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Physics Astrophysics

astro-ph Watch Astrophysics

Wednesday 15 April

Cosmology and Nongalactic Astrophysics

FAIR Universe Weak Lensing ML Uncertainty Challenge: Handling Uncertainties and Distribution Shifts for Precision Cosmology

Biwei Dai, Po-Wen Chang, Wahid Bhimji et al. (+15 more)

Weak gravitational lensing, the correlated distortion of background galaxy shapes by foreground structures, is a powerful probe of the matter distribution in our universe and allows accurate constraints on the cosmological model. In recent years, high-order statistics and machine learning (ML) techniques have been applied to weak lensing data to extract the nonlinear information beyond traditional two-point analysis. However, these methods typically rely on cosmological simulations, which poses several challenges: simulations are computationally expensive, limiting most realistic setups to a low training data regime; inaccurate modeling of systematics in the simulations create distribution shifts that can bias cosmological parameter constraints; and varying simulation setups across studies make method comparison difficult. To address these difficulties, we present the first weak lensing benchmark dataset with several realistic systematics and launch the FAIR Universe Weak Lensing Machine Learning Uncertainty Challenge. The challenge focuses on measuring the fundamental properties of the universe from weak lensing data with limited training set and potential distribution shifts, while providing a standardized benchmark for rigorous comparison across methods. Organized in two phases, the challenge will bring together the physics and ML communities to advance the methodologies for handling systematic uncertainties, data efficiency, and distribution shifts in weak lensing analysis with ML, ultimately facilitating the deployment of ML approaches into upcoming weak lensing survey analysis.
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All authors Biwei Dai, Po-Wen Chang, Wahid Bhimji, Paolo Calafiura, Ragansu Chakkappai, Yuan-Tang Chou, Sascha Diefenbacher, Jordan Dudley, Ibrahim Elsharkawy, Steven Farrell, Isabelle Guyon, Chris Harris, Elham E Khoda, Benjamin Nachman, David Rousseau, Uroš Seljak, Ihsan Ullah, Yulei Zhang

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

Astrophysical bounds on the high-energy evolution of neutrino mixing

Mauricio Bustamante, Qinrui Liu and Gabriela Barenboim

While conventional oscillation experiments measure neutrino mixing parameters with high precision, these measurements are strictly confined to sub-TeV scales. At higher energies, renormalization-group effects can cause these parameters to evolve with the transferred momentum, $Q$. High-energy and ultra-high-energy astrophysical neutrinos, spanning TeV to EeV energies, probe high values of $Q$ unreachable by conventional experiments, offering an unprecedented test of high-energy mixing. We use the flavor composition of these neutrinos – the relative proportions of $\nu_e$, $\nu_\mu$, and $\nu_\tau$ – to constrain this evolution, both phenomenologically and within dimension-6 Standard Model Effective Field Theory. We account for astrophysical uncertainties – an unavoidable requirement to obtain realistic results, even though this weakens the bounds. Although present IceCube measurements lack the sensitivity to detect this running, we forecast that upcoming multi-detector combinations will place unprecedented bounds on the high-energy evolution of neutrino mixing.
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High Energy Astrophysical Phenomena

Synchrotron-cooled plasma distribution in the outer magnetosphere of a neutron star

Mikhail V. Medvedev, Anatoly Spitkovsky and Alexander Philippov

The guiding center formalism is employed to analyze the motion of a charged relativistic particle in an inhomogeneous magnetic field, subject to magnetic mirroring and energy loss due to cooling. The governing equation for the evolution of the magnetic moment is derived. An example representing a neutron star (pulsar or magnetar) magnetosphere is presented to illustrate typical particle orbits. Notably, radiative losses are most pronounced near a trapped particle's turning point. Depending on the initial particle's pitch angle, energy loss can become catastrophic, resulting in the rapid migration of the particle into the loss cone and subsequent precipitation onto a neutron star. Conversely, particles with a larger pitch angle remain temporarily trapped and form a gradually decaying "cooled-loss-cone" or "funnel” distribution, characterized by the maximum momentum space particle density being located at the edge of the loss cone. The size of the loss cone is energy-dependent and scales as $\alpha_{c} \propto \gamma^{3/10}$. Synchrotron losses are strongest in a well-localized region of the magnetosphere, about a few hundred to a thousand star radii under typical pulsar and magnetar conditions. This region is a plausible site for synchrotron radiation originating in the outer magnetosphere, and could also be responsible for non-polar coherent pulsar emission, as well as weak fast radio bursts.
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Earth and Planetary Astrophysics

Thermophysical Properties of Europa's Surface Constrained by Galileo Photopolarimeter-Radiometer Temperature Measurements

L. Lange, S. Piqueux, P. O. Hayne et al. (+10 more)

Thermal measurements constrain the physical properties of icy satellite surfaces, including grain size, porosity, and regolith structure. On Europa, analyses of the Galileo Photopolarimeter-Radiometer (PPR) dataset revealed thermal inertia heterogeneities, but limited resolution hindered detailed characterization. We reanalyze the PPR dataset to derive maps of Europa's albedo and thermal inertia, and infer the microphysical properties of its icy regolith. Using the KRC thermal model, we fit brightness temperatures and interpret the results with conductivity models of porous ice to constrain grain size, porosity, and sintering processes. We find a mean Bond albedo of 0.64 pm 0.06 and a mean thermal inertia of 56 pm 17 tiu. Thermal inertia varies significantly, with a low-inertia equatorial band (39 pm 7 tiu) and higher values at mid-latitudes and on the trailing hemisphere, likely reflecting compositional differences. These values imply a porous regolith with grain sizes from micrometers to centimeters and an average porosity of 0.61 pm 0.1. Thermal inertia shows little correlation with geological units except for the Pwyll ejecta, which exhibit higher values. Instead, its agreement with sputtering rates suggests sputtering-driven sintering as a key process. Electron-driven sintering appears inefficient, while temperature-gradient metamorphism may enhance grain growth at depth. Modeled surface temperatures range from 67 to 148 K. These results provide a framework for interpreting future observations from Europa Clipper and JUICE.
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All authors L. Lange, S. Piqueux, P. O. Hayne, C. Mergny, A. Le Gall, F. Schmidt, J. Rathbun, J. Spencer, K. Sorli, S. Howes, C. Howett, C.S. Edwards, P.R. Christensen

