Cosmology and Nongalactic Astrophysics
The limits of lattice inflation: a cautionary tale
Will Barker, Benjamin Gladwyn and Sebastian Zell
Cosmological
lattice simulations have become important tools for studying non-perturbative dynamics in the early Universe. Many widely used codes, however, approximate the gravitational background by an exact Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime and neglect metric perturbations. We show that, during inflation, this approximation prevents the freezing of superhorizon modes. During slow roll, the
curvature power spectrum decays as $H^4$, while the deviation becomes substantially stronger during ultra-slow roll. As a result, inflationary observables can be significantly distorted. In contrast, reheating studies appear to be considerably less sensitive to the omission of metric perturbations. We propose a practical criterion for assessing the validity of FLRW simulations based on the inclusion of first-order metric perturbations, and implement it in CosmoLattice.
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Astrophysics of Galaxies
Intermediate-mass black hole seeding in galactic nuclei from star cluster migration
Stefano Torniamenti, Nils Hoyer, Nadine Neumayer et al. (+2 more)
Nuclear star clusters are one of the most favorable sites to host hierarchical black hole (BH) mergers, potentially bridging the gap from
stellar-mass to massive BHs. However, their assembly and the
evolution of their BH populations remain poorly constrained. We investigate the process of intermediate-mass BH (IMBH) seeding in
galactic nuclei from
star cluster migration. We introduce inSpyral, a new semi-analytic model that draws
star cluster populations from a
galaxy formation model (L-
Galaxies 2020),and integrates their
evolution across a wide range of spatial scales, from BH core dynamics to the orbital motion in the host
galaxy. We find that dynamical friction drives the inspiral of the most massive clusters in
galaxies with $M_{\mathrm{\star, gal}} \lesssim 5 \times 10^{10} \,\mathrm{M_\odot}$, seeding their
nuclei with IMBHs as early as $z \sim 6$. The BH mass distribution from BH mergers in migrating clusters extends to $\sim 300 \, \mathrm{M_\odot}$, a factor of five above the upper limit from in-situ formation. If clusters form with sub-parsec scale radii ($\lesssim 0.5 \, \mathrm{pc}$), hierarchical mergers significantly enhance BH mass growth before migration, and seed
galactic nuclei with IMBHs above $10^4 \, \mathrm{M_\odot}$. The most massive and highly spinning gravitational-wave events are well reproduced by BH mergers involving second-generation remnants that experienced relatively small relativistic kicks ($\lesssim 100 \, \mathrm{km \, s^{-1}}$). GW231123 is consistent with BH mergers between a third-generation primary and a second-generation secondary, which occur in
star clusters with mass $> 2 \times 10^{6} \, \mathrm{M_\odot}$.
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All authors Stefano Torniamenti, Nils Hoyer, Nadine Neumayer, Peter J. Smith, Manuel Arca Sedda
Astrophysics of Galaxies
An Analytic Model for Stellar Metallicity Gradient Residuals in Cold, Phase-Mixed Galactic Disks
Shaunak Modak, Zoe Hackshaw and Keith Hawkins
The distribution of
stellar metallicities over phase space in
galactic disks is sculpted by both
star formation and secular orbital transport processes. As a result, chemo-dynamical models that infer radial heating and migration histories from observations typically rely on sophisticated numerical modeling of
stellar distribution functions,
star formation histories, and various dynamical perturbations. Here, we develop a complementary minimal analytic model for constraining radial migration, using
stellar metallicity residuals relative to overarching
galactic metallicity gradients. Incorporating residuals imprinted during formation and produced dynamically, and assuming a cold, phase-mixed
stellar disk, we derive a closed-form expression for the resulting residual distribution. Applying our model to observed [Fe/H] residuals for
stars in the
Galactic thin disk, we find the root-mean-square amplitude of radial migration for
stars of age $\tau$ to be $\langle (\delta R_\mathrm{g})^2 \rangle^{1/2} \approx (2.79 \pm 0.07)\,\mathrm{kpc} \times [\tau/(6\,\mathrm{Gyr})]^{1/2}$, consistent with results derived from more complex numerical frameworks. Our results clarify the physical origins of covariances and degeneracies common across chemo-dynamical transport models, and demonstrate that
metallicity residuals provide a flexible, interpretable probe of radial migration in
galactic disks.
