Research Articles (Physics)

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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.
The clustering of active galactic nuclei and star-forming galaxies in the LoTSS Deep Fields
(Oxford University Press, 2025) Jarvis, Matthew; Hale, Catherine Laura; Best, Phillip
Using deep observations across three of the LOFAR Two-metre Sky Survey Deep Fields, this work measures the angular clustering of star-forming galaxies (SFGs) and low-excitation radio galaxies (LERGs) to 1.5 for faint sources, 200 Jy. We measure the angular auto-correlation of LOFAR sources in redshift bins and their cross-correlation with multiwavelength sources to measure the evolving galaxy bias for SFGs and LERGs. Our work shows the bias of the radio-selected SFGs increases from = at 0.2 to = at 1.2; faster than the assumed models adopted in previous LOFAR cosmology studies (at sensitivities where active galactic nuclei dominate), but in broad agreement with previous work. We further study the luminosity dependence of bias for SFGs and find little evidence for any luminosity dependence at fixed redshift, although uncertainties remain large for the sample sizes available. The LERG population instead shows a weaker redshift evolution with = at 0.7 to = at 1.2, though it is also consistent with the assumed bias evolution model () within the measured uncertainties. For those LERGs that reside in quiescent galaxies, there is weak evidence that they are more biased than the general LERG population and evolve from = at 0.7 to = at 1.2. This suggests the halo environment of radio sources may be related to their properties. These measurements can help constrain models for the bias evolution of these source populations, and can help inform multi-tracer analyses.
On the role of high speed electron beams in the generation of subsonic solitons on electron dynamic timescales
(American Institute of Physics, 2025) Bharuthram, Ramesh; Maharaj, Shimul Kumar
A comprehensive theoretical investigation of the effects of electron beams on high frequency electron-acoustic waves is conducted for plasmas comprising two warm (adiabatic) electron components, Boltzmann electrons, and immobile ions of which one or both adiabatic electron fluid components are modeled as drifting (beams). A systematic approach is followed, starting with a single beam model comprising cool electrons, warm beam electrons, and hot electrons consistent with Berthomier et al. [Phys. Plasmas 7, 2987–2994 (2000)] and then proceeding to models with asymmetric and symmetric counterstreaming electron beams. The subsonic character of the solitons in the nonlinear regime is attributed to the effect of the beam(s) that support(s) the directional change of the backward propagating fast (or both slow mode) waves in the model with a single (counterstreaming) beam(s). This results in the coupling of two wave modes, which decouple for higher beam speeds. The results of our study are generic to other plasma systems containing heavier inertial plasma components as the findings are very similar to ion beam effects on low frequency ion-acoustic waves reported by Zank and McKenzie [J. Plasma Phys. 39, 183–191 (1988)] and Lakhina et al. [Phys. Scr. 95, 105601 (2020)] in models with a single and counterstreaming ion beams, respectively. In fact, similar reasoning applies in validating the generation of subsonic waves in the above reports as it relates to the directional change(s) of the linear wave(s), which also explains the generation of subsonic waves in the paper by Berthomier and coworkers in a single beam model.
Deep uGMRT observations for enhanced calibration of 21cm arrays – I. First image and source catalogue
(Oxford University Press, 2025) Bull, Philip; Elahi, Khandakar Md Asif; Choudhuri, Samir
Radio-interferometric arrays require very precise calibration to detect the Epoch of Reionization 21-cm signal. A remarkably complete and accurate sky model is therefore needed in the patches of the sky used to perform the calibration. Instruments such as Hydrogen Epoch of Reionization Array (HERA), which use a redundant calibration strategy, also require a reference sky model to fix degenerate gain solutions. We have carried out a deep (20h) observation using the upgraded Giant Metrewave Radio Telescope (GMRT) to make a high-fidelity sky model of one of the HERA calibration fields GLEAM 02H (J0200–3053). Here, we present the results from a 16.7, MHz bandwidth data centred at 147.4, MHz. Using multiple GMRT pointings, we have made a 6.9° x 6.9° mosaic, which yields a median rms of 3.9+3.7-1.4 mJybeam−1 that reduces to ~ 2mJy beam−1 at source-free regions. In the overlapping patch, this rms is deeper than the GaLactic and Extragalactic All-sky MWA Survey (GLEAM) catalogue, which is used for HERA calibration. We produce a catalogue of 640 sources (26 percent extended) in the flux range 0.01 - 19.08Jy. The catalogue has a sub-arcsec positional accuracy, and the estimated fluxes are consistent with existing catalogues. The differential source counts are found to be deeper than GLEAM and consistent with LOw Frequency ARray Two Meter Sky Survey. Preliminary simulations of the sky models from GLEAM and our catalogue show ~ 10 - 25 per cent difference in the visibility amplitude, with relatively small phase difference (≈ 2°). Future work is planned for larger survey areas and wider bandwidth to reduce the rms and measure the in-band source spectral indices, which are expected to enhance the fidelity of the HERA calibration model.