Earth and Planetary Astrophysics

Simulating the interplay between the snowline pebble flux and ongoing planet formation and migration

Danila Astrakhantsev, Sebastiaan Krijt, Sofia Savvidou et al. (+1 more)

Pebble drift plays a central role in modern planet formation models. In this work we carry out planet formation simulations (including pebble accretion and migration) for a range of disc parameters to investigate (a) the impact of the snowline pebble mass flux on final planet orbits and masses, and (b) the back-reaction of growing and migrating planets on the snowline pebble fluxes in their natal discs. We find a strong correlation between the snowline pebble flux (at the time of protoplanet insertion) and the final planet mass. The correlation is continuous in disks with high turbulence levels ($\alpha=10^{-3}$), but exhibits a step function at lower turbulence ($\alpha=10^{-4}$), with giant planet formation requiring (initial) snowline pebble mass fluxes exceeding $100~\mathrm{M_\oplus Myr^{-1}}$. We find qualitative agreement between pebble mass fluxes inferred for discs aged ${\sim}1~\mathrm{Myr}$ and our planet-containing models, especially for larger disks ($\geq$40 au), high $\alpha$ ($10^{-3}$), and low $v_\mathrm{frag}$ ($3\mathrm{~m~s}^{-1}$). Additionally, giant planets in high turbulence disks are found to perturb the snowline pebble flux only temporarily (for ${\approx}10^{5-6}\mathrm{~yr}$) due to them quickly growing and migrating across the snowline. Our simulations show that currently observed pebble fluxes can indeed be used to constrain planet formation simulations, emphasizing that planet formation via pebble accretion is broadly in agreement with the currently available constraints from disc evolution as provided by JWST.
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All authors Danila Astrakhantsev, Sebastiaan Krijt, Sofia Savvidou, Bertram Bitsch

High Energy Astrophysical Phenomena

GRB 210704A: A Luminous Fast Blue Transient in a GRB Afterglow at $z = 2.34$

Daniëlle L. A. Pieterse, Andrew J. Levan, Maria E. Ravasio et al. (+27 more)

We present detailed, multi-wavelength analysis of GRB 210704A: a Fermi Gamma-ray Burst Monitor discovered and Fermi Large Area Telescope (LAT) detected gamma-ray burst (GRB). The burst is dominated by a short ($\approx 2$ s) pulse followed by weaker, softer emission. We line stack our afterglow spectrum and determine the most likely redshift to be $z = 2.34$. This is corroborated by the photometric redshift of the extended source underlying the GRB. The spectral energy distribution fit parameters, late-time imaging, as well as the GRB's energetics, spectral lag, and location point to a collapsar nature. Follow-up observations reveal excess optical/infrared emission with respect to a standard afterglow, peaking around $T_0 + 7$ d ($2$ d in the rest frame). The excess is extremely luminous ($M_{r} = -22.0$ mag) and rapidly evolving. Strikingly, it resembles the emission seen in recently discovered Einstein Probe fast X-ray transients EP241021a and EP240414a, as well as the population of luminous fast blue optical transients (LFBOTs). This provides a link between these sources and GRBs. Fermi/LAT observations imply a high Lorentz factor, making this a case where LFBOT-like emission is also associated with a powerful successfully launched jet. We model the excess as likely coming from an energetic refreshed shock.
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All authors Daniëlle L. A. Pieterse, Andrew J. Levan, Maria E. Ravasio, Jillian C. Rastinejad, Agnes P. C. van Hoof, Daniele B. Malesani, Nikhil Sarin, Gavin P. Lamb, Antonio Martin-Carrillo, Anya E. Nugent, Nial R. Tanvir, Peter G. Jonker, David Alexander Kann, José Feliciano Agüí Fernández, Edo Berger, Gregory Corcoran, Felice Cusano, Paolo D'Avanzo, Valerio D'Elia, Antonio de Ugarte Postigo, Dimple, Wen-fai Fong, Johan P.U. Fynbo, Luca Izzo, Elisabetta Maiorano, Andrea Melandri, Eliana Palazzi, Jonathan Quirola-Vásquez, Andrea Rossi, Alicia Rouco Escorial

Earth and Planetary Astrophysics

A Fast and Physically Grounded Ocean Model for GCMs: The Dynamical Slab Ocean Model of the Generic-PCM (rev. 3423)

Siddharth Bhatnagar, Francis Codron, Ehouarn Millour et al. (+5 more)

Ocean dynamics are often sidelined in exoplanet climate studies due to the high computational cost of fully coupled atmosphere-ocean general circulation models (GCMs). However, ocean heat transport (OHT) can play a critical role in shaping the climate and observables of terrestrial planets. As a compromise, most exoplanet GCMs rely on slab ocean models without OHT. Here, we present an improved compromise - a fast and physically grounded dynamical slab ocean model, implemented in the Generic Planetary Climate Model (Generic-PCM). The model extends previous frameworks by incorporating a Sverdrup balance formulation for wind-driven Ekman transport, the first application of the Gent-McWilliams parameterisation of mesoscale eddies in a slab ocean model, and a spectrally and thickness-dependent treatment of sea ice and snow albedo. In aquaplanet simulations, enabling OHT produces substantial changes in both surface climate and atmospheric circulation, including cooler tropical sea surface temperatures, reduced sea ice, and the emergence of a double-banded equatorial precipitation pattern driven by Ekman-induced upwelling. The resulting OHT profiles show first-order agreement with fully coupled atmosphere-ocean GCMs. Applied to modern Earth, the model reproduces key large-scale climate properties, including a global mean surface temperature of 13{\deg}C (within 1{\deg}C of observations), planetary albedo of 0.32 (within 0.01), and sea ice extent with significantly reduced seasonal biases relative to simulations without OHT. Due to model parallelisation, these improvements are achieved at almost no additional computation cost compared to OHT-disabled simulations run over the same number of model years. This enables long integrations, making the model particularly well suited for exoplanet and paleoclimate studies where broad parameter exploration is essential.
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All authors Siddharth Bhatnagar, Francis Codron, Ehouarn Millour, Emeline Bolmont, Maura Brunetti, Jérôme Kasparian, Martin Turbet, Guillaume Chaverot

