Research Articles (Physics)

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Euclid quick data release (Q1): XXX. the strong lensing discovery engine e – ensemble classification of strong gravitational lenses: lessons for data release 1★
(EDP Sciences, 2026) Holloway, Philip; Karagiannis, Dionysis; Verma, Aprajita
The Euclid Wide Survey (EWS) is expected to identify in the order of 100 000 galaxy-galaxy strong lenses across 14 000deg2. The Euclid Quick Data Release (Q1) of 63.1deg2 Euclid images provides an excellent opportunity to test our lens-finding ability, and to verify the anticipated lens frequency in the EWS. Following the Q1 data release, eight machine learning networks from five teams were applied to approximately one million images. This was followed by a citizen science inspection of a subset of around 100 000 images, of which 65% received high network scores, with the remainder randomly selected. The top scoring outputs were inspected by experts to establish confident (grade A), likely (grade B), possible (grade C), and unlikely lenses. In this paper we combine the citizen science and machine learning classifiers into an ensemble, demonstrating that a combined approach can produce a purer and more complete sample than the original individual classifiers. Using the expert-graded subset as ground truth, we find that this ensemble can provide a purity of 52 ± 2% (grade A/B lenses) with 50% completeness (for context, due to the rarity of lenses a random classifier would have a purity of 0.05% and the best machine learning network in this work achieved 7.3% purity for the same completeness). We discuss future lessons for the first major Euclid data release (DR1), where the big-data challenges will become more significant and will require analysing more than ∼300 million galaxies, and thus the time investment of both experts and citizens must be carefully managed.
Shape coexistence in 94Zr from a model-independent analysis
(Elsevier B.V., 2026) Garrett, Paul. E; Marchini, Naomi; Rocchini, Marco
Low-lying states of 94Zr were investigated via low-energy multi-step Coulomb excitation. From the measured γ -ray yields, 16 reduced E2 transition probabilities between low-spin states were determined, together with the spectroscopic quadrupole moments of the 21,2+ states. Based on this information, for the first time in the Zr isotopic chain, the shapes of the 01,2+ states including their deformation softness were inferred in a model-independent way using the quadrupole sum rules approach. The ground state of 94Zr possesses a rather diffuse shape associated with a spherical configuration, while the 02+ state is triaxial tending towards oblate and more strongly deformed. The observed features of shape coexistence in 94Zr are consistent with both Monte-Carlo shell-model predictions and IBM-CM calculations, and provide model-independent constraints on the shape character assigned in the IBM-CM to the intruder configuration in 92–96Zr.
Probing the large-scale structure with 21 cm-galaxy cross-bispectrum: estimates from simulations and forecasts for upcoming cosmological surveys
(American Astronomical Society, 2026) Spinelli, Marta; Noble, Leon; Majumdar, Suman
he redshifted 21 cm signal from the post-reionization epoch is highly non-Gaussian; thus, higher-order statistics, such as the bispectrum, are required to extract this non-Gaussian information. However, high signal-to-noise ratio (SNR) detection of the 21 cm auto-bispectrum will be hindered by the presence of residual systematics. Cross-correlating the 21 cm signal with galaxies offers a promising path to suppress this uncertainty from residual systematics and potentially increase the SNR. We present a comprehensive analysis of the H I-galaxy cross-bispectrum using the predictions of theoretical galaxy evolution models defined on large cosmological volumes. Our analysis includes the cross-bispectrum for different triangle sizes and shapes, as well as for different combinations of the H I and galaxy fields. We forecast the detectability of the 21 cm-galaxy cross-bispectrum at redshift z ≈ 1 with the Euclid-like galaxy survey and SKA-Mid observations in both the interferometric and single-dish modes of the survey. We find that the 21 cm-galaxy cross-bispectrum shows enhanced detectability compared to the 21 cm auto-bispectrum for all unique triangles in the interferometric mode of observations. We forecast a 10σ detection of the cross-bispectrum for squeezed-limit triangles and a 100σ detection for all shapes combined for scales of 0.2 Mpc−1 ≤ k1 ≤ 0.9 Mpc−1, with 100 hr of SKA-Mid observations per pointing. However, the detectability of the cross-bispectrum for large scales (k1 < 0.1 Mpc−1), which is accessible with the single-dish mode of the survey, is limited by cosmic variance. Additionally, the signal loss due to foreground removal further suppresses the detectability.
