Research Articles (Physics)

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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.
Investigating the h i mass–size relation using thesimbacosmological simulations
(Oxford University Press, 2026) Rabyang, Omphile; Elson, Ed
Observational studies have established a remarkably tight power-law relationship between the H i masses and sizes of late-type galaxies, known as the H i mass–size relation. This relation has been shown to persist across various models of a galaxy’s H i surface density profile. Using the simba cosmological simulations, we investigate the robustness of this relation under different feedback prescriptions, including cases where specific feedback mechanisms are absent. While the global properties of galaxies are significantly affected by changes in feedback, the H i mass–size relation remains intact. Moreover, its parameters consistently align with the best available empirical measurements. We analyse the H i mass distributions of galaxies and demonstrate that, regardless of the feedback scenario, galaxies within a given H i mass bin exhibit outer H i radial profiles well approximated by an exponential function. Furthermore, the exponential decline rate remains remarkably similar across different physical prescriptions. This behaviour is only valid within the (Formula presented) 1 M(Formula presented) pc(Formula presented) contour. We attribute the persistence of the H i mass–size relation to this inherent self-similarity in the H i mass distributions.
Simbasimulation: the effect of feedback physics on matter distribution in the cosmic web
(Oxford University Press, 2026) Dong, Chenze; Dedieu, Florian; Davé, Romeel
The discrepancy between the early-time estimation and late-time observation of the cosmic baryon content – the ‘missing baryon problem’ – is a long-standing problem in cosmology. Although recent studies with fast radio bursts (FRBs) have largely addressed this discrepancy, the precise spatial distribution of these baryons remains uncertain due to the effects of galaxy feedback. Cosmological hydrodynamical simulations such as Simba have shown that the partitioning of baryons between the intergalactic medium (IGM) and haloes is sensitive to feedback models, motivating the connection between baryon distribution and feedback physics. With the Simba simulation suite, this study investigates how feedback affects the distribution of matter within large-scale cosmic structures, with implications for FRB foreground modelling. We apply the T-web method to classify the cosmic web into different structures: knots, filaments, sheets, and voids. We then analyse how the different feedback variants of Simba affect the distribution of matter within each structure. Our results show that in Simba, the fractions of IGM gas in different cosmic web structures vary by only a few per cent under different feedback models. However, jet feedback produces noticeable changes in the gas distribution within structures, enhancing the diffuse IGM on the outskirts of filaments and knots, potentially biassing the empirical relation between matter distribution and dispersion measure. This research provides a new perspective on the impact of feedback on the IGM and motivates a refined data model for FRB foreground mapping.
Deblending the MIGHTEE-COSMOS survey with XID+: the resolved radio source counts to S 1.4 ≈ 5μJy
(Oxford University Press, 2026) Malefahlo, Eliab; Jarvis, Matt J.; Santos, Mario G.; Whittam, Imogen H.
Deep radio continuum surveys provide fundamental constraints on galaxy evolution, but source confusion limits sensitivity to the faintest sources. We present a complete framework for producing high-fidelity deblended radio catalogues from the confused MIGHTEE maps using the probabilistic deblending framework XID+ and prior positions from deep multi-wavelength data in the COSMOS field. To assess performance, we construct MIGHTEE-like simulations based on the Tiered Radio Extragalactic Continuum Simulation radio source population, ensuring a realistic distribution of star-forming galaxies and active galactic nuclei for validation. Through these simulations, we show that prior catalogue purity is the dominant factor controlling deblending accuracy: a high-purity prior, containing only sources with a high likelihood of radio detection, recovers accurate flux densities and reproduces input source counts down to ~ 3σ (where σ = thermal noise). On the other hand, a complete prior overestimates the source counts due to spurious detections. Our optimal strategy combines the high-purity prior with a mask that removes sources detected above 50µy. Applied to the ~1.3 deg2 area of the MIGHTEE-COSMOS field defined by overlapping multi-wavelength data, this procedure yields a deblended catalogue of 89 562 sources. The derived 1.4 GHz source counts agree with independent P(D) analyses and indicate that we resolve the radio background to ~ 4.8 µJy. We also define a recommended high-fidelity sample of 20 757 sources, based on detection significance, flux density, and goodness-of-fit, which provides reliable flux densities for individual sources in the confusion-limited regime.
