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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 13 March

Astrophysics of Galaxies

The ALPINE-CRISTAL-JWST Survey: Gas-phase abundance gradients of main sequence star-forming galaxies and their kinematics at $4 < z < 6$

Lilian L. Lee, Natascha M. Förster Schreiber, Seiji Fujimoto et al. (+50 more)

We present gas-phase radial metallicity profiles for 20 main-sequence galaxies at $4<z<6$, primarily based on JWST NIRSpec IFU observations obtained as part of the JWST-ALPINE-CRISTAL programme. Our study aims to connect the metallicity gradients of these galaxies with their kinematic properties from [CII]158$\mu$m ALMA observations. We mapped the radial profiles of oxygen abundance using the strong-line method leveraging the rich set of rest-frame optical emission lines. Linear fits to the annular-binned radial profiles show that, on average, the metallicity gradients are slightly positive with a median of $+0.039 \pm 0.010{\rm dexkpc^{-1}}$. There are no substantial systematic offsets in gradients when using different line diagnostics. However, only three galaxies show a gradient $>0.05{\rm dexkpc^{-1}}$ at $1\sigma$, and none have a significant negative gradient. We investigated the correlation between the metallicity gradients and the intrinsic gas velocity dispersion $\sigma_0$ as well as the $V_{\rm rot}/\sigma_0$ ratio of the disks. Combining our sample with mass-matched literature samples at $3<z<7$, we found a negative shallow correlation between $V_{\rm rot}/\sigma_0$ and the metallicity gradients, but no strong relationships with $\sigma_0$. As $V_{\rm rot}/\sigma_0$ increases towards later cosmic times, the observed negative trend with $V_{\rm rot}/\sigma_0$ is consistent with the overall cosmic evolution of metallicity gradients from high to low redshifts. This suggests that disk maturity plays a crucial role in shaping the radial metallicity gradients. [Abridged abstract]
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All authors Lilian L. Lee, Natascha M. Förster Schreiber, Seiji Fujimoto, Andreas L. Faisst, Rodrigo Herrera-Camus, Reinhard Genzel, Linda J. Tacconi, Dieter Lutz, Alvio Renzini, Ryan Sanders, Emily Wisnioski, Stijn Wuyts, Eleonora Parlanti, Gareth Jones, Hannah Übler, Daizhong Liu, Jianhang Chen, Ric I. Davies, Giulia Tozzi, Andreas Burkert, Sedona H. Price, Manuel Aravena, Médéric Boquien, Matthieu Béthermin, Elisabete da Cunha, Rebecca L. Davies, Ilse De Looze, Miroslava Dessauges-Zavadsky, Andrea Ferrara, Deanne B. Fisher, Steven Gillman, Michele Ginolfi, Edo Ibar, Anton M. Koekemoer, Juan Molina, Thorsten Naab, Mónica Relaño, Dominik A. Riechers, David B. Sanders, Justin S. Spilker, Livia Vallini, Giovanni Zamorani, Ambra Nanni, Poulomi Dam, Tanio Diaz-Santos, Diego Gómez-Espinoza, Ali Hadi, Ryota Ikeda, Ana Posses, Michael Romano, Amiel Sternberg, Vicente Villanueva, Wuji Wang

Cosmology and Nongalactic Astrophysics

Searching for Unparticles with the Cosmic Microwave Background

Oliver H. E. Philcox, Guilherme L. Pimentel and Chen Yang

Multi-field models of inflation typically assume that interactions between particles can be treated perturbatively. Strongly-coupled models provide an intriguing alternative and may offer novel inflationary phenomenology. We study the "unparticle" scenario, where the inflaton is weakly mixed with a strongly-coupled sector, specified by a (gapless) conformal field theory. For certain choices of conformal scaling dimension, $\Delta$, the exchange of unparticles leads to distinctive non-Gaussian features in the primordial curvature distribution, including bispectra with enhanced squeezed limits and oscillations close to the equilateral regime. Efficiently analyzing these models using Cosmic Microwave Background (CMB) data is a challenge since the shapes are non-factorizable in momenta and often highly degenerate with single-field self-interactions. Here, we overcome these limitations using a library of tools, including neural-network factorization schemes and optimal CMB estimators. Our pipeline condenses 161 non-separable templates into just 7 factorizable forms, with negligible loss of signal-to-noise. We apply the model to the Planck data, asking two key questions: (1) can we detect unparticles? (2) can we distinguish them from single-field self-interactions? Across $1\leq \Delta\leq 9$, we find a maximal signal-to-noise of $1.2\sigma$, implying no evidence for new physics. We also place the first CMB constraints on the modified consistency-condition-satisfying orthogonal bispectrum with $f^{\rm orth^*}_{\rm NL} = -12\pm12$. While many unparticle models are degenerate with single-field shapes, values of $\Delta$ close to half-integers have very different shapes, offering an intriguing future discovery channel. The methods developed herein can be directly applied to other classes of templates, motivating the exploration of models beyond the standard weakly-coupled paradigm.
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High Energy Astrophysical Phenomena

Distinguishing Kilonovae from Binary Neutron Star and Neutron Star-Black Hole Mergers

Ish Gupta, Yugesh Bhoge, Rahul Kashyap et al. (+1 more)

Kilonovae (KNe) are most informative when accompanied by a gravitational-wave signal, which can help identify the source as a binary neutron star (BNS) or a neutron star-black hole (NSBH) merger. However, future events will also be discovered serendipitously or through follow-up of other transients, without a confident identification of the progenitor. We ask whether the KN light curve alone can distinguish between these two progenitor channels. Using simulated BNS and NSBH populations together with semi-analytic light curve models, we compare their post-peak evolution across the optical $ugrizy$ bands, and quantify the separation between the two classes in each band with the area under the receiver-operating-characteristic curve (AUC). BNS and NSBH KNe populate distinct regions of the post-peak decline distribution, with BNS KNe fading faster in every band. The separation is cleanest in the blue $u$ and $g$ bands $5$ days after peak and in the redder $i$ band $10$ days after peak. Within $5$ days of peak, BNS KNe decline by $\gtrsim 6$ ($\gtrsim 4$) mag in $u$ ($g$) bands, whereas NSBH KNe fade by only $\sim 3$ ($\sim 1$) mag. Over $10$ days in $i$, NSBH KNe decline by $\sim 1$–$2$ mag against $\sim 3$–$6$ mag for BNS. We attribute this to the higher opacity of NSBH ejecta, which lengthens the photon-diffusion time and slows the decline in all bands, while a low opacity blue component drives the rapid early peak and decline of BNS KNe. Although the precise overlap is model-dependent, the qualitative separation persists across variations in the astrophysical population, the NS equation of state, and the controlled variation of ejecta model parameters, establishing the post-peak photometric decline as a viable EM-only diagnostic of whether a KN arose from a BNS or an NSBH merger.
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All authors Ish Gupta, Yugesh Bhoge, Rahul Kashyap, Mukul Bhattacharya

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Blazar Constraints on Axions through New Spectral Modulation Searches in 1ES 1959+650 & B2 1811+31

Andrea Giovanni De Marchi, Orion Ning and Tianzhuo Xiao

Blazars are unique astrophysical environments whose high-energy $\gamma$-ray spectra are susceptible to modulations in the presence of ultralight axions. We search for these modulations, induced by axion-photon mixing, in Fermi-LAT spectral data of previously unexplored blazar targets, focusing in particular on blazars 1ES 1959+650 and B2 1811+31, whose flare states provide a clean testbed for axion activity. In both cases, we find no evidence for axions, and set exclusion regions on the axion-photon coupling for masses between $10^{-9}$ eV $\lesssim$ $m_a$ $\lesssim$ $10^{-8}$ eV, with sensitivities typically reaching $g_{a \gamma \gamma} \sim 10^{-11} - 10^{-10}$ GeV$^{-1}$ depending on the assumed blazar modeling choices. We examine the broad impact of modeling uncertainties, finding that the resulting constraints can vary substantially across plausible configurations. We discuss the implications of these systematic effects and their relevance for similar blazar-like searches in the future.
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Astrophysics of Galaxies

