Research Articles (Physics)

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Dark matter fraction in disk-like galaxies over the past 10 Gyr
(EDP Sciences, 2025) Sharma, Gauri; van de Ven, Glenn; Salucci, Paolo
We present an observational study of the dark matter fraction in star-forming disk-like galaxies up to redshift z 25 selected from publicly available integral field spectroscopic surveys: KMOS3D, KGES, and KROSS. To model the H kinematics of these galaxies, we employed 3D forward modeling, which incorporates beam-smearing and inclination corrections and yields rotation curves. Subsequently, we corrected these rotation curves for gas pressure gradients, resulting in circular velocity curves or ‘intrinsic’ rotation curves. Our final sample comprises 263 rotationally supported galaxies with redshifts ranging from 06 z < 25, stellar masses within the range 90 log(Mstar [M]) < 115, and star formation rates between 049 logSFR [M yr 1] 25. We estimated the dark matter fraction of these galaxies by subtracting the baryonic mass from the total mass, where the total mass is derived from the intrinsic rotation curves. We provide novel observational evidence suggesting that at a fixed redshift, the dark matter fraction gradually increases with radius such that the outskirts of galaxies are dark matter dominated, similarly to local star-forming disk galaxies. This observed dark matter fraction exhibits a decreasing trend with increasing redshift, and on average, the fraction within the e ective radius (up to the outskirts) remains above 50%, similar to the galaxies in the local Universe. We investigated the relationships between dark matter, baryon surface density, and the circular velocity of galaxies. We observed that low stellar mass galaxies, with log(Mstar [M]) 100, undergo a higher degree of evolution, which may be attributed to the hierarchical merging of galaxies. We discuss several sources of uncertainties and current limitations in the field as well as their impact on the measurements of the dark matter fraction and its trend across galactic scales and cosmic time.
Synthesis and characterization of calcium manganese oxide powders by co-precipitation technique
(Taylor and Francis Ltd., 2025) Mahapatro, Ajit K; Pant, Megha; Pal Tandon, Ram
This work presents step by step procedure for synthesis of calcium manganese oxide (CaMnO3) prepared by co-precipitation method starting with stoichiometric amounts of calcium nitrate tetrahydrate and manganese nitrate tetrahydrate as precursors. The resulting powders of CaMnO3 are characterized for their crystallographic and spectroscopic properties. The X-ray diffraction patterns reveal formation of CaMnO3 consistent with the corresponding JCPDS. The Fourier transform infrared spectra represents the presence of Ca-O and Mn-O bond in the synthesized powders. The optical band gap of the samples is evaluated as 4.06–4.14 eV by studying the UV-Visible spectrum. The field emission scanning electron microscope images reveal irregular feature sizes with some nearly spherical particles in the synthesized samples. The currently prepared highly pure CaMnO3 attained can be consolidated into hot-pressed ceramics for measuring their electronic and thermoelectric properties to study their thermoelectric performance
Investigation of structural, morphological and temperature dependent electrical properties of CdO nanowires
(Taylor and Francis Ltd., 2025) Mahapatro, Ajit K.; Naresh; Punia, Pinki
Cadmium oxide (CdO) nanowires in the diameter range of 55-68 nm have been prepared using electrodeposition method. The calcinations of the nanowires have been done at medium temperatures of 450 °C. X-ray diffraction method is employed in order to analyze structural parameters whereas FTIR spectroscopy is used to further confirm the structure of the nanowires. The morphology of the prepared nanowires is analyzed with the FESEM images. The purity and elemental analysis of the synthesized CdO nanowires grown over a silicon substrate have been done using EDX spectra. The electrical properties are studied using a two-probe method with applied voltage ranging from −10 to 10 V and with a variation in temperature from 20 to 200 °C, the current is found to be varying from 6.93 to 21.29 nA. The increase in current with temperature indicates that the present samples can be utilized in various applications such as sensing, supercapacitor and other semiconducting applications.