Double pole S-matrix singularity in the continuum of 7Be
(Jagiellonian University, 2026) David Cardona Ochoa; Marek Ploszajczak; Nicolas Michel
The double pole singularity of the S-matrix, the so-called exceptional point, associated with the 5/2− doublet of resonances in the spectrum of7Be has been identified in the framework of the Gamow shell model. The exceptional point singularity is demonstrated by the coalescence of wave functions and spectral functions of the two resonances, as well as by the singular behavior of spectroscopic factors and electromagnetic transitions.
Euclid preparation: LXXXIV. The flat-sky approximation for the clustering of euclids photometric galaxies
(EDP Sciences, 2026) Matthewson W.L.; Durrer R.; Camera S.; Tutusaus I.
We compared the performance of the flat-sky approximation and Limber approximation for the clustering analysis of the photometric galaxy catalogue of Euclid. We studied a 6-bin configuration, representing the first data release (DR1), and a 13-bin configuration, representing the third and final data release (DR3). We find that the Limber approximation is sufficiently accurate for the analysis of the wide bins of DR1. Instead, the 13 bins of DR3 cannot be modelled accurately with the Limber approximation. Instead, the flat-sky approximation is accurate to below 5% in recovering the angular power spectra of galaxy number counts in both cases and can be used to simplify the computation of the full power spectrum in harmonic space for the data analysis of DR3.
Probing the j dependence of angular distributions and N = 20 shell rigidity via the 36S(p, d) 35S reaction
(American Physical Society, 2026) Flavigny, Freddy; Jongile, Sandile; Wiedeking, Michael
An investigation of the 𝑁=2036S nucleus has been performed through a detailed study of the 36S⁡(𝑝,𝑑)⁢35S neutron-removal reaction, employing a 66-MeV proton beam at iThemba Laboratory for Accelerator Based Sciences and an innovative target design. Using the high-resolution 𝐾 = 600 magnetic spectrometer, 98 states in 35S were identified up to 16-MeV excitation energy, including 47 previously unobserved states. Angular distributions and spectroscopic factors, including isobaric analog-state contributions, were extracted for 81 levels. A pronounced 𝑗 dependence in the angular distributions of ℓ=2 states provide refined insights into the spin-orbit splitting. Finite-range adiabatic distorted-wave approximation calculations qualitatively reproduce the observed 𝑗 dependence. Comparisons of the measured 1⁢𝑑5/2 spectroscopic strength distribution with large-scale shell-model and ab initio calculations show good agreement overall, and the robustness of the 𝑁=20 shell closure in 36S is confirmed when comparing the relatively low 𝑓⁡𝑝 orbital occupancies in 40Ca and 36S across the Fermi surface. This study underscores the utility of neutron-removal reactions in probing nuclear structure and the Fermi surface of 𝑠⁢𝑑 nuclei and beyond. The findings advance our understanding of shell evolution and offer constraining data for theoretical models.
Euclid preparation: LXXVIII. Full-shape modelling of two-point and three-point correlation functions in real space
(EDP Sciences, 2026) Guidi M.; Veropalumbo A.; Pugno A.; Moresco M.; Sefusatti E.; Porciani C.; Branchini E.; Breton M.-A.; Camacho Quevedo B.; Crocce M.
