Astrophysics of Galaxies
JWST Predictions for $z > 10$ Galaxies from the Renaissance Simulations – I: Photometry and Sizes
Samantha E Hardin, John H Wise and Emily K Troutman
JWST has enabled new high
redshift observations with 14 spectroscopically confirmed
galaxies at $z > 10$ to date, leading to a need for high
redshift, high resolution simulations to interpret these observations. We present the physical properties and mock observations of the
galaxies in the Renaissance Simulations to add to the growing database of high
redshift simulation data to guide and interpret observations. We find that they provide an accurate representation of the formation history of JWST's $z > 10$ discoveries and follow the trends observed in JWST
galaxies but extended to lower masses. The
stellar masses of the Renaissance
galaxies range from $\approx 10^{3}$ to $10^8 M_{\odot}$ and overlap well with the $z > 10$ JWST
galaxies with a
stellar mass range of about $10^{7}$ to $10^9 M_{\odot}$. The simulated SFRs increase from $10^{-4}$ to $10^1 M_{\odot}yr^{-1}$, overlapping the JWST
galaxies' lower SFRs in the range $1 - 20 M_{\odot}yr^{-1}$. These compact
galaxies show minimal morphology change as their
stellar masses increase with the majority of the half light radii between $1$ and $10$ pc and the majority of the half
stellar mass radii around $0.1$ kpc; their Sersic indices vary between $0$ and $4$. The Renaissance
galaxies are bluer and generally transition well into the absolute UV magnitudes of the JWST
galaxies in the main sequence of
galaxies. Overall, our simulations agree well with JWST's discoveries to date, making them a valuable tool in the continued effort to understand the high
redshift Universe.
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Cosmology and Nongalactic Astrophysics
A Consistent Implementation of Cluster Strong Lensing in Cosmological Simulation Light Cones
Cian Roche, Mark Vogelsberger, Michael McDonald et al. (+9 more)
Galaxy cluster strong gravitational
lensing plays a central role in precision cosmology, yet robust theoretical predictions have lagged behind an abundance of high-quality strong
lensing observations. This shortfall reflects both a mismatch between the geometry of the strong-
lensing problem and standard cubic simulation boxes, and the fundamental tension between simulation volume and resolution. Consequently, many current forecasts adopt hybrid approaches that extract individual lenses from simulations and combine them with analytic or observed source populations positioned near caustics. These methods often omit correlated and/or uncorrelated line-of-sight (LoS) structure, or include it in ways that do not preserve correlations across
redshift. Here we present a fully simulation-based procedure that generates strong-
lensing images directly from particle data, drawing the lens, source, and all intervening resolved objects self-consistently from the simulated large-scale structure. Our approach combines a structure-preserving remapping of the simulation volume into a
lensing-appropriate geometry with multi-plane ray tracing, enabling the use of uniform simulation boxes that resolve both cluster-scale primary lenses and high-
redshift source
galaxies. We demonstrate the method by generating example light cones and images using IllustrisTNG data, then use these results to conservatively quantify the impact of LoS structure on image configurations and critical-curve morphology. We find that uncorrelated LoS structure can shift the relative positions of lensed images by several arcseconds, introduces a $\sim 6\%$ scatter in the area of a cluster's primary critical curve, and changes the total critical area within 100$^{\prime\prime}$ of the cluster potential minimum by $16^{+20\%}_{-14\%}$ at a source plane
redshift of $z_s=4$.
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All authors Cian Roche, Mark Vogelsberger, Michael McDonald, Isaque Dutra, Priyamvada Natarajan, Xuejian Shen, Soumya Shreeram, R. Benton Metcalf, Keren Sharon, Simon Birrer, Wonki Lee, Massimo Meneghetti
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Exact Mass Conservation in Binary Neutron Star Merger Simulations
Boris Daszuta, Sebastiano Bernuzzi, Joan Fontbuté et al. (+4 more)
A long-standing problem in the simulation of
neutron star spacetimes is the treatment of
vacuum regions outside the
stars. The use of an artificial low-density atmosphere is a common robust approach within Eulerian hydrodynamics that, however, introduces
baryon-mass violation even with conservative numerical schemes. We propose a simple numerical
algorithm that ensures exact mass conservation by means of an appropriate local rescaling of the atmosphere. The scheme is combined with a low-order flux correction and it can be further augmented by a pseudo-
vacuum treatment that enforces strict
vacuum in the outer regions far from the central objects. We demonstrate the effectiveness of these
vacuum treatments with binary
neutron star mergers simulations spanning multiple orbits and the postmerger phase, and including a microphysical equation of state. The rescaling
algorithm guarantees mass and electron number conservation to round-off precision. The pseudo-
vacuum treatment shows slightly larger but approximately constant violations and can improve the computation of fast tail ejecta as well as provide convergent gravitational waves of quality comparable to the standard atmosphere. Overall, results from different atmosphere treatments and a two-code comparison suggest that current computations of gravitational waves and (dynamical) ejecta in the presence of an artifical atmosphere are robust, provided that conservative adaptive mesh refinement with flux correction is employed.
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All authors Boris Daszuta, Sebastiano Bernuzzi, Joan Fontbuté, Ruocheng Zhai, Alan Tsz-Lok Lam, Jacob Fields, David Radice
Astrophysics of Galaxies
The AURORA Survey: Multiple Balmer and Paschen Emission Lines for Individual Star-forming Galaxies at z=1.5-4.4. II. Implications for Nebular Dust Corrections, Nebular SFRs, and Differential Reddening
Naveen A. Reddy, Alice E. Shapley, Ryan L. Sanders et al. (+10 more)
We discuss the implications of the nebular
dust attenuation curves derived for 24
galaxies at z=1.5-4.4 with multiple detections of HI Balmer and Paschen recombination emission lines from the JWST/AURORA survey. The total attenuation of Ha is ~0.20 dex larger on average than the values obtained with the commonly adopted combination of the Balmer decrement and the
Galactic extinction curve. Nebular-line SFRs and SED-based SFRs are consistent on average when using the MOSDEF attenuation or SMC extinction curves for the latter. The relation between nebular and
stellar reddening is consistent with a scenario where the Paschen lines are sensitive to heavily reddened OB associations, while relatively unreddened OB associations contribute significantly to the Balmer line and UV continuum emission. There is a stark contrast between the low Rv (or steepness) of
stellar dust attenuation curves and the high Rv (or flatness) of nebular
dust attenuation curves. We suggest that the latter could be reflective of a more porous medium established by strong feedback from massive
stars. For the youngest
galaxy in the sample, the
stellar reddening curve is identical to the nebular attenuation curve, in accordance with our expectation that OB associations dominate the
stellar continuum emission at all wavelengths for this very young
galaxy. Larger samples will be needed to determine whether this conclusion holds for young
galaxies in general, and provide further insights into the
dust and metals mixing timescale on the scale of HII regions.
