Research Articles (Physics)

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The radio spectral energy distribution and star formation calibration in MIGHTEECOSMOS highly star-forming galaxies at 1.5
(Institute of Physics, 2025) Jarvis, Matt; Taylor, Russ; Whittam, Imogen H; An, Fangxia; Vaccari, Mattia
Studying the radio spectral energy distribution (SED) of distant galaxies is essential for understanding their assembly and evolution over cosmic time. We present rest-frame radio SEDs of a sample of 160 star-forming galaxies at 1.5 < z < 3.5 in the Cosmic Evolution Survey field as part of the MeerKAT International GHz Tiered Extragalactic Exploration project. MeerKAT observations combined with archival Very Large Array and Giant Metrewave Radio Telescope data allow us to determine the integrated mid-radio (ν = 1–10 GHz) continuum (MRC) luminosity and magnetic field strength. A Bayesian method is used to model the SEDs and to separate the free–free and synchrotron emission. We also calibrate the star formation rate (SFR) in radio both directly through SED analysis and indirectly through the infrared–radio correlation (IRRC). With a mean value of αnt ≃ 0.7, the synchrotron spectral index flattens with both redshift and specific SFR, indicating that cosmic rays are more energetic in the early Universe due to higher star formation activity. The magnetic field strength increases with redshift, B ∝ (1 + z) (0.7±0.1) , and SFR as B ∝ SFR0.3, suggesting a small-scale dynamo acting as its main amplification mechanism. Taking into account the evolution of the SEDs, the IRRC is redshift invariant, and it does not change with stellar mass at 1.5 < z < 3.5, although the correlation deviates from linearity. Similarly, we show that the SFR traced using the integrated MRC luminosity is redshift invariant.
The study of 110Cd with the (n,n′γ) reaction revisited
(Springer, 2026) Garrett, Paul; Bangay J; Jolie, Jan
Data from a previous study of 110Cd with the (n,n′γ) reaction with monoenergetic neutrons have been reanalysed with the aim of identifying additional low-intensity γ-ray transitions. The data set included excitation functions measured with neutron energies between 1.94 and 3.34 MeV, and γ-ray angular distributions performed at neutron energies of 2.6, 2.9, and 3.2 MeV. A total of 162 γ rays were placed in a level scheme comprising 69 levels (of which 58 γ-ray assignments and 10 levels are newly established) up to 3.3 MeV in excitation energy. Lifetimes, or limits, were established for many levels using the Doppler-shift attenuation technique allowing for the determination of an extended set of transition rates.
Isospin mixing in 64,66Ga reexamined via total absorption spectroscopy
(American Physical Society, 2025) Orce, José Nicolás; Parra, Selene; Nacher, Enrique
New measurements of the β decay of 64Ga and 66Ga have been carried out using total absorption spectroscopy at CERN-ISOLDE. The purpose of the study was to determine whether systemic effects such as Pandemonium have affected previous measurements and also determine the degree of isospin mixing in these proton-rich nuclei. Our results show that the β strength distribution of 64Ga was previously underestimated, while that of 66Ga agrees well with previous high-resolution measurements. The results allowed us to determine the amount of isospin mixing in the 0+ → 0+ transitions to the ground states of the daughter nuclei. From the extracted log ft values, we determined the isospin mixing parameter α for the two cases. They were found to be consistent with values for similar transitions in other nuclei. 64Ga exhibits the largest amount of isospin mixing in such nuclei. These findings improve our understanding of beta decay and have implications for nuclear structure models and medical applications of 66Ga in PET imaging.
