests of the CDM model

S. Nesseris, D. Sapone, M. Martinelli +112

The standard cosmological model is based on the fundamental assumptions of a spatially homogeneous and isotropic universe on large scales. An observational detection of a violation…

astro-ph.IM2024

Euclid. IV. The NISP Calibration Unit

Euclid Collaboration, F. Hormuth, K. Jahnke +332

The near-infrared calibration unit (NI-CU) on board Euclid's Near-Infrared Spectrometer and Photometer (NISP) is the first astronomical calibration lamp based on light-emitting dio…

astro-ph.GA2021

Discovery of Strongly Lensed Quasars in the Ultraviolet Near Infrared Optical Northern Survey (UNIONS)

J. H. H. Chan, C. Lemon, F. Courbin +13

We report the discovery of five new doubly-imaged lensed quasars from the first 2500 square degrees of the ongoing Canada-France Imaging Survey (CFIS), which is a component of the…

astro-ph.CO2025

Euclid: Exploring observational systematics in cluster cosmology -- a comprehensive analysis of cluster counts and clustering

A. Fumagalli, M. Costanzi, T. Castro +168

This study explores the impact of observational and modelling systematic effects on cluster number counts and cluster clustering and provides model prescriptions for their joint an…

astro-ph.GA2025

Euclid Quick Data Release (Q1) -- Data release overview

Euclid Collaboration, H. Aussel, I. Tereno +407

The first Euclid Quick Data Release, Q1, comprises 63.1 sq deg of the Euclid Deep Fields (EDFs) to nominal wide-survey depth. It encompasses visible and near-infrared space-based i…

astro-ph1997

Deconvolution with correct sampling

P. Magain, F. Courbin, S. Sohy

A new method for improving the resolution of astronomical images is presented. It is based on the principle that sampled data cannot be fully deconvolved without violating the samp…

astro-ph.CO2025

Euclid preparation. LXXIV. Euclidised observations of Hubble Frontier Fields and CLASH galaxy clusters

Euclid Collaboration, P. Bergamini, M. Meneghetti +263

We present HST2EUCLID, a novel Python code to generate Euclid realistic mock images in the , , , and photometric bands based on panchro…

astro-ph.GA2026

Euclid: Early Release Observations -- The star-formation history of massive early-type galaxies in the Perseus cluster

S. Martocchia, A. Boselli, J. -C. Cuillandre +157

The Euclid Early Release Observations (ERO) programme targeted the Perseus galaxy cluster in its central region over 0.7deg. We combined the exceptional image quality and depth…

astro-ph.GA2025

Euclid Quick Data Release (Q1). An investigation of optically faint, red objects in the Euclid Deep Fields

Euclid Collaboration, G. Girardi, G. Rodighiero +326

Our understanding of cosmic star-formation at used to largely rely on rest-frame UV observations. However, these observations overlook dusty and massive sources, resulting in…

astro-ph.GA2024

Euclid preparation. XLIX. Selecting active galactic nuclei using observed colours

Euclid Collaboration, L. Bisigello, M. Massimo +244

Euclid will cover over 14000 with two optical and near-infrared spectro-photometric instruments, and is expected to detect around ten million active galactic nuclei (AGN)…

astro-ph2002

On-axis spatially resolved spectroscopy of low redshift quasar host galaxies: HE 1503+0228 at z=0.135

F. Courbin, G. Letawe, P. Magain +8

We present the first result of a comprehensive spectroscopic study of quasar host galaxies. On-axis, spatially resolved spectra of low redshift quasars have been obtained with FORS…

astro-ph.CO2026

Euclid: The linear-construction covariance and cosmology

V. Lindholm, E. Sihvola, J. Valiviita +137

We study the properties of galaxy cluster 2-point correlation function covariance matrices estimated using the linear-construction (LC) method, which is computationally up to 20 ti…

astro-ph1998

Image Deconvolution of the Radio Ring PKS 1830-211

F. Courbin, C. Lidman, B. Frye +4

New high quality Keck and ESO images of PKS 1830-211 are presented. Applying a powerful new deconvolution algorithm to these optical and infrared data, both images of the flat spec…

astro-ph.GA2025

Euclid Quick Data Release (Q1). First Euclid statistical study of the active galactic nuclei contribution fraction