High Energy Astrophysical Phenomena

EP250302a: violent shell collision in a soft-X-ray-selected GRB-like transient

Shao-Yu Fu, Cui-Yuan Dai, Ai-Ling Wang et al. (+58 more)

The Einstein Probe opens a previously unexplored soft X-ray window onto gamma-ray bursts, filling a critical observational gap in the soft X-ray coverage of their prompt emission. In this letter, we present EP250302a, a soft-X-ray-selected, GRB-like transient at $z=1.131$ detected by the Einstein Probe. Follow-up observations from X-ray to radio reveal a narrow X-ray flare at $\sim 1.1$\, ks and subsequent achromatic optical and X-ray rebrightening. These features challenge a standard single-component afterglow model and indicate the need for multiple ejecta components. A violent collision between a late relativistic shell and the decelerated leading blast wave provides a plausible interpretation: the flare arises from internal dissipation of the late ejecta, while the rebrightening is powered by the shocked emission produced in the collision. Quantitative modeling constrains the kinetic energy ratio between the late shell and the initial ejecta to $E_{\rm k,iso,2}/E_{\rm k,iso,1} \sim 5$ (with $E_{\rm k,iso,2} \sim 10^{53}$~erg and $E_{\rm k,iso,1} \sim 2\times10^{52}$~erg), as well as the Lorentz factor contrast to $\Gamma_{2,0}/\Gamma_{1,0} \approx 0.98$–$2.27$, required to reproduce the observed flare luminosity and rebrightening amplitude. Such an energetic late shell can be launched in a radiatively inefficient second episode of central-engine activity. Thanks to the well-sampled, early-time multiband coverage facilitated by the EP trigger, EP250302a provides a valuable case to test the physical connection between central-engine activity and shell collisions.
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All authors Shao-Yu Fu, Cui-Yuan Dai, Ai-Ling Wang, Wei-Hua Lei, Dong Xu, Tao An, Jin-Jun Geng, Xiang-Yu Wang, Shuai-Qing Jiang, Zi-Pei Zhu, Xing Liu, Jie An, Lin-Bo He, Jun-Jie Jin, Yu Zhang, Jinlei Zhang, Zhou Fan, Xing Gao, Abdusamatjan Iskandar, Shahidin Yaqup, Tu-Hong Zhong, Ali Esamdin, Chun-Hai Bai, Yu Zhang, He Gao, Xue-Feng Wu, Daniele Bjørn Malesani, Luca Izzo, R. A. J. Eyles-Ferris, A. Saccardi, B. Schneider, J. Palmerio, N. R. Tanvir, Alexei Pozanenko, Nicolai Pankov, A. S. Moskvitin, O. I. Spiridonova, O. A. Maslennikova, A. Volnova, E. Klunko, V. Rumyantsev, A. Volvach, L. Volvach, Toktarkhan Komesh, Ernazar Abdikamalov, Dilda Berdikhan, Zhanat Maksut, Yuan-Chuan Zou, Hong-Zhou Wu, Yun-Wei Yu, Rong-Feng Shen, Yi-Han Wang, Hui Sun, Bin-Bin Zhang, Liang-Duan Liu, Ye Li, Valerio D'Elia, Ruben Salvaterra, Massimiliano De Pasquale, Bing Zhang, Wei-Min Yuan

Cosmology and Nongalactic Astrophysics

The Atacama Cosmology Telescope: A Test of the Gravitational Force Law on Cosmological Scales Using the Kinematic Sunyaev-Zeldovich Effect

Patricio A. Gallardo, Kris Pardo, Oliver H. E. Philcox et al. (+38 more)

The mean pairwise velocity of massive halos reflects the gravitational force law on cosmic scales. We combine cosmic microwave background intensity maps from the Atacama Cosmology Telescope and a galaxy catalog from the Sloan Digital Sky Survey to estimate the mean pairwise velocity using the kinematic Sunyaev-Zeldovich (kSZ) effect. On scales from 30 – 230 megaparsecs, we constrain the gravitational acceleration between pairs of halos at separation $r$ to be $g\propto 1/r^n$ with $n=2.1\pm 0.3$, which is consistent with Newtonian gravity in an expanding spacetime (i.e., the standard $\Lambda$CDM model). This constraint shows agreement with an inverse quadratic radial dependence over the large distances separating galaxy halos, as expected in standard cosmology. Upcoming surveys have the potential to rule out $n = 1$ at $10\sigma$ significance. Our results establish the kSZ effect as a powerful tool for testing gravity on cosmological scales.
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All authors Patricio A. Gallardo, Kris Pardo, Oliver H. E. Philcox, Nicholas Battaglia, Elia S. Battistelli, Rachel Bean, Erminia Calabrese, Steve K. Choi, Rolando Dünner, Mark Devlin, Joanna Dunkley, Simone Ferraro, Yilun Guan, Erin Healy, Carlos Hervías-Caimapo, Matt Hilton, Adam D. Hincks, John C. Hood II, Arthur Kosowsky, Adrien La Posta, Thibaut Louis, Mathew S. Madhavacheril, Jeff McMahon, Kavilan Moodley, Tony Mroczkowski, Sigurd Naess, Laura Newburgh, Michael D. Niemack, Lyman A. Page, Bruce Partridge, Roberto Puddu, Emmanuel Schaan, Neelima Sehgal, Cristóbal Sifón, David N. Spergel, Suzanne T. Staggs, Alexander van Engelen, Cristian Vargas, Eve M. Vavagiakis, Kasey Wagoner, Edward J. Wollack

High Energy Astrophysical Phenomena

The azimuthal structure of magnetically arrested disks during flux eruption events