We investigated the accuracy and range of validity of the perturbative model for the two-point (2PCF) and three-point (3PCF) correlation functions in real space in view of the forthcoming analysis of the Euclid mission spectroscopic sample. We took advantage of clustering measurements from four snapshots of the Flagship I N-body simulations at z = {0.9,1.2,1.5,1.8}, which mimic the expected galaxy population in the ideal case, i.e. in the absence of observational effects such as purity and completeness. For the 3PCF we considered all available triangular configurations given a minimal separation (rmin). We first assessed the model performance by fixing the cosmological parameters and evaluating the goodness of fit provided by the perturbative bias expansion in the joint analysis of the two statistics, finding an overall agreement with the data down to separations of 20 h-1 Mpc. Subsequently, we built on the state-of-the-art analysis and extended it to include the dependence on three cosmological parameters: the amplitude of scalar perturbations (As), the matter density (ωcdm), and the Hubble parameter (h). To achieve this goal, we developed an emulator capable of generating fast and robust modelling predictions for the two summary statistics, which thus enables an efficient sampling of the joint likelihood function. We therefore present the first joint full-shape analysis of the real-space 2PCF and 3PCF, testing the consistency and constraining power of the perturbative model across both probes and assessing its performance in a combined likelihood framework. We explored possible systematic uncertainties induced by the perturbative model at small scales, finding an optimal scale cut of rmin = 30 ha-1 Mpc for the 3PCF when imposing an additional limitation on the nearly isosceles triangular configurations included in the data vector. This work is part of a series of papers in which we validate theoretical models for galaxy clustering measurements in preparation for the Euclid mission.
Results from the investigation of temporal discontinuity in the hydrogen epoch of reionization array data
(Oxford University Press, 2026) Hailemariam, Mekuanint K; Morales, Miguel F; DeBoer, David R; Abdurashidova, Zara; de Lera Acedo, Eloy; Adams, Tyrone; Aguirre, James E; Baartman, Rushelle; Beardsley, Adam P; Bernardi, Gianni; Berkhout, Lindsay M; Billings, Tashalee S; Bowman, Judd D; Byrne, Ruby; Bull, Philip; Burba, Jacob; Cox, Tyler; Carey, Steven; Chen, Kai-Feng; Ghosh, Abhik; Choudhuri, Samir; Dexter, Matt; Dillon, Joshua S; Dynes, Scott; Ely, John; Eksteen, Nico; Fritz, Randall; Furlanetto, Steven R; Gehlot, Bharat Kumar; Razavi-Ghods, Nima; Gorce, Adelie; Gorthi, Deepthi; Halday, Ziyaad; Hazelton, Bryna J; Hewitt, Jacqueline N; Hickish, Jack; Mohamed-Hinds N; Huang, Tian; Jacobs, Daniel C; Josaitis, Alec; Kern, Nicholas S; Kerrigan, Joshua; Kittiwisit, Piyanat; Kolopanis, Matthew; Lanman, Adam; Liu, Adrian; Ma, Yin-Zhe; MacMahon, David H E; Malgas, Cresshim; Malan, Lourence; Malgas, Keith; Marero, Bradley; Martinot, Zachary E; McBride, Lisa; Mesinger, Andrei; Molewa, Mathakane; Nikolic, Bojan; Nuwegeld, Hans; Parsons, Aaron R; Patra, Nipanjana; Pascua, Robert; Plante, Paul La; Qin, Yuxiang; Rath, Eleanor; Riley, Daniel; Robnett, James; Rosie, Kathryn; Santos, Mario G; Gale-Sides, Kingsley; Sims, Peter; Singh, Saurabh; Storer, Dara; Swarts, Hilton; Tan, Jianrong; Ewall-Wice, Aaron; Wilensky, Michael J; Williams, Peter K G; van Wyngaarden, Pieter; Zheng, Haoxuan
We report systematic issues commonly observed in the Hydrogen Epoch of Reionization Array observations that cause abrupt changes in power over time, resulting in temporal discontinuities. To identify these effects, we applied the Temporal Discontinuity Index and Spectral Discontinuity Index metrics, which complement existing diagnostic tools by detecting discontinuities and revealing their potential relationships to bandpass and power-related issues. Analysis of 30 data sets, each corresponding to a single observing night, shows that such systematics appear consistently in many antennas and across multiple nights. Based on these metrics, we identify three main types of discontinuity-related issues: periodic broad-band discontinuities linked to Inter-Integrated Circuit (I2C) polling, broad-band discontinuities associated with degraded post-amplifier modules (PAMs), and sudden power changes related to the digital backend of the antenna system. The second type, associated with degraded PAMs, occurs less frequently within a single night compared to the periodic polling effect, though both are broadband. The third type affects the largest number of antennas and is most prevalent in the H6C data. The width of the discontinuities related to the digital backend corresponds to the frequency range handled by a single correlator box, scaled by the number of boxes involved. Although 30 data sets were examined, this paper presents a focused analysis of four representative nights to highlight the main discontinuity issues. We also present correlations between flagging due to discontinuities and flagging caused by other failure modes to investigate how these issues are interrelated.