Euclid quick data release (Q1): xxiii. the average far-infrared properties of euclid-selected star-forming galaxies
(EDP Sciences, 2026) Karagiannis, Dionysis; Hill, Ryley; Abghari, Arefe
The first Euclid Quick Data Release (Q1) contains millions of galaxies with excellent optical and near-infrared (IR) coverage. To complement this dataset, we investigate the average far-IR properties of Euclid-selected main sequence (MS) galaxies using existing Herschel and SCUBA-2 data. We used 17.6 deg2 (2.4 deg2) of overlapping Herschel (SCUBA-2) data, containing 2.6 million (240 000) MS galaxies. We binned the Euclid catalogue by stellar mass and photometric redshift and performed a stacking analysis following SimStack, which accounts for galaxy clustering and bin-to-bin correlations. We detected stacked far-IR flux densities across a significant fraction of the bins. We fitted modified blackbody spectral energy distributions in each bin and derived mean dust temperatures (Td), dust masses (Md), and star-formation rates (SFRs). We find similar mean SFRs compared to the Euclid catalogue, and we show that the average dust-to-stellar mass ratios decreased from z ≃ 1 to the present day. Average dust temperatures are largely independent of stellar mass and are well-described by the function T2 + (T1 − T2) e−t/τ, where t is the age of the Universe, T1 = (79.7 ± 7.4) K, T2 = (23.2 ± 0.1) K, and τ = (1.6 ± 0.1) Gyr. We argue that since the dust temperatures converge to a non-zero value below z = 1, the dust is now primarily heated by the existing cooler and older stellar population, as opposed to hot young stars in star-forming regions at higher redshifts. We show that since the dust temperatures are independent of stellar mass, the correlation between dust temperature and SFR depends on stellar mass. Lastly, we estimate the contribution of the Euclid catalogue to the cosmic IR background (CIB), finding that it accounts for > 60% of the CIB at 250, 350, and 500 μm. As the Euclid mission progresses, larger catalogues will allow us to probe the far-IR properties of MS galaxies out to higher redshifts and lower stellar masses, potentially recovering the complete CIB.
Euclid quick data release (Q1): XI. a first look at the fraction of bars in massive galaxies at z < 1★
(EDP Sciences, 2026) Karagiannis, Dionysis; Huertas-Company, Marc; Walmsley, Mike
Stellar bars are key structures in disc galaxies, driving angular momentum redistribution and influencing processes such as bulge growth and star formation. Quantifying the bar fraction as a function of redshift and stellar mass is therefore important for constraining the physical processes that drive disc formation and evolution across the history of the Universe. Leveraging the unprecedented resolution and survey area of the Euclid Q1 data release, combined with the Zoobot deep-learning model trained on citizen science labels, we identified 7711 barred galaxies with M* ≳ 1010 M⊙ in a magnitude-selected sample (IE < 20.5) spanning 63.1 deg2. We measured a mean bar fraction of 0.2–0.4, consistent with previous studies. At fixed redshift, massive galaxies exhibit higher bar fractions, while lower-mass systems show a steeper decline with redshift, suggesting earlier disc assembly in massive galaxies. Comparisons with cosmological simulations (e.g. TNG50, Auriga) reveal a broadly consistent bar fraction, but highlight overpredictions for high-mass systems, pointing to potential over-efficiency in central stellar mass build-up in simulations. A semi-empirical model (Decode) in which bar formation is regulated by the gas fraction broadly reproduces the observed bar fractions. These findings demonstrate the transformative potential of Euclid for galaxy morphology studies and underscore the importance of refining theoretical models to better reproduce observed trends. Future work will explore finer mass bins, environmental correlations, and additional morphological indicators.