Argyrios Loules, Antonios Nathanail and Ioannis Contopoulos

We analyze data from a standard 3D general-relativistic magnetohydrodynamics (GRMHD) simulation, focusing on equatorial slices in order to examine the details and the evolution of the azimuthal structure of the accreting matter. During flux eruption events, the non-axisymmetric features of the equatorial inner accretion disk are considerably enhanced, with this enhancement being more prominent close to the black hole. Our analysis of the azimuthal structure of the equatorial accretion disk finds that the matter distribution in the vicinity of the horizon is dominated by low azimuthal mode numbers, specifically by the $m = 2$, and $m = 1$ modes, indicating that the non-axisymmetry of the disk during flux eruption events is enhanced due to the emergence of features with a large angular size on the equatorial plane. Our results suggest that the morphology of the equatorial accretion flow close to the black hole is mainly determined by the formation and motion of vertical magnetic flux bundles. These bundles are formed when the initially horizontal magnetic field reconnects into a vertical configuration, effectively detaching from the black hole horizon. This reconnection occurs in a low-density, highly magnetized region on the equatorial plane that expands over time as more field lines undergo vertical reconfiguration. The resulting vertical flux tubes, filled with low-density plasma, are then transported outwards due to magnetic buoyancy. Our results present a detailed quantitative description of the morphology of MADs and of its evolution during flux eruptions, complemented by a description of the physical process by which excess magnetic flux is detached from the black hole, vertically reconfigured, and expelled.
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Cosmology and Nongalactic Astrophysics

An Improved Fit for Linear Halo Bias at High Redshift

Kuan Wang, Julian B. Muñoz and L. Y. Aaron Yung

High- to ultrahigh-redshift clustering of halos provides a powerful tool to understand cosmology and galaxy formation. However, theoretical predictions are not firmly established in the first billion years, where current and upcoming surveys are beginning to reach percent-level precision. Here we measure dark matter halo biases at $z=6$ - 19 from simulation data, and find they are $\sim$ 3 - 4$\%$ higher than canonical results calibrated at low $z$. We provide an updated linear-bias fit at these early times, reducing the mean systematic offset to $< 1\%$. These results will enable robust interpretation of early-Universe galaxy clustering from JWST, Roman, and intensity-mapping surveys.
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Solar and Stellar Astrophysics

The Damping and Instability of Ion-acoustic Waves in the Solar Wind: Solar Orbiter Observations

Hao Ran, Daniel Verscharen, Jesse Coburn et al. (+6 more)

Observations of solar wind velocity distribution functions (VDFs) commonly reveal fine-scale structures. These features strongly influence kinetic processes such as wave damping and instability, yet their role remains poorly understood. We use a Gaussian Mixture Model (GMM) to separate proton and $\alpha$-particle (fully ionized helium) VDFs from Solar Orbiter Proton and Alpha-particle Sensor (PAS) measurements, and assess how measured VDFs affect the damping of compressive fluctuations with the Arbitrary Linear Plasma Solver (ALPS). We analyze the dispersion relation and polarization properties of ion-acoustic (IA) waves in the solar wind. Protons and $\alpha$-particles are represented by the measured VDFs derived from PAS observations. For comparison, we also perform calculations using the bi-Maxwellian assumption for the VDFs. Fine-scale structures of the measured proton VDFs reduce the damping rate of IA waves, even when $T_e \simeq T_i$. In some cases, we find that the measured VDFs drive the IA mode unstable, while the corresponding bi-Maxwellian representations predict strong damping. These results demonstrate that resolving the fine-scale structures of VDFs is essential for accurately capturing the kinetic physics of the solar wind.
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All authors Hao Ran, Daniel Verscharen, Jesse Coburn, Georgios Nicolaou, Charalambos Ioannou, Xiangyu Wu, Jingting Liu, Kristopher Klein, Christopher Owen

High Energy Astrophysical Phenomena

Rapid-response 1.3 mm Observations of GRB 260127A with the Submillimeter Array

Garrett K. Keating, Tanmoy Laskar, Anna Y. Q. Ho et al. (+9 more)

We present the results from rapid-response 1.3 mm observations of GRB 260127A using the Submillimeter Array (SMA). SMA arrived on-source 12.6 minutes after the initial detection by the Neil Gehrels Swift Observatory, representing the earliest millimeter/submillimeter observations of a GRB to date. From these observations, we find a source with flux density $6.9\pm1.7$ mJy, consistent with the X-ray afterglow position but slightly offset from the optical afterglow position (2.7” offset, with the SMA detection having a 90% confidence radial position uncertainty of 0.9”). Subsequent observations 1.9 days later show no sources of emission, with a $3\sigma$ upper limit of 0.70 mJy. If the SMA detection is associated with GRB 260127A, we infer that the 1.3 mm light curve for GRB 260127A declined at least as fast as $t^{-0.5}$, suggesting that peak brightness of the event at this wavelength was reached in under a day. We discuss how these findings may be consistent with both forward shock and reverse shock afterglow scenarios, and implications for future millimeter/submillimeter observations of GRBs on these timescales.
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All authors Garrett K. Keating, Tanmoy Laskar, Anna Y. Q. Ho, Peter K. Blanchard, Kate D. Alexander, Edo Berger, Mark Gurwell, Tarraneh Eftekhari, Chloe T. Xu, Joshua Bennett Lovell, Ramprasad Rao, Peter K. G. Williams