MIGHTEE-H I: the direct detection of neutral hydrogen in galaxies at z > 0.25
(Oxford University Press, 2025) Jarvis, Matt; Santos, Mario; Sharma, Gauri
Atomic hydrogen constitutes the gas reservoir from which molecular gas and star formation in galaxies emerges. However, the weakness ofthe line meansit has been difficult to directly detect in all but the very local Universe. Here, we presentresultsfrom the first search using the MeerKAT International Tiered Extragalactic Exploration (MIGHTEE) Survey for high-redshift (z > 0.25) H I emission from individual galaxies. By searching for 21-cm emission centred on the position and redshift of optically selected emission-line galaxies we overcome difficulties that hinder untargeted searches. We detect 11 galaxies at z > 0.25, forming the first sample of z > 0.25 detections with an interferometer, with the highest redshift detection at z = 0.3841. We find they have much larger H I masses than their low-redshift H I-selected counterparts for a given stellar mass. This can be explained by the much larger cosmological volume probed at these high redshifts, and does not require any evolution of the H I mass function. We make the first-ever measurement of the baryonic Tully–Fisher relation (bTFr) with H I at z > 0.25 and find consistency with the local bTFr, but with tentative evidence of a flattening in the relation at these redshifts for higher-mass objects. This may signify evolution, in line with predictions from hydrodynamic simulations, or that the molecular gas mass in these high-mass galaxies could be significant. This study paves the way for future studies of H I beyond the local Universe, using both searches targeted at known objects and via pure H I selection.
Evidence for inverse Compton scattering in high-redshift Lyman-break galaxies
(Oxford University Press, 2025) Whittam, Imogen H.; Jarvis, Matthew J.; Taylor, Andrew Russell; Vaccari, Mattia
Radio continuum emission provides a unique opportunity to study star formation unbiased by dust obscuration. However, if radio observations are to be used to accurately trace star formation to high redshifts, it is crucial that the physical processes that affect the radio emission from star-forming galaxies are well understood. While inverse Compton (IC) losses from the cosmic microwave background (CMB) are negligible in the local universe, the rapid increase in the strength of the CMB energy density with redshift [∼ (1 + z)4] means that this effect becomes increasingly important at z ≿ 3. Using a sample of ∼ 200 000 high-redshift (3 < z < 5) Lyman-break galaxies selected in the rest-frame ultraviolet (UV), we have stacked radio observations from the MIGHTEE survey to estimate their 1.4-GHz flux densities. We find that for a given rest-frame UV magnitude, the 1.4-GHz flux density and luminosity decrease with redshift. We compare these results to the theoretical predicted effect of energy losses due to IC scattering off the CMB, and find that the observed decrease is consistent with this explanation. We discuss other possible causes for the observed decrease in radio flux density with redshift at a given UV magnitude, such as a top-heavy initial mass function at high redshift or an evolution of the dust properties, but suggest that IC scattering is the most compelling explanation.