Triaxial nuclear shapes from simple ratios of electric-quadrupole matrix elements
(Elsevier Inc., 2025) Orce, José Nicolás; Lawrie, Elena Atanassova
Theoretical models often invoke axially-asymmetric nuclear shapes to explain elusive collective phenomena, but such an assumption is not always easy to confirm experimentally. The only model-independent measurement of the nuclear axial asymmetry (or triaxiality) γ is based on rotational invariants of zero-coupled products of the electric-quadrupole (E2) operator — the Kumar-Cline sum rule analysis — which generally requires knowledge of a large number of E2 matrix elements connecting the state of interest. We propose an alternative method to determine γ using only two E2 matrix elements, which are among the easiest to measure. This approach is based on a standard rotational description of a nucleus with stable triaxial deformation, where all underlying assumptions are either empirically proven or unnecessary. It is applied to the 2+ states of the ground-state and the γ bands of even–even nuclei and is model-independent provided these 2+ states have rotational nature. This technique was applied to a number of deformed even–even nuclei for which the ratio of the energies of the yrast 4+ and 2+ states was R4/2> 2.4. Where sufficient experimental data were available for performing Kumar-Cline analysis, good agreement was observed between the γ values deduced in these two approaches. The agreement shows that (i) the 2+ states of the selected nuclei have indeed rotational nature, and (ii) the proposed method represents a simple and reliable deduction of γ. In the present work more than 60 even–even rotating nuclei were associated with axially-asymmetric nuclear shapes.
Multi-tracer power spectra and bispectra: formalism
(Institute of Physics, 2024) Karagiannis, Dionysios; Maartens, Roy; Fonseca, José; Camera, Stefano; Clarkson, Chris
The power spectrum and bispectrum of dark matter tracers are key and complementary probes of the Universe. Next-generation surveys will deliver good measurements of the bispectrum, opening the door to improved cosmological constraints and the breaking of parameter degeneracies, from the combination of the power spectrum and bispectrum. Multi-tracer power spectra have been used to suppress cosmic variance and mitigate the effects of nuisance parameters and systematics. We present a bispectrum multi-tracer formalism that can be applied to next-generation survey data. Then we perform a simple Fisher analysis to illustrate qualitatively the improved precision on primordial non-Gaussianity that is expected to come from the bispectrum multi-tracer. In addition, we investigate the parametric dependence of conditional errors from multi-tracer power spectra and multi-tracer bispectra, on the differences between the biases and the number densities of two tracers. Our results suggest that optimal constraints arise from maximising the ratio of number densities, the difference between the linear biases, the difference between the quadratic biases, and the difference between the products b 1 b Φ for each tracer, where b Φ is the bias for the primordial potential.
Towards cosmography of the local universe
(National University of Ireland Maynooth, 2024) Adamek, Julian; Clarkson, Chris; Durrer, Ruth
Anisotropies in the distance–redshift relation of cosmological sources are expected due to large-scale inhomogeneities in the local Universe. When the observed sources are tracing a large-scale matter flow in a general spacetime geometry, the distance–redshift relation with its anisotropies can be described with a geometrical prediction that generalises the well-known Friedmann-Lemaître-Robertson-Walker result. Furthermore, it turns out that a finite set of multipole coefficients contain the full information about a finite-order truncation of the distance–redshift relation of a given observer. The multipoles of the distance–redshift relation are interesting new cosmological observables that have a direct physical interpretation in terms of kinematical quantities of the underlying matter flow. Using light cones extracted from N-body simulations we quantify the anisotropies expected in a Λ cold dark matter cosmology by running a Markov chain Monte Carlo analysis on the observed data. In this observational approach the survey selection implements an implicit smoothing scale over which the effective rest frame of matter is fitted. The perceived anisotropy therefore depends significantly on the redshift range and distribution of sources. We find that the multipoles of the expansion rate, as well as the observer’s velocity with respect to the large-scale matter flow, can be determined robustly with our approach.