Astrophysics of Galaxies

The splash beneath the largest radio bubble in a cluster core

H. R. Russell, P. E. J. Nulsen, A. C. Fabian et al. (+3 more)

We present a 100 ks XRISM Resolve observation of the Ophiuchus cluster that measures turbulence and bulk motion in the wake of the largest radio bubble on the sky. We detect a significant velocity shift of $-80\pm20$ km/s from the cluster centre to the bubble's wake and a clear increase in velocity dispersion from $135\pm10$ km/s to $210\pm20$ km/s. The measured bulk velocity in the wake is low and suggests that the bubble's trajectory is inclined with respect to the line of sight. If we subdivide the bubble's wake, fitting spectra simultaneously with cross-region responses, we find that the velocity shift and dispersion increase are primarily detected in the very centre of the wake. This is consistent with the expected updraft, or `splash', found beneath buoyantly rising radio bubbles. In the cluster's cool core, the turbulent kinetic energy is only 1% of the thermal energy radiated over a cooling timescale of 7 Gyr, and even falls short, by a factor of 5, of the thermal energy radiated over the bubble's rise time. Whilst turbulent energy generated in the large wake region may provide additional heating, this propagates too slowly to prevent rapid cooling across the core. The turbulent-dissipation heating rate is a factor of ~3 below the cooling luminosity. Despite the vast power of the giant radio bubble in the Ophiuchus cluster, the gas motions in the wake are remarkably modest and turbulent-dissipation appears unable to prevent rapid cooling.
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All authors H. R. Russell, P. E. J. Nulsen, A. C. Fabian, B. R. McNamara, J. S. Sanders, N. Werner

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Emergent structure in the binary black hole mass distribution and implications for population-based cosmology

Vasco Gennari, Tom Bertheas and Nicola Tamanini

Gravitational waves provide a powerful probe of both the astrophysical processes driving black hole mergers and the dynamics of the Universe, but these measurements rely on accurately inferring the unknown underlying population. We perform an agnostic reconstruction of the primary mass distribution using B-splines, characterising the emergence of structure with increasing model complexity. Using the latest gravitational-wave transient catalog, GWTC-4.0, we identify multiple mass features and find evidence suggesting a logarithmic hierarchy in the population. We show that this structure directly impacts measurements of the Hubble constant, primarily through features at the population boundaries. Finally, we introduce an approach that isolates a subpopulation of low-mass events to mitigate modelling systematics, providing a promising path toward robust population-based cosmology with future datasets.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th

Quantum correction to the diffusion term in stochastic inflation from composite-operator matching in Soft de Sitter Effective Theory

Martin Beneke, Patrick Hager and Andrea F. Sanfilippo

In the framework of Soft de Sitter Effective Theory (SdSET), the Fokker-Planck equation for the late-time dynamics of the massless minimally coupled scalar field and its extension to the Kramers-Moyal equation are obtained from operator mixing of composite operators of the effective superhorizon field. We construct the formalism for composite-operator renormalisation, mixing and matching in dimensional regularisation, allowing for computations beyond the leading order. The general formalism is illustrated in free SdSET, which already features non-trivial structures including the well-known diffusion coefficient for stochastic inflation. As explicit examples in the interacting theory, we renormalise the one-loop bispectrum and the two-loop one-point function of the composite operator $\varphi_+^2$, and match them onto their full-theory counterparts. These results allow us to determine the next-to-leading order (two-loop) correction to the diffusion term of the Fokker-Planck equation of stochastic inflation for the first time.
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Astrophysics of Galaxies

Stream on: Evolution of stellar shells and streams - A case study

Johannes Stoiber, Lucas M. Valenzuela, Rhea-Silvia Remus et al. (+1 more)

Tidal stellar shells and streams are two of the most intriguing low-surface-brightness features within galaxies, consisting of stars accreted from satellite galaxies. A crucial ingredient in determining which type of feature will be formed is the orbit of the satellite galaxy. Additionally, the distribution of stars from these satellite galaxies within the merger remnant and the original location of these stars within the progenitor satellite galaxy provide important clues about the deposition of the stellar component in the resulting galaxy. We utilize the cosmological hydrodynamical simulation Magneticum Pathfinder and expand on the work by Valenzuela & Remus (2024) and Stoiber et al. (2025) to present a case study for the formation of a stream and a shell system. We analyze their orbits and the distributions of stellar particles within their host galaxy and compare them to their initial location within the progenitor satellite galaxy. We find that the orbit of the stream progenitor is more circular than the progenitor of the shell system. The stellar particles of the stream from different initial radii are found at roughly the same distances with respect to the host galaxy. However, the part of the stream visible in mock observations - not hidden by the host galaxy - consists of stars from within the core of the progenitor ($r/r_{1/2} < 1$). On the other hand, the stellar particles of the shell system retain their radial ordering: Stars that were initially at small radii in the satellite galaxy also remain closer to the center of the host galaxy.
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All authors Johannes Stoiber, Lucas M. Valenzuela, Rhea-Silvia Remus, Klaus Dolag

Instrumentation and Methods for Astrophysics

Combining spectroscopy and wavefront control at deep contrast with photonic lanterns

Mona El Morsy, Olivier Guyon, Barnaby Norris et al. (+7 more)

HWO aims to directly image objects orbiting Sun-like stars, using a 6-m telescope capable of high-contrast imaging ($10^{-10}$) and spectroscopy to search for biosignatures in planets located in the habitable zone. Recent laboratory demonstrations and ground-based telescope projects have shown the effectiveness of SMFs in spectroscopy, paving the way for SMF-fed spectrographs in future space missions like HWO. SMFs enhance spectral stability and reduce modal noise. HWO spectroscopy will need extended integration times, potentially lasting weeks. During these observations, the wavefront must be precisely measured and maintained to achieve the deep contrast and robust calibration of starlight contamination necessary for exoplanet characterization. We show that photonic lanterns (PLs) are ideally suited to meet these requirements. PLs are compact devices that couple light over a broader angular range than SMFs, ensuring higher throughput, converting a multimode input into multiple single-mode outputs. Positioned at the focal plane, they measure the complex amplitude of the coherent starlight within $\sim$ 2 l/D of the planet image, acting as compact wavefront sensors. Among the different variants of PLs that have emerged, the Hybrid-Mode Selective Photonic Lantern (HMSPL) is particularly attractive, as it directs object light into a central SMF feeding a mid-R spectrograph for exoplanet spectroscopy, while the adjacent SMFs route surrounding speckle light to a low-R spectrograph for rapid wavefront sensing. This dual function eliminates non-common path aberrations, optimizing injection efficiency and background suppression. We introduce HMSPL's dual role and planned tests at UTSA's high-contrast imaging lab and at SCExAO at the Subaru Telescope.
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All authors Mona El Morsy, Olivier Guyon, Barnaby Norris, Sergio Leon-Saval, Sebastien Vievard, Julien Lozi, Thayne Currie, Yoo Jung Kim, Michael Fitzgerald, Nemanja Jovanovic