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Cosmology and Nongalactic Astrophysics
Constraints with CMB lensing on dark matter decays to massive decay products
Anna Bencke, Nanoom Lee and Marc Kamionkowski
Motivated by the recent measurements by the Dark Energy Spectroscopic Instrument (DESI) which suggest a late-time matter density approximately 5% lower than that inferred from Planck we investigate models in which dark matter decays to two less massive, and thus warm, states. The decaying dark matter (DDM) models are parameterized by the fraction $f$ of dark matter that decays, the decay rate $\Gamma$, and the fraction $\varepsilon$ of the mass retained by the decay products. To efficiently explore the warm decay product regime, we employ CLASSIER-DDM, a modified version of the public Boltzmann solver CLASS that solves the perturbation equations with DDM via an integral-equation method. We consider DESI DR2
baryon acoustic oscillations and Planck 2018 CMB data including
lensing, and find that DDM models are not favored over the $\Lambda$CDM model. This result arises because CMB
lensing tightly constrains the velocity kicks imparted to decay products. For example, for $f\simeq0.5$, we find $1\sigma$ constraints to the decay-product kick velocities an order of $10^{-2}$ to $10^{-3}$ times the speed of light for decay
redshifts from shortly after recombination until today. Nonetheless, the allowed parameter space includes models with sufficient power suppression at small-scales to potentially address
dwarf galaxy anomalies. Our results also suggest that explanations for DESI that involve dark-matter decays to one massive and one massless particle will be constrained by CMB
lensing.
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High Energy Astrophysical Phenomena
A Multimessenger Analysis of the High-Energy Milky Way: Source Populations Contribute Significantly to IceCube's Galactic Neutrino Flux
Alisha Roberts, Ilias Cholis, Dan Hooper et al. (+1 more)
We perform a joint analysis of the high-energy
neutrino emission observed from the
Galactic Plane by IceCube and the diffuse ultra-high-energy gamma-ray emission measured by LHAASO. We compare this data to models that include diffuse emission from
cosmic-ray interactions in the interstellar medium, unresolved TeV
halos, and unresolved
Galactic neutrino sources. We find that the gamma-ray emission can be explained by a combination of diffuse processes and unresolved TeV
halos. The observed
neutrino emission cannot be generated by
cosmic-ray interactions in the interstellar medium alone, but requires contributions from one or more unresolved source populations. Across a wide range of assumptions about
Galactic cosmic-ray transport, we find that
Galactic neutrino sources contribute significantly to the
neutrino flux observed from the
Galactic Plane and are likely responsible for most of this emission.
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All authors Alisha Roberts, Ilias Cholis, Dan Hooper, Samyak Jain
Astrophysics of Galaxies
Black hole mergers from dense star clusters with realistic binary populations
Christopher E. O'Connor, Kyle Kremer, Saloni Agrawal et al. (+5 more)
We present a suite of 24 full-lifetime simulations of dense
star clusters with the Cluster Monte Carlo (CMC) code, featuring updated input physics and a realistic distribution of initial binary systems. The latter encompasses a mass-dependent binary fraction, period distribution, and eccentricity distribution based on observations of well-studied
stellar populations in the
Solar neighborhood and nearby
star-forming regions. We predict the
cosmic rate, masses, and
spins of binary black hole (BBH) mergers formed through dynamical assembly,
primordial binary
evolution, and hierarchical mergers within dense clusters. As with previous model grids with fewer binaries, dynamically assembled first-generation (1G) mergers dominate the rate of cluster-derived mergers, and the total merger rate is consistent with that inferred from LIGO-Virgo-KAGRA observations as of GWTC-5.0. Our models naturally reproduce key features of the inferred BBH population, including the broken-power-law behavior of the primary BH mass spectrum for $m_1 \gtrsim 20 M_\odot$, the shallower (steeper) slope of the secondary mass spectrum relative to the primary for $m_2 \lesssim 10 M_\odot$ ($m_2 \gtrsim 30 M_\odot$), and the shape of the mass-ratio distribution in the low- and high-mass domains. We predict broad distributions of the
spin parameters $\chi_{\mathrm{eff}}$ and $\chi_{\mathrm{p}}$, consistent with previous studies of dynamical assembly in clusters. The merger rate from
primordial binary systems within clusters is a small fraction of the total; however, their merger products are frequently involved in subsequent hierarchical mergers, with the result that the hierarchical merger rate evolves more steeply than the 1G dynamical merger rate with
redshift.