Foreground removal in HI 21 cm intensity mapping under frequency-dependent beam distortions
(EDP Sciences, 2026) Spinelli, Marta; Gkogkou, Athanasia; Bonjean, Victor
Context. Neutral hydrogen (HI) intensity mapping with single-dish experiments is a powerful approach for probing cosmology in the post-reionization epoch. It is challenging to extract it, however, because of the bright foregrounds, which are stronger than the HI signal by more than four orders of magnitude. While all methods perform well when a Gaussian beam is assumed that is degraded to the lowest resolution, most methods degrade significantly in a more realistic beam model. Aims. The complexity introduced by frequency-dependent beam effects means that we need methods that explicitly account for the instrument response. We investigate the performance of SDecGMCA. This method extends DecGMCA to spherical data by combining sparse component separation with beam deconvolution. Our goal is to evaluate this method in comparison with established foreground removal techniques by assessing its ability to recover the cosmological HI signal from single-dish intensity mapping observations under varying beam conditions. Methods. We used simulated HI signals and foregrounds informed by existing observational and theoretical models that cover the frequency ranges relevant to MeerKAT and SKA-Mid. The foreground removal techniques we tested fall into two main categories: model-fitting methods (polynomial and parametric), and blind source separation methods (PCA, ICA, GMCA, and SDecGMCA). Their effectiveness was evaluated based on the recovery of the HI angular and frequency power spectra under progressively more realistic beam conditions. Results. While all methods performed adequately under a uniform degraded beam, SDecGMCA remained robust when frequency-dependent beam distortions were introduced. For an oscillating beam, SDecGMCA suppressed the spurious spectral peak at kν-0.3 and achieved an accuracy of 5% at intermediate angular scales (10-<-<-200); it outperformed other methods. Furthermore, the masking of bright Galactic regions significantly improved the recovery of the HI signal, in particular, for SDecGMCA, which benefited most when contaminated lines of sight were excluded. The beam inversion, however, remained intrinsically unstable beyond 200. This sets a practical limit on the method. Conclusions. Our findings highlight the limitations of simple fitting and standard blind source separation methods for realistic beam effects, and they establish SDecGMCA as a particularly promising approach for future single-dish intensity mapping surveys. Its robustness for various beam models, combined with the improvements that can be achieved through masking strategies and forthcoming refinements to its thresholding scheme, suggest that SDecGMCA might provide reliable spherical harmonics reconstructions of the HI power spectrum in upcoming experiments.
The cosmos-web ring: spectroscopic confirmation of the background source at z = 5.1
(EDP Sciences, 2025) Vaccari, Mattia; Shuntov, Marko; Jin, Shuowen
We report the spectroscopic confirmation of the background source of the most distant Einstein ring known to date, the COSMOS-Web ring. This system consists of a complete Einstein ring at z = 5.1, which is lensed by a massive early-type galaxy at z ∼ 2. The redshift z = 5.1043 ± 0.0004 is unambiguously identified with our NOEMA and Keck/MOSFIRE spectroscopy; the NOEMA observations reveal the CO(4–3) and CO(5–4) lines at >8σ, and the MOSFIRE data detect [O ii] at ∼6σ. Using multiwavelength photometry spanning near-infrared to radio bands, we find that the lensed galaxy is a dust-obscured starburst (M? ∼ 1.8 × 1010 M, SFRIR ∼ 60 M yr−1) with a high star formation efficiency (gas depletion time τdep < 100 Myr), as indicated by the [C i](1–0) non-detection. The redshift confirmation re-validates that the total lens mass budget within the Einstein radius is fully accounted for by the stellar and dark matter components, without the need of modifying the initial mass function or dark matter distribution profile. This work paves the way for detailed studies and future follow-ups of this unique lensing system, which is an ideal laboratory for studying mass distribution at z ∼ 2 and physical conditions of star formation at z ∼ 5. © The Authors 2025.
Redshift drift in relativistic n-body simulations
(National University of Ireland Maynooth, 2025) Clarkson, Chris; Oestreicher, Alexander; Adamek, Julian
The cosmological redshift drift promises to be the first observable directly measuring the evolution of the cosmic expansion rate and should be detectable with upcoming surveys by the Square Kilometre Array and the Extremely Large Telescope. To prepare for these upcoming measurements we study the redshift drift in detail using the relativistic N-body code gevolution, focusing on inhomogeneity-induced fluctuations. Using a ray-tracer, we calculate the redshift drift directly from the light cone at two different time steps. To investigate observer-dependent biases we consider 10 different observers. We find that inhomogeneity-induced fluctuations in the redshift drift can in extreme cases be of the same order as the cosmic signal for z ≲ 0.15. By comparing our results to first-order perturbation theory, we find that the extreme outliers are due to peculiar motion in over-densities and can be described by first-order perturbation theory to percent precision. We calculate angular power spectra that fit very well with our predictions based on perturbation theory at linear scales and show a surprisingly large non-linear signal. This shows that redshift drift not only has the power to measure the background expansion, but could also deliver information about the velocity and acceleration fields in clusters.