Impacts and statistical mitigation of missing data on the 21 cm power spectrum: a case study with the hydrogen epoch of reionization array
(Institute of Physics, 2025) Bull, Philip; Kittiwisit, Piyanat; Chen, Kai-Feng
The precise characterization and mitigation of systematic effects is one of the biggest roadblocks impeding the detection of the fluctuations of cosmological 21 cm signals. Missing data in radio cosmological experiments, often due to radio frequency interference (RFI), pose a particular challenge to power spectrum analysis as this could lead to the ringing of bright foreground modes in the Fourier space, heavily contaminating the cosmological signals. Here we show that the problem of missing data becomes even more arduous in the presence of systematic effects. Using a realistic numerical simulation, we demonstrate that partially flagged data combined with systematic effects can introduce significant foreground ringing. We show that such an effect can be mitigated through inpainting the missing data. We present a rigorous statistical framework that incorporates the process of inpainting missing data into a quadratic estimator of the 21 cm power spectrum. Under this framework, the uncertainties associated with our inpainting method and its impact on power spectrum statistics can be understood. These results are applied to the latest Phase II observations taken by the Hydrogen Epoch of Reionization Array, forming a crucial component in power spectrum analyses as we move toward detecting 21 cm signals in the ever more noisy RFI environment.
Meerkat discovery of a mightee odd radio circle
(Oxford University Press, 2025) Jarvis, Matt; Taylor, Russell; Norris, Ray
We present the discovery of a new Odd Radio Circle (ORC J0219−0505) in 1.2 GHz radio continuum data from the MIGHTEE survey taken with the MeerKAT telescope. The radio-bright host is a massive elliptical galaxy, which shows extended stellar structure, possibly tidal tails or shells, suggesting recent interactions or mergers. The radio ring has a diameter of 35 arcsec, corresponding to 114 kpc at the host galaxy redshift of zspec = 0.196. This MIGHTEE ORC is a factor 3–5 smaller than previous ORCs with central elliptical galaxies. The discovery of this MIGHTEE ORC in a deep but relatively small-area radio survey implies that more ORCs will be found in deeper surveys. While the small numbers currently available are insufficient to estimate the flux density distribution, this is consistent with the simplest hypothesis that ORCs have a flux density distribution similar to that of the general population of extragalactic radio sources.
Expanding covariant cosmography of the local universe: incorporating the snap and axial symmetry
(Institute of Physics, 2025) Maartens, Roy; Clarkson, Chris; Kalbouneh, Basheer
Studies show that the model-independent, fully non-perturbative covariant cosmographic approach is suitable for analyzing the local Universe (z ≲ 0.1). However, accurately characterizing large and inhomogeneous mass distributions requires the fourth-order term in the redshift expansion of the covariant luminosity distance dL (zn ). We calculate the covariant snap parameter S and its spherical harmonic multipole moments using the matter expansion tensor and the evolution equations for lightray bundles. The fourth-order term adds 36 degrees of freedom, since the highest independent multipole of the snap is the 32-pole (dotriacontapole) (ℓ=5). Including this term helps to de-bias estimations of the covariant deceleration parameter. Given that observations suggest axially symmetric anisotropies in the Hubble diagram for z ≲ 0.1 and theory shows that only a subset of multipoles contributes to the signal, we demonstrate that only 12 degrees of freedom are needed for a model-independent description of the local universe. We use an analytical axisymmetric model of the local Universe, with data that matches the Zwicky Transient Facility survey, in order to provide a numerical example of the amplitude of the snap multipoles and to forecast precision.
Disparate effects of circumgalactic medium angular momentum in IllustrisTNG and SIMBA
(EDP Sciences, 2025) Davé, Romeel; Liu, Kexin; Guo, Hong
In this study, we examine the role of the circumgalactic medium (CGM) angular momentum (jCGM) on star formation in galaxies, whose influence is currently not well understood. The analysis utilises central galaxies from two hydrodynamical simulations, SIMBA and IllustrisTNG. We observe a substantial divergence in how star formation rates correlate with CGM angular momentum between the two simulations. Specifically, quenched galaxies in IllustrisTNG show higher jCGM than their star-forming counterparts with similar stellar masses, while the reverse is true in SIMBA. This difference is attributed to the distinct active galactic nucleus (AGN) feedback mechanisms active in each simulation. Moreover, both simulations demonstrate similar correlations between jCGM and environmental angular momentum (jEnv) in star-forming galaxies, but these correlations change notably when kinetic AGN feedback is present. In IllustrisTNG, quenched galaxies consistently show higher jCGM compared to their star-forming counterparts with the same jEnv, a trend not seen in SIMBA. Examining different AGN feedback models in SIMBA, we further confirm that AGN feedback significantly influences the CGM gas distribution, although the relationship between the cold gas fraction and the star formation rate (SFR) remains largely stable across different feedback scenarios.