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All authors Naveen A. Reddy, Alice E. Shapley, Ryan L. Sanders, Michael W. Topping, Max Pettini, Natascha M. Forster Schreiber, Charles C. Steidel, Leonardo Clarke, Richard S. Ellis, Anthony J. Pahl, Garth D. Illingworth, Mariska Kriek, Desika Narayanan
Astrophysics of Galaxies
High-ionization coronal lines trace quasar-like activity in recently quenched galaxies at high redshift
F. Valentino, K. Ito, M. Farcy et al. (+31 more)
We report the detection of the high-ionization line [NeV]$\lambda$3427 in the JWST/NIRSpec archival spectra of 6 massive quenched
galaxies at $z \sim 1.5-4.5$, identified from a parent sample of 87 systems. With an ionization potential of approximately 97 eV, [NeV] can only be produced by strong
nuclear activity in these massive systems, providing a clean and unambiguous tracer of highly accreting supermassive black holes uncontaminated by residual
star formation. For 4 of the 6 [NeV]-detected systems, we detect broad H$\alpha$ emission ($\mathrm{FWHM} \gtrsim 4000$ km s$^{-1}$), yielding black hole masses of $M_{\rm BH} = 10^{8.5-9.5}\,M_\odot$, consistent with local scaling relations with
stellar mass and velocity dispersion. The [NeV] luminosities imply
quasar-like bolometric outputs ($L_{\rm bol} = 10^{45-46}$ erg s$^{-1}$) and Eddington ratios of $\lambda_{\rm Edd} \approx 10$-$50$%, with black hole
accretion rates of a few $M_\odot$ yr$^{-1}$ that match or exceed the residual
star formation rates in the most extreme cases. The strongest [NeV] emitters are preferentially found in the youngest post-starburst systems ($D_n4000 \lesssim 1.3$), while old quenched
galaxies are systematically devoid of such activity, a trend independently reproduced by theoretical models. These results reveal that intense, radiatively efficient SMBH growth can persist several hundred Myr after the main quenching epoch, with duty cycles of approximately 100-200 Myr. They also underscore the importance of very high
accretion episodes and rates in the theoretical models that seek to reproduce the earliest quenched
galaxies in the universe.
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All authors F. Valentino, K. Ito, M. Farcy, F. Fontanot, C. Lagos, G. De Lucia, M. Hirschmann, G. Brammer, V. Kokorev, M. Hamadouche, P. Zhu, G. Scarpe, A. Pensabene, K. E. Whitaker, W. M. Baker, P. Araya-Araya, J. Antwi-Danso, D. Ceverino, A. L. Faisst, S. Fujimoto, S. Gillman, O. Ilbert, C. K. Jespersen, T. Kakimoto, M. Kubo, A. W. S. Man, G. Magdis, M. Onodera, R. Shimakawa, M. Tanaka, S. Toft, L. Xie, J. R. Weaver, P.-F. Wu
Solar and Stellar Astrophysics · Cross-listed from hep-ph
Millicharged Particle Constraints from Asymptotic Giant Branch Stars
Damiano F.G. Fiorillo, Giuseppe Lucente, Jeremy Sakstein et al. (+1 more)
We investigate the effect of millicharged particles (MCPs) with electric charge $qe\ll e$ and mass $m_\chi$ on the late-stage
evolution phases of low-mass
stars in globular clusters. We predict the $R_2$ parameter – the ratio of the number of
stars in the asymptotic
giant branch (AGB) phase to the number of
stars in the horizontal branch (HB) phase – and compare it against globular cluster data. While the production of MCPs shortens both the HB and AGB lifetimes, a larger reduction in the AGB phase arises from the higher temperatures in the helium-burning shell. We find the strongest bounds in the range $10\,\mathrm{keV}\lesssim m_\chi\lesssim 100\,\mathrm{keV}$, reaching charges as small as $q\simeq 5\times10^{-13}$ and surpassing existing constraints by up to two orders of magnitude.
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All authors Damiano F.G. Fiorillo, Giuseppe Lucente, Jeremy Sakstein, Edoardo Vitagliano
Earth and Planetary Astrophysics
Parameter resolution of near-Earth asteroids using LISA
Sara Marques and Oliver Jennrich
The detection of near-Earth asteroids (NEAs) is critical for planetary defense and for advancing our understanding of the small-body population in the
Solar System. Traditional detection techniques, including optical and radar, are the cornerstone of NEA discoveries. However, these are limited by observational constraints. We investigate whether the
Laser Interferometer Space
Antenna (LISA), a future space-borne gravitational wave detector, might detect and constrain the parameters of NEAs through their gravitational effect on the spacecraft test masses during a close approach at the minimum orbital intersection distance. We modeled the gravitational perturbations of the test masses on the LISA spacecraft exerted by a passing NEA. Based on this, we computed its signal-to-noise ratio (S/N) to determine detectability using the LISA requirements. Furthermore, we used the Fisher information formalism to estimate the uncertainties on the state vector and mass of the asteroid given it is detected. These estimates provide a first-order assessment of the LISA capability to resolve NEA parameters under favorable encounter geometries. The Fisher information study showed that the fractional uncertainty on the asteroid mass scales as the inverse of the S/N. Consequently, a detection with an S/N $\geq 5$ yields a mass determination with an uncertainty of $\sim20\%$ at most. In contrast, the state vectors exhibit considerably larger uncertainties as they depend significantly on the geometry of the close approach. Nevertheless, for very high S/N cases, this precision may be comparable to the uncertainties obtained by some of the current observational methods. The analysis of the correlation
matrices confirms that each close encounter produces a specific signal and provides a practical means to assign independent error bars to the recovered state vector.