HF-Induced Modulation and Electron Temperature Effects in PMSE: VHF Spectral Diagnostics and Dusty Plasma Interpretation
(John Wiley and Sons Inc, 2025) Kosch, Michael Jurgen; Mahmoudian, Alireza; Vazifehkhah, Mehrdad
This study presents the first experimental investigation of Polar Mesospheric Summer Echoes (PMSE) response to high-frequency (HF) pump power modulation using the EISCAT VHF radar system. Two modulation schemes were employed during a recent campaign: stepped-power modulation (24 July 2019) and quasi-continuous power sweeping (26 July 2019). Coherent VHF radar spectra were analyzed to evaluate the impact of HF heating on PMSE characteristics. Results consistently show a contraction in the VHF spectral area with increasing HF pump power (40–80 kW), indicating suppression of small-scale electron density irregularities. This spectral narrowing is attributed to enhanced diffusion and dust charging processes driven by elevated electron temperatures. The ratio of diffusion to charging timescales (Formula presented.) is used as a key diagnostic to interpret these changes. Numerical simulations incorporating realistic dust cloud parameters reproduce the observed trends and reveal layer-specific responses, with lower PMSE layers exhibiting stronger overshoots and higher dust densities. These findings demonstrate that the spectral area under the VHF echo serves as a sensitive proxy for electron temperature enhancements during HF heating, offering a valuable diagnostic tool for studying mesospheric turbulence and dusty plasma dynamics.
Euclid preparation LXXIV. Euclidised observations of Hubble Frontier Fields and CLASH galaxy clusters
(EDP Sciences, 2025) Karagiannis, Dionysios; Bergamini P.; Meneghetti M
We present HST2EUCLID, a novel Python code to generate Euclid realistic mock images in the HE, JE, YE, and IE photometric bands based on panchromatic Hubble Space Telescope observations. The software was used to create a simulated database of Euclid images for the 27 galaxy clusters observed during the Cluster Lensing And Supernova survey with Hubble (CLASH) and the Hubble Frontier Fields (HFF) program. Since the mock images were generated from real observations, they incorporate, by construction, all the complexity of the observed galaxy clusters. The simulated Euclid data of the galaxy cluster MACS J0416.1−2403 were then used to explore the possibility of developing strong lensing models based on the Euclid data. In this context, complementary photometric or spectroscopic follow-up campaigns are required to measure the redshifts of multiple images and cluster member galaxies. By Euclidising six parallel blank fields obtained during the HFF program, we provide an estimate of the number of galaxies detectable in Euclid images per deg2 per magnitude bin (number counts) and the distribution of the galaxy sizes. Finally, we present a preview of the Chandra Deep Field South that will be observed during the Euclid Deep Survey and two examples of galaxy-scale strong lensing systems residing in regions of the sky covered by the Euclid Wide Survey. The methodology developed in this work lends itself to several additional applications, as simulated Euclid fields based on HST (or JWST) imaging with extensive spectroscopic information can be used to validate the feasibility of legacy science cases or to train deep learning techniques in advance, thus preparing for a timely exploitation of the Euclid Survey data.
Euclid preparation LXXV. Estimating galaxy physical properties using CatBoost chained regressors with attention
(EDP Sciences, 2025) Karagiannis, Dionysios; Humphrey A.; Cunha P.A.C.
The Euclid Space Telescope will image about 14 000 deg2 of the extragalactic sky at visible and near-infrared wavelengths, providing a dataset of unprecedented size and richness that will facilitate a multitude of studies into the evolution of galaxies. Although spectroscopy will also be available for some of the galaxies, in the vast majority of cases the main source of information will come from broadband images and data products thereof (i.e. photometry). Therefore, there is a pressing need to identify or develop scalable yet reliable methodologies to estimate the redshift and physical properties of galaxies using broadband photometry from Euclid. Optionally, such methods could also include ground-based optical photometry. To address this need, we present a novel method developed as part of a ‘data challenge’ within the Euclid Collaboration to estimate the redshift, stellar mass, star-formation rate, specific star-formation rate, E(B − V), and age of galaxies using mock Euclid and ground-based photometry. The main novelty of our property-estimation pipeline is its use of the CatBoost implementation of gradient-boosted regression-trees together with chained regression and an intelligent, automatic optimisation of the training data. The pipeline also includes a computationally efficient method to estimate prediction uncertainties, and, in the absence of ground-truth labels, it provides accurate predictions for metrics of model performance up to z ∼ 2. We applied our pipeline to several datasets consisting of mock Euclid broadband photometry and mock ground-based ugriz photometry, with the objective of evaluating the performance of our methodology for estimating the redshift and physical properties of galaxies detected in the Euclid Wide Survey. The statistical metrics of prediction residuals vary depending on which mock catalogue and filters are tested. Nonetheless, the quality of our photometric redshift and physical property estimates are highly competitive overall, validating our modelling approach. However, at z ≳ 3.5, the relative sparsity of galaxies resulted in unreliable redshift and physical property estimates, which we argue could be mitigated by building catalogues with better sampling of z ≳ 3.5 galaxies or by switching to the use of spectral energy distribution fitting in this regime. We also find that the inclusion of ground-based optical photometry significantly improves the quality of the property estimation, highlighting the importance of combining Euclid data with ancillary ground-based data from such surveys as the Vera C. Rubin Observatory Legacy Survey of Space and Time and UNIONS.