MIGHTEE: the dark matter haloes, duty cycle, and mechanical feedback from radio-AGN up to z ∼ 2.5
(Oxford University Press, 2026) Jarvis, Matthew; Whittam, Imogen H
Radio-AGNs (active galactic nuclei) are observed to be more strongly clustered than non-active galaxies, though it is unclear whether this is simply due to their preference for massive host galaxies, or if they reside in distinct environments beyond this mass dependence. Using data from three fields covered by the MIGHTEE survey, we measure the angular two-point cross-correlation functions with a large, stellar mass-limited population of near-infrared selected galaxies, overcoming limitations of previous single-deep-field studies. By fitting halo occupation distribution models, we infer the galaxy bias parameters, b, for radio-AGN in three redshift ranges with median redshifts of (Formula presented), (Formula presented), and (Formula presented), finding (Formula presented), (Formula presented), and (Formula presented), respectively. The typical dark matter halo mass decreases with increasing redshift: (Formula presented), (Formula presented), and (Formula presented), which we attribute to the increased abundance of cold gas required to fuel AGN activity at earlier times. The AGN duty cycle is determined to be (Formula presented) per cent, and we estimate that the total energy radiated by radio-jets over (Formula presented) is (Formula presented) per halo, which is sufficient to account for the observed excess heating of gas beyond that of gravitational collapse. Comparing the typical dark matter halo masses to the values obtained for the control sample, we find that the halo masses of radio-AGN are (Formula presented), (Formula presented), and (Formula presented) times greater than those of the stellar mass- and redshift-matched galaxies. This difference could arise because AGN feedback suppresses stellar mass growth while leaving halo mass unchanged, or because radio-AGN preferentially reside in earlier forming haloes which are more strongly clustered.
Fathomer survey. Iii. Preliminary higalaxy identification results
(American Astronomical Society, 2026) Shu, Shuanghao; Li, Yichao; Yang, Wenxiu; Wang, Jiaxin; Hu, Wenkai; Deng, Furen
We present the H i galaxy observation results of FATHOMER, a pilot drift scan survey by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). The survey comprises 28 hr of observations over seven nights in 2021, covering a 60 deg2 sky area in the frequency range 1.05–1.45 GHz. The H i galaxies are identified using both a matched-filtering algorithm and the SoFiA source-finding pipeline, which yield consistent detections. We derive the velocity width (W50), flux density, and Hi mass for detected galaxies. A total of 702 galaxies are identified with H i mass above 106.2 M⊙, signal-to-noise ratio greater than 5, and redshift z < 0.09. Among these, 331 are previously known from the ALFALFA survey. Of the newly detected sources, 9 have spectroscopic confirmation from the Sloan Digital Sky Survey (SDSS), 285 are matched to SDSS or DESI photometric data, and 77 lack optical counterparts–possible candidates for dark or faint galaxies. Comparison with ALFALFA shows that FAST enables the detection of galaxies at higher redshifts and with lower Hi fluxes, despite the radio frequency interference (RFI) and partial data masking. A preliminary Hi mass function analysis reveals a higher characteristic mass and steeper low-mass slope than ALFALFA, indicating FAST’s enhanced sensitivity to massive and distant H i systems. These results demonstrate FAST’s strong potential for future deep H i surveys and highlight the importance of improved RFI mitigation and completeness correction.