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Astrophysics of Galaxies
A Rapid Evolution in the Observed Mbh/M* Relation at z > 3 Revealed via Spectro-photometric SED-Modeling
Ansh R. Gupta, Anthony Taylor, Emma Curtis-Lake et al. (+33 more)
Spectroscopic observations from JWST have uncovered a plethora of active
galactic nuclei (AGN) at z > 4 with black hole (BH) mass (Mbh) to
stellar mass (M*) ratios significantly above the local relation when using standard virial mass scaling relations. However, M* estimates of AGN may be inaccurate due to limitations in spectral energy distribution (SED) fitting codes, exemplified by a lack of physically-motivated AGN line emission models. Here, we fit NIRSpec/PRISM spectra of 39
galaxies at z ~ 3.5-7 selected as broad-line AGN from the CEERS and RUBIES surveys. Applying kinematic decompositions from NIRSpec/G395M spectra, we fit their continuum and narrow-component line fluxes using the BEAGLE-AGN SED fitting tool. While limitations of BEAGLE-AGN make it difficult to model little red dots (LRDs), we find that M* estimates of non-LRDs are, surprisingly, only modestly impacted by the inclusion or not of AGN narrow-line region (NLR) and continuum emission model components. We further find that non-LRD AGN at z < 3.5 are consistent with the local Mbh/M* relation while those at z > 4.5 display elevated ratios. While we cannot rule out observational biases or systematic uncertainties as partial causes, this transition over just ~500 Myr is driven entirely by changes in M* rather than an evolving Mbh distribution. These findings are consistent with models in which rapid BH growth results in elevated Mbh/M* ratios at early times, with a swift late-time assembly of host
galaxies returning sources to the local relation at z < 4.
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All authors Ansh R. Gupta, Anthony Taylor, Emma Curtis-Lake, Maddie Silcock, Óscar A. Chávez Ortiz, Steven L. Finkelstein, Hollis B. Akins, Bren E. Backhaus, Guillermo Barro, Laura Bisigello, Madisyn Brooks, Caitlin M. Casey, Stephane Charlot, Jacopo Chevallard, Anna Feltre, Giovanni Gandolfi, Mauro Giavalisco, Norman A. Grogin, Michaela Hirschmann, Tiger Yu-Yang Hsiao, Junehyoung Jeon, Shardha Jogee, Jeyhan S. Kartaltepe, Dale D. Kocevski, Anton M. Koekemoer, Vasily Kokorev, Gene C. K. Leung, Ray A. Lucas, Fabio Pacucci, Nor Pirzkal, Adele Plat, Rachel S. Somerville, Jonathan R. Trump, Alba Vidal-García, Xin Wang, L. Y. Aaron Yung
Instrumentation and Methods for Astrophysics
Choosing the right MCMC sampler: a systematic benchmark of gradient-free methods
Colin M. Poppelaars and Marcel P. van Daalen
We present a set of metrics and methods for testing and comparing a range of modern gradient-free Markov Chain Monte Carlo (MCMC) samplers against the commonly used Metropolis-Hastings (MH)
algorithm. The goal is to quantify key performance metrics, including sampler ergodicity, robustness and overall likelihood performance. To provide a controlled and interpretable testbed, we use the Rosenbrock function and Neal's funnel as representative unimodal cases, while Gaussian random likelihood landscapes in three, five, and eight dimensions serve as
multimodal test scenarios. The samplers considered include affine-invariant moves from the literature, such as the stretch and walk moves, the differential
evolution move, and the snooker move. We additionally introduce two novel variations: a modified stretch move that incorporates a Principal Component Analysis (PCA) transformation, and a hybrid blend move that combines features of both differential
evolution and stretch dynamics. Beyond sampler evaluation, we demonstrate reconstructing likelihood landscapes from sampled points using a quadtree
algorithm. Additionally, we explore the use of optimisation
algorithms to refine the best parameter set in terms of its likelihood, and find consistent improvements in log-likelihood values, with the post-sampling gain becoming more significant in higher-dimensional problems. Our comparative results of sampler testing show that the differential
evolution algorithm, when tuned to a target acceptance fraction of 25%, consistently outperforms all other samplers in terms of ergodicity, robustness, and likelihood performance.
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High Energy Astrophysical Phenomena · Cross-listed from hep-th
Axions Create Singularities on Extremal Horizons
Gary T. Horowitz, Maciej Kolanowski, Grant N. Remmen et al. (+1 more)
We show that
axions cause extremal black holes to have singular horizons. This is true for almost all values of the
axion mass and coupling provided the black hole is rotating and has some arbitrarily small nonzero charge. When the
axion mass becomes large, these singularities are related to the recently discovered singularities induced by higher-derivative corrections to the Einstein-Maxwell equations. Away from extremality, this effect produces anomalously large
tidal forces in the vicinity of near-extremal horizons, causing breakdown of the effective theory.
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All authors Gary T. Horowitz, Maciej Kolanowski, Grant N. Remmen, Jorge E. Santos
Astrophysics of Galaxies
RUBIES: The Evolution of the Ionization Parameter from 0 < z < 9
Nikko J. Cleri, Zach J. Lewis, Joel Leja et al. (+10 more)
The dimensionless ionization parameter, U=q/c, where q is the ratio of the local ionizing
photon flux to the local hydrogen density, is a key metric to parameterize nebular conditions. Prior to JWST, the rest-frame optical emission lines and their ratios which trace the ionization parameter (e.g., O32=[OIII]/[OII]) were inaccessible at high
redshifts. Here we quantify, for the first time, the
evolution of the ionization parameter in
galaxies across the last 13 billion years of
cosmic time by comparing JWST/NIRSpec PRISM and G395M spectroscopy of 434
galaxies at 3<z<9 from the RUBIES survey with z<3 samples from SDSS, LEGA-C, and KBSS. We leverage a large suite of photoionization models to infer U from [OIII] and [OII]. We find that U increases with
redshift and specific
star formation rate (sSFR), and decreases with
stellar mass. Crucially, and in contrast to previous linear best-fit calibrations, our inference results in a systematic uncertainty in logU of ~0.3 dex at zero measurement uncertainty due to the wide range of models that predict the same O32 ratio without informative priors. We compare to SPHINX20 and LUMEN simulations and find that the simulated
galaxies exhibit higher O32 ratios at fixed
redshift and
stellar mass compared to RUBIES observations. Finally, we combine the predictive power of observed and inferred quantities with multivariate relations to estimate U from
redshift,
stellar mass, and sSFR for use where O32 is not available. We find that U increases at fixed
stellar mass and sSFR by a factor of ~4 from z=2 to z=6, demonstrating that the
redshift evolution encapsulates physics beyond that traced by
stellar mass and sSFR alone. Finally, we show that a toy model with the first order assumption that HII region volume is proportional to
galaxy volume can explain the excess
redshift dependence of logU as being consistent with observed
evolution in
galaxy sizes.