Euclid preparation LXXIV. Euclidised observations of Hubble Frontier Fields and CLASH galaxy clusters
(EDP Sciences, 2025) Karagiannis, Dionysios; Bergamini P.; Meneghetti M
We present HST2EUCLID, a novel Python code to generate Euclid realistic mock images in the HE, JE, YE, and IE photometric bands based on panchromatic Hubble Space Telescope observations. The software was used to create a simulated database of Euclid images for the 27 galaxy clusters observed during the Cluster Lensing And Supernova survey with Hubble (CLASH) and the Hubble Frontier Fields (HFF) program. Since the mock images were generated from real observations, they incorporate, by construction, all the complexity of the observed galaxy clusters. The simulated Euclid data of the galaxy cluster MACS J0416.1−2403 were then used to explore the possibility of developing strong lensing models based on the Euclid data. In this context, complementary photometric or spectroscopic follow-up campaigns are required to measure the redshifts of multiple images and cluster member galaxies. By Euclidising six parallel blank fields obtained during the HFF program, we provide an estimate of the number of galaxies detectable in Euclid images per deg2 per magnitude bin (number counts) and the distribution of the galaxy sizes. Finally, we present a preview of the Chandra Deep Field South that will be observed during the Euclid Deep Survey and two examples of galaxy-scale strong lensing systems residing in regions of the sky covered by the Euclid Wide Survey. The methodology developed in this work lends itself to several additional applications, as simulated Euclid fields based on HST (or JWST) imaging with extensive spectroscopic information can be used to validate the feasibility of legacy science cases or to train deep learning techniques in advance, thus preparing for a timely exploitation of the Euclid Survey data.
Transforming African food systems: perspectives from the food systems network for Africa (FSNet-Africa)
(Elsevier B.V.,, 2025) Isingizwe, Frederic; Jokonya, Osden; Dorvlo, Selorm Yaotse.
African food systems face significant challenges, including poverty, inequality, climate change, and unsustainable practices. To ensure access to safe and nutritious food while addressing socio-economic and environmental issues, fundamental changes are necessary. A collaborative and inclusive research agenda that engages diverse stakeholders through case-study research, aligning with continent-wide frameworks such as Agenda 2063, the CAADP, and the Sustainable Development Goals (SDGs), is vital. There are few cross-case analyses that bring together empirical case study research to evaluate and provide holistic appraisals of African food systems. This perspectives paper aims to provide such a synthesis from the empirical case studies generated under the Food Systems Research Network for Africa (FSNet-Africa) project. 19 case study projects in six African countries, were conducted by 83 researchers. Five key focus areas were identified: food system governance, indigenous crops and African foods, innovations for sustainable production among small-scale farmers, consumer preferences, and food loss and waste. The findings emphasise an urgent need for collaboration to address food security and nutrition challenges in Africa. Major priorities for transforming African food systems include inclusive engagement and the integration of indigenous knowledge to improve local food choices and resilience, and reducing food loss through capacity-building efforts and changing perceptions of waste. Future research should focus on governance, indigenous crops, and innovations in sustainable production to drive a transformative shift in African food systems. These priority areas will be critical for the next global and regional development agenda, reflecting the needs and aspirations of underrepresented communities across Africa.
Operational solar spectral irradiance measurements from the Extreme Ultraviolet Sensor (EUVS) on the GOES-R series.
(Institute of Physics, 2025) Snow, Martin; McClintock, William E.; MacHol, Janet L.
