Research Articles (Physics)

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Synthesis and NO2 sensing characteristics of Mg-functionalized VO2(M) Nanorods
(Elsevier Ltd, 2025) Mabakachaba, Boitumelo Mafalo; Halindintwali, Sylvain; Numan, Nagla
Herein, we report the synthesis, characterization, and potential NO2 gas sensing application of pristine and Mg-doped VO2(M) nanorods sensors. The gas sensing properties of both sensors were tested for various analytes, i.e., CO, CH4, H2S, NO2, SO2 while varying operating temperatures. The sensors demonstrated substantial sensing performance at working temperature of about 120°C, where VO2-Mg outperformed the pristine sensor with a response value of about 59.3%. At ambient temperature (∼25°C), the response values for pristine and VO2-Mg were 3.29% and 6.35%, respectively. The Mg-dopant's catalytic activity alters the electrical characteristics and adsorbed oxygen species on the sensor surface, leading to improved sensing performance. VO2(M)-based sensor‘s sensing mechanism fits the Freundlich isotherm model, thus making the sensors suitable for detecting NO2 at high and ambient temperatures.
Damping mechanism of the isoscalar giant monopole resonance in 58Ni
(Elsevier B.V, 2025) Mabika, Phumzile Zandile; Bahini ATriambak, Smarajit; Rebeiro, Bernadette
Following the success achieved in explaining the origin of fine structure observed in the isoscalar giant quadrupole resonance (ISGQR) and the isovector giant dipole resonance (IVGDR), fine structure in the region of the isoscalar giant monopole resonance (ISGMR) were investigated using the wavelet analysis in order to investigate the role of different mechanisms contributing to its decay width. In this context, high-energy resolution ISGMR data on many nuclei were acquired at the iThemba Laboratory for Accelerator Based Sciences (iThemba LABS). The experimental scales extracted from these data are compared to different theoretical approaches performed in the framework of quasiparticle random phase approximation (QRPA) and beyond-QRPA including complex configurations using both non-relativistic and relativistic density functional theory. The role of Landau fragmentation was highlighted while the inclusion of coupling between one particle-one hole (1p-1h) and two particle-two hole (2p-2h) configurations modify the strength distributions and wavelet scales indicating the importance of the spreading width.
Euclid preparation: LXVI. Impact of line-of-sight projections on the covariance between galaxy cluster multi-wavelength observable properties: Insights from hydrodynamic simulations
(EDP Sciences, 2025) Karagiannis, Dionysios; Ragagnin, Antonio; Saro, Alex
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 information on the scatter, skewness, and covariance of various mass-observable relations in galaxy clusters in cosmological hydrodynamic simulations. This information will help future analyses improve the general approach to accretion histories and projection effects, as well as to model mass-observable relations for cosmology studies. Methods. We identified galaxy clusters in Magneticum Box2b simulations with masses of M200c > 1014 M⊙ at redshifts of z = 0.24 and z = 0.90. Our analysis included Euclid-derived properties such as richness, stellar mass, lensing mass, and concentration. Additionally, we investigated complementary multi-wavelength data, including X-ray luminosity, integrated Compton-y parameter, gas mass, and temperature. We then examined the impact of projection effects on mass-observable residuals and correlations. Results. We find that at intermediate redshift (z = 0.24), projection effects have the greatest impact of lensing concentration, richness, and gas mass in terms of the scatter and skewness of the log-residuals of scaling relations. The contribution of projection effects can be significant enough to boost a spurious hot-versus cold-baryon correlations and consequently hide underlying correlations due to halo accretion histories. At high redshift (z = 0.9), the richness has a much lower scatter (of log-residuals), while the quantity that is most impacted by projection effects is the lensing mass. The lensing concentration reconstruction, in particular, is affected by deviations of the reduced-shear profile shape from that derived using a Navarro-Frenk-White (NFW) profile; the amount of interlopers in the line of sight, on the other hand, is not as important.
