Explanipedia

Euclid: Early Release Observations -- A combined strong and weak lensing solution for Abell 2390 beyond its virial radius Open

J. M. Diego, G. Congedo, R. Gavazzi, T. Schrabback, Hakim Atek , et al. · 2025

Euclid/ is currently mapping the distribution of matter in the Universe in detail via the weak lensing signature of billions of distant galaxies. The weak lensing signal is most prominent around galaxy clusters and can extend up to distanc…

Euclid preparation. Controlling angular systematics in the Euclid spectroscopic galaxy sample Open

M.Y Elkhashab, B. R. Granett, E Sefusatti, C. Scarlata, Bonnabelle Zabelle , et al. · 2025

We present the strategy to identify and mitigate potential sources of angular systematics in the Euclid spectroscopic galaxy survey, and we quantify their impact on galaxy clustering measurements and cosmological parameter estimation. We f…

Euclid Quick Data Release (Q1): Identification of massive galaxy candidates at the end of the Epoch of Reionisation Open

K. I. Caputi, Conor McPartland, G. Desprez, A Biviano, G. Girardi , et al. · 2025

Probing the presence and properties of massive galaxies at high redshift is one of the most critical tests for galaxy formation models. In this work, we search for galaxies with stellar masses M* > 10^10.25 Msun at z in [5,7], i.e., toward…

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

Euclid Collaboration, Natalie Allen, P. A. Oesch, R. A. A. Bowler, Sune Toft , et al. · 2025

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) remains poorly constrained due to the small volumes of exis…

Euclid Quick Data Release (Q1). Searching for giant gravitational arcs in galaxy clusters with mask region-based convolutional neural networks Open

L. Bazzanini, G. Angora, P. Bergamini, Ana Acebrón, C. Grillo , et al. · 2025

Strong gravitational lensing (SL) by galaxy clusters is a powerful probe of their inner mass distribution and a key test bed for cosmological models. However, the detection of SL events in wide-field surveys such as Euclid requires robust,…

Euclid: Quick Data Release (Q1)- The connection between galaxy close encounters and radio activity Open

M. Magliocchetti, Antonio La Marca, L. Bisigello, M. Bondi, F. Ricci , et al. · 2025

Using the large statistics provided by both Euclid and the LOFAR surveys, we present the first large-scale study of the connection between radio emission, its morphology, and the merging properties of the hosts of radio sources up to z=2. …

Euclid: An emulator for baryonic effects on the matter bispectrum Open

P.A Burger, Giovanni Aricò, Laila Linke, Raúl E. Angulo, Jeger C. Broxterman , et al. · 2025

The Euclid mission and other next-generation large-scale structure surveys will enable high-precision measurements of the cosmic matter distribution. Understanding the impact of baryonic processes such as star formation and active galactic…

Euclid: Systematic uncertainties from the halo mass conversion on galaxy cluster number count data analyses Open

T. Gayoux, Pier-Stefano Corasaniti, T. R. G. Richardson, Scott T. Kay, A.M.C Le Brun , et al. · 2025

The large catalogues of galaxy clusters expected from the Euclid survey will enable cosmological analyses of cluster number counts that require accurate cosmological model predictions. One possibility is to use parametric fits calibrated a…

Euclid Quick Data Release (Q1). Characteristics and limitations of the spectroscopic measurements Open

V. Le Brun, M. Béthermin, M. Moresco, D. Vibert, D. Vergani , et al. · 2025

The spectroscopy processing function (SPE PF) of the Euclid pipeline is dedicated to the automatic analysis of 1D spectra to determine redshifts, line fluxes, and spectral classifications. The first Euclid Quick Data Release (Q1) delivers …

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

Alessandra Fumagalli, M. Costanzi, S. Di Domizio, A. Saro, S Borgani , et al. · 2025

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 analysis, in the context of the \Euclid survey. Using 1000 \E…

Euclid preparation. Cosmology Likelihood for Observables in Euclid (CLOE). 6: Impact of systematic uncertainties on the cosmological analysis Open