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All authors Nikko J. Cleri, Zach J. Lewis, Joel Leja, Jakob M. Helton, Emilie Burnham, Olivia Curtis, Anna de Graaff, Michaela Hirschmann, Harley Katz, Michael V. Maseda, Ian McConachie, Adele Plat, Lucie Scharre
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Toward a Phenomenologically Acceptable Quantum Cyclic Universe
Sean M. Carroll, Nadiia Diachenko and Saakshi Dulani
We put forward a
quantum model of cosmology that is exactly periodic but avoids the Boltzmann
Brain problem. If the universe is described by a
quantum state evolving unitarily in a finite-dimensional
Hilbert space, its
evolution will be recurrent: given enough time, the state will return arbitrarily close to its initial state. There is a worry that such a scenario cannot be phenomenologically acceptable, because the state will spend most of its time in a high-
entropy equilibrium macrostate, with rare fluctuations downward in
entropy, and the vast majority of observers will be minimal fluctuations away from
equilibrium, or “Boltzmann
Brains." Here we show that this is not necessarily true. If the differences in energy
eigenvalues are commensurable, the
evolution is not simple recurrent, but exactly periodic. Moreover, if the state starts at minimum thermodynamic
entropy, its
evolution can feature a distinguished
entropy excursion that is much more pronounced than one would expect from the conventional expression $P(\Delta S) \propto \exp(-\Delta S)$. This excursion could represent our Big Bang, with relatively few Boltzmann fluctuations occurring in the subsequent
equilibrium phase before a Big Crunch occurs and the cycle begins again. We speculate on the spacetime interpretation of this kind of
quantum universe.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Dark Energy Stars in Finch-Skea Spacetime with a Schwarzschild-(Anti)-de Sitter Exterior
Muhamad Ashraf Azman
In this work, the effects of the cosmological constant on dark energy
stars in Finch-Skea spacetime are systematically investigated within the framework of Einstein
gravity. A static and anisotropic
stellar configuration composed of ordinary matter and dark energy is constructed by employing the complexity factor formalism to obtain the temporal metric potential. The interior solution is smoothly matched to the exterior Schwarzschild-(anti-)de Sitter spacetime through appropriate boundary conditions. The influence of positive and negative cosmological constants on the structural and stability properties of the compact
star candidate Vela X-1 is investigated in detail. The results show that positive values of the cosmological constant produce larger and less compact configurations, whereas negative values lead to denser and more compact
stars with stronger gravitational effects. The energy conditions are satisfied throughout the
stellar interior for all considered cases. However, sufficiently large values of the cosmological constant introduce deviations from hydrostatic
equilibrium and affect the causal and dynamical stability behavior of the model. Overall, the results demonstrate that the cosmological constant plays an important role in determining the compactness,
equilibrium and stability behavior of dark energy
stars in Finch-Skea spacetime.
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Instrumentation and Methods for Astrophysics
Experiments on Settling of Granular and Cohesive Material in Low Gravity
Matthias Keulen, Timo Giese, Kolja Joeris et al. (+1 more)
The regolith of rocky bodies, such as
planets or asteroids, generally settles under
gravity conditions different from those of Earth. The behavior of granular material is not easily scalable for different gravities. To predict these highly complex systems where cohesive inter particle forces can be comparable to gravitational forces, we need simulations and experiments. We did experiments on settling of three different granular samples in varying reduced gravities and examined their packing densities. We used a high precision linear stage to artificially induce reduced gravities inside the zero $g$ environment provided by the ZARM drop tower and observe the settling of our samples. The three samples were fine basalt with particle diameters of $1\text{-}200\,\mu$m, coarse basalt with $2\text{-}5\,$mm and glass beads with $750\text{-}1000\,\mu$m. The artificial gravities were $150,\,250,\,500,\,750$ and $1000\,$mm/s$^2$ and therefore ranged from large asteroid
gravity to almost moon
gravity. We saw the granular samples have higher volumes in lower gravities and therefore lower packing densities, we also saw the fine basalt be the most sensitive to changes in
gravity, up to $+19.6\,\%$ in volume for $250\,$mm/s$^2$, followed by the coarse basalt particles, up to $+12.2\,\%$ for $150\,$mm/s$^2$ and the glass beads packing density being the least sensitive to changes in
gravity, up to $+4.25\,\%$ for $250\,$mm/s$^2$. With these experiments we show change in volume is not solely dependent of particle size but also roughness and uniformity, we provide real life experimental data to validate theoretical works and highlight the role of cohesive forces in low
gravity environments.