Euclid quick data release (Q1): xxix. the strong-lensing discovery engine d: double-source-plane lens candidates
(EDP Sciences, 2026) Karagiannis, Dionysis; Li, Tian; Collett, Thomas
Strong gravitational-lensing systems with multiple source planes are powerful tools for probing the density profiles and dark matter substructure of galaxies. The ratio of the Einstein radii is related to the dark energy equation of state through the cosmological scaling factor β. Galaxy-scale double-source-plane lenses (DSPLs) are extremely rare, however. We report the discovery of four new galaxy-scale DSPL candidates in the Euclid Quick Release 1 (Q1) data. These systems were initially identified through a combination of machine-learning lens-finding models and subsequent visual inspection from citizens and experts. We applied the widel -used LensPop lens-forecasting model to predict that the full Euclid survey will discover 1700 DSPLs. This scales to 6 ± 3 DSPLs in 63 deg2, which is the area of Q1. The number of discoveries in this work is broadly consistent with this forecast. We present lens models for each DSPL and infer their β values. Our initial Q1 sample demonstrates that Euclid promises to discover these rare objects
MIGHTEE H Iobservations of low surface brightness and ultra-diffuse galaxies in the XMM-LSS field
(EDP Sciences, 2026) Jarvis, Matt J.; Sharma, Gauri; Adams, Elizabeth A. K
Untargeted neutral hydrogen (H I) surveys are well suited to identifying low surface brightness galaxies (LSBGs) that are gas rich, and they offer a complementary view to optically selected populations. We examined the LSBG population as identified via stellar and gaseous content using the MIGHTEE H I XMM-LSS early science data and the publicly available catalogs of optically identified LSBGs. There is currently little overlap between these datasets, with only three galaxies commonly detected. We performed surface brightness photometry of selected MIGHTEE H I detections to find 29 LSBGs, and 26 of these meet the size requirement (Reff > 1.5 kpc) to be ultra-diffuse galaxies (UDGs). Furthermore, we extracted H I spectra at the location of all optically identified galaxies, placing upper limits on the H I-to-stellar mass ratio in these systems. While the H I-identified population overall tends toward bluer colors, the H I-identified and the optically selected samples mostly overlap in mean effective surface brightness, effective radii, and color. Although it is not straightforward to discern why the H I-identified LSBGs were missed in optical searches, this work highlights the utility of H I surveys in finding these faint systems. The H I-identified LSBGs are gas rich compared to the general H I-selected population. Furthermore, three out of four H I-selected UDGs with available kinematics show no systematic offset from the baryonic Tully-Fisher relation, although we are biased away from sources with low rotational velocities due to the low spectral resolution of the data. This work demonstrates the utility of H I observations for finding and characterizing the low surface brightness Universe.