Revealing cosmological fluctuations in 21 cm intensity maps with MeerKLASS: from maps to power spectra
(Springer Science and Business Media BV, 2026) Fonseca, José; Santos, Mario G.; Spinelli, Marta; Wang, Jingying
Mapping the integrated 21 cm emission line from dark matter-tracing neutral hydrogen gas is the primary science goal for MeerKLASS (MeerKAT’s Large Area Synoptic Survey). Prior to the arrival of MeerKAT, this intensity mapping technique had only been tested on a couple of pre-existing single-dish radio telescopes with a handful of observational hours with which to make early pioneering detections. The 64-dish MeerKAT array, precursor to the SKA Observatory (SKAO), can scan the sky in auto-correlation (or single-dish) mode and perform intensity mapping across large sky areas, presenting the exciting potential for a wide area (≳10,000deg2) spectroscopic survey across redshift 0.4
Bayesian recalibration of flux scale factors in diffuse radio maps using low-resolution absolute radiometers
(Oxford University Press, 2025) Bull, Philip; Nasirudin, Ainulnabilah
The Haslam 408 MHz all-sky map is widely used as a template to model the diffuse Galactic synchrotron emission at radio and microwave frequencies. Recent studies have suggested that there are large uncorrected flux scale errors in this map, however. We investigate the possibility of statistically recalibrating the Haslam map using absolutely calibrated (but low angular resolution) radio experiments designed to measure the 21cm global signal at low frequencies. We construct a Gibbs sampling scheme to recover the full joint posterior distribution of ∼50 000 parameters, representing the true sky brightness temperature field, as-yet uncorrected flux scale factors, and synchrotron power-law spectral indices. With the idealized full-sky simulated data, we perform a joint analysis of a resolution diffuse map at 408 MHz and multiband 21cm global signal data with resolution under different assumptions about (1) noise levels in the maps, (2) sky coverage, and (3) synchrotron spectral index information. For our fiducial scenario in which the global signal experiment has a 50 mK noise rms per coarse pixel in each of 20 frequency bins between 50 and 150 MHz - the typical range for a global signal experiment, we find that the notional Haslam flux scale factors can be recovered in most (but not all) sub-regions of the sky to an accuracy of. In all cases we are able to rectify the sky map to within ∼5 K of the true brightness temperature. Our method can be used to correct the Haslam map once maps obtained from global experiments are available.
Transverse velocities in real-time cosmology: position drift in relativistic n-body simulations
(National University of Ireland Maynooth, 2025) Clarkson, Chris; Oestreicher, Alexander; Adamek, Julian
The era of real-time cosmology has begun. It is now possible to directly measure the apparent drift of high-redshift astronomical sources across the sky in real time. This so-called position drift provides a valuable probe of the peculiar velocity field and cosmic structure formation by giving direct access to the transverse velocity, which is notoriously difficult to measure and is typically inferred statistically from the density field in a model-dependent way. To fully exploit this new window into the Universe, it is essential to understand how cosmological structures affect position drift measurements. Here we present the first position drift study based on the general relativistic N-body simulation code gevolution. We calculate the position drift directly from the past light cone for ten different observers and compare the results to predictions from linear perturbation theory. At linear order, the position drift is directly proportional to the transverse velocity on the sky. This linear approximation reproduces our non-linear simulation results to within about 5%. We calculate power spectra for the position drift, splitting the signal into an E-and B-mode and compare the former to linear expectations, finding good agreement. The B-mode is suppressed on linear scales, but has similar amplitude as the E-mode on non-linear scales. We further demonstrate that light-cone inhomogeneities induce biases in the dipole of the drift, introducing redshift dependence of both the amplitude and direction. Although our analysis is not yet sufficient for a firm conclusion, our results suggest that these effects alone cannot explain the possible redshift-dependent dipole in Gaia DR3 data reported in the literature.