Astrophysics of Galaxies

Cold vs. Hot Gas Accretion and Angular Momentum in FIRE Simulations: From Halo to Galaxy Scales

Imran Sultan, Claude-André Faucher-Giguère, Jonathan Stern et al. (+1 more)

We present a systematic study of gas accretion and angular momentum in the circumgalactic medium (CGM) using high-resolution FIRE cosmological simulations. Our analysis includes halos spanning the critical $\sim 10^{12}\ \mathrm{M}_{\odot}$ scale where several transitions have been identified, including inner CGM virialization, the transition from bursty to steady star formation, and the emergence of thin disks. We find that the temperature of inflowing gas is correlated with the virialization of the inner CGM. CGM inflows are almost entirely cold ($T < 10^5$ K) in pre-virialized halos, while hot inflows ($T > 10^5$ K) dominate in virialized halos. When hot inflows dominate, cooling generally occurs simultaneously with circularization at galaxy radii. The dominance of hot inflows onto massive galaxies persists even at high redshift, where cold streams may coexist. Consistent with previous studies, cold inflows have higher specific angular momentum than dark matter and hot gas. However, in bursty, low-mass galaxies, cold inflows do not circularize prior to star formation, while in steady, massive galaxies, hot inflows circularize, cool, and form stars with disk-like kinematics. We additionally find that in bursty galaxies, accreted gas typically forms stars after residing in the galaxy for less than $\sim 5$ galaxy free-fall times, while in steady galaxies, gas can persist for up to $\sim 25$ free-fall times before forming stars. This highlights a key difference between star formation in bursty galaxies fed by cold accretion and steady equilibrium disks fed by hot accretion.
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All authors Imran Sultan, Claude-André Faucher-Giguère, Jonathan Stern, Guochao Sun

Astrophysics of Galaxies

Deep Imaging Meets Motion: Complementing Stream Photometry Through Planetary Nebula Kinematics

Lucas M. Valenzuela, Johannes Stoiber and Rhea-Silvia Remus

The combination of deep imaging data and kinematic measurements in galaxy outskirts promises to reveal extensive insights into the structure and history of individual galaxies. From a census of tidal features around galaxies from the Magneticum simulation, we disentangle the dynamics for a selected stellar stream from the underlying halo by identifying the stream progenitor galaxy. While these dynamics are challenging to measure observationally, we show that they are effectively obtained through planetary nebulae (PNe) as tracers, which we model in the simulation using the PN framework PICS (PNe In Cosmological Simulations). We find that the PNe in the brightest 1.5 mag of their luminosity function are sufficient to recover the underlying stellar dynamics of the massive stream. We thereby establish PNe as an attractive alternative to expensive deep IFU observations, where combining low-surface-brightness observations and PN dynamical measurements will enhance our ability to constrain the gravitational potential of galaxies.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Fast neural network surrogate for multimodal effective-one-body gravitational waveforms from generically precessing compact binaries

Christopher Whittall and Geraint Pratten

Gravitational waveform templates are a key ingredient for the detection and characterization of gravitational waves emitted by compact binary mergers in the universe. These templates must be physically accurate and extensive, but also highly computationally efficient, two requirements that are often in tension. One solution to this problem is the development of surrogate models, which are fast, data-driven models trained to predict the output of a slower, physically realistic waveform model. In this article we build on existing work to incorporate machine learning techniques into the conventional reduced order surrogate framework, with a focus on extending coverage to waveform models that describe generically precessing quasicircular binaries. In particular, we present SEOBNRv5PHM_NNSur7dq10, a reduced order neural network surrogate of the SEOBNRv5PHM waveform model, valid up to mass ratios 1:10 for precessing quasicircular binary black hole systems with arbitrary spin magnitudes and orientations. The faithfulness of the surrogate to SEOBNRv5PHM is validated, and the surrogate is successfully applied to Bayesian parameter inference using both real and injected gravitational wave data. The surrogate is approximately 5 times faster than SEOBNRv5PHM when evaluating a single waveform on a CPU, and nearly 1000 times faster per-waveform when amortizing the cost over large waveform batches on a GPU.
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Astrophysics of Galaxies

Could the high-mass black holes from gravitational-wave observations be explained by lensing?

Ritesh Harshe, R. Prasad and Parameswaran Ajith

The high-mass ($M \gtrsim 30 M_\odot$) black holes (BHs) from the gravitational-wave (GW) observations of LIGO and Virgo came as a surprise to many astronomers. While the collapse of metal-poor massive stars could produce such BHs, gravitational lensing has been invoked to explain their high masses. Broadhurst, Diego, and Smoot (henceforth BDS) argued that the mass distribution of BHs in coalescing binaries is very similar to that of the galactic BHs, and the inferred high masses are the result of neglecting the lensing magnification. They also proposed a redshift distribution of binary BH (BBH) mergers to explain the observed LIGO-Virgo mass distribution. We ask whether such a model is consistent with different aspects of the GW observations: 1) the observed number of BBH mergers, 2) the distribution of their redshifted total mass and apparent luminosity distance, 3) the non-detection of strongly lensed events, and 4) the non-observation of the stochastic GW background. By simulating lensed BBH mergers with the BDS model and comparing them with observations, we conclude that no choice of BDS model parameters is consistent with all aspects of the observations. Lensing magnification is not a viable explanation for the high-mass BHs discovered by LIGO and Virgo.
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Instrumentation and Methods for Astrophysics

Visplot: A visibility plot and observation scheduling tool for astronomical observatories