Euclid preparation: LX. the use of HST images as input for weak-lensing image simulations
(EDP Sciences, 2025) Karagiannis, Dionysios; Scognamiglio, Diana; Schrabback, Tim
Data from the Euclid space telescope will enable cosmic shear measurements to be carried out with very small statistical errors, necessitating a corresponding level of systematic error control. A common approach to correct for shear biases involves calibrating shape measurement methods using image simulations with known input shear. Given their high resolution, galaxies observed with the Hubble Space Telescope (HST) can, in principle, be utilised to emulate Euclid observations of sheared galaxy images with realistic morphologies. In this work, we employ a GalSim-based testing environment to investigate whether uncertainties in the HST point spread function (PSF) model or in data processing techniques introduce significant biases in weak-lensing (WL) shear calibration. We used single Sérsic galaxy models to simulate both HST and Euclid observations. We then 'Euclidised' our HST simulations and compared the results with the directly simulated Euclid-like images. For this comparison, we utilised a moment-based shape measurement algorithm and galaxy model fits. Through the Euclidisation procedure, we e_ectively reduced the residual multiplicative biases in shear measurements to sub-percent levels. This achievement was made possible by employing either the native pixel scales of the instruments, utilising the Lanczos15 interpolation kernel, correcting for noise correlations, and ensuring consistent galaxy signal-to-noise ratios between simulation branches. Alternatively, a finer pixel scale can be employed alongside deeper HST data. However, the Euclidisation procedure requires further analysis on the impact of the correlated noise, to estimate calibration bias. We found that additive biases can be mitigated by applying a post-deconvolution isotropisation in the Euclidisation set-up. Additionally, we conducted an in-depth analysis of the accuracy of TinyTim HST PSF models using star fields observed in the F606W and F814W filters. We observe that F606W images exhibit a broader scatter in the recovered best-fit focus, compared to those in the F814W filter. Estimating the focus value for the F606W filter in lower stellar density regimes has allowed us to reveal significant statistical uncertainties
Towards lifetime measurement of excited states in 120Sn using thermal neutron capture
(Elsevier B.V., 2025) Garrett, Paul; Wu, Frank; Andreoiu, Corina
The intruder bands in Sn isotopes, based on the 2p-2h excitation across the Z=50 proton shell gap, are well-known to exhibit shape coexistence near the neutron mid-shell region. The spectroscopic signatures are enhanced E0 transitions between the 0+ band heads and enhanced E2 transitions within rotational bands built on these 0+ band heads. However, lifetime information for the excited 0+ states is incomplete. Experimental details for the neutron-capture reaction and analysis procedures are described, and the first result of the 21+ lifetime demonstrates proper calibration of the setup.
Constraining primordial non-Gaussianity by combining photometric galaxy and 21 cm intensity mapping surveys
(Springer Nature, 2025) Kopana, Mponeng; Maartens, Roy; Jolicoeur, Sheean
The fluctuations produced during cosmic inflation may exhibit non-Gaussian characteristics that are imprinted in the large-scale structure of the Universe. This non-Gaussian imprint is an ultra-large scale signal that can be detected using the power spectrum. We focus on the local-type non-Gaussianity fNL and employ a multi-tracer analysis that combines different probes in order to mitigate cosmic variance and maximize the non-Gaussian signal. In our previous paper, we showed that combining spectroscopic galaxy surveys with 21 cm intensity mapping surveys in interferometer mode could lead to a ∼ 20–30% improvement in the precision on this non-Gaussian signal. Here we combine the same 21 cm experiments, including also single-dish surveys, with photometric galaxy surveys. The 21 cm single-dish surveys are based on MeerKAT and SKAO and the interferometric surveys are alike to HIRAX and PUMA. We implement foreground-avoidance filters and utilize models for the 21 cm thermal noise associated with single-dish and interferometer modes. The photometric galaxy surveys are similar to the DES and LSST. Our multi-tracer Fisher forecasts show a better precision for the combination of the photometric galaxy surveys and 21 cm interferometric surveys than with the 21 cm single-dish surveys – leading to at most an improvement of 23% in the former case and 16% in the latter case. Furthermore, we examine the impact of varying the foreground filter parameter, redshift range and sky area on the derived constraint. We find that the fNL constraint is highly sensitive to both the redshift range and sky area. The foreground filter parameter shows negligible effect.