Euclid quick data release (q1): xviii. first euclid statistical study of the active galactic nuclei contribution fraction
(EDP Sciences, 2026) Karagiannis, Dionysios; Margalef-Bentabol B; Wang, Lingyu
Active galactic nuclei (AGN) are an important phase in galaxy evolution. However, they can be difficult to identify due to their varied observational signatures. Furthermore, to understand the impact of an AGN on its host galaxy, it is important to quantify the strength of the AGN with respect to the host galaxy. We developed a deep learning (DL) model to identify AGN in imaging data by deriving the contribution of the central point source. The model was trained with Euclidised mock galaxy images in which we artificially injected different levels of AGN, in the form of varying contributions of the point spread function (PSF). Our DL-based method can precisely and accurately recover the injected AGN contribution fraction, fPSF, with a mean difference between the predicted and true fPSF of −0.0078 and an overall root mean square error of 0.051. With this new method, we move beyond the simplistic AGN versus non-AGN classification and are able to precisely quantify the AGN contribution and study galaxy evolution across a continuous spectrum of AGN activity. We applied our method to a stellar-mass-limited sample (with M* ≥ 109.8 M⊙ and 0.5 ≤ z ≤ 2.0) selected from the first Euclid quick data release (Q1) and, using a threshold of fPSF > 0.2, we identified 61 432 ± 70 AGN over 63.1 deg2 (9.8 ± 0.1% of our sample). We compared these DL-selected AGN with AGN selected in the X-ray, mid-infrared (MIR), and via optical spectroscopy and investigated their overlapping fractions depending on different thresholds on the PSF contribution. We find that the overlap increases with increasing X-ray or bolometric AGN luminosity. We observe a positive correlation between the luminosity in the IE filter of the AGN and the host galaxy stellar mass, suggesting that supermassive black holes (SMBHs) generally grow faster (in absolute terms, i.e. the luminosity of the PSF component is larger) in more massive galaxies. Moreover, the mean relative contribution of the AGN is higher in the quiescent galaxy population than in the star-forming population. In terms of absolute power, starburst galaxies, as well as the most massive galaxies (across the star-formation main sequence), tend to host the most luminous AGN, indicating concomitant assembly of the SMBH and the host galaxy.
Euclid quick data release (q1): iii. NIR processing and data products
(EDP Sciences, 2026) Karagiannis, Dionysios; Polenta, Gianluca; Frailis, Marco
This paper describes the near-infrared processing function (NIR PF) that processes NIR images from the Near-Infrared Spectrometer and Photometer (NISP) instrument on board the Euclid satellite. NIR PF consists of three main components: (i) a common pre-processing stage for both photometric (NIR) and spectroscopic (SIR) data to remove instrumental effects; (ii) astrometric and photometric calibration of NIR data, along with catalogue extraction; and (iii) resampling and stacking. The necessary calibration products are generated using dedicated pipelines that process observations from both the early performance verification (PV) phase in 2023 and the nominal survey operations. After outlining the pipelineś structure and algorithms, we describe its application to Euclid Q1 images. For Q1, we achieved an astrometric accuracy of 5–8 mas, a relative photometric accuracy of 5 mmag, along with an absolute flux calibration limited by the 1% uncertainty of the Hubble Space Telescope (HST) CALSPEC database. We characterised the point spread function (PSF), which we found to be very stable across the focal plane. Finally, we discuss current limitations of NIR PF that will be improved upon for future data releases.
Euclid quick data release (Q1): I. data release overview
(EDP Sciences, 2026) Karagiannis, Dionysios; Aussel, Hervé; Tereno I.
The first Euclid Quick Data Release, Q1, comprises 63.1 deg2 of the Euclid Deep Fields (EDFs) to the nominal wide-survey depth. It encompasses visible and near-infrared space-based imaging and spectroscopic data, ground-based photometry in the u, g, r, i, and z bands, as well as corresponding masks. Overall, Q1 contains about 30 million objects in three areas near the ecliptic poles around EDF-North and EDF-South, as well as the EDF-Fornax field in the constellation of the same name. The purpose of this data release – and its associated technical papers – is twofold. First, it is meant to inform the community of the enormous potential of the Euclid survey data, to describe what is contained in these data, and to help prepare expectations for the forthcoming first major data release DR1. Second, it enables a wide range of initial scientific projects with wide-survey Euclid data, ranging from the early Universe to the Solar System. The Q1 data were processed with early versions of the processing pipelines, which already demonstrate a good performance, with numerous improvements in implementation compared to pre-launch development. In this paper, we describe the sky areas released in Q1, the observations, a top-level view of the data processing of Euclid and associated external data, the Q1 photometric masks, and how to access the data. We also give an overview of initial scientific results obtained using the Q1 dataset by Euclid Consortium scientists, and conclude with important caveats when using the data. As a complementary product, Q1 also contains observations of a star-forming area in Lynd’s Dark Nebula 1641 in the Orion A Cloud, observed for technical purposes during Euclid’s performance-verification phase. This is a unique target, of a type not commonly found in Euclid’s nominal sky survey.