Emanuel Gafton and Illa R. Losada

We present Visplot, a free and open-source tool designed for interactive construction and refinement of nightly telescope observing schedules through a graphical user interface. The software performs hardware-aware observability analysis by explicitly incorporating telescope-specific limits alongside astronomical constraints, in order to determine feasible observation windows for both sidereal and non-sidereal targets. It also generates observing schedules that can be rapidly adapted to changing conditions. Visplot is a browser-based JavaScript application that can be used without installation, while remaining fully customizable through self-hosted deployments. The software computes target altitudes for the specified observatory coordinates on a discretized time grid spanning the entire observing night. Observability windows for individual targets are then derived by evaluating their altitude profiles against the intersection of astronomical constraints (airmass, moon distance, twilight), mechanical telescope boundaries (altitude and hour-angle limits), and custom temporal restrictions defined in coordinated universal time (UTC) or local sidereal time (LST). The scheduling engine operates within these observability windows, selecting and ordering observations using a multi-constraint heuristic optimization scheme. Mandatory targets are scheduled deterministically, while the remaining target pool is ranked using a weighted scoring function that balances user-defined priority, target urgency, altitude, and telescope slew overhead. Originally developed to address operational scheduling requirements at the Nordic Optical Telescope (NOT), Visplot has been in continuous use for a decade and has grown beyond its original development to support astronomers at multiple observatories worldwide, demonstrating its practical value in real-world observational workflows.
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Cosmology and Nongalactic Astrophysics

TDCOSMO XXV: Measuring H0 to 6.5% precision with quasar strong lensing and maximally flexible mass-sheet dynamics

William Sheu, Tommaso Treu, Martin Millon et al. (+16 more)

We present a blind time-delay cosmography measurement of the Hubble-Lemaître constant $H_0$ based on the quadruply imaged quasar SDSSJ1433+6007. Our analysis combines deep Hubble Space Telescope imaging, extended time-delay monitoring from the Wendelstein and Maidanak Observatories, and spatially resolved stellar kinematics from the Keck Cosmic Web Imager and Reionization Mapper. We build a robust lens model to reconstruct the mass distribution and high-signal-to-noise kinematic maps to break the mass-sheet degeneracy (MSD), explicitly accounting for the lens galaxy's oblateness, rotation, and anisotropy. Furthermore, we constrain the external convergence ($\kappa_{\rm ext}$) by characterizing the line-of-sight environment using wide-field photometry from the Dark Energy Spectroscopic Instrument (DESI) Legacy Survey data release 10. We incorporate these constraints into our joint lensing and dynamical model, running multiple iterations to estimate random and systematic uncertainties. Accounting for maximal flexibility of the mass-sheet transformation, and assuming a flat $\Lambda$CDM cosmology and an $\Omega_{\rm m, 0}$ prior from DESI data release 2, we infer $H_0 = 73.2^{+4.8}_{-4.7}$ km s$^{-1}$ Mpc$^{-1}$ (a $6.5\%$ precision), and an internal mass-sheet parameter $\lambda_{\rm int}=1.12^{+0.05}_{-0.06}$. Notably, $\lambda_{\rm int}$ is $2\sigma$ away from unity for this system, highlighting the importance of treating it as a free parameter. Our $H_0$ measurement is consistent with the result from our 2025 milestone paper, and it will be included in our next hierarchical analysis to improve the overall precision. Moving forward, the comprehensive pipeline demonstrated herein establishes a robust framework that can be readily applied to future strongly lensed systems to further refine cosmological constraints.
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All authors William Sheu, Tommaso Treu, Martin Millon, Frédéric Dux, Devon Williams, Shawn Knabel, Simon Birrer, Pritom Mozumdar, Giacomo Queirolo, Anowar J. Shajib, Michele Cappellari, Kenneth C. Wong, Ildar M. Asfandiyarov, Otabek A. Burkhonov, Frédéric Courbin, Shuhrat A. Ehgamberdiev, Sofía Rojas-Ruiz, Asadulla M. Shaymanov, Talat A. Akhunov

Astrophysics of Galaxies

The Radial and Vertical Structure of Molecular Gas in the Edge-On Galaxy NGC 4565

Grace Krahm, Adam K. Leroy, Jiayi Sun et al. (+11 more)

We present high-resolution (0.94" $\approx$ 55 pc) ALMA CO(2-1) and 13CO(2-1) observations of the highly inclined (i~87.5 deg) galaxy NGC 4565 covering out to galactocentric radius Rgal > $\pm$ 17 kpc. The combination of sensitivity and resolution enables the detection of CO emission well into the HI-dominated outer disk while isolating individual molecular clouds across the full extent of the galaxy. Although often described as an edge-on Milky Way analog, the molecular gas profile of NGC 4565 has a central gap which is more similar to M31. The 13CO/12CO ratio remains consistent at 0.086 $\pm$ 0.009 from Rgal = 5-13 kpc. Based on fits to position-velocity slices, the molecular disk remains thin, with a FWHM scale height of 79.1 $\pm$ 1.6 pc measured from the vertical intensity profile with little evidence for vertical flaring. Molecular clouds in NGC 4565 show sizes, linewidths, and surface densities consistent with those found in similar environments in PHANGS-ALMA galaxies and in M31. We identify a prominent star-forming complex on the ring-an overdensity of molecular gas we term the East Ring Pileup. This feature hosts a compact, multiwavelength-bright region, which we call the Jewel. Effects of galaxy inclination on molecular cloud radius, velocity dispersion, surface density, and virial parameter appear as second-order effects that are strongest in velocity dispersion. At this resolution, GMCs are preferentially aligned with the disk of the galaxy and horizontally elongated by a factor of~2.
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All authors Grace Krahm, Adam K. Leroy, Jiayi Sun, Kijeong Yim, Eric W. Koch, Tony Wong, Deanne Fisher, Erik Rosolowsky, Karin Sandstrom, Dyas Utomo, Jesse van de Sande, Marie Martig, Amelia Fraser-McKelvie, Michael R. Hayden