Euclid Collaboration, B. Margalef-Bentabol, L. Wang +331

Active galactic nuclei (AGN) play a key role in galaxy evolution but are challenging to identify due to their varied observational signatures. Furthermore, understanding their impa…

astro-ph.CO2026

Euclid: Galaxy SED reconstruction in the PHZ processing function: impact on the PSF and the role of medium-band filters

Euclid Collaboration, F. Tarsitano, C. Schreiber +301

Weak lensing surveys require accurate correction for the point spread function (PSF) when measuring galaxy shapes. For a diffraction-limited PSF, as arises in space-based missions,…

astro-ph.IM2025

Euclid Quick Data Release (Q1): From images to multiwavelength catalogues: the Euclid MERge Processing Function

Euclid Collaboration, E. Romelli, M. Kümmel +345

The Euclid satellite is an ESA mission that was launched in July 2023. \Euclid is working in its regular observing mode with the target of observing an area of $14\,000~\text{deg}^…

astro-ph.CO2022

Euclid preparation: XX. The Complete Calibration of the Color-Redshift Relation survey: LBT observations and data release

Euclid Collaboration, R. Saglia, S. De Nicola +183

The Complete Calibration of the Color-Redshift Relation survey (C3R2) is a spectroscopic programme designed to empirically calibrate the galaxy color-redshift relation to the Eucli…

astro-ph.CO2013

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses XI. Techniques for time delay measurement in presence of microlensing

M. Tewes, F. Courbin, G. Meylan

Measuring time delays between the multiple images of gravitationally lensed quasars is now recognized as a competitive way to constrain the cosmological parameters, and it is compl…

astro-ph.CO2020

HOLISMOKES -- I. Highly Optimised Lensing Investigations of Supernovae, Microlensing Objects, and Kinematics of Ellipticals and Spirals

S. H. Suyu, S. Huber, R. Cañameras +10

We present the HOLISMOKES programme on strong gravitational lensing of supernovae as a probe of supernova (SN) physics and cosmology. We investigate the effects of microlensing on…

astro-ph2000

Exploring the gravitationally lensed system HE 1104-1805: Near-IR Spectroscopy

F. Courbin, C. Lidman, G. Meylan +2

(Abridged) A new technique for the spatial deconvolution of spectra is applied to near-IR (0.95 - 2.50 micron) NTT/SOFI spectra of the lensed, radio-quiet quasar HE 1104-1805. The…

astro-ph2004

A deep, narrow J-band search for proto-galactic Lyman Alpha emission at redshifts z~9

J. P. Willis, F. Courbin

We present a deep, narrow J-band search for proto--galactic Lyman Alpha emission at redshifts z~9. We combine an exceptionally deep image of the Hubble Deep Field South, obtained u…

astro-ph.GA2025

Euclid: Early Release Observations -- The surface brightness and colour profiles of the far outskirts of galaxies in the Perseus cluster

M. Mondelin, F. Bournaud, J. -C. Cuillandre +110

The Perseus field captured by Euclid as part of its Early Release Observations provides a unique opportunity to study cluster environment ranging from outskirts to dense regions. L…

astro-ph.CO2026

Euclid: Photometric redshift calibration with the clustering redshifts technique

W. d'Assignies, M. Manera, C. Padilla +172

Aims: The precision of cosmological constraints from imaging surveys hinges on accurately estimating the redshift distribution of tomographic bins, especially their mean r…

astro-ph.GA2026

Euclid: A UV-faint quasar in a highly luminous star-forming host galaxy at

S. Belladitta, R. Decarli, E. Bañados +180

Constraining the co-evolution of supermassive black holes and their host galaxies in the first billion years after the Big Bang is essential for understanding the formation of the…

astro-ph.CO2025

Euclid preparation LX. The use of HST images as input for weak-lensing image simulations