A Spectral Atlas for Quiescent Galaxies

Massissilia L. Hamadouche, Jacqueline Antwi-Danso, Aliza Beverage et al. (+1 more)

Key absorption features in the spectra of massive quiescent galaxies reveal a wealth of information about their stellar populations and, in some cases, the properties of gas within and around them. With the spectroscopic capabilities of JWST, we are now able to probe deeper and farther into the near-infrared than ever before. It is therefore crucial that we fully understand the origins of observed spectral absorption and emission features. The goal of this document is to collate important rest-frame optical to near-infrared (NIR) spectral features of quiescent galaxies in the context of their physical origin (e.g., stellar photospheres, the interstellar medium, or a combination thereof). We present a look-up table summarizing key information, including a “diagnostic” column indicating whether lines are most sensitive to age, metallicity, surface gravity (IMF sensitivity), $\alpha$-enhancement, electron temperature or gas density. This compilation is intended to serve as a practical reference for interpreting rest-optical-NIR spectral features in quiescent galaxies, particularly as JWST spectroscopy enables increasingly detailed studies of their stellar populations and surrounding gas.
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All authors Massissilia L. Hamadouche, Jacqueline Antwi-Danso, Aliza Beverage, Katherine E. Whitaker

High Energy Astrophysical Phenomena

Implications of a Cosmogenic Origin of KM3-230213A for Ultra-High-Energy Protons

A. R. Alhebsi, Arjen van Vliet, Domenik Ehlert et al. (+1 more)

A significant neutrino event with an estimated energy between $72\,\mathrm{PeV}$ and $2.6\,\mathrm{EeV}$ was recently observed by the KM3NeT experiment (KM3-230213A). When interpreted as cosmogenic in origin, this event can provide constraints on several phenomenological parameters of UHE proton sources. In this study, we present the best fit to the spectrum and composition of UHECRs that is consistent with multi-messenger constraints, including the detection of a single neutrino event by the KM3NeT detector in the energy range of KM3-230213A. From the best fit, we obtain the 68% CL constraints on the parameters of a two-population model of UHECRs, comprising a mixed-composition population and a subdominant UHE proton population. Our results indicate that the detection of a single neutrino event in the energy range of KM3-230213A solely with the KM3NeT exposure requires strongly evolving UHE proton sources, consistent with high-luminosity active galactic nuclei. On the other hand, including the null observations from the Pierre Auger and IceCube observatories disfavors such strong evolution. In both cases, the observed proton fraction of UHECRs is primarily constrained by the composition data to be $\sim 20\%$ at $20\,\mathrm{EeV}$.
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All authors A. R. Alhebsi, Arjen van Vliet, Domenik Ehlert, Satyendra Thoudam

High Energy Astrophysical Phenomena

Critical slowing down and bulk viscosity in binary neutron star mergers

Jamie M. Karthein, Maneesha Sushama Pradeep and Rachel Steinhorst

Hydrodynamic simulations of neutron star mergers rely on the clear separation between the strong-interaction, weak-interaction, and hydrodynamic timescales. In this effective framework, weak Urca interactions are typically the slowest microscopic processes, and therefore the Urca rate determines the bulk-viscous dissipation. This assumed hierarchy of dissipative mechanisms can be decisively altered, without invalidating hydrodynamics, if the trajectory of the matter in a neutron star merger passes through the vicinity of a possible low temperature QCD critical point. The enhanced density fluctuations lead to critical slowing down and rapid growth of transport coefficients including bulk viscosity. While this growth is regulated by finite-time effects, finite-size effects, and the breakdown of hydrodynamic scale separation, which bound the correlation length, we demonstrate that the QCD contribution to bulk viscosity can rival the electroweak contribution in realistic conditions. Thus, critical dynamics could leave observable imprints on the hydrodynamic evolution of neutron star mergers.
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Cosmology and Nongalactic Astrophysics

Primordial non-Gaussianity constraints on dissipative inflation

Santiago Agüí Salcedo, Thomas Colas, Petar Suman et al. (+3 more)

Dissipative effects appear in many early-Universe scenarios, yet their universal observational signatures and systematic confrontation with data remain largely unexplored. We employ the Open Effective Field Theory of Inflation (Open EFToI) to consistently incorporate dissipative and stochastic effects while preserving scale invariance. Dissipation enhances specific interaction channels of the Goldstone mode, generating distinctive primordial non-Gaussian signatures, beyond those generically produced by standard EFToI. In the weak-dissipation regime, this includes folded bispectrum shapes observationally more favoured than both the equilateral and orthogonal templates. Using the Modal bispectrum pipeline with the Planck CMB data, we obtain the likelihood and derive the first model-independent bounds on early-Universe dissipation. We find a marginalised upper bound on the dissipation scale $\gamma \leq 384\,H$ and a lower bound on the sound speed $c_s \geq 0.38$ at $95\%$ confidence level. The maximum likelihood for best-fit models reveals a degeneracy between $\gamma$ and $c_s$. These results open a model-independent window for probing departures from minimal inflation and discriminating between early-Universe scenarios with stochastic noise and dissipative effects.
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All authors Santiago Agüí Salcedo, Thomas Colas, Petar Suman, Bowei Zhang, James Fergusson, E.P.S. Shellard

Astrophysics of Galaxies

A hot, nebular-dominated galaxy interacting with a pristine PopIII system uncovered by JWST

Henriette Reumert, Kasper E. Heintz, Clara L. Pollock et al. (+6 more)

The discovery of galaxies with extremely strong nebular continuum emission at high redshifts provide novel, unique insights into the conditions under which the first super-massive stars formed. Here we identify a galaxy at redshift $z=5.124$ observed by the JWST CAPERS survey that exhibits a prominent turnover in the rest-frame UV continuum and a pronounced Balmer `jump'. We model the entire JWST/NIRSpec Prism spectrum from rest-frame UV to optical wavelength, finding that a dominant ($>95\%$) nebular continuum emission can accurately reproduce the spectral shape across all wavelengths. We tested an alternative model with strong damped Ly$\alpha$ absorption (DLA), but found that it is not able to match the shape of the turnover without invoking a large freedom in the redshift of the absorber. The nebular continuum emission model reveals a hot ($T = (5.3\pm 0.2)\times 10^{4}$ K) and dense ($n_e = (5.4\pm 0.8)\times 10^{3} {\rm cm^{-3}}$) nebular region powering the origin of the spectral shape. We also note the presence of a `blue' candidate companion source potentially at the same redshift, offset by 3 kpc to the main galaxy. Intriguingly, the spectrum of this source show several hints of hydrogen and helium lines, but no metal lines are detected. We theorize that this companion galaxy might be comprised mainly of Population III (PopIII) stellar remnants and potentially powers the nebular continuum emission seen in the main galaxy. These results have important implications for the presence of a potential dominant population of super-massive and PopIII stars and their consequent excess UV brightness for a significant fraction of galaxies at cosmic dawn.
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All authors Henriette Reumert, Kasper E. Heintz, Clara L. Pollock, Alex J. Cameron, Gabriel B. Brammer, Albert Sneppen, Joris Witstok, Chamilla Terp, Darach Watson

Solar and Stellar Astrophysics

Exploring the surface of HD 189733 via Doppler shadow analysis of planetary transits