In search of truth: In memory of Balraj Singh
(Elsevier B.V, 2025) Orce, José Nicolás; Pritychenko, Boris; Kibédi, Tibor
Born in Punjab (India) in December 1941, Balraj Singh is not only the single most prolific nuclear data evaluator and disseminator of nuclear structure and decay data with 148 evaluations in Nuclear Data Sheets — 85 as the first and often only author — plus other journals, but his upmost curiosity and dedication brought him to be one of the finest nuclear physicists, with an everlasting influence on many of us. Balraj passed away about a year ago on 9 October 2023 in Ottawa, Ontario (Canada) at the age of 81, and at Atomic Data and Nuclear Data Tables we would like to commemorate some of his scientific achievements.
The multiple classes of ultra-diffuse galaxies: can we tell them apart?
(Oxford University Press, 2025) Jarrett, Thomas H; Buzzo, Maria Luisa; Forbes, Duncan A
This study compiles stellar populations and internal properties of ultra-diffuse galaxies (UDGs) to highlight correlations with their local environment, globular cluster (GC) richness, and star formation histories. Complementing our sample of 88 UDGs, we include 36 low surface brightness dwarf galaxies with UDG-like properties, referred to as NUDGes (nearly UDGs). All galaxies were studied using the same spectral energy distribution fitting methodology to explore what sets UDGs apart from other galaxies. We show that NUDGes are similar to UDGs in all properties except for being, by definition, smaller and having higher surface brightness. We find that UDGs and NUDGes show similar behaviours in their GC populations, with the most metal-poor galaxies hosting consistently more GCs on average. This suggests that GC content may provide an effective way to distinguish extreme galaxies within the low surface brightness regime alongside traditional parameters like size and surface brightness. We confirm previous results using clustering algorithms that UDGs split into two main classes, which might be associated with the formation pathways of a puffy dwarf and a failed galaxy. The clustering applied to the UDGs + NUDGes data set yields an equivalent result. The difference in mass contained in the GC system suggests that galaxies in different environments have not simply evolved from one another but may have formed through distinct processes.
The hobby-eberly telescope dark energy experiment survey (HETDEX) active galactic nuclei catalog: the fourth data release
(American Astronomical Society, 2025) Jarvis, Matt; Liu, Chenxu; Gebhardt, Karl
We present the active galactic nuclei (AGN) catalog from the fourth data release (HDR4) of the Hobby-Eberly Telescope Dark Energy Experiment Survey (HETDEX). HETDEX is an untargeted spectroscopic survey. HDR4 contains 345,874 Integral Field Unit observations from 2017 January to 2023 August covering an effective area of 62.9 deg2. With no imaging preselection, our spectroscopic confirmed AGN sample includes low-luminosity AGN, narrow-line AGN, and/or red AGN down to g ∼ 25. This catalog has 15,940 AGN across the redshifts of z = 0.1 ∼ 4.6, giving a raw AGN number density of 253.4 deg−2. Among them, 10,499 (66%) have redshifts either confirmed by line pairs or matched to the Sloan Digital Sky Survey Quasar Catalog. For the remaining 5441 AGN, 2083 are single broad-line AGN candidates, while the remaining 3358 are single intermediate broad-line (full width at half-maximum, FWHM ∼1200 km s−1) AGN candidates. A total of 4060 (39%) of the 10,499 redshift-confirmed AGN have emission-line regions 3σ more extended than the image quality, which could be strong outflows blowing into the outskirts of the host galaxies or ionized intergalactic medium.