The fast hi 21cm absorption blind survey. II. statistical exploration for associated and intervening systems
(American Astronomical Society, 2025) Hu, Wenkai; Wang, Yougang; Li, Yichao
We present an extragalactic H I 21 cm absorption lines catalog from a blind search at z ≤ 0.35, using drift-scan data collected in 1325.6 hr by the ongoing Commensal Radio Astronomy Fast Survey and FAST All Sky H I Survey, which spans a sky area of 6072.0 deg2 and covers 84,533 radio sources with a flux density greater than 12 mJy. Fourteen previously identified H I absorbers and 20 newly discovered H I absorbers were detected, comprising 15 associated systems, 10 intervening systems, and nine systems with undetermined classifications. Through spectral stacking, the mean peak optical path, mean velocity-integrated optical path, mean FWHM, and mean H I column density are measured to be 0.47 and 0.30; 27.19 and 4.36 km s−1; 42.61 and 9.33 km s−1; 0.49 and 0.08 Ts × 1020 cm−2 K−1, for the associated and intervening samples, respectively. Statistical analysis also reveals that associated systems tend to be hosted by red (g − r > 0.7) galaxies at lower redshifts, whereas galaxies hosting intervening H I absorption are typically found at higher redshifts and are of a bluer (g − r ≤ 0.7) type. A noticeable difference is observed in the positions of foregrounds, backgrounds of intervening systems, and high-redshift and low-redshift associated systems on the Wide-field Infrared Survey Explorer color–color diagram. All identified foreground sources in our sample have W1 – W2 magnitudes below 0.8, suggesting no active galactic nuclei (AGNs). In contrast, backgrounds of intervening systems tend to have W1 – W2 magnitudes above 0.8, indicating AGN presence. For associated absorption, most low-redshift (z ≤ 0.5) systems show W1 – W2 values below 0.8, while higher-redshift associated absorption (z > 0.5) displays a broader range of W1 − W2 values.
The fast hi 21cm absorption blind survey. ii. statistical exploration for associated and intervening systems
(American Astronomical Society, 2025) Hu, Wenkai; Wang, Yougang; Li, Yichao
We present an extragalactic H I 21 cm absorption lines catalog from a blind search at z ≤ 0.35, using drift-scan data collected in 1325.6 hr by the ongoing Commensal Radio Astronomy Fast Survey and FAST All Sky H I Survey, which spans a sky area of 6072.0 deg2 and covers 84,533 radio sources with a flux density greater than 12 mJy. Fourteen previously identified H I absorbers and 20 newly discovered H I absorbers were detected, comprising 15 associated systems, 10 intervening systems, and nine systems with undetermined classifications. Through spectral stacking, the mean peak optical path, mean velocity-integrated optical path, mean FWHM, and mean H I column density are measured to be 0.47 and 0.30; 27.19 and 4.36 km s−1; 42.61 and 9.33 km s−1; 0.49 and 0.08 Ts × 1020 cm−2 K−1, for the associated and intervening samples, respectively. Statistical analysis also reveals that associated systems tend to be hosted by red (g − r > 0.7) galaxies at lower redshifts, whereas galaxies hosting intervening H I absorption are typically found at higher redshifts and are of a bluer (g − r ≤ 0.7) type. A noticeable difference is observed in the positions of foregrounds, backgrounds of intervening systems, and high-redshift and low-redshift associated systems on the Wide-field Infrared Survey Explorer color–color diagram. All identified foreground sources in our sample have W1 – W2 magnitudes below 0.8, suggesting no active galactic nuclei (AGNs). In contrast, backgrounds of intervening systems tend to have W1 – W2 magnitudes above 0.8, indicating AGN presence. For associated absorption, most low-redshift (z ≤ 0.5) systems show W1 – W2 values below 0.8, while higher-redshift associated absorption (z > 0.5) displays a broader range of W1 − W2 values.