Euclid quick data release (q1): xiv. a first view of the star-forming main sequence in the euclid deep fields
(EDP Sciences, 2026) Karagiannis, Dionysios; Enia, Andrea; Pozzetti, Lucia
The star-forming main sequence (SFMS) is a tight relation observed between stellar masses and star formation rates (SFR) in a population of galaxies. This relation is observed at different redshifts, in various morphological, and environmental domains, and is key to understanding the underlying relations between a galaxy budget of cold gas and its stellar content. Euclid Quick Data Release 1 (Q1) gives us the opportunity to investigate this fundamental relation in galaxy formation and evolution. We complement the Euclid release with public IRAC observations of the Euclid Deep Fields, improving the quality of recovered photometric redshifts, stellar masses, and SFRs, as is shown both with simulations and a comparison with available spectroscopic redshifts. From Q1 data alone, we recover more than ∼30 k galaxies with log10(M*/M⊙) > 11, giving a precise constraint of the SFMS at the high-mass end. We investigated the SFMS, in a redshift interval between 0.2 and 3.0, comparing our results with the existing literature and fitting them with a parameterisation taking into account the presence of a bending of the relation at the high-mass end, depending on the bending mass, M0. We find good agreement with previous results in terms of M0 values, and an increasing trend for the relation scatter at higher stellar masses. We also investigate the distribution of physical (e.g. dust absorption, AV, and formation age) and morphological properties (e.g., Sérsic index and radius) in the SFR–stellar mass plane, and their relation with the SFMS. These results highlight the potential of Euclid in studying the fundamental scaling relations that regulate galaxy formation and evolution in anticipation of the forthcoming Data Release 1.
Euclid: field-level inference of primordial non-gaussianity and cosmic initial conditions
(EDP Sciences, 2026) Karagiannis, Dionysios; Andrews, Adam; Jasche, Jens
A primary target of the Euclid space mission is to constrain early-universe physics by searching for deviations from a primordial Gaussian random field. A significant detection of primordial non-Gaussianity would rule out the simplest models of cosmic inflation and transform our understanding of the origin of the Universe. This paper forecasts how well field-level inference of galaxy redshift surveys can constrain the amplitude of local primordial non-Gaussianity, f NLlocal, within a Bayesian hierarchical framework, in the upcoming Euclid data. We designed and simulated mock datasets and performed Markov chain Monte Carlo analyses using a full-field forward modelling approach. By including the formation history of the cosmic matter field in the analysis, the method takes into account all available probes of primordial non-Gaussianity, and goes beyond statistical summary estimators of f NLlocal. Probes include, for example, two-point and higher-order statistics, peculiar velocity fields, and scale-dependent galaxy biases. Furthermore, the method simultaneously handles systematic survey effects, such as selection effects, survey geometries, and galaxy biases. The forecast shows that, using simulated Euclid data, the method can achieve a precision of σ(f NLlocal) = 2.6 (68.3% confidence level), assuming a grid resolution of ΔL = 31.25 h −1 Mpc and a cut-off scale of k NF = 0.1 h Mpc−1. We also provide data products, including realistic simulations with non-zero values of f NLlocal and maps of adiabatic curvature fluctuations. The results underscore the feasibility and advantages of field-level inference to constrain f NLlocal in galaxy redshift surveys. Our approach consistently captures all the information available in the large-scale structure to constrain f NLlocal, and resolves the degeneracy between early-universe physics and late-time gravitational effects, while mitigating the impact of systematic and observational effects.