L Blot, K Tanidis, G Cañas-Herrera, P. Carrilho, Marco Bonici , et al. · 2025

Extracting cosmological information from the Euclid galaxy survey will require modelling numerous systematic effects during the inference process. This implies varying a large number of nuisance parameters, which have to be marginalised ov…

Euclid preparation. Cosmology Likelihood for Observables in Euclid (CLOE). 3. Inference and Forecasts Open

G Cañas-Herrera, L.W.K Goh, L Blot, Marco Bonici, S Camera , et al. · 2025

The Euclid mission aims to measure the positions, shapes, and redshifts of over a billion galaxies to provide unprecedented constraints on the nature of dark matter and dark energy. Achieving this goal requires a continuous reassessment of…

Euclid preparation. Cosmology Likelihood for Observables in Euclid (CLOE). 4: Validation and Performance Open

M. Martinelli, M. Martinelli, D Sciotti, L Blot, Marco Bonici , et al. · 2025

The Euclid satellite will provide data on the clustering of galaxies and on the distortion of their measured shapes, which can be used to constrain and test the cosmological model. However, the increase in precision places strong requireme…

Euclid preparation: Towards a DR1 application of higher-order weak lensing statistics Open

S Vinciguerra, Filippo Bouchè, N. Martinet, Lina Castiblanco, Cora Uhlemann , et al. · 2025

This is the second paper in the HOWLS (higher-order weak lensing statistics) series exploring the usage of non-Gaussian statistics for cosmology inference within \textit{Euclid}. With respect to our first paper, we develop a full tomograph…

Euclid: Discovery of bright $z\simeq7$ Lyman-break galaxies in UltraVISTA and Euclid COSMOS Open

R. G. Varadaraj, R. A. A. Bowler, M. J. Jarvis, J. R. Weaver, Eduardo Bañados , et al. · 2025

We present a search for $z\simeq7$ Lyman-break galaxies using the $1.72 \, \rm{deg}^2$ near-infrared UltraVISTA survey in the COSMOS field, reaching $5\,σ$ depths in $Y$ of 26.2. We incorporate deep optical and Spitzer imaging for a full s…

Euclid : Star clusters in IC 342, NGC 2403, and Holmberg II Open

S. S. Larsen, A. M. N. Ferguson, J. Howell, F. Annibali, J.-C. Cuillandre , et al. · 2025

We examine the star cluster populations in the three nearby (3.20–3.45 Mpc) galaxies IC 342, NGC 2403, and Holmberg II, observed as part of the Euclid Early Release Observations programme. Our main focus in this paper is old globular clust…

Euclid preparation. Methodology for validating the Euclid Catalogue of Galaxy Clusters using external data Open

J.-B. Mélin, S. A. Stanford, Alex Widmer, Paula Tarrío, J. G. Bartlett , et al. · 2025

We present our methodology for identifying known clusters as counterparts to objects in the Euclid Catalogue of Galaxy Clusters (ECGC). Euclid is expected to detect a large number of optically-selected galaxy clusters over the approximatel…

Euclid: Photometric redshift calibration performance with the clustering-redshifts technique in the Flagship 2 simulation Open

William d’Assignies D., Marc Manera, C. Padilla Aranda, O. Ilbert, H. Hildebrandt , et al. · 2025

Aims. The precision of cosmological constraints from imaging surveys hinges on an accurately estimated redshift distribution n ( z ) of the tomographic bins, especially their mean redshifts. We assess the effectiveness of the clustering-re…

Euclid Quick Data Release (Q1). Optical and near-infrared identification and classification of point-like X-ray selected sources Open

W. Roster, M. Salvato, R. Shirley, R. Shirley, Hermine Landt , et al. · 2025

To better understand the role of active galactic nuclei (AGN) in galaxy evolution, it is crucial to work with a complete and pure AGN sample. X-ray surveys are key to doing so, but their larger positional uncertainties complicate counterpa…

Euclid preparation. Establishing the quality of the 2D reconstruction of the filaments of the cosmic web with DisPerSE using Euclid photometric redshifts Open