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All authors Christopher E. O'Connor, Kyle Kremer, Saloni Agrawal, Elena González Prieto, Fulya K{\i}roğlu, Maia A. S. Martinez, Claire S. Ye, Frederic A. Rasio
Earth and Planetary Astrophysics
Resolving protoplanetary H-alpha emission with the high-resolution spectrograph RISTRETTO
J.W. Blackman, C. Mordasini, G.-D. Marleau et al. (+4 more)
Thousands of
exoplanets have been discovered to date, but only a handful of them are young
planets in the latter stages of their formation. H-alpha emission is a strong tracer of this process, but it is difficult to isolate the planetary H-alpha signal from the
stellar signal due to the small angular separation. RISTRETTO is a high-resolution (R~140,000) integral-field unit spectrograph with an attached coronagraph and extreme adaptive system that is currently under construction. Used in tandem with the VLT, its resolving power and seven-spaxel layout is designed to characterise the atmospheres of
exoplanets in reflected light. It can also be leveraged to obtain spatially and spectrally resolved observations of planetary H-alpha emission lines. Using a combination of synthetic and real observations, we determined the detection limits for theoretical observations of protoplanets with on-sky separations of 37-600 mas (the equivalent of 4-70 AU at 113 pc). We used theoretical BT-Settl photospheric spectra, observed HARPS spectra of PDS70, and a model for the line emission at the planetary
accretion shock to estimate the planetary H-alpha signal. Models with the PyEchelle simulator show that the H-alpha emission from theoretical objects similar to the four known protoplanet candidates (PDS70b, PDS70c, WISPIT2b, and 2MJ1612b) can be spectrally resolved with VLT/RISTRETTO down to a line flux between $F\sim(1.4-2.7)\times10^{-16} erg \;s^{-1} cm^{-2}$ with a 1 hour exposure. We show that the planetary H-alpha line can be spatially resolved from that of its
stellar host and that the shape of the line can be used to constrain the pre-shock density (n0) and velocity (v0), thereby enabling new constraints on the
accretion rate and flow geometry. This study and the instrument act as a pathfinder for the next generation of high-resolution spectrographs such as ELT/PCS and ELT/ANDES.
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All authors J.W. Blackman, C. Mordasini, G.-D. Marleau, C. Lovis, M. Bugatti, Y. Aoyama, N. Blind
High Energy Astrophysical Phenomena
Barak Rom and Eliot Quataert
We study the impact of collisions involving red
giants (RGs) in the dense
stellar environments of
galactic nuclei. We analytically estimate when collisions with main-sequence
stars or
stellar-mass black holes can strip a RG's envelope via ram pressure or
accretion-driven shocks, or eject its helium core through gravitational
recoil. At high velocities, $v\gtrsim10^3~{\rm km/s}$, collisions with main-sequence
stars efficiently deplete the RG population. At lower velocities, collisions with
stellar-mass BHs typically dominate over
stellar encounters, but the overall RG destruction rate is low and does not significantly affect the RG population. Nonetheless, these collisions produce low-mass helium white
dwarfs, which are the stripped cores of the disrupted RGs, at a rate of $\sim 500~~{\rm Gyr}^{-1}$. Helium white
dwarfs can produce an interesting class of white
dwarf tidal disruption events around $\sim 10^{5-6} M_\odot$ massive black holes where Carbon-Oxygen white
dwarfs cannot be tidally disrupted outside the horizon. Applied to our own
Galactic Center, we quantify the impact of collisions on the observed population of RGs, as well as the effects of their intrinsic scarcity due to short RG lifetimes. We find that the RG projected density flattens within $\sim1$”, primarily due to collisions for fainter RGs and their short lifetimes for more luminous RGs.