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All authors Matthias Keulen, Timo Giese, Kolja Joeris, Jonathan Kollmer
Instrumentation and Methods for Astrophysics
The EPS Research Astro-RAG Platform: A Unified Open-Science Infrastructure for Cross-Epoch Astrophysical Kinematic Analysis, LLM-Assisted Research Workflows, and Educational Outreach
David C. Flynn
Correction (August 2026): A previously reported cross-epoch omega sign reversal was caused by a formula implementation error. Using the corrected canonical equation, all eight Tier-1 Z1 rotators yield positive omega values (median +12.621 rad Gyr^-1). The KROSS intermediate-
redshift omega values are withdrawn because their boundary points were template-derived. The z = 0 SPARC result is unchanged. See CORRECTIONS.md for details. The EPS Research Astro-RAG Platform v1.0 is an open-science infrastructure providing five machine-readable astrophysical corpora, 149 verified executable Jupyter notebooks, a QuickStart reproducibility pathway, a High-School Exploration Track, and a roadmap for LLM-assisted
retrieval-augmented generation (RAG) workflows. The platform spans
redshift z = 0 to z approx 6 and provides a unified kinematic
dataset connecting HI 21cm rotation curves, Milky Way globular cluster dynamics, intermediate-
redshift KMOS/KROSS kinematics, and ALMA [CII] morpho-kinematics under a common schema. The five corpora contain 2,064 total records: 438 HI
galaxies (Unified HI v7.0), 129
dwarf/irregular
galaxies (
Dwarf/Irregular v1.0), 174 Milky Way globular clusters (GC v1.3.2), 1,292 intermediate-
redshift galaxies (IntZ v1.0), and 31 ALPINE
galaxies at z = 4.26-5.68 (Z1). The Unified HI corpus preserves full SPARC photometric decomposition, including Vgas, Vdisk, Vbul, and surface brightness profiles, augmented with THINGS, LITTLE THINGS, and WALLABY DR2. The unifying scientific framework is the omega kinematic correction. Under the corrected formula, the z = 0 SPARC mean is +7.06 km s^-1 kpc^-1 (+7.22 rad Gyr^-1), and the Z1 median is +12.621 rad Gyr^-1. The earlier sign reversal is withdrawn. All corpora are released under CC BY 4.0 at Zenodo with permanent DOIs, and the platform is archived at https://github.com/eps-research/rag-corpus-series.
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Cosmology and Nongalactic Astrophysics · Cross-listed from cs.AI
Physics Is All You Need? A Case Study in Physicist-Supervised AI Development of Scientific Software
Nhat-Minh Nguyen
Are AI
agents tools, co-authors, or researchers? We present a quantified case study ($N=1$): a physicist supervising an AI coding
agent (Claude Code, Sonnet and Opus models) over 12 work days and 57 sessions to build CLAX-PT, a differentiable one-loop perturbation theory module in JAX. We documented and classified 15 supervision events by intervention level. The
agent resolved ten autonomously by iterating against oracle tests. Two more by the physicist's domain knowledge. The three it could not – all evaded oracle detection – share a common property: the
agent treated symptom reduction as root-cause resolution. It spent 33 of the 57 sessions adjusting coefficients within a code architecture that could not represent the target physics, and could not re-evaluate its CLASS-PT branch choice even when prompted to reconsider; only an injected physics concept (anisotropic BAO damping) triggered the redesign. Separately, the
agent committed a calibrated correction that passed all oracle tests but corresponded to no quantity in the theory, predicting wrong values at any other cosmology. The fudge factor was caught and replaced within the same session. Three supervision practices proved critical for catching what oracle tests missed: testing at diverse parameter points beyond the fiducial calibration; shared changelogs that surfaced stalled exploration across sessions; and an explicit rule against unphysical numerical patches. In this case, supervision design, not model capability, determined whether the
agent's output was trustworthy. Closing the gap would require
agents that propose architectural alternatives rather than optimize within a given structure, and distinguish predictive adequacy from explanatory correctness – capabilities not exhibited here, not obviously addressed by scaling alone. [Abridged.]
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Cosmology and Nongalactic Astrophysics
Augmented Correlation Functions for Spectroscopic Galaxy Surveys
Davide Bianchi
Galaxy redshift surveys encode a wealth of information generated by nonlinear gravitational
evolution,
galaxy bias, and
redshift-space distortions, only part of which is accessible through standard two-point statistics. Motivated by the need for flexible and computationally efficient alternatives, we introduce the augmented correlation function, a general framework in which an arbitrary transformation of the
galaxy field defines additional “latent” dimensions that extend the standard two-point correlation function and isolate clustering properties averaged out in conventional analyses. As a proof of concept, we study a latent variable constructed from the pairwise gradient of the inverse
Laplacian of the
galaxy density field, showing that the resulting statistics naturally distinguish clustering regimes associated with infalling and outflowing pairs. Using Fisher forecasts based on $z=1$
halo catalogues from the Quijote simulations within $\nu\Lambda\mathrm{CDM}$ cosmology, we find that the augmented correlation systematically yields tighter constraints on all cosmological parameters considered. Although these improvements should be regarded as indicative given the exploratory nature of the analysis and the limitations of Fisher forecasts and simulations, our results demonstrate the potential of augmented correlations as a flexible framework for extracting additional information from spectroscopic
galaxy surveys.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Characterization of Spurious Charge in SENSEI Skipper-CCDs
Yikai Wu, Ansh Desai, Sho Uemura et al. (+16 more)
Skipper Charge-Coupled Devices (Skipper-CCDs) are a leading technology in the search for sub-GeV dark matter and coherent elastic
neutrino-
nucleus scattering. A key background for rare-event searches with these detectors arises from "spurious charge" – single-electron events generated when charges are transferred through the active region to the serial register, and across the serial register to the readout stage. We present a characterization of spurious charge in both the active region and the serial register of SENSEI Skipper-CCDs, and show that, in a well-shielded low-background environment, the dominant contribution originates in the serial register during Skipper readout, when horizontal clocks are held at constant voltage between pixel transfers. Motivated by this finding, we develop a "tri-level" clocking scheme in which the held-low phase is raised to an intermediate voltage during readout to suppress trap-mediated charge generation. Using the SENSEI detector near the MINOS cavern, we measure a serial-register single-electron density of $(2.9 \pm 0.1) \times 10^{-5}$ electrons/pixel/image under standard SENSEI readout conditions, reduced to $(4.0 \pm 0.4) \times 10^{-6}$ electrons/pixel/image with tri-level clocking – a factor of $\sim$7 improvement. This technique offers a promising path to lower backgrounds in current and future Skipper-CCD experiments.