Angular correlation functions of bright Lyman-break galaxies at 3 ≲ z ≲ 5
(Oxford University Press, 2025) Ye, Isabelle; Bull, Philip; Bowler, Rebecca A.A; Cochrane, Rachel K; Adams, Nathan J; Jarvis, Matt J.
We investigate the clustering of Lyman-break galaxies at redshifts of 3 ≲ z ≲ 5 within the COSMOS field by measuring the angular two-point correlation function. Our robust sample of ∼60 000 bright (mUV ≲ 27) Lyman-break galaxies was selected based on spectral energy distribution fitting across 14 photometric bands spanning optical and near-infrared wavelengths. We constrained both the 1- and 2-halo terms at separations up to 300 arcsec, finding an excess in the correlation function at scales corresponding to <20 kpc, consistent with enhancement due to clumps in the same galaxy or interactions on this scale. We then performed Bayesian model fits on the correlation functions to infer the Halo Occupation Distribution parameters, star formation duty cycle, and galaxy bias in three redshift bins. We examined several cases where different combinations of parameters were varied, showing that our data can constrain the slope of the satellite occupation function, which previous studies have fixed. For an MUV-limited sub-sample, we found galaxy bias values of bg = 3.18+0.14−0.14 at z ≃ 3, bg = 3.58+0.27−0.29 at z ≃ 4, bg = 4.27+0.25−0.26 at z ≃ 5. The duty cycle values are 0.62+0.25−0.26, 0.40+0.34−0.22, and 0.39+0.31−0.20, respectively. These results suggest that, as the redshift increases, there is a slight decrease in the host halo masses and a shorter time-scale for star formation in bright galaxies, at a fixed rest-frame UV luminosity threshold.
Sensitivity of nexo to 136xe charged-current interactions: background-free searches for solar neutrinos and fermionic dark matter
(American Physical Society, 2025) Lindsay, R; Mngonyama, S; Ngwadla, X; Ondze, J. C. Nzobadila; Triambak, S; Tyuka, O.A.
We study the sensitivity of nEXO to solar neutrino charged-current interactions, νe+136XeCs_ + e−, as well as analogous interactions predicted by models of fermionic dark matter. Due to the recently observed low-lying isomeric states of136Cs, these interactions will create a time-delayed coincident signal observable in the scintillation channel. Here we develop a detailed Monte Carlo simulation of scintillation emission, propagation, and detection in the nEXO detector to model these signals under different assumptions about the timing resolution of the photosensor readout. We show this correlated signal can be used to achieve background discrimination on the order of 10−9, enabling nEXO to make background-free measurements of solar neutrinos above the reaction threshold of 0.668 MeV. We project that nEXO could measure the flux of neutrinos from the carbon-nitrogen-oxygen cycle with a statistical uncertainty of 25%, thus contributing a novel and competitive measurement toward addressing the solar metallicity problem. Additionally, nEXO could measure the mean energy of the7Be neutrinos with a precision of σ ≤ 1.5 keV and could determine the survival probability of7Be and pep solar ν with precision comparable to the state of the art. These quantities are sensitive to the Sun's core temperature and to nonstandard neutrino interactions, respectively. Furthermore, the strong background suppression would allow nEXO to search for charged-current interactions of fermionic dark matter in the mass range mχ = 0.668–7 MeV with a sensitivity up to three orders of magnitude better than current limits.*Also at: University of Chinese Academy of Sciences, Beijing China. © (2025), (American Physical Society). All rights reserved.
Estimation of backgrounds from jets misidentified as τ-leptons using the universal fake factor method with the atlas detector
(Springer Nature, 2025) Zormpa O.; Zou W.; Zormpa O.; Zorbas T.G.; Zoch K.