Radio galaxies in simba: a mightee comparison
(University of the Western Cape, 2024) Whittam, Imogen H; Thomas, Nicole L; Hale, Catherine L
We present a qualitative comparison between the host and black hole properties of radio galaxies in the MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) survey with the radio galaxy population in the SIMBA suite of cosmological hydrodynamical simulations. The MIGHTEE data include a ∼1 deg2 pointing of the COSMOS field observed at 1.28 GHz with the MeerKAT radio telescope and cross-matched with multiwavelength counterparts to provide classifications of high- and low-excitation radio galaxies (HERGs and LERGs) along with their corresponding host properties. We compare the properties of the MIGHTEE HERGs and LERGs with that predicted by the SIMBA simulations where HERGs and LERGs are defined as radio galaxies dominated by cold or hot mode accretion, respectively. We consider stellar masses M∗, star formation rates SFR, AGN bolometric luminosity Lbol , and Eddington fraction fEdd , as a function of 1.4 GHz radio luminosity and redshift. In both MIGHTEE and SIMBA, the properties of HERGs and LERGs are similar across all properties apart from SFRs due to differences in host cold gas content in SIMBA. We predict a population of HERGs with low fEdd in SIMBA that are confirmed in the MIGHTEE observations and tied to the faint population at low z. The predictions from SIMBA with the MIGHTEE observations describe a regime where our understanding of the radio galaxy dichotomy breaks down, challenging our understanding of the role of AGN accretion and feedback in the faint population of radio galaxies
Model-agnostic assessment of dark energy after DESI DR1 BAO
(Institute of Physics, 2025) Dinda, Bikash; Maartens, Roy
Baryon acoustic oscillation measurements by the Dark Energy Spectroscopic Instrument (Data Release 1) have revealed exciting results that show evidence for dynamical dark energy at ∼ 3σ when combined with cosmic microwave background and type Ia supernova observations. These measurements are based on the w 0 w a CDM model of dark energy. The evidence is less in other dark energy models such as the wCDM model. In order to avoid imposing a dark energy model, we reconstruct the distance measures and the equation of the state of dark energy independent of any dark energy model and driven only by observational data. Our results show that the model-agnostic (in terms of late-time models) evidence for dynamical dark energy from DESI is not significant. Our analysis also provides model-independent constraints on cosmological parameters such as the Hubble constant and the matter-energy density parameter at present. Although we used CMB distance priors (not full CMB data) from a ΛCDM early-time model, our results remain largely similar for other cosmological models, provided that these models do not differ significantly from the standard model.
The multiple classes of ultra-diffuse galaxies: can we tell them apart?
(Oxford University Press, 2024) Jarrett, Thomas H.; Buzzo, Maria Luisa; Forbes, Duncan A
This study compiles stellar populations and internal properties of ultra-diffuse galaxies (UDGs) to highlight correlations with their local environment, globular cluster (GC) richness, and star formation histories. Complementing our sample of 88 UDGs, we include 36 low surface brightness dwarf galaxies with UDG-like properties, referred to as NUDGes (nearly UDGs). All galaxies were studied using the same spectral energy distribution fitting methodology to explore what sets UDGs apart from other galaxies. We show that NUDGes are similar to UDGs in all properties except for being, by definition, smaller and having higher surface brightness. We find that UDGs and NUDGes show similar behaviours in their GC populations, with the most metal-poor galaxies hosting consistently more GCs on average. This suggests that GC content may provide an effective way to distinguish extreme galaxies within the low surface brightness regime alongside traditional parameters like size and surface brightness. We confirm previous results using clustering algorithms that UDGs split into two main classes, which might be associated with the formation pathways of a puffy dwarf and a failed galaxy. The clustering applied to the UDGs + NUDGes data set yields an equivalent result. The difference in mass contained in the GC system suggests that galaxies in different environments have not simply evolved from one another but may have formed through distinct processes.
A classifier-based approach to multiclass anomaly detection for astronomical transients
(Oxford University Press, 2025) Lochner, Michelle.; Gupta, Rithwik.; Muthukrishna, Daniel.