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All authors Yikai Wu, Ansh Desai, Sho Uemura, Ana M. Botti, Brenda A. Cervantes-Vergara, Fernando Chierchie, Alex Drlica-Wagner, Rouven Essig, Juan Estrada, Erez Etzion, Guillermo Fernandez Moroni, Miqueas Gamero, Stephen E. Holland, Ian Lawson, Steffon Luoma, Nathan A. Saffold, Miguel Sofo-Haro, Javier Tiffenberg, Tomer Volansky
Cosmology and Nongalactic Astrophysics
Late-time Quantum Vacuum Decay and its Cosmological Implications
Yang Bai, Sida Lu and Nicholas Orlofsky
The existence of a landscape of metastable
vacua raises the possibility that our Universe may have undergone
quantum vacuum decay at late times. This work explores how such a transition can be tested with cosmological observables, focusing on precision distance measurements and
cosmic microwave background (CMB) anisotropies. A set of phenomenological models is constructed in which late-time
quantum tunneling changes the
vacuum energy and may convert a subcomponent of dark matter into dark radiation, possibly accompanied by domain-wall production. The resulting expansion histories are compared with DESI DR2
baryon acoustic oscillation data;
supernova distance measurements from DES-Dovekie, Pantheon+, and Union3; and a compressed CMB likelihood. For
quantum-tunneling models, current cosmological distance measurements still allow a 50% decrease in the total
vacuum energy for a transition
redshift $z_t<1$. The model with dark-matter conversion and domain-wall production provides a good fit to resolve the tension between cosmological observables and the $\Lambda$CDM model, with a preferred transition around $z_t \sim 7$ and about 10% of dark matter participating in the transition. Additionally, CMB anisotropy constraints from bubble nucleation and the associated domain-wall network are derived and shown to strongly restrict slow or sparse late transitions. Applied to the minimal
quantum-tunneling model, these constraints allow an $\mathcal{O}(10\%)$ decrease in the total
vacuum energy for a transition
redshift $z_t$ of order unity. For nonminimal models, dark-matter-density-dependent tunneling can proceed rapidly enough to evade such bounds. These results demonstrate that late-time
quantum vacuum decay is a testable cosmological phenomenon and provide a concrete observational handle on metastable-
vacuum physics motivated by landscape scenarios.
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Instrumentation and Methods for Astrophysics
From Images to Orbits: A Hubble 2030s Astrometric Legacy for the M31-M33 Star Cluster Systems
Borja Anguiano, Benjamin J. Gibson and Sten Hasselquist
The most irreplaceable capability of HST in the 2030s is not only its angular resolution or its UV–optical sensitivity, but its accumulated time baseline. We recommend a Hubble Local Group Astrometric Legacy that would obtain matched 2030s ACS/WFC and WFC3/UVIS imaging of selected M31 and M33
star cluster fields, combine those observations with a careful astrometric audit of the existing archive, and deliver public transverse velocity products through MAST. PHAT and PHATTER already provide exceptional first epochs across the nearest large external spirals, resolving tens to hundreds of millions of
stars and identifying thousands of
star clusters and compact background reference objects. Earlier targeted HST programs, dating back to the mid 90's, can extend the temporal baseline in selected cases, but only after camera, chip, filter, dithering, crowding, and reference-frame triage. A coherent 2030s repeat campaign would turn the best of this archive into bulk cluster motions, enabling the first systematic orbital mapping of
star cluster populations beyond the Milky Way. These measurements would constrain disk heating, cluster disruption,
accretion histories, stream associations, the M31–M33 interaction, and the mass distributions of Local Group spirals. The same program would also preserve and stress-test the calibration infrastructure needed for high-stability optical/UV astrophysics in the HWO era:
geometric-distortion solutions, PSF and CTE modeling, matched-epoch observing strategies, long-term reference frames, and durable public high-level products.
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Cosmology and Nongalactic Astrophysics
Efficient computation of the galaxy angular bispectrum in redshift space
Zucheng Gao, Zvonimir Vlah and Anthony Challinor
Efficient computation of the angular bispectrum is an essential part of modelling large-scale structure observations, but it still remains an extremely challenging task. In this work, we compute the tree-level, unequal-time angular bispectrum in both real and
redshift space. By deriving full-sky results, we show that the bispectrum can be expressed as a sum of products of two angular power spectra, enabling the use of our recently developed flat-sky approximation to enhance computational efficiency significantly. This flat-sky formalism preserves key line-of-sight mode information while discarding extraneous full-sky contributions. We validate our approach by comparing it with direct full-sky integration, finding excellent agreement across a wide range of scales and
redshifts for all bispectrum configurations. At
redshift $z = 1$, we achieve sub-percent agreement (for multipoles $\ell \gtrsim 5$) between full-sky and flat-sky results for equilateral, squeezed, and folded configurations, using narrow Gaussian radial window functions ($\sigma_z = 0.01$) in both equal-time and unequal-time scenarios. On small scales, where direct full-sky integration becomes computationally prohibitive, our results align with the Limber approximation (where applicable), confirming the robustness and accuracy of our implementation. To facilitate future studies, we provide a Python implementation of our results, which is publicly available on GitHub.
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Cosmology and Nongalactic Astrophysics
Signals from the early Universe: a comprehensive search for primordial features in Planck CMB datasets
Antonio Raffaelli, Mario Ballardini and Nicola Barbieri
We investigate the presence of
primordial oscillatory features in measurements of CMB anisotropies through a systematic comparison of phenomenological templates. Building upon previous searches for
primordial features using Planck data, we compare the full PR3 legacy release with the PR4 (NPIPE) processing to assess how the results depend on the choice of CMB maps and likelihood framework. To maximise our sensitivity to rapidly varying oscillatory signals, we employ unbinned likelihoods. We find that several previously reported indications of oscillatory structure persist across different analyses, although none attains global statistical significance. Furthermore, some anomalies reported in earlier studies are substantially reduced when updated to the new versions of the CamSpec likelihood using Planck PR4 products. For all templates considered, we identify a small number of frequencies in the range $\omega \sim 10-100$ that improve the fit to the CMB data by up to $\Delta\chi^2 \simeq -10$ to $-15$ relative to the featureless reference model. However, this improvement is not supported by a
Bayesian model comparison. The inclusion of three or four additional parameters can reduces the overall predictability of the feature models and leads to an Occam penalty. Finally, after properly accounting for the look-elsewhere effect, the significance of the preferred frequencies is reduced, corresponding to a global statistical significance of at most $2.6\sigma$. We present forecasts for forthcoming CMB experiments, highlighting the decisive role of next-generation polarisation measurements in distinguishing genuine
primordial oscillations from statistical fluctuations and modelling systematics. The upper bounds or uncertainties on the feature amplitudes, expected from the combination of SO and LiteBIRD, improve by more than one order of magnitude.