Beginning in early 2017, the first of four Extreme Ultraviolet Sensor (EUVS) instruments began taking solar spectral irradiance measurements from geostationary orbit. The new series of Geostationary Operational Environmental Satellites (GOES) operated by NOAA in the USA makes high-cadence (1 second) measurements of emission from all layers of the solar atmosphere from the photosphere up through the corona. The A channel observes 25.6 (He II), 28.4 (Fe XV), and 30.4 (He II) nm. Channel B measures 117 (C III), 121.5 (Lyman alpha), 133 (C II), and 140 (Si IV) nm, while the C channel measures the Mg II features around 280 nm. The C channel also reports the Mg II core-towing ratio. Channels A and B make 1-second integrations, while the C channel integrates over a 3-second interval. In addition, these individual measurements are combined to create an empirical model spectrum from 5 to 127 nm with a 30-second cadence. In this presentation we will describe the instruments, their calibration, the public data products, and how to retrieve the data from the NOAA web pages.
Hers-3: an exceptional einstein cross reveals a massive dark matter halo
(Institute of Physics, 2025) Baker, Andrew J.; Cox, Pierre; Butler, Kirsty M.
We present a study of HerS-3, a dusty star-forming galaxy at zspec = 3.0607, which is gravitationally amplified into an Einstein cross with a fifth image of the background galaxy seen at the center of the cross. Detailed 1 mm spectroscopy and imaging with NOEMA and the Atacama Large Millimeter/submillimeter Array resolve the individual images and show that each of the five images display a series of molecular lines that have similar central velocities, unambiguously confirming that they have identical redshifts. The Hubble Space Telescope F110W image reveals a foreground lensing group of four galaxies with a photometric redshift zphot ∼ 1.0. Lens models that only include the four visible galaxies are unable to reproduce the properties of HerS-3. By adding a fifth massive component, lying southeast of the brightest galaxy of the group, the source reconstruction is able to match the peak emission, shape, and orientation for each of the five images. The fact that no galaxy is detected near that position indicates the presence of a massive dark matter halo in the lensing galaxy group. In the source plane, HerS-3 appears as an infrared luminous starburst galaxy seen nearly edge on. The serendipitous discovery of this exceptional Einstein cross offers a potential laboratory for exploring at small spatial scales a nuclear starburst at the peak of cosmic evolution and studying the properties of a massive dark matter halo associated with the lensing galaxy group.
The superMIGHTEE project: meerkat and GMRT together to unveil the deep radio sky
(Institute of Physics, 2025) Taylor, Russ A.; Lal, Dharam Vir; Sekhar, Srikrishna
An international team of researchers has come together to undertake an ultra-broadband exploration of the deep radio sky. The superMIGHTEE project combines data from the MIGHTEE project, using the precursor Square Kilometre Array MeerKAT telescope in South Africa, with observations from the upgraded Giant Metrewave Radio Telescope (uGMRT) in India to produce deep images at several μJy sensitivity over a frequency range of 200 MHz-2.5 GHz, with an angular resolution of a few arcseconds. This paper describes the initial superMIGHTEE uGMRT data release, comprising total intensity continuum images covering a total of 9.9 deg2 at 650 MHz and 6.9 deg2 at 400 MHz in the XMM-LSS, COSMOS, and E-CDFS deep fields. The associated radio source catalogues include 27,101 sources at 650 MHz and 10,946 sources at 400 MHz. The redshift distribution of the sources extends to z ∼ 4 with a median value of z = 1. An overview of the broadband spectra of the sources, in combination with the MeerKAT MIGHTEE 1280 MHz data, reveals a clear change in spectral properties at the transition from an active galactic nuclei-dominated population to a population dominated by star-forming galaxies at flux densities of a few mJy. At higher frequencies, the star-forming galaxy population exhibits an optically thin synchrotron spectral index indicative of energy injection from supernovae. At lower frequencies, the spectra flatten significantly with decreasing flux density, and the fraction of sources with peaked spectra increases. This is the first superMIGHTEE uGMRT data release. Subsequent releases will include spectro-polarimetric and spectral line image cubes, as well as images at lower frequencies. The goal of the superMIGHTEE ultra-wideband data set is to enhance our understanding of the evolution of active galactic nuclei and star-forming galaxies over cosmic time, shed light on the evolution of neutral hydrogen, and explore the origins and evolution of cosmic magnetic fields in clusters, filaments, and galaxies.

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