Automating real-time anomaly detection is essential for identifying rare transients, with modern survey telescopes generating tens of thousands of alerts per night, and future telescopes, such as the Vera C. Rubin Observatory, projected to increase this number dramatically. Currently, most anomaly detection algorithms for astronomical transients rely either on hand-crafted features extracted from light curves or on features generated through unsupervised representation learning, coupled with standard anomaly detection algorithms. In this work, we introduce an alternative approach: using the penultimate layer of a neural network classifier as the latent space for anomaly detection. We then propose a novel method, Multi-Class Isolation Forests, which trains separate isolation forests for each class to derive an anomaly score for a light curve from its latent space representation. This approach significantly outperforms a standard isolation forest. We also use a simpler input method for real-time transient classifiers which circumvents the need for interpolation and helps the neural network handle irregular sampling and model inter-passband relationships. Our anomaly detection pipeline identifies rare classes including kilonovae, pair-instability supernovae, and intermediate luminosity transients shortly after trigger on simulated Zwicky Transient Facility light curves. Using a sample of our simulations matching the population of anomalies expected in nature (54 anomalies and 12 040 common transients), our method discovered anomalies (recall) after following up the top 2000 () ranked transients. Our novel method shows that classifiers can be effectively repurposed for real-time anomaly detection.
Matvis: a matrix-based visibility simulator for fast forward modelling of many-element 21 cm arrays
(Oxford University Press, 2025) Kittiwisit, Piyanat; Bull, Philip; Murray, Steven
Detection of the faint 21 cm line emission from the Cosmic Dawn and Epoch of Reionization will require not only exquisite control over instrumental calibration and systematics to achieve the necessary dynamic range of observations but also validation of analysis techniques to demonstrate their statistical properties and signal loss characteristics. A key ingredient in achieving this is the ability to perform high-fidelity simulations of the kinds of data that are produced by the large, many-element, radio interferometric arrays that have been purpose-built for these studies. The large scale of these arrays presents a computational challenge, as one must simulate a detailed sky and instrumental model across many hundreds of frequency channels, thousands of time samples, and tens of thousands of baselines for arrays with hundreds of antennas. In this paper, we present a fast matrix-based method for simulating radio interferometric measurements (visibilities) at the necessary scale. We achieve this through judicious use of primary beam interpolation, fast approximations for coordinate transforms, and a vectorized outer product to expand per-antenna quantities to per-baseline visibilities, coupled with standard parallelization techniques. We validate the results of this method, implemented in the publicly available matvis code, against a high-precision reference simulator, and explore its computational scaling on a variety of problems.
Timing and noise analysis of five millisecond pulsars observed with MeerKAT
(Oxford University Press, 2025) Andrianomena, Sambatra; Geyer, Marisa; Enwelum, U
Millisecond pulsars (MSPs) in binary systems are precise laboratories for tests of gravity and the physics of dense matter. Their orbits can show relativistic effects that provide a measurement of the neutron star mass and the pulsars are included in timing array experiments that search for gravitational waves. Neutron star mass measurements are key to eventually solving the neutron star equation of state and these can be obtained by a measure of the Shapiro delay if the orbit is viewed near edge-on. Here, we report on the timing and noise analysis of five MSPs observed with the MeerKAT radio telescope: PSRs J0900–3144, J0921–5202, J1216–6410, J1327–0755, and J1543–5149. We searched for the Shapiro delay in all of the pulsars and obtain weak detections for PSRs J0900–3144, J1216–6410, and J1327–0755. We report a higher significance detection of the Shapiro delay for PSR J1543–5149, giving a precise pulsar mass of Mp = 1.349+0.043-0.061M☉ and companion white-dwarf mass Mc = 0.223+0.005-0.007M☉. This is an atypically low-mass measurement for a recycled MSP. In addition to these Shapiro delays, we also obtain timing model parameters including proper motions and parallax constraints for most of the pulsars.
Probing the cosmological principle with weak lensing shear
(Institute of Physics, 2025) Adam, James; Maartens, Roy; Larena, Julien
The Cosmological Principle is a cornerstone of the standard model of cosmology and shapes how we view the Universe and our place within it. It is imperative, then, to devise multiple observational tests which can identify and quantify possible violations of this foundational principle. One possible method of probing large-scale anisotropies involves the use of weak gravitational lensing. We revisit this approach in order to analyse the imprint of late-time anisotropic expansion on cosmic shear. We show that the cross-correlation of shear Eand B-modes on large scales can be used to constrain the magnitude (and possibly direction) of anisotropic expansion. We estimate the signal to noise for multipoles 10 ≲ ℓ ≲ 100 that is achievable by a Euclid-like survey. Our findings suggest that such a survey could detect the E-B signal for reasonable values of the late-time anisotropy parameter.

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