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High Energy Astrophysical Phenomena
The Northern Cross Fast Radio Burst project: VI. The INCART public database
L. Bruno, G. Bernardi, M. Pilia et al. (+7 more)
Fast
radio bursts (FRBs) are bright (Jansky-level) and short-duration ($\sim 1$ ms) flashes of extragalactic origin. Observations of single events have now been complemented by large-area surveys, delivering FRB catalogues and enabling the first population studies. The Northern Cross (NC)
radio interferometer is one of the instruments performing observations of FRBs. In this work, we present the Italian Northern Cross Atlas of
Radio Transients (INCART), a public platform for the distribution of data products from the NC. INCART makes available to the community the FRBs observed by the NC through manageable frequency-time series
datasets and catalogues with best-fit physical parameters. The design of INCART guarantees the possibility of scientific re-analysis of the FRB properties, in view also of future releases of the processing pipeline. Furthermore, INCART focuses on long-term storage optimisation, which is a key aspect of state-of-the-art instrumentation. Public access to the FRB data from the NC maximises the legacy value of the collection, facilitates the synergy with other publicly-available catalogues, and fosters research group collaborations.
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All authors L. Bruno, G. Bernardi, M. Pilia, D. Pelliciari, A. Geminardi, F. Fiori, V. Galluzzi, G. Naldi, M. Trudu, A. Zanichelli
Earth and Planetary Astrophysics
The Architecture of the 14 Herculis System Suggests Primordial Ejection of a Massive Planet
Tiger Lu, Sarah C. Millholland, Malena Rice et al. (+6 more)
The 14 Herculis system hosts two super-Jupiters on eccentric, significantly misaligned orbits. This orbital architecture represents a dynamical puzzle that demands explanation. In this work, we reproduce the system's dynamical history and current architecture using a large suite of N-body simulations of
planet-
planet scattering. Our results demonstrate that
planet-
planet scattering is able to reproduce 14 Her's peculiar orbital architecture, but only if additional massive bodies were initially present in the system that were subsequently ejected. The mass of any such ejected
planet can in turn constrain the system's initial configuration. We also analyze the present-day secular
evolution of the system and conclude that while there are most likely nontrivial eccentricity and inclination oscillations currently occurring, the magnitudes of these oscillations are not strong enough to allow
tidal forces to meaningfully alter the system's architecture. Finally, we discuss how forthcoming observations from future
Gaia data releases and the Roman mission may situate 14 Her's dynamical history within a broader, population-level framework.
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All authors Tiger Lu, Sarah C. Millholland, Malena Rice, Brennen Black, Daniella C. Bardalez Gagliuffi, William O. Balmer, Laurent Pueyo, Mark R. Giovinazzi, Timothy D. Brandt
High Energy Astrophysical Phenomena
A new completely parameter-free clustering algorithm for unsupervised classification of BATSE gamma-ray bursts
Soumita Modak
Cluster analysis is a widely applied machine learning technique to understand the existing patterns in the population of gamma-ray bursts (GRBs), in order to explore their physical sources. In the present scenario, the number of clusters corresponding to differentiable groups is still under conflict, in spite of numerous attempts with the state-of-the-art clustering procedures. This crucial unknown parameter needs to be evaluated, either directly or indirectly in terms of other tuning parameters, to produce the clusters in GRBs through implementation of an appropriate clustering
algorithm. While most of the applied
algorithms reached two physically explained groups of merger and collapsar predominated by the short and long bursts respectively, other statistical approaches violated this binary partition. However, physical establishment of any additional cluster(s) is not yet confirmed. Therefore, we propose a new
algorithm, from a different stream of clustering referred to as `completely parameter-free', which carries out the classification of GRBs in a manner that has not been tried so far. It indicates two main groups, of short and long duration bursts from the BATSE sample, compatible with the merger-collapsar theory.
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Solar and Stellar Astrophysics
Determining the incidence rate of magnetic $\delta$ Scuti candidates with CoRoT
Gautam Paul, Coralie Neiner, Claude Catala et al. (+1 more)
$\delta$ Scuti
stars are pulsating
stars constituting the $\delta$ Scuti instability strip in the Hertzsprung-Russell (HR) diagram, which consists of A and F
stars. They are in the transition region between high-mass hot
stars and low-mass
solar-like
stars, making understanding their
magnetic properties essential to painting a complete picture of magnetism across the HR diagram. Also, discovering
magnetic stars allows for magneto-asteroseismology, which can be used to determine the internal rotation profile, internal
magnetic field strength, and the efficiency of mixing and transport processes more accurately than classical asteroseismology. To date, surface
magnetic fields have been detected in 13 $\delta$ Scuti
stars. However, the overall incidence rate of magnetism in these
stars remains unknown. Fossil
magnetic fields are detected in 10% of OBA
stars. We investigated the incidence rate of surface
magnetic fields among $\delta$ Scuti
stars using photometric data from the CoRoT space mission. We analyzed long-duration light curves of $\sim$ 1750 $\delta$ Scuti
stars to search for rotational modulation - a photometric signature that indicates chemical or temperature spots at the
stellar surface, usually caused by
magnetic fields. We identified 147 rotational variables that we designate as
magnetic candidates, thus potentially increasing the known population of
magnetic $\delta$ Scuti
stars drastically and suggesting an incidence rate of fossil
magnetic fields in $\delta$ Scuti
stars similar to the incidence rate in OBA
stars in general. Our analysis also revealed a few $\delta$ Scuti – $\gamma$ Dor hybrid
stars in the sample. We determined the rotation periods and projected rotation velocities of the
magnetic candidates in order to select suitable targets for follow-up spectropolarimetric observations aimed at confirming and characterizing their
magnetic fields.