E. C. Gonçalves, E. Cristo, W. Dethier et al. (+6 more)

Transmission spectroscopy has greatly advanced the study of exoplanet atmospheres, but stellar surface heterogeneities can contaminate transit spectra. Characterising how stellar spectra vary across the stellar disc is therefore essential to disentangle stellar and planetary contributions. Transit observations can probe the local stellar spectra along the planet's transit chord. We study centre-to-limb variations of line profiles across the surface of HD 189733 using the ESPRESSO spectrograph. Building on previous work, we assess the feasibility of applying the Doppler shadow technique with ESPRESSO and compare the results with solar observations and numerical simulations. We analyse spectra obtained during two transits of HD 189733 b. Each spectrum was cross-correlated with two masks of selected Fe I lines, producing four sets of cross-correlation functions (CCFs). Using a Doppler shadow methodology, we retrieved local stellar profiles along the transit chord. These were compared with previous studies, with disc-resolved solar spectra from IAG ATLAS and with transit simulations generated using SOAPv4 and synthetic spectra from Turbospectrum based on MARCS stellar atmosphere models under LTE and NLTE conditions. For three Fe I CCF sets we detect a statistically significant increase in line depth from stellar limb to centre, consistent with Turbospectrum predictions, although solar data show a weaker gradient. For one CCF set we also find that line widths decrease from limb to centre, consistent with solar observations but not reproduced by the simulations. These results demonstrate the capability of ESPRESSO to measure centre-to-limb variations of spectral line profiles on other stars. While the local CCF profiles of HD 189733 agree with solar data, discrepancies in line widths suggest that additional physical processes are required to reproduce the observed profiles.
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All authors E. C. Gonçalves, E. Cristo, W. Dethier, N. C. Santos, S. G. Sousa, P. T. P. Viana, T. Azevedo Silva, R. Allart, V. Bourrier

Solar and Stellar Astrophysics

Quasi-Periodic Fast-Mode Wave Trains Associated with the 2015-Jun-22 M6.5 Flare in AR~12371: Observations and 3D MHD Modeling

Tongjiang Wang, Wei Liu, Leon Ofman et al. (+2 more)

Quasi-periodic fast-propagating (QFP) wave trains are a distinctive form of magnetohydrodynamic disturbance frequently observed in the solar corona. Yet their excitation mechanism and propagation characteristics are not well understood. In this study, we investigate a well-observed QFP wave event associated with an M6.5-class flare and coronal mass ejection that occurred in active region (AR) 12371 on 2015 June 22 by combining multi-wavelength observations from SDO/AIA and HMI with data-inspired 3D MHD simulations. The QFP wave trains propagating at high speeds of 1140$-$1760 km~s$^{-1}$ are detected in the AIA 171 Å\ channel, following global EUV wave fronts visible at 171 and 193~Å\ traveling at considerably lower speeds of 300$-$510 km~s$^{-1}$. Wavelet analysis reveals consistent 2–4 minutes periodicities in both the QFPs and flare quasi-periodic pulsations (QPPs) observed in UV/EUV and hard X-ray emissions, suggesting a common origin likely linked to intermittent magnetic reconnection. Guided by these observations, we construct realistic 3D MHD models incorporating dense fan-loop structures and periodic drivers applied at different locations. The simulations reproduce the key characteristics of the observed wave trains. Comparison between cases with and without a coronal background (non-loop plasma emission) indicates that coronal density structuring significantly modifies the detected wave amplitudes and propagation patterns. Our results highlight the importance of realistic coronal magnetic configurations in modeling QFP dynamics and suggest that their observed association with fan loops in AIA 171 Å\ may represent a temperature-dependent visibility effect rather than a genuine confinement of the waves.
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All authors Tongjiang Wang, Wei Liu, Leon Ofman, Xudong Sun, Meng Jin

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Ultralight Dark Matter: Undergraduate Physics in Modern Cosmology

Timothy D. Wiser

Ultralight dark matter is a hypothetical class of particle with a number of interesting theoretical and experimental properties, many of which are best understood by direct analogy with or application of undergraduate physics. We present a series of exercises and discussions which may inspire the reader to bring contemporary research on ultralight dark matter into the undergraduate classroom.
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Cosmology and Nongalactic Astrophysics

A 2% determination of $N_{\rm eff}$ from primordial element abundance, cosmic microwave background, and baryon acoustic oscillation measurements

Samuel Goldstein and J. Colin Hill

We present a new constraint on the effective number of relativistic species in the early universe, $N_{\rm eff}$, by combining recent primordial helium abundance measurements from the Large Binocular Telescope $Y_p$ Project with primordial deuterium abundance data, cosmic microwave background (CMB) observations from $\it{Planck}$, the Atacama Cosmology Telescope, and the South Pole Telescope, and baryon acoustic oscillation (BAO) data from the Dark Energy Spectroscopic Instrument, yielding $N_{\rm eff}=2.990\pm0.070$ (68% C.L.). This is the tightest constraint on $N_{\rm eff}$ to date, and is in excellent agreement with the standard model prediction of $N_{\rm eff}=3.044$. Furthermore, we constrain excess contributions to $N_{\rm eff}$ beyond the three neutrino species, finding $\Delta N_{\rm eff}<0.107$ (95% C.L.). This bound nearly approaches the minimum contribution to $\Delta N_{\rm eff}$ from a light spin-3/2 particle that decoupled at any time after inflation ended. Our baseline analysis does not include large-scale $\it{Planck}$ polarization information, enabling a fully consistent combination of state-of-the-art CMB and BAO measurements. As a byproduct, we show that current $N_{\rm eff}$ bounds are essentially insensitive to the inclusion or exclusion of optical depth constraints inferred from large-scale CMB polarization data, making $N_{\rm eff}$ highly robust in this regard. Our constraints place stringent limits on light particles in the early Universe and on a broad range of models aimed at increasing the CMB-inferred value of the Hubble constant.
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Cosmology and Nongalactic Astrophysics

Comparison of Cross-Correlation Methods for Line Intensity Mapping

Samuel H. Kramer, Patrick C. Breysse, Anthony R. Pullen et al. (+4 more)

Line intensity mapping (LIM) is a technique for producing 3D maps of the Universe by scanning the sky with a spectrometer sensitive to a range of wavelengths corresponding to the redshifted spectral lines of atoms or molecules, such as hydrogen or carbon, commonly found in galaxies and the diffuse media around them. While LIM experiments have successfully detected the 21 cm line of neutral hydrogen, other lines that reveal large-scale structure or astrophysical processes remain undetected. Many LIM experiments are in development or are underway to fill this gap, but will likely suffer from contamination from systematics, like Galactic foregrounds, or noise. Cross-correlation techniques offer the smoothest route for making detections and constraining astrophysical processes in this regime. In this work, we apply three cross-correlation techniques (stacking, the conditional voxel intensity distribution (CVID), and the cross power spectrum) to simulated LIM maps produced using [CII] luminosity models for a pathfinder LIM experiment (EXCLAIM). We find that these cross-correlation techniques allow for mean detection of the target signal line ([CII]) at redshifts 2.5-3.5 at the 3.9$\sigma$, 3.7$\sigma$, and 4.2$\sigma$ level, respectively, and offer moderate constraints on the line emission model. Under a futuristic scenario with reduced noise, the techniques improve substantially, with detections at the 35.4$\sigma$, 76.6$\sigma$, and 38.8$\sigma$ levels and percent-level constraints. Each technique offers unique information, with the strongest constraints achieved by using the three techniques in combination.
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All authors Samuel H. Kramer, Patrick C. Breysse, Anthony R. Pullen, Faizah K. Siddique, Eric R. Switzer, Peter T. Timbie, Dongwoo Chung

High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Challenging the Weak Cosmic Censorship with Phantom Fields