Processes with τ-leptons in the final state are important for Standard Model measurements and searches for physics beyond the Standard Model. The ATLAS experiment at the Large Hadron Collider observes τ-leptons produced in proton–proton collisions only through their decay products. Data analyses involving hadronically decaying τ-leptons face challenges due to backgrounds from jets misidentified as τ-leptons that are not modelled reliably by Monte Carlo simulations. Data-driven methods such as the fake-factor method allow such misidentified backgrounds to be predicted by measuring transfer factors, known as fake factors, in data from dedicated regions. This paper describes a refined technique for determining the fake factors, the Universal Fake Factor method. It evaluates the fake factors for a signal region by using fake factors from samples enriched in different sources of jets misidentified as τ-leptons (light-quark, gluon, b-quark, and pile-up jets). Each fake factor is calculated as a linear combination of fake factors measured in these different enriched samples. For the full Run 2 data set, the systematic uncertainty of the calculated fake factors, evaluated using W(μν) enriched event sample, ranges from 15 to 35% depending on the τ-lepton’s transverse momentum and charged-particle decay multiplicity.
Cosmological peculiar velocities in general relativity
(National University of Ireland Maynooth, 2026) Clarkson, Chris; Maartens, Roy
We reconsider the late-time evolution of galaxy peculiar velocities in the 1 + 3 covariant approach to cosmological perturbation theory. It has recently been claimed that this approach predicts substan-tially stronger growth of peculiar velocities than standard metric-based perturbation theory – on the grounds that the covariant treatment is fully relativistic whereas standard treatments are effectively Newtonian. We show that this is not the case. When the covariant equations are applied consistently, the 1 + 3 approach reproduces exactly the standard perturbative result for peculiar-velocity growth. The stronger growth laws claimed in recent work arise from an inconsistent treatment of the cou-pled covariant system, in which terms constrained by the field equations are treated as if they were independent sources. Further claims are made that the stronger bulk flows can mimic accelerated expansion in a dust universe. We argue that these claims rest on a confusion between the kinematics of an arbitrarily chosen observer congruence and the physical expansion of the matter congruence traced by galaxies. We conclude that the standard treatment of peculiar velocities is correct and fully relativistic – and does not lead to anomalous bulk flows or to apparent accelerated expansion.
Design of a high voltage delivery system for noble liquid time projection chambers
(Elsevier B.V., 2026) Angelico E.; Pagani L.; Angelico E.; Bernard E.P.; Chana B.
Noble liquid time projection chambers (TPCs) are a leading technology in the detection of ionizing radiation, particularly in applications such as accelerator neutrino physics, dark matter detection, and neutrinoless double beta decay. This paper addresses the design considerations for implementing stable high voltage (HV) systems within large noble liquid TPCs, with a focus on the nEXO experiment. Utilizing insights from prior HV research and experimental investigations, we outline factors influencing HV stability and discuss design choices to improve stability and prevent electrical discharges. A novel HV delivery system concept is presented, tailored for the nEXO TPC, which incorporates these design considerations while also meeting the stringent radiopurity requirements of the nEXO neutrinoless double beta decay search. These design considerations and their specific implementation towards a HV delivery system offer guidance to future experiments applying high voltage in noble liquid environments.
Visualising relativistic effects in redshift space distortions of large scale structure
(Institute of Physics, 2026) Paul, Pritha; Clarkson, Chris
Observing large scale structure in redshift space gives rise to the well known redshift space distortions whereby a spherical distribution of galaxies is distorted into an ellipsoid along the line of sight of the observer. This effect is important on linear scales and so can be thought of as a Newtonian correction to the density perturbation even though their physical origin is in the Doppler effect. On larger scales subtler aspects of the Doppler and gravitational redshift effects give rise to further distortions in redshift space. These further contort objects beyond an ellipsoidal compression, into shapes with broken line-of-sight symmetry such as an egg- or bean-like shapes. In this paper, we aim to qualitatively picture how large over-dense regions, including clusters or superclusters, and under-dense regions, such as voids, undergoing infall or outflow respectively, become distorted in redshift space when higher-order relativistic effects are taken into account. This will contribute when analysing structure in real space such as stacking voids which are no longer radially symmetric when these effects are included.