The tracking tapered gridded estimator for the 21-cm power spectrum from MWA drift scan observations-II. the missing frequency channels
(Oxford University Press, 2025) Chatterjee, Suman; Elahi, Khandakar Md Asif; Bharadwaj, Somnath
Missing frequency channels pose a problem in estimating the redshifted 21-cm power spectrum from radio-interferometric visibility data. This is particularly severe for the Murchison Widefield Array (MWA), which has a periodic pattern of missing channels that introduces spikes along. The Tracking Tapered Gridded Estimator (TTGE) overcomes this by first correlating the visibilities in the frequency domain to estimate the multifrequency angular power spectrum (MAPS) that has no missing frequency separation. We perform a Fourier transform along to estimate. Simulations demonstrate that the TTGE can estimate without any artefacts due to missing channels. However, the spikes persist for the actual foreground-dominated data. A detailed investigation, considering both simulations and actual data, reveals that the spikes originate from a combination of the missing channels and the strong spectral dependence of the foregrounds. We propose and demonstrate a technique to mitigate the spikes. Applying this, we find the values of in the region and 0.35 \, {\rm Mpc^{-1}}$]]> to be consistent with zero within the expected statistical fluctuations. We obtain the upper limit of at for the mean-squared brightness temperature fluctuations of the epoch of reionization (EoR) 21-cm signal. This upper limit is from min of observation for a single pointing direction. We expect tighter constraints when we combine all 162 different pointing directions of the drift scan observation.
Euclid IV. The NISP Calibration Unit
(EDP Sciences, 2025) Karagiannis, Dionysios; Hormuth, Felix; Jahnke, Knud
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 diodes (LEDs) to be operated in space. Euclid is a mission in ESA’s Cosmic Vision 2015–2025 framework to explore the dark universe and provide a next-level characterisation of the nature of gravitation, dark matter, and dark energy. Calibrating photometric and spectrometric measurements of galaxies to better than 1.5% accuracy in a survey homogeneously mapping ∼14 000 deg2 of extragalactic sky requires a very detailed characterisation of near-infrared (NIR) detector properties as well as constant monitoring of them in flight. To cover two of the main contributions – relative pixel-to-pixel sensitivity and non-linearity characteristics – and to support other calibration activities, NI-CU was designed to provide spatially approximately homogeneous (<12% variations) and temporally stable illumination (0.1–0.2% over 1200 s) over the NISP detector plane with minimal power consumption and energy dissipation. NI-CU covers the spectral range ∼[900,1900] nm – at cryo-operating temperature – at five fixed independent wavelengths to capture wavelength-dependent behaviour of the detectors, with fluence over a dynamic range of ≳100 from ∼15 ph s−1 pixel−1 to >1500 ph s−1 pixel−1. For this functionality, NI-CU is based on LEDs. We describe the rationale behind the decision and design process, the challenges in sourcing the right LEDs, and the qualification process and lessons learned. We also provide a description of the completed NI-CU, its capabilities, and performance as well as its limits. NI-CU has been integrated into NISP and the Euclid satellite, and since Euclid’s launch in July 2023, it has started supporting survey operations.
Going deeper into the dark with COSMOS-Web JWST unveils the total contribution of radio-selected NIR-faint galaxies to the cosmic star formation rate density
(EDP Sciences, 2025) Vaccari, Mattia; Harish, Santosh; Gentile, Fabrizio
We present the first follow-up with JWST of radio-selected near-infrared (NIR)-faint galaxies as part of the COSMOS-Web survey. By selecting galaxies detected at radio frequencies (S3 GHz > 11.5 µJy; i.e., S/N > 5) and with faint counterparts at NIR wavelengths (F150W > 26.1 mag), we collected a sample of 127 likely dusty star-forming galaxies (DSFGs). We estimated their physical properties through SED fitting, computed the first radio luminosity function for these types of sources and their contribution to the total cosmic star formation rate density. Our analysis confirms that these sources represent a population of highly dust-obscured (hAvi ∼ 3.5 mag) massive (hM?i ∼ 1010.8 M) and star-forming galaxies (hSFRi ∼ 300 M yr−1) located at hzi ∼ 3.6, representing the high-redshift tail of the full distribution of radio sources. Our results also indicate that these galaxies could dominate the bright end of the radio luminosity function and reach a total contribution to the cosmic star formation rate density equal to that estimated only considering NIR-bright sources at z ∼ 4.5. Finally, our analysis further confirms that the radio selection can be employed to collect statistically significant samples of DSFGs, representing a complementary alternative to the other selections based on JWST colors or detection at FIR/(sub)millimeter wavelengths.