Euclid Collaboration, D. Scognamiglio, T. Schrabback +245

Data from the Euclid space telescope will enable cosmic shear measurements with very small statistical errors, requiring corresponding systematic error control level. A common appr…

astro-ph.GA2024

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

Euclid Collaboration, B. Aussel, S. Kruk +255

The Euclid mission is expected to image millions of galaxies with high resolution, providing an extensive dataset to study galaxy evolution. We investigate the application of deep…

astro-ph.CO2024

Euclid preparation. Simulations and nonlinearities beyond CDM. 1. Numerical methods and validation

Euclid Collaboration, J. Adamek, B. Fiorini +268

To constrain models beyond CDM, the development of the Euclid analysis pipeline requires simulations that capture the nonlinear phenomenology of such models. We present an over…

astro-ph.GA2019

Twisted quasar light curves: implications for continuum reverberation mapping of accretion disks

J. H-H. Chan, M. Millon, V. Bonvin +1

With the advent of high-cadence and multi-band photometric monitoring facilities, continuum reverberation mapping is becoming of increasing importance to measure the physical size…

astro-ph2002

Quasar Lensing

F. Courbin, P. Saha, P. L. Schechter

Massive structures, such as galaxies, act as strong gravitational lenses on background sources. When the background source is a quasar, several lensed images are seen, as magnified…

astro-ph.CO2024

Euclid preparation. XXXIX. The effect of baryons on the Halo Mass Function

Euclid Collaboration, T. Castro, S. Borgani +220

The Euclid photometric survey of galaxy clusters stands as a powerful cosmological tool, with the capacity to significantly propel our understanding of the Universe. Despite being…

astro-ph.CO2025

Euclid: Forecasts on CDM consistency tests with growth rate data

I. Ocampo, D. Sapone, S. Nesseris +156

The large-scale structure (LSS) of the Universe is an important probe for deviations from the canonical cosmological constant and cold dark matter (CDM) model. A statistic…

astro-ph.CO2024

Euclid: Field-level inference of primordial non-Gaussianity and cosmic initial conditions

A. Andrews, J. Jasche, G. Lavaux +147

A primary target of the \Euclid space mission is to constrain early-universe physics by searching for deviations from a primordial Gaussian random field. A significant detection of…

astro-ph1995

Photometric monitoring (1987 to 1994) of the gravitational lens candidate UM 425

F. Courbin, P. Magain, M. Remy +6

We present the results of a 7 year long photometric monitoring of two components (A and B) of UM 425, thought to be images, separated by 6.5", of the same z = 1.47 quasar. These co…

astro-ph2007

COSMOGRAIL: the COSmological MOnitoring of GRAvItational Lenses V. The time delay in SDSS J1650+4251

C. Vuissoz, F. Courbin, D. Sluse +8

Aims: Our aim is to measure the time delay between the two gravitationally lensed images of the z = 1.547 quasar SDSS J1650+4251, in order to estimate the Hubble constant H_0. Meth…

astro-ph2000

Exploring the gravitationally lensed system HE1104-1805: VLT spectroscopy of the lens at z=0.729

C. Lidman, F. Courbin, J. -P. Kneib +3

Using FORS2, mounted on Kueyen (UT2 of the VLT), we have obtained the redshift of the lensing galaxy in the gravitational lens system HE1104-1805. We measure z=0.729, in good agree…

astro-ph.CO2025

Euclid preparation. Simulating thousands of Euclid spectroscopic skies

Euclid Collaboration, P. Monaco, G. Parimbelli +303

We present two extensive sets of 3500+1000 simulations of dark matter haloes on the past light cone, and two corresponding sets of simulated (`mock') galaxy catalogues that represe…

astro-ph2007

On-axis spectroscopy of the host galaxies of 20 optically luminous quasars at z~0.3

G. Letawe, P. Magain, F. Courbin +4

We present the analysis of a sample of 20 bright low-redshift quasars (M_B<-23 and z < 0.35) observed spectroscopically with the VLT. The FORS1 spectra, obtained in Multi Object Sp…

astro-ph.CO2024

Euclid: Testing photometric selection of emission-line galaxy targets

M. S. Cagliari, B. R. Granett, L. Guzzo +144

Multi-object spectroscopic galaxy surveys typically make use of photometric and colour criteria to select targets. Conversely, the Euclid NISP slitless spectrograph will record spe…

astro-ph.GA2017

MUSE-inspired view of the quasar Q2059-360, its Lyman alpha blob, and its neighborhood