HETDEX public data release 1: source catalog 2 and data cubes from ∼90 deg2 of integral-field optical spectroscopy
(American Astronomical Society, 2026) Jarvis, Matthew; Mentuch Cooper, Erin; Gebhardt, Karl
The Hobby–Eberly Telescope Dark Energy Experiment (HETDEX) is a wide-field, integral-field spectroscopic survey designed to map the large-scale distribution of Lyα-emitting galaxies (LAEs) at 1.88 < z < 3.52 and constrain dark energy at cosmic noon. Using the 10 m Hobby–Eberly Telescope and the Visible Integral-Field Replicable Unit (IFU) Spectrograph, HETDEX obtains >35,000 spectra per exposure over 3500–5500 Å at R ∼ 800 with (Formula presented) ∼1.″8 image quality, enabling an untargeted census of emission-line galaxies across 540 deg2. We present HETDEX Public Data Release 1 (PDR1), comprising 431,713 IFU observations covering 86.67 deg2 of noncontiguous sky in the Spring (13h, +51°) and Fall (1 (Formula presented) .h 5, 0°) fields, along with legacy regions (Cosmic Evolution Survey, Great Observations Origins Deep Survey North, North Ecliptic Pole, SA22). PDR1 includes the HETDEX Public Source Catalog 2 (HPSC2), an expanded and reprocessed version of E. Mentuch Cooper et al. (2023) incorporating four additional years of data, improved quality control, and new machine learning classifiers. HPSC2 contains 426,654 LAEs, 491,411 [O II] emitters, 19,457 low-z galaxies, 18,303 active galactic nuclei, and 150,608 stars, providing coordinates, redshifts or stellar velocities, and 1D spectra for each source. Because the data cubes use local sky subtraction optimized for faint emission-line detection, they are not suited for absolute surface-brightness measurements or very extended nearby galaxies. Appendix materials include the full detection catalog, the 1.6 million–candidate LAE sample, and raw detection databases. All products are publicly accessible through the HETDEX data portal (https://hetdex.org/data-results/), including access to a public JupyterLab. HPSC2 is also publicly available via Zenodo (doi:10.5281/zenodo.19581262).
Unbiased analysis of primordial non-Gaussianity: the multipoles of the full relativistic power spectrum
(Institute of Physics, 2026) Guedezounme, Sêcloka; Clarkson, Chris; Camera, Stefano; Jolicoeur, Sheean; Maartens, Roy
A major goal of ongoing and future cosmological surveys of the large-scale structure is to measure local type primordial non-Gaussianity in the galaxy power spectrum through the scale-dependent bias. General relativistic effects have been shown to be degenerate with this measurement and therefore one needs to consider a non-Newtonian approach. In this work, we develop a consistent framework to compute integrated effects, including lensing convergence, time delay, and integrated Sachs-Wolfe, along with the local relativistic projection and wide-separation corrections in the multipoles of the power spectrum. We show that, for a Euclid-like Hα-line galaxy survey and a MegaMapper-like Lyman-break galaxy survey, ignoring these effects leads to a bias on the best fit measurement of the amplitude of primordial non-Gaussianity, f NL, of around 3σ and 20σ respectively. When we include these corrections, the uncertainty in our knowledge of the luminosity function leads to further uncertainty in our measurement of f NL. However, we show that this degeneracy can be partly mitigated by using a bright-faint multi-tracer analysis, where the observed galaxy sample is subdivided into two separate populations based on luminosity. This provides a 15–20% improvement on the forecasted constraints of local type f NL. In addition, we present a novel calculation of the full multi-tracer covariance with the inclusion of wide-separation corrections. All of these results are implemented in the Python code CosmoWAP.

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