Covariant cosmography in the presence of local structures: comparing exact solutions and perturbation theory
(Institute of Physics, 2026) Sarma, Maharshi; Marinoni, Christia; Kalbouneh, Bashee; Clarkson, Chris; Maartens, Roy
Recent observational evidence of axially symmetric anisotropies in the local cosmic expansion rate motivates an investigation of whether they can be accounted for within the Lemaître– Tolman-Bondi (LTB) framework with an off-center observer. Within this setting, we compute the exact relativistic luminosity distance via the Sachs equation and compare it with the approximate expression obtained from the covariant cosmographic approach (including Hubble, deceleration, jerk and curvature parameters). This comparison allows us to identify the regimes in which the covariant cosmographic method remains reliable. In addition, we compare the LTB relativistic distance for small inhomogeneities with the corresponding result derived from linear perturbation theory (LPT) in the standard cosmological model. This analysis establishes a precise correspondence between the LTB and LPT approaches, offering a consistent dictionary for the interpretation of the observed anisotropies of the large-scale gravitational field. We test luminosity distance reconstructions in a spherically symmetric overdensity with an off-center observer. For moderate central density contrasts (δc ≲ 1), LPT reproduces the exact distance within 10% for observers inside the typical size of the structure. However, Covariant Cosmography (CC) extends this regime of validity upto δc ≲ 2.5. At larger radii, the situation reverses: for observers at three times the characteristic size, LPT remains accurate up to δc ≲ 3, while CC already exceeds 10% error for δc ≳ 1.5. At sufficiently large distances from the structure, both methods converge to the exact solution. Thus, CC is essential for accurate distance estimates near dense regions, while LPT remains reliable at larger separations. This analysis will be instrumental in interpreting expansion-rate anisotropies, facilitating investigations of the local Universe beyond the FLRW framework with a fully non-perturbative metric approach.
Prospects for measuring the doppler magnification dipole with LSST and DESI
(Oxford University Press, 2026) Clarkson, Chris; Bull, Philip; Ye, Isabelle; Guandalin, Caroline; Nasirudin, Ainulnabilah
We forecast the detectability of the Doppler magnification dipole with a joint analysis of galaxy spectroscopic redshifts and size measurements. The Doppler magnification arises from an apparent size variation caused by galaxies’ peculiar velocities when mapping them from redshift space to real space. This phenomenon is the dominant contribution to the convergence at low redshifts ((Formula presented) 0.5). A practical observational strategy is to cross-correlate a galaxy number count tracer, e.g. from the Dark Energy Spectroscopic Instrument (DESI) Bright Galaxy Survey, with the convergence field reconstructed from galaxy size measurements obtained by the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST). To assess the achievable precision of galaxy size measurements, we simulate LSST Y1-quality galaxy images with Galsim and measure them with the Galight profile fitting package. Our investigations, based on galaxy populations from LSST’s synthetic galaxy catalogue cosmoDC2, show that the variance due to intrinsic galaxy size variation dominates over size measurement errors as expected, but may be lower than previous studies have suggested. Under our analysis assumptions, the Doppler magnification dipole would be detectable with a signal-to-noise ratio (Formula presented) in multiple redshift bins between (Formula presented) with DESI spectroscopic redshifts and LSST imaging.
Collectivity of the deformed structure in 96zr from complementary coulomb-excitation and β-decay measurements
(Elsevier B.V., 2026-06) Maqungo L.; Triambak S.; Garrett P.E.; Zielińska M.; Rocchini M.
The B(E2;22+→01+) value in 96Zr was determined from a Coulomb-excitation measurement with 12C and 16O beams performed at the Maier-Leibnitz Laboratory with a Q3D magnetic spectrograph. High-precision γ -ray branching ratios in the decay of the 22+ state in 96Zr, and a new value of the 22+→21+ multipole mixing ratio, were obtained from a complementary β -decay experiment, performed using the GRIFFIN spectrometer at the TRIUMF-ISAC facility. Combining these results yields B(E2;22+→02+)=38.9(57) W.u. which is in agreement with the previous measurement, but considerably more precise. The observed differences between the properties of structures built on the 02+ states in 94Zr and 96Zr are discussed in the context of possible triple shape coexistence in Zr nuclei.

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