P. L. North, R. A. Marino, C. Gorgoni +6

The radio-quiet quasar Q2059-360 at redshift is known to be close to a small Lyman blob (LAB) and to be absorbed by a proximate damped Ly (PDLA) system. Here, we…

astro-ph.IM2025

Euclid Quick Data Release (Q1). From simulations to sky: Advancing machine-learning lens detection with real Euclid data

Euclid Collaboration, N. E. P. Lines, T. E. Collett +301

In the era of large-scale surveys like Euclid, machine learning has become an essential tool for identifying rare yet scientifically valuable objects, such as strong gravitational…

astro-ph2007

ZEN2: A narrow J-band search for z~9 Lya emitting galaxies directed towards three lensing clusters

J. P. Willis, F. Courbin, J. P. Kneib +1

We present the results of a continuing survey to detect Lya emitting galaxies at redshifts z~9: the ZEN ("z equals nine'') survey. We have obtained deep VLT/ISAAC observations in t…

astro-ph.CO2025

Cosmology Likelihood for Observables in \Euclid (CLOE). 1. Theoretical recipe

Euclid Collaboration, V. F. Cardone, S. Joudaki +323

As the statistical precision of cosmological measurements increases, the accuracy of the theoretical description of these measurements needs to increase correspondingly in order to…

astro-ph.IM2015

Evaluating the effect of stellar multiplicity on the PSF of space-based weak lensing surveys

T. Kuntzer, F. Courbin, G. Meylan

The next generation of space-based telescopes used for weak lensing surveys will require exquisite point spread function (PSF) determination. Previously negligible effects may beco…

astro-ph.GA2025

Euclid preparation. Predicting star-forming galaxy scaling relations with the spectral stacking code SpectraPyle

Euclid Collaboration, S. Quai, L. Pozzetti +309

We introduce SpectraPyle, a versatile spectral stacking pipeline developed for the Euclid mission's NISP spectroscopic surveys, aimed at extracting faint emission lines and spectra…

astro-ph2004

An optical time delay for the double gravitational lens system FBQ 0951+2635

P. Jakobsson, J. Hjorth, I. Burud +3

We present optical R-band light curves of the double gravitationally lensed quasar FBQ 0951+2635 from observations obtained at the Nordic Optical Telescope between March 1999 and J…

astro-ph.CO2025

Euclid: Relativistic effects in the dipole of the 2-point correlation function

F. Lepori, S. Schulz, I. Tutusaus +130

Gravitational redshift and Doppler effects give rise to an antisymmetric component of the galaxy correlation function when cross-correlating two galaxy populations or two different…

astro-ph.IM2024

Euclid. III. The NISP Instrument

Euclid Collaboration, K. Jahnke, W. Gillard +434

The Near-Infrared Spectrometer and Photometer (NISP) on board the Euclid satellite provides multiband photometry and R>=450 slitless grism spectroscopy in the 950-2020nm wavelength…

astro-ph2007

Discovery of a Probable Physical Triple Quasar

S. G. Djorgovski, F. Courbin, G. Meylan +4

We report the discovery of the first known probable case of a physical triple quasar (not a gravitational lens). A previously known double system, QQ 1429-008 at z = 2.076, is show…

astro-ph2002

Cosmic alignment towards the radio Einstein ring PKS 1830-211 ?

F. Courbin, G. Meylan, J. P. Kneib +1

Optical and near-IR Hubble Space Telescope and Gemini-North adaptive optics images, further improved through deconvolution, are used to explore the gravitationally lensed radio sou…

astro-ph2007

DECPHOT: an optimal deconvolution-based photometric reduction method

M. Gillon, P. Magain, V. Chantry +5

A high accuracy photometric reduction method is needed to take full advantage of the potential of the transit method for the detection and characterization of exoplanets, especiall…

astro-ph.CO2020

STRIDES: a 3.9 per cent measurement of the Hubble constant from the strong lens system DES J0408-5354