Isomer depletion of Mo 93m triggered by inelastic nuclear scattering rather than nuclear excitation by electron capture
(American Physical Society, 2026) Lawrie, Elena Atanassova; Ding, Bing; Jia, Chenxu
Isomer depletion serves as a prerequisite for a variety of important applications. Several mechanisms are proposed to trigger the isomer depletion. In the previous work [Chiara et al., Nature (London) 554, 216 (2018).NATUAS0028-083610.1038/nature25483], isomer depletion with an exceptionally high probability in Mo93m was reported and attributed to nuclear excitation by electron capture (NEEC). However, contradictory probability values were subsequently reported from both experimental and theoretical aspects. This Letter reports a new and more precise measurement of the isomer depletion of high-energy Mo93m ions during the slowing-down processes in lead and carbon foils via a low-background beam-based experimental approach. By employing a purified isomer beam, the depletion probabilities are determined to be 2.0(2)×10-5 in lead and 4.7(13)×10-6 in carbon, agreeing well with the inelastic nuclear scattering calculations. We conclude that the observed isomer depletion in Mo93m arises from inelastic nuclear scattering rather than the previously proposed NEEC mechanism.
Star-forming galaxies in the cosmic web in the last 11 Gyr
(EDP Sciences, 2026) Davé, Romeel; Jego, Baptiste; Kraljic, Katarina
We investigate how the star formation activity of galaxies depends on their position within the cosmic web using the SIMBA cosmological simulation from redshift z = 3 to z = 0. While previous studies have found that galaxies closer to filaments tend to be more massive and quenched, it remains unclear whether these trends reflect intrinsic environmental effects or changes in the galaxy population mix. To address this, here we focus exclusively on star-forming galaxies, robustly selected using both the specific star formation rate (sSFR) and gas depletion timescale criteria to isolate the direct impact of the cosmic web on star-forming galaxies. We reconstructed the 3D cosmic web skeleton using DISPERSE and computed each galaxy’s distance to its nearest filament. After explicitly removing the stellar-mass dependence of all quantities, we examined the deviations in star formation rate (SFR), sSFR, molecular and atomic gas depletion timescales, and gas fractions as a function of this distance. We found a clear and redshift-dependent modulation of star formation with filament proximity: at high redshift (z ≳ 2), galaxies closer to filaments show enhanced SFR and gas accretion, reflecting efficient filament-fed growth. At z = 0, we observe a V-shaped trend in the sSFR and depletion timescales, with minima at intermediate distances (∼0.25 cMpc) and a surprising upturn very close to the filament cores, suggesting a resumed accretion in the densest environments. These effects are not driven by mergers and are primarily associated with satellite galaxies at low redshift. Our results demonstrate that large-scale cosmic web proximity modulates star formation in star-forming galaxies through a combination of gas supply regulation and environmental processing, with different mechanisms dominating across cosmic time
fftvis: a non-uniform fast fourier transform based interferometric visibility simulator
(Oxford University Press, 2025) Kittiwisit, Piyanat; Cox, Tyler A.; Murray, Steven G.
The detection and characterization of the 21cm signal from the Epoch of Reionization (EoR) demands extraordinary precision in radio interferometric observations and analysis. For modern low-frequency arrays, achieving the dynamic range necessary to detect this signal requires simulation frameworks to validate analysis techniques and characterize systematic effects. However, the computational expense of direct visibility calculations grows rapidly with sky model complexity and array size, posing a potential bottleneck for scalable forward modelling. In this paper, we present fftvis, a high-performance visibility simulator built on the Flatiron Non-Uniform Fast-Fourier Transform (finufft) algorithm. We show that fftvis matches the well-validated matvis simulator to near numerical precision while delivering substantial runtime reductions, up to two orders of magnitude for dense, many-element arrays. We provide a detailed description of the fftvis algorithm and benchmark its computational performance, memory footprint, and numerical accuracy against matvis, including a validation study against analytic solutions for diffuse sky models. We further assess the utility of fftvis in validating 21cm analysis pipelines through a study of the dynamic range in simulated delay and fringe-rate spectra. Our results establish fftvis as a fast, precise, and scalable simulation tool for 21cm cosmology experiments, enabling end-to-end validation of analysis pipelines
Semiempirical constraints on the HI mass function of star-forming galaxies and ΩHI at z∼ 0.37 from interferometric surveys