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Solar and Stellar Astrophysics
Encounters of star clusters as a possible source of disturbances in their internal structure
M. D. Sizova, L. A. Maksimova and S. V. Vereshchagin
We searched for past close encounters of the Hyades and Pleiades with all 5736 clusters of the Hunt & Reffert catalog, integrating orbits with galpy over the last 100 Myr and validating candidates by Monte Carlo. Most nominally close pairs are unstable under catalog errors; only two remain reliable: Pleiades and HSC 751 and Hyades and HSC 2986. HSC 2986 coincides with the
star-forming cloud Corona Australis, which the Hyades crossed about 5 Myr ago, passing ~11 pc from its dense core. Such interactions may be the cause of the mini-clusters discovered in the Pleiades.
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Cosmology and Nongalactic Astrophysics
Probing the fate of large primordial perturbations with exoplanets
Théo Paré and Julien Lavalle
We propose ultra-wide-orbit
exoplanets as a novel probe of small-scale dark matter objects. These systems are highly sensitive to gravitational perturbations that could be induced by a
Galactic population of compact
baryon-free dark matter objects – whether point-like or extended. Focusing on ultra-compact minihalos, which may arise from large
primordial perturbations deviating from the canonical scale-invariant power spectrum, we derive new constraints on their injection scale and amplitude. These constraints complement existing dynamical limits and are expected to improve with upcoming
exoplanet surveys. Furthermore, the detection of additional loosely bound
exoplanets with these surveys could significantly tighten these constraints. Beyond constraints, we also identify characteristic observational signatures in these systems that could help trace a population of dark matter objects. All this strengthens the potential of exoplanetary science to probe the dark universe back to its very
primordial properties.
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Solar and Stellar Astrophysics
The impact of the white dwarf initial-final mass relation on star clusters' ages inferred from their cooling sequence
Maurizio Salaris, Santi Cassisi and Luigi R. Bedin
We have investigated and quantified how the choice of the white
dwarf (WD) initial-final mass relation (IFMRs) affects the age determination of
star clusters from the luminosity function of their cooling sequences. We have performed a purely theoretical differential analysis using recent semi-empirical IFMRs across three age regimes: ~ 10 Gyr (old ages), ~ 1 Gyr (intermediate ages), and ~ 100 Myr (young ages), respectively. For each regime, we have considered the age of a representative cluster whose entire WD sequence has already been observed and analysed, and calculated theoretical luminosity functions (varying the IFMR) that include realistic observational errors and binning. We have found that for old ages (as those of globular clusters), the choice of the semi-empirical IFMR introduces age offsets of at most ~0.6 +- 0.2 Gyr, while for intermediate ages the impact is reduced to 0.2 +- 0.1 Gyr, and it becomes negligible at young ages. Additionally, we have employed the
metallicity-dependent IFMR derived by a recent grid of theoretical
stellar evolution models to study whether the predicted
metallicity dependence impacts the ages of old clusters with subsolar metal content. We found that neglecting this predicted
metallicity dependence in old metal-poor globular clusters can lead to an age underestimate of up to 0.8 +-0.2 Gyr. All these age offsets should be interpreted as a systematic uncertainty associated with the choice of the IFMR.