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All authors Gautam Paul, Coralie Neiner, Claude Catala, Jonathan Labadie-Bartz
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Supermassive black hole seeds from direct collapse of CDM-curvature peaks
Marco Galoppo, Marco Bruni and Tomohiro Harada
We study black hole (BH) formation from the nonlinear growth and collapse of
primordial perturbations during the matter-dominated era. Modelling cold dark matter (CDM) as pressureless
dust, we describe the collapse in a fully nonlinear relativistic framework using the Lemaître-Tolman-Bondi (LTB) and quasi-spherical Szekeres solutions as exact perturbations of a spatially-flat Friedmann-Lemaître-Robertson-Walker (FLRW) $\Lambda$CDM background. At first order in relativistic scalar perturbation theory, the growing mode of any relevant quantity can be expressed in terms of the conserved gauge-invariant
curvature perturbation $\mathcal{R}_c$, which acts as a potential for the 3-
curvature of hypersurfaces orthogonal to the matter 4-velocity. We use this result to express the active gravitational mass and
curvature functions of the LTB and Szekeres models in terms of the initial values of $\mathcal{R}_c$ and its spatial derivatives. From these initial
curvature data we derive: (i) the turn-around, collapse, and apparent-horizon formation times, and (ii) the regularity conditions required for BH formation. We show that sinusoidal and Gaussian profiles do not provide viable BH-forming channels, whereas broad compensated
curvature peaks, naturally predicted by peak theory, do. We then estimate the formation times of $10^{3}-10^{6}~\mathrm{M}_\odot$ massive BH seeds produced by the direct collapse of
primordial CDM
curvature peaks, finding full BH formation at
redshifts $z>5$, with core collapse beginning at $10 \lesssim z \lesssim 16$. Finally, we characterize the local dynamics and singularity type of the collapse (point-like, cigar-like, or pancake-like) directly from the initial comoving
curvature data, clarifying the role of the initial shear in selecting the collapse end-state.
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Cosmology and Nongalactic Astrophysics
Cosmo-PINN: A Physics-Informed Neural Network for Cosmological Reconstruction
Andronikos Paliathanasis
We introduce Cosmo-PINN, a Physics-Informed Neural Network for reconstruction of the cosmological theory. In this work we demonstrate the application of the Cosmo-PINN in the reconstruction of the dark energy equation of state parameter $w_{DE}\left( z\right) $ directly from late-time cosmological observations. This framework overcomes the main limitation shared by Gaussian Process and Artificial Neural Network reconstruction approaches, where the recovered solution is driven by the data and it is not necessarily true that it is physically consistent, by
embedding the cosmological constraints directly into the loss function as constraints, ensuring that the reconstructed quantities satisfy the physical laws at every point during the training. For the training of the network, we employed background data, and specifically the
Baryon Acoustic Oscillation from DESI DR2, the
Cosmic Chronometers and three different
Supernova compilations, while we simultaneously introduce the cosmological parameters $% H_{0},~\Omega _{m0}$ and $r_{\mathrm{drag}}$ as trained parameters. The reconstruction shows that the trained $w_{DE}\left( z\right) $ crosses the phantom divide around $z=0.5$ in agreement with the value obtained by the Chevallier-Polarski-Linder model. In the quintessence scenario, the dark energy equation of state parameter is forced to the $\Lambda $CDM limit in the past, that is $w_{DE}\left( z\right) \rightarrow -1 $. Finally, we demonstrate the significance of imposing the physical constraints within the loss function by comparing the Cosmo-PINN reconstruction against a purely data-driven neural network with the same architecture.
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Earth and Planetary Astrophysics
The evolution and internal structure of Neptunes and sub-Neptunes II. Convective mixing and thermal conductivity
Mark Eberlein and Ravit Helled
Sub-Neptunes and Neptunes are often modeled with distinct, fully convective layers. Yet, there are several arguments for compositions gradients that can inhibit convection. In these regions, energy transport depends on the thermal conductivity and radiative opacity. We compare three thermal conductivity models and investigate their impact on planetary
evolution accounting for the possibility of convective mixing eroding composition gradients. Using a modified version of MESA, we model the
evolution of
planets with masses of Mp=5, 10, 15 Mearth and three initial
entropies. We implement thermal conductivities for: pure water, fully ionized matter, and constant electron conductivity. Convective mixing complicates the relation between conductivity,
evolution, and radius. For hot forming
planets with a large composition gradient, where the heavy-element mass fraction changes gradually from the core to the envelope, convective mixing has a large impact on the radius
evolution. In this case, the thermal conductivity is less relevant and the radii converge to similar values after billions of years. For cold forming
planets or narrow composition gradients, convective mixing is less efficient. If the composition profile is not altered significantly, the thermal conductivity becomes critical. It determines how much energy can be trapped beneath stable composition gradients. For intermediate initial
entropies, high thermal conductivity inhibits convection. Further work is required to determine the thermal conductivity for various mixtures expected in sub-Neptune and Neptunes at high densities and temperatures. In addition, further constraints on the
entropy and composition profile after formation can reduce the degeneracy of the planetary
evolution, in particular, the dependence of the radius with time.
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Earth and Planetary Astrophysics
The Shape of (486958) Arrokoth
Simon B. Porter, Kelsi N. Singer, Paul M. Schenk et al. (+6 more)
Here we present an updated shape model of (486958) Arrokoth, the bilobate Kuiper Belt Object (KBO) which the NASA New Horizons spacecraft flew past in 2019. This updated shape model uses all of the resolved images of Arrokoth obtained by the New Horizons LOng Range Reconnaissance Imager (LORRI). We developed an updated shape modeling
algorithm which allowed the shape and rotational pole of Arrokoth to be fit to much better quality with an efficient use of GPU-accelerated features. The resulting model of Arrokoth's contact binary shape is significantly thicker and of larger volume than the one previously published immediately after the flyby by Spencer et al (2020). We show that Arrokoth's smaller lobe Weeyo is roughly spherical in shape, while the larger lobe Wenu is more flattened, with the volume ratio between the lobes being roughly 2:1. Owing to Wenu's oblate shape, Arrokoth's rotational lightcurve would have significantly lower mean reflectance when viewed from subobserver latitudes that would have shown lightcurve variation. We discuss the impact this may have on estimates of the frequency of contact binaries in the Kuiper Belt. We also discuss the implications of this shape for the formation of Arrokoth, particularly in the context of the Streaming Instability.
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All authors Simon B. Porter, Kelsi N. Singer, Paul M. Schenk, Anne J. Verbiscer, Susan D. Benecchi, John R. Spencer, Joel Wm. Parker, Pontus Brandt, S. Alan Stern