(EDP Sciences, 2025) Elson, Ed; Jarvis, M J; Sinigaglia, F
Context. The H I mass function (HIMF) is a crucial tool for understanding the evolution of the H I content in galaxies over cosmic time and, hence, to constraining both the baryon cycle in galaxy evolution and the reionization history of the Universe. Aims. We aim to derive semiempirical constraints at z ∼ 0.37 by combining literature results on the stellar mass function from optical surveys with recent findings on the MHI − M? scaling relation derived via spectral stacking analysis applied to 21 cm line interfero-metric data from the MIGHTEE and CHILES surveys, conducted with the MeerKAT and VLA radio telescopes, respectively. Methods. We drew synthetic stellar mass samples directly from the publicly available results underlying the analysis of the COS-MOS2020 galaxy photometric sample. We then converted M? into MHI using analytical fitting functions to the data points from H I stacking. We next fit a Schechter function to the median HIMF from all the samples via Monte Carlo Markov chains. We finally derived the posterior distribution for ΩHI by integrating the models for the HIMF built from the posteriors samples of the Schechter parameters. Results. We find a deviation of the HIMF at z ∼ 0.37 from the results at z ∼ 0 from the ALFALFA survey and at z ∼ 1 from uGMRT data. Our results for ΩHI are in broad agreement with other literature results and follow the overall trend on ΩHI as a function of redshift. The derived value ΩHI = (7.02+0.59 −0.52) × 10−4 at z ∼ 0.37 from the combined analysis deviates by ∼2.9σ from the ALFALFA result at z ∼ 0. Conclusions. Our findings regarding the HIMF and ΩHI derived from deep, state-of-the-art interferometric surveys differ from previous literature results at z ∼ 0 and z ∼ 1. We are unable to confirm at this stage whether these differences are due to cosmic evolution consistent with a smooth transition of the H I content of galaxies over the last 8 Gyr or due to selection biases and systematics.
A 15 Mpc rotating galaxy filament at redshift z = 0.032
(Oxford University Press, 2025) Jarvis M.J.; Tudorache, Madalina N.; Jung S.L.
Understanding the cold atomic hydrogen gas (H I) within cosmic filaments has the potential to pin down the relationship between the low density gas in the cosmic web and how the galaxies that lie within it grow using this material. We report the discovery of a cosmic filament using 14 H I-selected galaxies that form a very thin elongated structure of 1.7 Mpc. These galaxies are embedded within a much larger cosmic web filament, traced by optical galaxies, that spans at least ∼ 15 Mpc. We find that the spin axes of the H I galaxies are significantly more strongly aligned with the cosmic web filament ( cos ψ|= 0.64 ± 0.05) than cosmological simulations predict, with the optically selected galaxies showing alignment to a lesser degree ( cos ψ| = 0.55 ± 0.05). This structure demonstrates that within the cosmic filament, the angular momentum of galaxies is closely connected to the large-scale filamentary structure. We also find strong evidence that the galaxies are orbiting around the spine of the filament, making this one of the largest rotating structures discovered thus far, and from which we can infer that there is transfer of angular momentum from the filament to the individual galaxies. The abundance of H I galaxies along the filament and the low dynamical temperature of the galaxies within the filament indicates that this filament is at an early evolutionary stage where the imprint of cosmic matter flow on galaxies has been preserved over cosmic time.
Renzo's rule revisited: a statistical study of galaxies' baryon-dark matter coupling
(Oxford University Press, 2025) Jarvis, Matt J.; Ko, Enoch; Yasin, Tariq
We present a systematic statistical analysis of an informal astrophysical phenomenon known as Renzo's rule (or Sancisi's law), which states that 'for any feature in a galaxy's luminosity profile, there is a corresponding feature in the rotation curve, and vice versa'. This is often posed as a challenge for the standard Λ cold dark matter (CDM) model while supporting alternative theories such as modified Newtonian dynamics (MOND). Indeed, we identify clear features in the dwarf spiral NGC 1560 - a prime example for Renzo's rule - and find correlation statistics which support Renzo's rule with a slight preference for MOND over CDM halo fits. However, a broader analysis on galaxies in the Spitzer Photometry & Accurate Rotation Curves (SPARC) data base reveals an excess of features in rotation curves that lack clear baryonic counterparts, with correlation statistics deviating up to on average from that predicted by both MOND and CDM haloes, challenging the validity of Renzo's rule. Thus we do not find clear evidence for Renzo's rule in present galaxy data overall. We additionally perform mock tests, which show that a definitive test of Renzo's rule is primarily limited by the lack of clearly resolved baryonic features in current galaxy data.