Measurement of radon exhalation and emanation in synthesized coal fly ash-based geopolymer paste for building applications
(Elsevier B.V., 2025) Ntsa, Evral; Lindsay, Robert; Mouele, Emile Salomon Massima; Mukaba, Jean Luc; Petrik, Leslie Felicia
This study examines the radon exhalation potential of CFA and CFA-based GPP products, focusing on their elemental composition, structural properties, and radon containment capabilities. The particle size analysis result revealed that a substantial portion of CFA particles are fine, contributing to a greater surface area, which increased the potential for radon emanation. SEM analysis highlighted microstructural differences, with denser structures in the geopolymer products. XRF result revealed reductions in potassium (⁴⁰K), uranium (²³⁵U, ²³⁸U), and thorium (²²⁶Ra) progenitors in CFA-based GPP products compared to CFA, and resulted in lower radioactivity due to the dilution effect of fillers and additives. XRD analysis showed the presence of crystalline phases such as quartz, mullite and amorphous phases in CFA and in the CFA-based GPP. The amorphous glassy phase in CFA, being rich in SiO₂ and Al₂O₃ precursors was critical for forming the aluminosilicate geopolymer network, that reduced porosity and trapped radon progenitors. Variations in CaO content and the formation of Ca containing mineral phases enhanced radon retention in CFA-base GPP products. Density measurements indicated that higher-density products exhibited lower permeability, reducing radon exhalation. Radioactivity measurements showed that CFA emitted 684 Bq/kg, above the world average of 420 Bq/kg and CFA-based GPP emitted between 408 and 459 Bq/kg. These findings underscored the need for controlling formulations and curing conditions to mitigate radon emanations of CFA-based products such as geopolymers.
H I asymmetries in spatially resolved simba galaxies
(Oxford University Press, 2025) Davé, Romeel; Hank, Nadine A.N.; Verheijen, Marc A.W.
We present a study of the neutral atomic hydrogen (H I) content of spatially resolved, low-redshift galaxies in the SIMBA cosmological simulations. We create synthetic H I data cubes designed to match observations from the Apertif Medium-Deep H I imaging survey, and follow an observational approach to derive the H I size–mass relation. The H I size–mass relation for sIMBA is in broad agreement with the observed relation to within 0.1 dex, but SIMBA galaxies are slightly smaller than expected at fixed H I mass. We quantify the H I spectral (Aflux) and morphological (Amod) asymmetries of the galaxies and motivate standardizing the relative spatial resolution when comparing Amod values in a sample that spans several orders of magnitude in H I mass. Galaxies are classified into three categories (isolated, interacted, or merged) based on their dynamical histories over the preceding ∼2 Gyr to contextualize disturbances in their H I reservoirs. We determine that the interacted and merged categories have higher mean asymmetries than the isolated category, with a larger separation between the categories’ Amod distributions than between their Aflux distributions. For the interacted and merged categories, we find an inverse correlation between baryonic mass and Amod that is not observed between baryonic mass and Aflux. These results, coupled with the weak correlation found between Aflux and Amod, highlight the limitations of only using Aflux to infer the H I distributions of spatially unresolved H I detections.