A. J. Shajib, S. Birrer, T. Treu +88

We present a blind time-delay cosmographic analysis for the lens system DES J04085354. This system is extraordinary for the presence of two sets of multiple images at different…

astro-ph.CO2025

Euclid: Quick Data Release (Q1) -- Watching ICM-selected galaxy clusters with Euclid eyes -- prospects of Euclid data in the context of large SZ and X-ray based surveys

M. Klein, K. George, J. J. Mohr +144

Galaxy clusters detected through their X-ray emission or Sunyaev--Zeldovich effect (SZE), both produced by the intra-cluster medium (ICM), are key probes in cosmological and astrop…

astro-ph.GA2025

Euclid Quick Data Release (Q1). Galaxy shapes and alignments in the cosmic web

Euclid Collaboration, C. Laigle, C. Gouin +341

Galaxy morphologies and shape orientations are expected to correlate with their large-scale environment, since they grow by accreting matter from the cosmic web and are subject to…

astro-ph.CO2024

Euclid preparation. Improving cosmological constraints using a new multi-tracer method with the spectroscopic and photometric samples

Euclid Collaboration, F. Dournac, A. Blanchard +240

Future data provided by the Euclid mission will allow us to better understand the cosmic history of the Universe. A metric of its performance is the figure-of-merit (FoM) of dark e…

astro-ph.CO2022

Euclid: Testing the Copernican principle with next-generation surveys

D. Camarena, V. Marra, Z. Sakr +112

The Copernican principle, the notion that we are not at a special location in the Universe, is one of the cornerstones of modern cosmology and its violation would invalidate the Fr…

astro-ph.CO2026

The PAU Survey and Euclid: Analysing photometric redshifts from realistically simulated narrow-band photometry with Flagship 2

A. Wittje, H. Hildebrandt, D. Navarro-Gironés +154

The study of the large-scale structure of the Universe and the distribution of galaxies has been greatly advanced by the application of various types of photometric redshift estima…

astro-ph.GA2022

Gravitationally lensed quasars in Gaia -- IV. 150 new lenses, quasar pairs, and projected quasars

C. Lemon, T. Anguita, M. Auger +8

We report the spectroscopic follow-up of 175 lensed quasar candidates selected using Gaia Data Release 2 observations following Lemon et al. 2019. Systems include 86 confirmed lens…

astro-ph2008

Microlensing variability in the gravitationally lensed quasar QSO 2237+0305 = the Einstein Cross. II. Energy profile of the accretion disk

A. Eigenbrod, F. Courbin, G. Meylan +4

We present the continuation of our long-term spectroscopic monitoring of the gravitationally lensed quasar QSO 2237+0305. We investigate the chromatic variations observed in the UV…

astro-ph1997

Detection of the lensing galaxy in HE 1104-1805

F. Courbin, C. Lidman, P. Magain

We report on deep IR imaging of the double quasar HE 1104-1805. A new image deconvolution technique has been applied to the data in order to optimally combine the numerous frames o…

astro-ph.CO2026

Euclid preparation. LXXXIX. Accurate and precise data-driven angular power spectrum covariances

Euclid Collaboration, K. Naidoo, J. Ruiz-Zapatero +280

We develop techniques for generating accurate and precise internal covariances for measurements of clustering and weak-lensing angular power spectra. These methods have been design…

astro-ph.CO2025

Euclid preparation. XLI. Galaxy power spectrum modelling in real space

Euclid Collaboration, A. Pezzotta, C. Moretti +246

We investigate the accuracy of the perturbative galaxy bias expansion in view of the forthcoming analysis of the Euclid spectroscopic galaxy samples. We compare the performance of…

astro-ph.CO2025

Euclid preparation. BAO analysis of photometric galaxy clustering in configuration space

Euclid Collaboration, V. Duret, S. Escoffier +286

With about 1.5 billion galaxies expected to be observed, the very large number of objects in the Euclid photometric survey will allow for precise studies of galaxy clustering from…

astro-ph.GA2025

Euclid preparation. Spatially resolved stellar populations of local galaxies with Euclid: a proof of concept using synthetic images with the TNG50 simulation

Euclid Collaboration, Abdurro'uf, C. Tortora +286

The European Space Agency's Euclid mission will observe approximately 14,000 of the extragalactic sky and deliver high-quality imaging for many galaxies. The depth a…