Euclid: the early release observations lens search experiment
(EDP Sciences, 2025) Vaccari, Mattia; Barroso, Javier Alejandro Acevedo; 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.
Rhino: a large horn antenna for detecting the 21 cm global signal
(Oxford University Press, 2025) Bull, Philip; El-Makadema, Ahmed; Garsden, Hugh
The sky-averaged brightness temperature of the 21 cm line from neutral hydrogen provides a sensitive probe of the thermal state of the intergalactic medium, particularly before and during Cosmic Dawn and the Epoch of Reionization. This ‘global signal’ is faint, on the order of tens to hundreds of millikelvin, and spectrally relatively smooth, making it exceedingly difficult to disentangle from foreground radio emission and instrumental artefacts. In this paper, we introduce RHINO, an experiment based around a large horn antenna operating from 60 to 85 MHz. Horn antennas are highly characterizable and provide excellent shielding from their immediate environment, which are potentially decisive advantages when it comes to the beam measurement and modelling problems that are particularly challenging for this kind of experiment. The system also includes a novel continuous wave calibration source to control correlated gain fluctuations, allowing continuous monitoring of the overall gain level without needing to rapidly switch between the sky and a calibration source. Here, we describe the basic RHINO concept, including the antenna design, EM simulations, and receiver electronics. We use a basic simulation and analysis pipeline to study the impact of the limited bandwidth on recovery of physical 21 cm global signal model parameters, and discuss a basic calibration scheme that incorporates the continuous wave signal. Finally, we report on the current state of a scaled-down prototype system under construction at Jodrell Bank Observatory.
Euclid preparation: LVII. observational expectations for redshift z < 7 active galactic nuclei in the euclid wide and deep surveys
(EDP Sciences, 2025) Karagiannis, Dionysis; Selwood, Matthew; Fotopoulou, Sotiria
We forecast the expected population of active galactic nuclei (AGN) observable in the Euclid Wide Survey (EWS) and Euclid Deep Survey (EDS). Starting from an X-ray luminosity function (XLF), we generated volume-limited samples of the AGN expected in the Euclid survey footprints. Each AGN was assigned a spectral energy distribution (SED) appropriate for its X-ray luminosity and redshift, with perturbations sampled from empirical distributions. The photometric detectability of each AGN was assessed via mock observations of the assigned SED. We estimate 40 million AGN will be detectable in at least one Euclid band in the EWS and 0.24 million in the EDS, corresponding to surface densities of 2.8 × 103 deg-2 and 4.7 × 103 deg-2. The relative uncertainty on our expectation for Euclid detectable AGN is 6.7% for the EWS and 12.5% for the EDS, driven by the uncertainty of the XLF. Employing Euclid-only colour selection criteria on our simulated data we select a sample of 4.8 × 106 (331 deg-2 ) AGN in the EWS and 1.7 × 104 (346 deg-2 ) in the EDS, amounting to 10% and 8% of the AGN detectable in the EWS and EDS. Including ancillary Rubin/LSST bands improves the completeness and purity of AGN selection. These data roughly double the total number of selected AGN to comprise 21% and 15% of the Euclid detectable AGN in the EWS and EDS. The total expected sample of colour-selected AGN contains 6.0 × 106 (74%) unobscured AGN and 2.1 × 106 (26%) obscured AGN, covering 0.02 ≤ z ≲ 5.2 and 43 ≤ log10(Lbol/erg s-1 ) ≤ 47. With these simple colour cuts expected surface densities are already comparable to the yield of modern X-ray and mid-infrared surveys of similar area. The EWS sample is most comparable to the WISE C75 AGN selection and the EDS sample is most similar to the yield of the collated Spitzer cryogenic surveys when considering Euclid bands alone, or the XXL-3XLSS survey AGN sample when also considering selection with ancillary optical bands. We project that 15% (7.6%) of the total Euclid detectable population in the EWS (EDS) will exhibit X-ray fluxes that could be detected in the XMM-COSMOS survey, showing that the vast majority of Euclid-detected AGN would not be detectable in modern medium-depth X-ray surveys

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