Giovanni Caridi, Fabrizio Corelli and Paolo Pani

Penrose's weak cosmic censorship conjecture asserts that spacetime singularities produced by gravitational collapse are generically hidden behind event horizons, thus preventing them from causally influencing distant observers and preserving the predictability of the exterior region. In this work, we probe this conjecture in a setup that deliberately violates one of its central assumptions - the dominant energy condition - by considering the spherical collapse of a phantom scalar field with negative energy density. In principle, such a field could produce a Schwarzschild geometry with negative mass and therefore no event horizon. Our aim is to assess whether, once the dominant energy condition is abandoned, the fully coupled evolution of matter and geometry can dynamically generate or expose naked singularities, thereby probing the robustness of cosmic censorship. To this end, we perform high-accuracy numerical relativity simulations based on fourth-order finite-difference schemes. Starting from smooth, asymptotically flat initial data representing regular phantom scalar wave packets, we follow their fully nonlinear evolution through collapse or dispersion. While an ordinary (positive-energy) scalar field exhibits the standard Choptuik critical behavior at the threshold of black-hole formation, the phantom field displays qualitatively different dynamics. For all amplitudes considered, we find no evidence for trapped surfaces, naked singularities, or alternative stationary end states. Instead, the phantom scalar field always disperses, suggesting that cosmic censorship remains dynamically preserved even in the presence of negative-energy matter.
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Cosmology and Nongalactic Astrophysics

Negative Masses and Spatial Curvature: Effects on the neutrino mass tension in LambdaCDM and extended cosmologies

Hayyim Pulido-Hernández and Jorge L. Cervantes-Cota

We investigate the impact of spatial curvature, $\Omega_k$, and dynamical dark energy on the cosmological constraints of the neutrino mass sum, $\sum m_\nu$. Using a joint analysis of the latest CMB (Planck and ACT DR6), BAO (DESI DR2) and SNe Ia (DESY5 and DES-Dovekie) datasets, we perform an exploration of the neutrino mass parameter space. To mitigate prior-driven biases near the physical boundary, we implement a symmetric extension wrapper that allows for effective negative masses. We find that the inclusion of spatial curvature significantly modifies the posterior distributions, exhibiting a smooth transition across the $\sum m_\nu = 0$ threshold. In the $\Lambda$CDM + $\Omega_k$ + $\sum m_{\nu,\mathrm{eff}}$ framework, we obtain $\sum m_{\nu,\mathrm{eff}} = -0.011^{+0.052}_{-0.050}$, reducing the tension with the terrestrial lower limit of 0.06 eV from $2.59\sigma$ for the $\Lambda$CDM + $\sum m_{\nu,\mathrm{eff}}$ model to $1.17\sigma$. For the most flexible scenario $w_0 w_a$CDM + $\Omega_k$ + $\sum m_{\nu,\mathrm{eff}}$, we find $\sum m_{\nu,\mathrm{eff}} = -0.07 \pm 0.11$ with a tension of $1.13\sigma$, illustrating how the increased parameter freedom notably degrades the precision of the mass estimate compared to simpler extensions. Our results demonstrate that current cosmological bounds on $\sum m_\nu$ are heavily influenced by boundary effects and geometric degeneracies.
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Instrumentation and Methods for Astrophysics

A Commensal Radio-Only Cosmic Ray Detector at the Owens Valley Radio Observatory Long Wavelength Array

Kathryn A. Plant, Andrew Romero-Wolf, Gregg Hallinan et al. (+46 more)

The brief (10 nanoseconds) transient radio emission from cosmic ray air showers carries key information about the energy and mass composition of high energy cosmic rays, but anthropogenic radio frequency interference has historically prevented radio-based cosmic ray studies from being carried out independently from other types of detectors. We describe a cosmic ray detection system for the Owens Valley Radio Observatory Long Wavelength Array that searches for radio emission from cosmic ray air showers without relying on an external trigger, and runs alongside the other observing modes of the array. The OVRO-LWA, located in Eastern California, recently completed an expansion to 352 dual-polarization antennas and new signal processing infrastructure. In order to detect cosmic rays in the presence of radio frequency interference (RFI), initial event classification and RFI rejection is performed on Field Programmable Gate Array boards, which each process a sampled voltage timeseries from both polarizations of a subarray of 32 antennas. Each board uses dedicated RFI veto antennas outside the air shower radio footprint to reject RFI events. We present the trigger design, RFI flagging strategy, and candidate cosmic rays.
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All authors Kathryn A. Plant, Andrew Romero-Wolf, Gregg Hallinan, Marin M. Anderson, Judd D. Bowman, Ruby Byrne, Bin Chen, Xingyao Chen, Morgan Catha, Sherry Chhabra, Larry D'Addario, Ivey Davis, Jayce Dowell, Katherine Elder, Dale Gary, Charlie Harnach, Greg Hellbourg, Jack Hickish, Rick Hobbs, David Hodge, Mark Hodges, Yuping Huang, Andrea Isella, Daniel C. Jacobs, Ghislain Kemby, John T. Klinefelter, Matthew Kolopanis, Nikita Kosogorov, James Lamb, Casey Law, Nivedita Mahesh, Surajit Mondal, Brian O'Donnell, Corey Posner, Travis Powell, Vinand Prayag, Andres Rizo, Jun Shi, Greg Taylor, Jordan Trim, Mike Virgin, Akshatha Vydula, Sandy Weinreb, Scott White, David Woody, Sijie Yu, Thomas Zentmeyer, Peijin Zhang, T. Joseph W. Lazio

Instrumentation and Methods for Astrophysics

Optimizing Foreground Modelling for Global 21cm Cosmology with GPU-Accelerated Nested Sampling

Jacob L. Tutt, Peter H. Sims, Joe H. N. Pattison et al. (+3 more)

The global 21-cm signal provides a powerful probe of early-Universe astrophysics, but its detection is hindered by Galactic foregrounds that are orders of magnitude brighter than the signal and distortions introduced by beam chromaticity. These challenges require accurate foreground modelling, rigorous Bayesian model comparison, and robust validation frameworks. In this work, we substantially accelerate global 21-cm inference by exploiting GPU architectures, enabling likelihood evaluations to achieve near-constant wall-clock time across a wide range of model dimensionalities and data volumes. Combined with algorithmic parallelisation of Nested Sampling, this reduces the total inference runtime of this work from hundreds of CPU-years to approximately two GPU-days, corresponding to a cost reduction of over two orders of magnitude. Leveraging this capability, we advance the physically motivated forward-modelling approach, in which foregrounds are represented by a discrete set of sky regions by introducing a novel, observation-dependent sky-partitioning scheme that defines regions using the antenna beam-convolved sky power of a given observing window. We show that this scheme improves modelling performance in three ways: firstly, by enforcing a strictly nested region hierarchy that enables clear identification of the Occam penalty in the Bayesian evidence, facilitating principled optimisation of model complexity; secondly, by enabling more accurate recovery of spatially varying spectral indices, with posterior estimates centred within physically plausible ranges; and thirdly, by allowing complex foregrounds to be modelled for robust global 21-cm signal inference using substantially fewer parameters. Overall, this approach achieves validated recovery at lower region counts, corresponding to an approximate 40% reduction in foreground-model dimensionality.
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All authors Jacob L. Tutt, Peter H. Sims, Joe H. N. Pattison, Dominic J. Anstey, Samuel A. K. Leeney, Eloy de Lera Acedo

Astrophysics of Galaxies

Euclid preparation. Far-infrared predictions for Euclid galaxy catalogues: cluster, protocluster, and field

Euclid Collaboration: A. Parmar, D. L. Clements, M. Bolzonella et al. (+296 more)