High-significance detection of correlation between the unresolved gamma-ray background and the large-scale cosmic structure
(Institute of Physics, 2025) Camera, Stefano; Thakore, Bhashin; Negro, Michela
Our understanding of the γ-ray sky has improved dramatically in the past decade, however, the unresolved γ-ray background (UGRB) still has a potential wealth of information about the faintest γ-ray sources pervading the Universe. Statistical cross-correlations with tracers of cosmic structure can indirectly identify the populations that most characterize the γ-ray background. In this study, we analyze the angular correlation between the γ-ray background and the matter distribution in the Universe as traced by gravitational lensing, leveraging more than a decade of observations from the Fermi-Large Area Telescope (LAT) and 3 years of data from the Dark Energy Survey (DES). We detect a correlation at signal-to-noise ratio of 8.9. Most of the statistical significance comes from large scales, demonstrating, for the first time, that a substantial portion of the UGRB aligns with the mass clustering of the Universe as traced by weak lensing. Blazars provide a plausible explanation for this signal, especially if those contributing to the correlation reside in halos of large mass (∼ 1014 M ⊙) and account for approximately 30-40% of the UGRB above 10 GeV. Additionally, we observe a preference for a curved γ-ray energy spectrum, with a log-parabolic shape being favored over a power-law. We also discuss the possibility of modifications to the blazar model and the inclusion of additional γ-ray sources, such as star-forming galaxies, misalinged active galactic nuclei, or particle dark matter.
Radio continuum spectra of SFGs in the XMM-LSS Field below threshold
(Oxford University Press, 2025) Ocran E.F.; Taylor, Andrew Russell; Vaccari, Mattia
This study investigates the radio spectral properties of KS-selected star-forming galaxies (SFGs) in the XMM-LSS (multimirror mission large-scale structure) field using extensive multiwavelength data. By employing various diagnostics, SFGs are distinguished from quiescent galaxies and AGN across seven redshift bins (0.1 ≤ z ≤ 3.0). The broad-band radio frequency spectral energy distribution is analysed at observer-frame frequencies from 144 to 1500 MHz using median stacking techniques correcting for median flux boosting. We investigate the relationship between the radio spectral index, α (where S ∝ να) and redshift (z). Our analysis reveals no significant inverse correlation between α and z, indicating that the radio spectrum remains independent with varying redshift. We fit the stacked median radio SEDs with a power law (PL), curved power law (CPL), and double power-law (DPL) models. For the DPL and CPL models, we observe a consistent steepening of the low-frequency spectral index across all redshift bins. For the CPL model, the curvature term q is greater than zero in all redshift bins. Model comparisons indicate that spectra are generally well fitted by all the models considered. At 1500 MHz, SFGs display both a steep synchrotron component and a flat free–free emission component, with a thermal fraction consistently around 11 per cent to 18 per cent. Further deep radio observations, with higher resolution to better deal with source blending and confusion noise and wider frequency coverage to better separate non-thermal and thermal radio emission, are required to reveal the detailed physical processes, thus clarifying the nature of radio sources.
The resolved and eco g3 initiative: drivers of h i content and x-ray emission in galaxy groups
(Institute of Physics, 2025) Baker, Andrew J.; Hutchens, Zackary L.; Kannappan, Sheila J.
Adding to the RESOLVE and ECO Gas in Galaxy Groups (G3) initiative, we examine possible drivers of group-integrated H i-to-halo mass ratios (MHI,grp/Mhalo) and group X-ray emission, including group halo mass (Mhalo), virialization as probed by crossing time (tcross), presence of active galactic nuclei (AGN), and group-integrated fractional stellar mass growth rate (FSMGRgrp). G3 groups span Mhalo = 1011−1014.5 M⊙ with comprehensive H i gas and AGN information, which we combine with X-ray stacking of ROSAT All-Sky data. We detect hot gas emission exceeding AGN and X-ray binary backgrounds confidently for Mhalo = 1012.6−1014 M⊙ and unambiguously for Mhalo > 1014 M⊙, reflecting an inverse dependence of MHI,grp/Mhalo and hot gas emission on halo mass. At fixed halo mass, MHI,grp/Mhalo transitions to greater spread below tcross ∼ 2 Gyr. Dividing groups across this transition, lower-tcross groups show elevated X-ray emission compared to higher-tcross groups for Mhalo > 1013.3 M⊙, but this trend reverses for Mhalo = 1012.6−1013.3 M⊙. Additionally, AGN-hosting halos below Mhalo ∼ 1012.1 M⊙ exhibit a broad, ∼0.25 dex deep valley in MHI,grp/Mhalo compared to non-AGN-hosting halos with correspondingly reduced FSMGRgrp. When diluted by non-AGN-hosting halos, this valley becomes shallower and narrower, falling roughly between M halo = 10 11.5 M ⊙ and M halo = 10 12.1 M ⊙ in the overall MHI,grp/Mhalo vs. Mhalo relation. We may also detect a second, less easily interpreted valley at Mhalo ∼ 1013 M⊙. Neither valley matches theoretical predictions of a deeper valley located at or above M halo = 10 12.1 M ⊙ .