Earth and Planetary Astrophysics

Icy Volatile Enhancements in Evolving Protoplanetary Disks

Elizabeth Yunerman, Ellen Price and Karin Öberg

Protoplanetary disk ice lines shape a multitude of planet formation processes, setting the environmental composition through evolution. Ice line locations depend on molecular sublimation and deposition properties, but in dynamic disks where temperature and density structures change, so do the expected compositions of planets and planetesimals. In turbulent viscous disks with particle drift, thermal evolution, and desorption/adsorption, Price et al. 2021 demonstrated that the CO/H$_2$O ice ratio beyond the CO ice line can become enhanced by $\sim10\times$. We expand on their work by incorporating additional carbon, nitrogen, and oxygen species, more particle sizes, and a broader disk parameter exploration. We find that before $\sim0.5$Myr, volatile ices are enhanced relative to H$_2$O as the outer disk is desiccated by drift, while at later disk times outward advection and volatile deposition further increase relative volatile icy enhancements beyond the evolving critical disk radius. The outcome of these combined relative icy enhancement to H$_2$O mechanisms is solid C/O $\sim$ N/O $\sim1$ beyond the hypervolatile ice lines, much higher than expected in static disks. Hypervolatiles (N$_2$, CO, and CH$_4$) robustly increase to $\sim100\times$ across the explored parameter space, while mid-volatiles (CO$_2$ and NH$_3$) are sensitive to model choices, with enhancements ranging from $\sim2-50\times$. Together these results demonstrate that coupling disk dynamics with simple sublimation and deposition chemistry is fundamental to predicting grain, planetesimal, and planetary compositions, particularly the role of advection in redistributing volatiles across disk radii.
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High Energy Astrophysical Phenomena · Cross-listed from hep-th

Gravitational Sommerfeld Effects: Formalism, Renormalization, and Perturbation to $O(G^{10})$

Chih-Hao Chang, Chia-Hsien Shen and Zihan Zhou

In the effective field theory (EFT) description of binary inspirals, the radiated gravitational waveform receives universal corrections from the curved background, the so-called “tail effects”, that resum into the so-called “Sommerfeld factor”. We develop a systematic framework for computing this gravitational Sommerfeld factor for scalar perturbations with the presence of tidal effects on the system. Using the worldline EFT, we recast the diagrammatic resummation as a solution to the $d$-dimensional wave equation with a localized source, and derive a closed-form expression for the Sommerfeld factor in terms of the EFT connection matrix. We prove that the phase of the Sommerfeld factor is exactly the same as elastic Compton scattering phase shift when there is no tidal dissipation. By combining the renormalization techniques in EFT with the Mano–Suzuki–Takasugi method in black hole perturbation theory, we analytically solve the Sommerfeld factor for both the magnitude and phase to $O(G^{10})$ for the $\ell = 0, 1, 2$ partial waves. We further establish a new renormalization group equation for the radiative multipole moments, whose exact solution yields an improved resummation of the waveform beyond the universal tail logarithms. These high-precision data and exact relations pave the way for future waveform resummation.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Electro-Weak Phase Transitions and Collider Signals in the Aligned 2-Higgs Doublet Model

Angela Conaci, Stefania De Curtis, Luigi Delle Rose et al. (+4 more)

We show that the Aligned 2-Higgs Doublet Model (A2HDM) is a framework able to simultaneously accommodate strong first order electro-weak phase transitions, in turn generating detectable gravitational waves as well as a variety of Higgs boson signals (involving both the Standard Model state and its companions, both neutral and charged) accessible at the Large Hadron Collider (LHC). We map the corresponding expanse of parameter space where such a phenomenology is realised in terms of the relative values of the masses of the discovered Higgs boson and the extended Higgs sector states of this model: two neutral ones (a CP-even and a CP-odd) plus a pair of charged ones. We find that both the Laser Interferometer Space Antenna experiment and High-Luminosity LHC can test such a scenario within their lifetime. This study thus sets the stage for a two-prong complementary approach able to scrutinise the extended Higgs sector of the A2HDM in both its high and low temperature manifestations.
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All authors Angela Conaci, Stefania De Curtis, Luigi Delle Rose, Atri Dey, Anirban Karan, Stefano Moretti, Maimoona Razzaq

High Energy Astrophysical Phenomena

Search for CBCs with SSM Components in Data from The First Part of LVK Fourth Observing Run

Ines Bentara

Star evolution models predict the lightest compact objects in the universe to have masses greater than that of the Sun. Nonetheless, alternative scenarios could lead to the formation of sub-solar mass (SSM) compact objects, such as primordial black holes (PBHs). The LIGO-Virgo-KAGRA Collaboration (LVK) has performed a search for gravitational-wave (GW) signals from compact binary coalescences (CBCs) including at least one SSM component during the first part of their fourth observing run (O4a), reporting no statistically significant candidate. This non-detection sets upper limits on the merger rate of such systems, which can be used to constrain PBH formation models and the fraction of dark matter (DM) in PBHs. For PBH binaries forming at late times, the fraction of DM in PBHs is constrained to be <= 1 for masses above 0.9 M_sun in the case of monochromatic mass functions. In the early-formation scenario, this fraction is limited to $\le 7\%$ at 1 $M_\odot$ and $\le 40\%$ at 0.35 $M_\odot$.
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Astrophysics of Galaxies

A Salpeter-like filament linear density function across nearby molecular clouds

Guo-Yin Zhang, Alexander Men'shchikov and Jin-Zeng Li

The high-mass slope of the stellar initial mass function (IMF), first measured by Salpeter in 1955, appears nearly universal across star-forming environments, yet its physical origin remains unknown. Using the multiscale extraction method getsf, we measure the filament linear density function (FLDF) across seven nearby molecular clouds ($140-920$ pc) spanning a wide range of star-forming activity. The FLDF slope shows no systematic trend with spatial scale. Combining all clouds and scales, the composite FLDF follows a power law ${\rm d}N/{\rm d}\log\Lambda \propto \Lambda^{-\alpha}$ with $\alpha \approx 1.40$, close to the Salpeter value of $1.35$, and the same composite slope is found in every cloud despite an order-of-magnitude spread in their supercritical-filament fractions. The close similarity between the composite FLDF slope and the Salpeter value suggests a possible physical link between the hierarchical filamentary structure of the cold interstellar medium and the IMF.
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