The MAMBO mock galaxy catalogue, based on the Millennium Simulation with empirically assigned galaxy properties, provides predictions of FIR fluxes and physical parameters of Euclid-detectable galaxies. Predicted FIR flux distributions confirm that only the brightest Euclid sources will be detectable in existing FIR surveys. We employ stacking to measure the mean dust properties as a function of stellar mass and redshift. We find dust temperatures and infrared luminosities increase with redshift across all mass bins, while dust masses remain roughly constant. FIR number counts from MAMBO show overall good agreement with observations, and the total infrared luminosity function reproduces published estimates across most redshift ranges, extending to z~10. Comparing the Euclid Wide and Deep Surveys, we find that the EDS recovers the total IRLF to fainter luminosities and higher redshifts (up to z~6 in $I_E$), although its detectability falls below 80% at z>4, whereas the EWS becomes strongly incomplete beyond z~2. We also examine the dependence of the IRLF on environment. Schechter fits indicate that the faint-end slope $\alpha$ flattens with redshift for cluster and protocluster galaxies, while remaining approximately constant for field populations. Imposing additional detection limits from Herschel-PACS and SPIRE shows that only the most luminous ($L_{IR}$ > $10^{12.5}$ $L_{\odot}$) galaxies remain detectable at z~4, but the limited MAMBO area (3.14$deg^2$) is inadequate for statistically robust (>3$\sigma$) constraints. Survey areas at least 30 times larger are required. Overall, the MAMBO FIR extension reproduces key number count and IRLF trends, provides realistic predictions for FIR-detected Euclid galaxies, and highlights the importance of synergies with current and future FIR/sub-mm facilities to probe environmental dependence with sufficient depth and area.
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All authors Euclid Collaboration: A. Parmar, D. L. Clements, M. Bolzonella, O. Cucciati, L. Pozzetti, H. Dannerbauer, G. Castignani, S. Serjeant, L. Wang, R. Hill, D. Scott, J. G. Sorce, M. Magliocchetti, F. Pace, T. T. Thai, N. Aghanim, B. Altieri, S. Andreon, N. Auricchio, C. Baccigalupi, M. Baldi, S. Bardelli, A. Biviano, W. Bon, E. Branchini, M. Brescia, J. Brinchmann, S. Camera, G. Cañas-Herrera, V. Capobianco, C. Carbone, J. Carretero, S. Casas, M. Castellano, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, C. J. Conselice, L. Conversi, Y. Copin, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, G. De Lucia, H. Dole, M. Douspis, F. Dubath, F. Ducret, C. A. J. Duncan, X. Dupac, S. Escoffier, M. Farina, R. Farinelli, S. Ferriol, F. Finelli, S. Fotopoulou, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, C. Giocoli, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, E. Keihänen, S. Kermiche, A. Kiessling, B. Kubik, M. Kümmel, M. Kunz, H. Kurki-Suonio, A. M. C. Le Brun, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, D. Maino, E. Maiorano, O. Mansutti, S. Marcin, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, S. Maurogordato, E. Medinaceli, S. Mei, M. Melchior, Y. Mellier, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, R. Nakajima, C. Neissner, S.-M. Niemi, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, F. Raison, R. Rebolo, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, R. Saglia, Z. Sakr, A. G. Sánchez, D. Sapone, B. Sartoris, P. Schneider, T. Schrabback, A. Secroun, E. Sefusatti, G. Seidel, M. Seiffert, S. Serrano, P. Simon, C. Sirignano, G. Sirri, L. Stanco, J. Steinwagner, P. Tallada-Crespí, A. N. Taylor, H. I. Teplitz, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, L. Valenziano, J. Valiviita, T. Vassallo, A. Veropalumbo, Y. Wang, J. Weller, G. Zamorani, F. M. Zerbi, E. Zucca, V. Allevato, M. Ballardini, E. Bozzo, C. Burigana, R. Cabanac, A. Cappi, D. Di Ferdinando, J. A. Escartin Vigo, L. Gabarra, W. G. Hartley, S. Matthew, M. Maturi, N. Mauri, R. B. Metcalf, A. Pezzotta, M. Pöntinen, C. Porciani, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Viel, M. Wiesmann, Y. Akrami, S. Anselmi, M. Archidiacono, F. Atrio-Barandela, P. Bergamini, D. Bertacca, M. Bethermin, A. Blanchard, L. Blot, H. Böhringer, M. Bonici, S. Borgani, M. L. Brown, S. Bruton, A. Calabro, B. Camacho Quevedo, F. Caro, C. S. Carvalho, T. Castro, F. Cogato, S. Conseil, A. R. Cooray, S. Davini, G. Desprez, A. Díaz-Sánchez, J. J. Diaz, S. Di Domizio, J. M. Diego, P. Dimauro, M. Y. Elkhashab, A. Enia, Y. Fang, A. G. Ferrari, A. Finoguenov, A. Fontana, F. Fontanot, A. Franco, K. Ganga, J. García-Bellido, T. Gasparetto, V. Gautard, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, M. Guidi, C. M. Gutierrez, A. Hall, S. Hemmati, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, A. Loureiro, J. Macias-Perez, G. Maggio, C. Mancini, F. Mannucci, R. Maoli, C. J. A. P. Martins, L. Maurin, M. Miluzio, P. Monaco, C. Moretti, G. Morgante, K. Naidoo, P. Natoli, A. Navarro-Alsina, S. Nesseris, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, A. Pisani, D. Potter, S. Quai, M. Radovich, P.-F. Rocci, G. Rodighiero, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, D. Sciotti, E. Sellentin, F. Shankar, L. C. Smith, K. Tanidis, C. Tao, G. Testera, R. Teyssier, S. Tosi, A. Troja, M. Tucci, C. Valieri, A. Venhola, D. Vergani, G. Verza, P. Vielzeuf, N. A. Walton

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Axion search with telescope for radio astronomy (ASTRA): forecast for observations between 0.5 and 4~GHz

Utkarsh Bhura, David J. E. Marsh, Bradley R. Johnson et al. (+8 more)

Axion dark matter (DM) is predicted to convert into radio waves in neutron star magnetospheres. We assess the detectability of this signal using a 5 m radio telescope to be installed at the Fan Mountain Observatory, operating in the UHF, L- and S-bands from 0.5 to 4~GHz. We demonstrate that such a telescope can search new parameter space for axion-like particles over a broad range from $2\,\mu\text{eV}<m_a<17\,\mu\text{eV}$ for axion-photon couplings $g_{a\gamma\gamma} \gtrsim 2\times 10^{-12}\text{ GeV}^{-1}$ with a three year observing period assuming the standard halo model – improving neutron star observations by more than an order of magnitude. The search is broadband and is thus complementary to other techniques in the same frequency range. We describe in detail our neutron star population model, noise model, and proposed observing strategy. Most constraining power comes from neutron stars at the Galactic centre, where the smooth DM halo is densest. If a DM spike exists at the Galactic centre, the search is sensitive in the QCD axion model band. UHF and L-band observations (0.5 to 2~GHz) represent the pathfinder phase of a wider program we call “Axion Search with Telescope for Radio Astronomy” (ASTRA). Future higher mass searches aimed at discovery potential for the post-inflation axion require further hardware development to cover S, C, X and Ku bands (2 to 18~GHz).
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All authors Utkarsh Bhura, David J. E. Marsh, Bradley R. Johnson, Karl van Bibber, Mallory Helfenbein, Bradley J. Kavanagh, Matthew Nelson, Ciaran A. J. O'Hare, Giovanni Pierobon, Gray Rybka, Luca Visinelli

Earth and Planetary Astrophysics

Clustering Astronomical Orbital Synthetic Data Using Advanced Feature Extraction and Dimensionality Reduction Techniques

Eraldo Pereira Marinho, Nelson Callegari Junior, Fabricio Aparecido Breve et al. (+1 more)