Improved reconstruction of highly boosted -lepton pairs in the decay channels with the ATLAS detector
(Springer Nature, 2025) Leeuw, Lerothodi; Zwalinski, Lukasz; Zormpa, Olga
This paper presents a new -lepton reconstruction and identification procedure at the ATLAS detector at the Large Hadron Collider, which leads to significantly improved performance in the case of physics processes where a highly boosted pair of -leptons is produced and one -lepton decays into a muon and two neutrinos , and the other decays into hadrons and one neutrino. By removing the muon information from the signals used for reconstruction and identification of the candidate in the boosted pair, the efficiency is raised to the level expected for an isolated. The new procedure is validated by selecting a sample of highly boosted candidates from the data sample of 140 of proton–proton collisions at 13 TeV recorded with the ATLAS detector. Good agreement is found between data and simulation predictions in both the signal region and in a background validation region. The results presented in this paper demonstrate the effectiveness of the reconstruction with muon removal in enhancing the signal sensitivity of the boosted channel at the ATLAS detector.
Test of lepton flavour universality in W-boson decays into electrons and τ-leptons using pp collisions at = 13 TeV with the ATLAS detector
(Springer Science and Business Media Deutschland GmbH, 2025) Leeuw, Lerothodi; Aad, Georges; Aakvaag, Erlend
A measurement of the ratio of the branching fractions, Rτ/e = B(W → τν)/B(W → eν), is performed using a sample of W bosons originating from top-quark decays to final states containing τ-leptons or electrons. This measurement uses pp collisions at = 13 TeV, collected by the ATLAS experiment at the Large Hadron Collider during Run 2, corresponding to an integrated luminosity of 140 fb−1. The W → τντ (with τ → eνeντ) and W → eνe decays are distinguished using the differences in the impact parameter distributions and transverse momentum spectra of the electrons. The measured ratio of branching fractions Rτ/e = 0.975 ± 0.012 (stat.) ± 0.020 (syst.), is consistent with the Standard Model assumption of lepton flavour universality in W-boson decays.
Euclid preparation LXIII. Simulations and non-linearities beyond Lambda cold dark matter. 2. Results from non-standard simulations
(EDP Sciences, 2025) Karagiannis, Dionysis
The Euclid mission will measure cosmological parameters with unprecedented precision. To distinguish between cosmological models, it is essential to generate realistic mock observables from cosmological simulations that were run in both the standard Λ-cold-dark-matter (ΛCDM) paradigm and in many non-standard models beyond ΛCDM. We present the scientific results from a suite of cosmological N-body simulations using non-standard models including dynamical dark energy, k-essence, interacting dark energy, modified gravity, massive neutrinos, and primordial non-Gaussianities. We investigate how these models affect the large-scale-structure formation and evolution in addition to providing synthetic observables that can be used to test and constrain these models with Euclid data. We developed a custom pipeline based on the Rockstar halo finder and the nbodykit large-scale structure toolkit to analyse the particle output of non-standard simulations and generate mock observables such as halo and void catalogues, mass density fields, and power spectra in a consistent way. We compare these observables with those from the standard ΛCDM model and quantify the deviations. We find that non-standard cosmological models can leave large imprints on the synthetic observables that we have generated. Our results demonstrate that non-standard cosmological N-body simulations provide valuable insights into the physics of dark energy and dark matter, which is essential to maximising the scientific return of Euclid.
Euclid: the early release observations lens search experiment
(EDP Sciences, 2025) Vaccari, Mattia; Acevedo Barroso, Javier A.; O'Riordan, Conor M.