Nicola Malavasi, Florian Sarron, Ulrike Kuchner, C. Laigle, Katarina Kraljic , et al. · 2025

Cosmic filaments are prominent structures of the matter distribution of the Universe. Modern detection algorithms are an efficient way to identify filaments in large-scale observational surveys of galaxies. Many of these methods were origi…

Euclid: Photometric redshift calibration with self-organising maps Open

W. Roster, A. H. Wright, H. Hildebrandt, Robert Reischke, O. Ilbert , et al. · 2025

The Euclid survey aims to trace the evolution of cosmic structures up to redshift $z$ $\sim$ 3 and beyond. Its success depends critically on obtaining highly accurate mean redshifts for ensembles of galaxies $n(z)$ in all tomographic bins,…

Euclid: Forecasts on $Λ$CDM consistency tests with growth rate data Open

Indira Ocampo, D Sapone, Savvas Nesseris, George Alestas, J García-Bellido , et al. · 2025

The large-scale structure (LSS) of the Universe is an important probe for deviations from the canonical cosmological constant $Λ$ and cold dark matter ($Λ$CDM) model. A statistically significant detection of any deviations would signify th…

Euclid Quick Data Release (Q1). A probabilistic classification of quenched galaxies Open

Y. Ascasíbar, Y. Ascasíbar, G. Verdoes Kleijn, G de Lucia, G de Lucia , et al. · 2025

Investigating what drives the quenching of star formation in galaxies is key to understanding their evolution. The Euclid mission will provide rich spatial and spectral data from optical to infrared wavelengths for millions of galaxies, an…

Euclid preparation: Expected constraints on initial conditions Open

F Finelli, Y Akrami, A. H. Andrews, M. Ballardini, S. Casas , et al. · 2025

The Euclid mission of the European Space Agency will deliver galaxy and cosmic shear surveys, which will be used to constrain initial conditions and statistics of primordial fluctuations. We present highlights for the Euclid scientific cap…

Euclid preparation. Simulating thousands of Euclid spectroscopic skies Open

Pierluigi Monaco, Gabriele Parimbelli, M.Y Elkhashab, J. Salvalaggio, T. Castro , et al. · 2025

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 represent the Euclid spectroscopic sample. The simulations were pr…

Euclid VI. NISP-P optical ghosts Open

Ken Paterson, M. Schirmer, M Schirmer, K. Okumura, K Jahnke , et al. · 2025

The Near-Infrared Spectrometer and Photometer (NISP) onboard Euclid includes several optical elements in its path, which introduce artefacts into the data from non-nominal light paths. To ensure uncontaminated source photometry, these arte…

Euclid: Early Release Observations of ram-pressure stripping in the Perseus cluster Open

K. George, A. Boselli, J.-C. Cuillandre, M. Kümmel, A. Lançon , et al. · 2025

Euclid is delivering optical and near-infrared imaging data over 14 000 deg 2 on the sky at spatial resolution and surface brightness levels that can be used to understand the morphological transformation of galaxies within groups and clus…

Euclid preparation. Full-shape modelling of 2-point and 3-point correlation functions in real space Open

M Guidi, A. Veropalumbo, A. Pugno, M. Moresco, E Sefusatti , et al. · 2025

We investigate the accuracy and range of validity of the perturbative model for the 2-point (2PCF) and 3-point (3PCF) correlation functions in real space in view of the forthcoming analysis of the Euclid mission spectroscopic sample. We ta…

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 Open

Mary Beth Klein, Koshy George, J. J. Mohr, B Altieri, Luca Amendola , et al. · 2025

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 astrophysical studies. To maximise the scientific return of such …

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

Kammila Naidoo, Jaime Ruiz-Zapatero, N Tessore, B. Joachimi, A. Loureiro , et al. · 2025

We develop techniques for generating accurate and precise internal covariances for measurements of clustering and weak lensing angular power spectra. These methods are designed to produce non-singular and unbiased covariances for Euclid's …

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