The dynamics of Saturn's satellite system offer a rich framework for studying orbital stability and resonance interactions. Traditional methods for analysing such systems, including Fourier analysis and stability metrics, struggle with the scale and complexity of modern datasets. This study introduces a machine learning-based pipeline for clustering approximately 22,300 simulated satellite orbits, addressing these challenges with advanced feature extraction and dimensionality reduction techniques. The key to this approach is using MiniRocket, which efficiently transforms 400 timesteps into a 9,996-dimensional feature space, capturing intricate temporal patterns. Additional automated feature extraction and dimensionality reduction techniques refine the data, enabling robust clustering analysis. This pipeline reveals stability regions, resonance structures, and other key behaviours in Saturn's satellite system, providing new insights into their long-term dynamical evolution. By integrating computational tools with traditional celestial mechanics techniques, this study offers a scalable and interpretable methodology for analysing large-scale orbital datasets and advancing the exploration of planetary dynamics.
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All authors Eraldo Pereira Marinho, Nelson Callegari Junior, Fabricio Aparecido Breve, Caetano Mazzoni Ranieri

Earth and Planetary Astrophysics

Ortho-Para Chemistry of H2CO in the Protoplanetary Disk TW Hya

M. Gaillard, A. Faure, P. Hily-Blant et al. (+4 more)

The spatial distribution of the chemical reservoirs in protoplanetary disks is key to elucidate the composition of planets, especially habitable ones. However, the partitioning of the main elements among the refractory and volatile phases is still elusive. Key parameters such as the carbon-to-oxygen C/O elemental ratio and the ionization fraction remain poorly constrained, with the latter potentially orders of magnitude lower than in the interstellar medium. Moreover, the thermal structure of the gas is also poorly known, despite its deep influence on gas-phase chemistry. In this context, ortho-to-para ratios could provide selective and sensitive probes. Recent ALMA observations have measured the spatially resolved column density of ortho-and para-H2CO in the transition disk orbiting TW Hya and derived the radial profile of the ortho-to-para ratio. Yet, current disk models do not include the nuclear-spin-resolved chemistry required to interpret these observations. The present work aims to fill this gap, by combining a parametric disk physical model of TW Hya with the UGAN network, updated to include a comprehensive description of the nuclear-spin-resolved chemistry of formaldehyde. This new model reproduces the observed column density of H2CO to within a factor of 2, as well as the measured ortho-to-para ratio which varies from 1.5 in the outer disk to 3 inside 90au. In particular the low value of this ratio beyond 90au is well explained by our model. However, the statistical value of 3 measured below 70au cannot be reproduced, suggesting that additional processes involving ices may be involved. Our parameter space exploration shows that the abundance of H2CO is highly sensitive to the C/O elemental ratio and to the cosmic-ray ionization rate. Future observations of ortho-and para-H2CO, based on well selected rotational transitions, in a large sample of disks, appear highly desirable.
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All authors M. Gaillard, A. Faure, P. Hily-Blant, R. Le Gal, S. Lee, H. Nomura, K. Furuya

Earth and Planetary Astrophysics

Connecting JWST Silicate Cloud Observations to Exoplanet Cloud Microphysics with Nimbus

Sven Kiefer, Caroline V. Morley and Melanie Rowland

The unprecedented accuracy of JWST has led to the detection of silicate clouds in exoplanet atmospheres, allowing for the first time to probe cloud formation in extreme environments. While parametrized cloud descriptions can fit these observations, the results do not fully agree with microphysical models. To bridge this gap, we developed Nimbus, a fast microphysical cloud model that can constrain cloud formation processes from observations and utilize Virga, an equilibrium condensation model balancing gravitational settling and diffusion. Using both models, we investigate WASP-107 b, WASP-17 b, VHS-1256 b, and YSES-1 c to determine their cloud structure and constrain cloud formation processes. Our results show that all four planets have cluster-sized silicate particles (r ~ 1 nm) at high altitudes. Within Nimbus and Virga, these particles can only be explained by highly inefficient cloud particle settling (fsed < 0.1) or by inefficient growth rates due to low sticking coefficients (s < 0.0001). Our results also show that the sticking coefficient is directly linked to the vertical extent of clouds and can therefore be constrained using the broad shape of the spectral energy distribution. The sticking coefficients found for VHS-1256 b and YSES-1 c are in agreement with expectations from laboratory experiments under Earth-like conditions (0.01 < s < 0.3). Panchromatic observations were crucial to achieve these constraints. Future cloud studies should therefore aim to combine observational data from 1 micron to 10 micron whenever possible.
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Earth and Planetary Astrophysics

exoALMA XX: Tomographic Detection of Embedded Planets in Protoplanetary Disks

Andres F. Izquierdo, Jaehan Bae, Stefano Facchini et al. (+32 more)

The exoALMA Large Program has revealed a wealth of substructures in the dust and molecular line emission of several protoplanetary discs, suggesting that planet formation may unfold within highly dynamic environments. Using synthetic observations of planet-disc interactions and disc instabilities, we demonstrate how the origin of these substructures can be investigated through a tomographic study of molecular lines, extending the scope of the analysis beyond line-centroid kinematics alone. Our results indicate that with only a few hours of ALMA integration at moderate angular resolution ($0.15''-0.30''$), it is possible to identify the key signatures driven by planets more massive than 0.1% of the stellar mass. These signatures manifest not only as deviations from Keplerian motion but also as localized line broadening, enabling accurate constraints on the orbital radius and azimuthal location of the planets. We further show that a diagnostic based on line skewness in spectrally resolved observations can help distinguish between planetary and instability-driven signatures, owing to the distinct degrees of velocity coherence associated with each mechanism. Finally, we apply this tomographic analysis to exoALMA CO line data for the discs of HD 135344B and MWC 758. In HD 135344B, we identify strongly localized velocity and line-width perturbations, suggesting the possibility of three massive planets embedded in the disc: one at $R=95$ au, exterior to the continuum substructures, and two within dust gaps at $R=41$ au and $R=73$ au. For MWC 758, the dominance of vertical-velocity spirals over localized signatures is consistent with predictions from models of moderate disc eccentricities or warps, potentially induced by a substellar companion in the inner regions of the system.
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All authors Andres F. Izquierdo, Jaehan Bae, Stefano Facchini, Ewine F. van Dishoeck, Marcelo Barraza-Alfaro, Myriam Benisty, Richard Teague, Jochen Stadler, Sean M. Andrews, Gianni Cataldi, Nicolas Cuello, Pietro Curone, Ian Czekala, Daniele Fasano, Mario Flock, Misato Fukagawa, Maria Galloway-Sprietsma, Cassandra Hall, Jane Huang, John D. Ilee, Andrea Isella, Jensen Lawrence, Geoffroy Lesur, Giuseppe Lodato, Cristiano Longarini, Ryan A. Loomis, François Menard, Christophe Pinte, Daniel J. Price, Giovanni Rosotti, Leonardo Testi, David J. Wilner, Andrew J. Winter, Lisa Wölfer, Brianna Zawadzki

Earth and Planetary Astrophysics

exoALMA XXIII. Estimating Disk and Planet Properties from Dust Morphologies with DBNets2.0

Alessandro Ruzza, Giuseppe Lodato, Giovanni Rosotti et al. (+21 more)