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-resolution IE band and the lower-resolution YE, JE, and HE bands. Each extended source brighter than magnitude 23 in IE was inspected by 41 expert human classifiers. This amounts to 12 086 stamps of 1000 × 1000. We found 3 grade A and 13 grade B candidates. We assessed the validity of these 16 candidates by modelling them and checking that they are consistent with a single source lensed by a plausible mass distribution. Five of the candidates pass this check, five others are rejected by the modelling, and six are inconclusive. Extrapolating from the five successfully modelled candidates, we infer that the full 14 000 deg2 of the Euclid Wide Survey should contain 100 000+-7030000000 galaxy-galaxy lenses that are both discoverable through visual inspection and have valid lens models. This is consistent with theoretical forecasts of 170 000 discoverable galaxy-galaxy lenses in Euclid. Our five modelled lenses have Einstein radii in the range 000 . 68 < θE < 100 . 24, but their Einstein radius distribution is on the higher side when compared to theoretical forecasts. This suggests that our methodology is likely missing small-Einstein-radius systems. Whilst it is implausible to visually inspect the full Euclid dataset, our results corroborate the promise that Euclid will ultimately deliver a sample of around 105 galaxy-scale lenses.
Euclid V. The Flagship galaxy mock catalogue: A comprehensive simulation for the Euclid mission
(EDP Sciences, 2025) Karagiannis, Dionysios; Castander, Francisco Javier; Fosalba, Pablo
We present the Flagship galaxy mock, a simulated catalogue of billions of galaxies designed to support the scientific exploitation of the Euclid mission. Euclid is a medium-class mission of the European Space Agency optimised to determine the properties of dark matter and dark energy on the largest scales of the Universe. It probes structure formation over more than 10 billion years primarily from the combination of weak gravitational lensing and galaxy clustering data. The breadth of Euclid’s data will also foster a wide variety of scientific analyses. The Flagship simulation was developed to provide a realistic approximation to the galaxies that will be observed by Euclid and used in its scientific exploitation. We ran a state-of-the-art N-body simulation with four trillion particles, producing a lightcone on the fly. From the dark matter particles, we produced a catalogue of 16 billion haloes in one octant of the sky in the lightcone up to redshift z = 3. We then populated these haloes with mock galaxies using a halo occupation distribution and abundance-matching approach, calibrating the free parameters of the galaxy mock against observed correlations and other basic galaxy properties. Modelled galaxy properties include luminosity and flux in several bands, redshifts, positions and velocities, spectral energy distributions, shapes and sizes, stellar masses, star formation rates, metallicities, emission line fluxes, and lensing properties. We selected a final sample of 3.4 billion galaxies with a magnitude cut of HE < 26, where we are complete. We have performed a comprehensive set of validation tests to check the similarity to observational data and theoretical models. In particular, our catalogue is able to closely reproduce the main characteristics of the weak lensing and galaxy clustering samples to be used in the mission main cosmological analysis. Moreover, given its depth and completeness, this new galaxy mock also provides the community with a powerful tool for developing a wide range of scientific analyses beyond the Euclid mission.
On the relationship between the cosmic web and the alignment of galaxies and AGN jets
(Oxford University Press, 2025) Jarvis, Matthew J.; Jung, Seoyoung Lyla; Whittam, Imogen H.
The impact of active galactic nuclei (AGNs) on the evolution of galaxies explains the steep decrease in the number density of the most massive galaxies in the Universe. However, the fuelling of the AGN and the efficiency of this feedback largely depend on their environment. We use data from the Low Frequency Array Two-metre Sky Survey Data Release 2 (DR2), the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys, and the Sloan Digital Sky Survey DR12 to make the first study of the orientations of radio jets and their optical counterpart in relation to the cosmic web environment. We find that close to filaments (≲11 Mpc), galaxies tend to have their optical major axes aligned with the nearest filaments. On the other hand, radio jets, which are generally aligned perpendicularly to the optical major axis of the host galaxy, show more randomized orientations with respect to host galaxies within ≲8 Mpc of filaments. These results support the scenario that massive galaxies in cosmic filaments grow by numerous mergers directed along the orientation of the filaments while experiencing chaotic accretion of gas on to the central black hole. The AGN-driven jets consequently have a strong impact preferentially along the minor axes of dark matter haloes within filaments. We discuss the implications of these results for large-scale radio jet alignments, intrinsic alignments between galaxies, and the azimuthal anisotropy of the distribution of circumgalactic medium and anisotropic quenching.

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