The exoALMA large program provided an unprecedented view of the morphology and kinematics of 15 circumstellar disks, offering a biased but homogenous and well-characterized sample for population-level analysis. Continuum observations revealed numerous dust substructures, known to be potential signatures of embedded planets. We analyze the observed dust morphologies with the simulation-based inference tool DBNets2.0, assuming these are due to embedded planets at fixed locations, to infer the system properties. We estimate the putative planet mass, the disk $\alpha$-viscosity, scale-height, and dust Stokes number that would reproduce 19 substructures in 13 of the 15 exoALMA disks. We compare our results with literature estimates derived with different methods, and find good agreement in most cases. We further explore the implications of the inferred disk properties for accretion, showing that for the Herbig stars in our sample, the implied viscous accretion timescales are too long to account for their observed stellar accretion rates. Regarding planet migration, our results favor inward migration, with only three putative planets expected to migrate outward. Finally, we check for correlations of the inferred disk and planet properties with the disks' gas-to-dust mass ratio, non-axisymmetry index, and masses of the gas, dust, and host stars, finding no remarkable trend.
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All authors Alessandro Ruzza, Giuseppe Lodato, Giovanni Rosotti, Philip J. Armitage, Stefano Facchini, Sean M. Andrews, Jaehan Bae, Marcelo Barraza-Alfaro, Myriam Benisty, Pietro Curone, Daniele Fasano, Cassandra Hall, Thomas Hilder, Andrés F. Izquierdo, Cristiano Longarini, François Ménard, Christophe Pinte, Jochen Stadler, Richard Teague, Jason Terry, David J. Wilner, Andrew J. Winter, Tomohiro C. Yoshida, Brianna Zawadzki

Cosmology and Nongalactic Astrophysics

Euclid preparation. Simulated galaxy catalogues for non-standard cosmological models

Euclid Collaboration: M.-A. Breton, P. Fosalba, S. Avila et al. (+288 more)

Stage-IV galaxy surveys will provide the opportunity to test cosmological models and the underlying theory of gravity with unparalleled precision. In this context, it is crucial for the Euclid mission to leverage its spectroscopic and photometric probes to systematically investigate and incorporate non-standard cosmological models, including modified gravity, alternative dark energy scenarios, massive neutrinos, and primordial non-Gaussianity. We produce and release publicly simulated galaxy catalogues from a broad suite of non-standard cosmological simulations, which we processed through a model-independent analytical pipeline, making use of Rockstar for halo identification, and a modified version of the SciPic library for the galaxy-halo connection using the halo occupation distribution framework. We investigate their galaxy-clustering characteristics via the multipoles of the 2PCF in redshift space and VDG, a highly performant model for galaxy clustering. Across a wide range of models, the linear growth rate multiplied by the matter density within spheres of radius 12,Mpc, fs12, exhibits a notable robustness to the choice of cosmological template. Compared to previous works, our study extends this result to numerous scenarios with markedly distinct gravitational or dark energy dynamics. We find that the most of the scatter in cosmological parameter inference already appears when using the cosmological model of the simulations as templates. Using a `wrong' template can also introduce an additional scatter, although with smaller amplitude. Often, we find deviations much larger than error bars, meaning that the Gaussian approximation for the covariance might need to be further studied. Future cosmological investigations must broaden their scope to include a diverse array of non-standard theoretical frameworks, extending beyond LCDM and rudimentary dynamic dark energy models.
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All authors Euclid Collaboration: M.-A. Breton, P. Fosalba, S. Avila, M. Baldi, C. Carbone, M. Kärcher, G. Rácz, M. Bolzonella, F. J. Castander, C. Giocoli, K. Koyama, A. M. C. Le Brun, L. Pozzetti, A. G. Adame, V. Gonzalez-Perez, G. Yepes, B. Altieri, S. Andreon, C. Baccigalupi, S. Bardelli, P. Battaglia, A. Biviano, E. Branchini, M. Brescia, S. Camera, V. Capobianco, V. F. Cardone, J. Carretero, M. Castellano, G. Castignani, S. Cavuoti, A. Cimatti, C. Colodro-Conde, G. Congedo, L. Conversi, Y. Copin, A. Costille, F. Courbin, H. M. Courtois, A. Da Silva, H. Degaudenzi, S. de la Torre, G. De Lucia, H. Dole, M. Douspis, F. Dubath, C. A. J. Duncan, X. Dupac, S. Dusini, S. Escoffier, M. Farina, R. Farinelli, S. Farrens, F. Faustini, S. Ferriol, F. Finelli, S. Fotopoulou, N. Fourmanoit, M. Frailis, E. Franceschi, M. Fumana, S. Galeotta, K. George, B. Gillis, J. Gracia-Carpio, A. Grazian, F. Grupp, S. V. H. Haugan, W. Holmes, F. Hormuth, A. Hornstrup, K. Jahnke, M. Jhabvala, B. Joachimi, S. Kermiche, A. Kiessling, M. Kilbinger, B. Kubik, M. Kunz, H. Kurki-Suonio, S. Ligori, P. B. Lilje, V. Lindholm, I. Lloro, G. Mainetti, O. Mansutti, O. Marggraf, M. Martinelli, N. Martinet, F. Marulli, R. J. Massey, E. Medinaceli, S. Mei, M. Meneghetti, E. Merlin, G. Meylan, A. Mora, M. Moresco, L. Moscardini, C. Neissner, S.-M. Niemi, J. W. Nightingale, C. Padilla, S. Paltani, F. Pasian, K. Pedersen, V. Pettorino, S. Pires, G. Polenta, M. Poncet, L. A. Popa, F. Raison, A. Renzi, J. Rhodes, G. Riccio, E. Romelli, M. Roncarelli, R. Saglia, Z. Sakr, D. Sapone, B. Sartoris, A. Secroun, G. Seidel, E. Sihvola, P. Simon, C. Sirignano, G. Sirri, A. Spurio Mancini, L. Stanco, P. Tallada-Crespí, A. N. Taylor, I. Tereno, N. Tessore, S. Toft, R. Toledo-Moreo, F. Torradeflot, I. Tutusaus, E. A. Valentijn, J. Valiviita, T. Vassallo, G. Verdoes Kleijn, Y. Wang, J. Weller, G. Zamorani, F. M. Zerbi, E. Zucca, M. Ballardini, A. Boucaud, E. Bozzo, C. Burigana, R. Cabanac, M. Calabrese, A. Cappi, T. Castro, J. A. Escartin Vigo, G. Fabbian, L. Gabarra, J. García-Bellido, S. Hemmati, J. Macias-Perez, R. Maoli, J. Martín-Fleitas, N. Mauri, R. B. Metcalf, P. Monaco, A. Pezzotta, M. Pöntinen, I. Risso, V. Scottez, M. Sereno, M. Tenti, M. Tucci, M. Viel, M. Wiesmann, Y. Akrami, I. T. Andika, G. Angora, M. Archidiacono, F. Atrio-Barandela, L. Bazzanini, J. Bel, D. Bertacca, M. Bethermin, F. Beutler, A. Blanchard, L. Blot, M. Bonici, S. Borgani, M. L. Brown, S. Bruton, B. Camacho Quevedo, F. Caro, C. S. Carvalho, F. Cogato, A. R. Cooray, S. Davini, G. Desprez, A. Díaz-Sánchez, S. Di Domizio, J. M. Diego, V. Duret, A. Eggemeier, M. Y. Elkhashab, A. Enia, Y. Fang, A. Finoguenov, F. Fontanot, A. Franco, K. Ganga, T. Gasparetto, R. Gavazzi, E. Gaztanaga, F. Giacomini, F. Gianotti, G. Gozaliasl, A. Gruppuso, M. Guidi, C. M. Gutierrez, A. Hall, H. Hildebrandt, J. Hjorth, J. J. E. Kajava, Y. Kang, V. Kansal, D. Karagiannis, K. Kiiveri, J. Kim, C. C. Kirkpatrick, S. Kruk, M. Lattanzi, J. Le Graet, L. Legrand, M. Lembo, F. Lepori, G. Leroy, G. F. Lesci, J. Lesgourgues, T. I. Liaudat, S. J. Liu, X. Lopez Lopez, M. Magliocchetti, A. Manjón-García, F. Mannucci, C. J. A. P. Martins, L. Maurin, M. Miluzio, A. Montoro, C. Moretti, G. Morgante, S. Nadathur, K. Naidoo, A. Navarro-Alsina, S. Nesseris, L. Pagano, D. Paoletti, F. Passalacqua, K. Paterson, L. Patrizii, C. Pattison, A. Pisani, D. Potter, G. W. Pratt, S. Quai, M. Radovich, K. Rojas, W. Roster, S. Sacquegna, M. Sahlén, D. B. Sanders, E. Sarpa, A. Schneider, M. Schultheis, D. Sciotti, E. Sellentin, L. C. Smith, J. G. Sorce, K. Tanidis, F. Tarsitano, G. Testera, R. Teyssier, S. Tosi, A. Troja, C. Valieri, A. Venhola, D. Vergani, F. Vernizzi, G. Verza, S. Vinciguerra, N. A. Walton, A. H. Wright, H. W. Yeung

Astrophysics of Galaxies

Structural Parameters of the Globular Cluster M 15

M. V. Petkova, G. P. Petrov, N. M. Kacharov et al. (+1 more)

We present a detailed analysis of the structural parameters of the globular cluster M 15 using g- and i-band photometric data from Pan-STARRS1 DR2. The central coordinates ($X_{\rm{C}}, Y_{\rm{C}}$), ellipticity ($\epsilon$), and position angle (PA) are derived via two independent methods: ellipse fitting of the two-dimensional stellar number isodensity distribution and Markov Chain Monte Carlo (MCMC) sampling. Our analysis of 38 stellar density intervals reveals a cluster center offset by only $4\,.\!\!^{\prime\prime}1\pm9\,.\!\!^{\prime\prime}6$ from the commonly accepted in the literature value, a good agreement on the order of our map resolution. We find a radial variation in the ellipticity, with a mean value of $\epsilon=0.09\pm0.02$ for the inner region ($R\leq4\,.\!\!^{\prime}5$) and $\epsilon=0.04\pm0.02$ for the outer region ($R>4\,.\!\!^{\prime}5$), where the errors correspond to $1\sigma$. The MCMC analysis of 75 datasets yields a mean $\epsilon=0.022\pm0.005$ for the entire cluster. The PA remains constant with increasing distance from the cluster center, $\rm{PA}=44\,.\!\!{\rm{^\circ}}4\pm16\,.\!\!{\rm{^\circ}}2$, and the MCMC method providing a consistent value of $\rm{PA}=46\,.\!\!{\rm{^\circ}}6\pm7\,.\!\!{\rm{^\circ}}1$. Our results are in agreement with some recent studies but challenge others, suggesting that a single $\epsilon$ value may be insufficient to fully characterize the overall oblateness of M 15 due to incompleteness and crowding effects in its core.
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All authors M. V. Petkova, G. P. Petrov, N. M. Kacharov, P. L. Nedialkov

Cosmology and Nongalactic Astrophysics

When Dark Energy Turns On: Constraints on a Critical Emergence Model

Mahdi Najafi, Mahdi Habibollahi, Masoume Reyhani et al. (+4 more)

We investigate a specific emergent dark energy scenario, known as critically emergent dark energy (CEDE), in which dark energy is effectively absent in the early Universe and becomes dynamically relevant only after a critical cosmic epoch through a phase transition. We constrain this model using recent cosmological observations, including cosmic microwave background (CMB) data from Planck 2018, baryon acoustic oscillation (BAO) measurements from SDSS and DESI DR2, and two independent Type Ia supernova compilations, PantheonPlus and Union3. Our results show that within the CEDE framework a dark energy phase transition is not ruled out. In particular, CMB-only, CMB+SDSS, and CMB+DESI datasets provide evidence for a nonzero transition scale factor and, according to standard statistical indicators such as $\Delta\chi^2$ and Bayesian evidence, can favor CEDE over the $\Lambda$CDM model. At the same time, we find that CEDE does not fully resolve the Hubble constant tension. Overall, our analysis indicates that dark energy models featuring a phase transition remain a viable and phenomenologically interesting extension of the standard cosmological framework. Upcoming high-precision cosmological surveys will be essential to further assess whether such emergent dark energy scenarios represent a genuine departure from $\Lambda$CDM or an effective description of current data.
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All authors Mahdi Najafi, Mahdi Habibollahi, Masoume Reyhani, Eleonora Di Valentino, Supriya Pan, Javad T. Firouzjaee, Weiqiang Yang

High Energy Astrophysical Phenomena

The elusive cyclotron line in 4U 1901+03: hidden, yet present

Elena Ambrosi, Antonino D' Aì, Giancarlo Cusumano et al. (+8 more)

Context. Cyclotron resonant scattering features (CRSFs) in accreting X-ray pulsars are often difficult to detect, especially when shallow or variable. Recent studies have shown that combining spectral and timing analyses enhances their detectability. Aims. We investigated the evolution of energy-resolved pulse profiles of the X-ray pulsar 4U 1901+03 during its 2019 giant outburst, focusing on the 30-40 keV range where there have been disputed claims of a cyclotron line detection. Methods. We analysed four NuSTAR observations of 4U 1901+03 at different luminosities. We studied energy-resolved pulse profiles using harmonic decomposition, cross-correlation analysis, energy-phase maps, and pulsed-fraction spectra. We also used Bayesian spectral modelling to assess the presence and properties of a cyclotron line. Results. We detected significant spectral-timing variability in the 30-40 keV range, which becomes stronger at lower luminosities. We found a pronounced drop in the pulsed fraction near 35 keV only in the lowest accretion state and in the first harmonic of one intermediate-luminosity observation. Adopting a Bayesian informative approach, we find evidence for a cyclotron line in all examined energy spectra, with an average centroid energy of E_cyc approx 32 keV (varying by only 1.6%), and an anti-correlation between line depth and luminosity. Conclusions. We show that a combined spectral-timing approach is more sensitive than phase-averaged spectroscopy to shallow cyclotron features. The luminosity-dependent evolution of pulse profiles and cyclotron line depth point to a drastic change in the emission geometry and accretion flow structure.
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All authors Elena Ambrosi, Antonino D' Aì, Giancarlo Cusumano, Carlo Ferrigno, Ekaterina Sokolova-Lapa, Dimitrios K. Maniadakis, Antonio Tutone, Georgios Vasilopulous, Peter Kretschmar, Christian Malacaria, Fabio Pintore

Cosmology and Nongalactic Astrophysics

Ridged Lagrangian Perturbation Theory (RLPT)

Francisco-Shu Kitaura and Francesco Sinigaglia

Galaxy surveys demand fast large-scale structure forward models that preserve large-scale phases while providing realistic nonlinear morphology at fixed force resolution. Single-step Lagrangian Perturbation Theory (LPT) solvers are efficient, but they typically yield overly diffuse filaments and knots and underpredict small-scale clustering. We introduce Ridged Lagrangian Perturbation Theory (RLPT), a modular two-step scheme: a standard long-range LPT/ALPT transport is followed by a single post-processing Eulerian ridging update that reconstructs a short-range, curl-free displacement from the realised density field through a smooth scale separation and a Poisson inversion. This explicit completion layer is inexpensive, preserves the large-scale solution, and provides a small set of transparent parameters to tune the short-range response. We test RLPT against particle-mesh and $N$-body references and find that one additional ridging step systematically improves both nonlinear power and field-level agreement relative to 2LPT/ALPT baselines. Finally, we demonstrate that ridging can be repurposed as a deterministic subgrid relocation model: even when the underlying dark-matter field is only "good enough" on the mesh, ridging enables controlled tuning of tracer clustering beyond the nominal resolution, which is particularly relevant for mock-galaxy production and observational systematics sensitive to close pairs.
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