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High Energy Astrophysical Phenomena
Centaurus A Inner Lobes – I. Hydrodynamic modeling of a Precessing Jet
Rita C. Anjos and Brian Reville
We present a numerical investigation into the precessing jets of the inner lobes of Centaurus A, focusing on their dynamical
evolution and interaction with the surrounding medium. Using three-dimensional relativistic hydrodynamic simulations, we model the development of large-scale jet and lobe structures driven by precession. Our setup incorporates physically motivated parameters to reproduce observed morphological features. We compare the resulting structures from our simulations with observed
radio images of Centaurus A, particularly focusing on the S-shaped morphology, the distribution of bright emission regions, and the observed asymmetry between the northern and southern lobes. Our findings indicate a precession period of 1.8 Myr, which reproduces observational characteristics. This study explores the role of jet precession in shaping the inner lobes of Centaurus A.
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Earth and Planetary Astrophysics
The Edges of Planetary Systems: Falling Off the Kuiper Cliff in a Dissipating Gas Disk
Rixin Li and Eugene Chiang
Probably the last planetesimals to have formed from
dust in the
solar nebula are Cold Classical Kuiper belt objects (CCKBOs). To the extent that they are isolated and unchanged since birth, CCKBOs offer direct insights into nebular processes. Their population density drops abruptly beyond a heliocentric radius of $\sim$47 au, a feature known as the "Kuiper Cliff". We show with global, 1D (radial), time-dependent models how gaseous protoplanetary disks that disperse from
magnetic and photoevaporative winds leave behind planetesimal disks with Cliff-like outer edges. The gas disperses from the inside out, creating transitional disks whose inner cavities expand from $\lesssim$ 1 au to $\gtrsim$ 100 au. Gas at the cavity boundary presents a pressure maximum toward which
dust particles drift, triggering the streaming instability which clumps
dust into planetesimals massive enough to decouple from gas. The receding cavity wall thus paves a disk of planetesimals which truncates when
dust and gas are spent. With no fine-tuning, we show how a generic gas disk clearing from the inside out reproduces the Kuiper Cliff and the CCKB surface density. Connecting these global 1D results with published local 3D simulations of
dust and gas, we see how many properties of the CCKB – its radial extent, total mass, individual object sizes, and binary statistics – follow from the streaming instability at work in a late-stage transition disk.
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Cosmology and Nongalactic Astrophysics
Impact of 21-cm foreground mitigation strategies on reionization power spectrum constraints
Sambit K. Giri and Florent Mertens
The 21-cm signal probes the intergalactic medium during the Epoch of Reionization (EoR) but is overwhelmed by astrophysical foregrounds orders of magnitude stronger than the cosmological signal. We evaluate two mitigation strategies: (i) Foreground Avoidance, restricting analysis to the EoR window in
Fourier space, and (ii) Foreground Removal via Gaussian Process Regression, which exploits spectral smoothness to statistically separate contaminants and reclaim modes within the contaminated wedge. Both introduce systematic biases of up to $\approx$1$\sigma$ in astrophysical parameters such as the minimum
star-forming
halo mass and ionising escape fraction, with avoidance posteriors consistently broader than removal owing to its restricted visibility coverage. The global reionization history is recovered within the 95% credible interval, though the neutral fraction at late reionization epochs shows a persistent bias reflecting the difficulty of its inference from the power spectrum alone. Multi-
redshift inference is susceptible to contamination from poorly mitigated bins. Excluding such bins significantly reduces parameter biases, but identifying them requires independent quality metrics. When restricted to identical length scales, both strategies recover similar power spectra, yielding posteriors in similar regions.
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Solar and Stellar Astrophysics
Enigmatic Line Broadening During Solar Flares: Magnetic Field Broadening?
Thomas Gomez, Adam Kowalski, Cole Tamburri et al. (+2 more)
The origin of the extreme broadening observed in chromospheric metal lines during
solar and
stellar flares, particularly Mg II h&k and Ca II H&K, remains poorly understood. These lines often display Lorentzian like wings whose widths exceed standard Stark broadening predictions by factors of approx. 30, with no known collisional mechanism capable of producing such enhancements. We posit that
magnetic fields are responsible for this additional broadening due to the increase of
magnetic activity during
flares. A
magnetic-field distribution of the form where P(B) goes as B^-3 reproduces the observed Mg II profile wings while leaving H I Balmer lines and optically thin transitions largely unaffected. To explain the broadening using
magnetic fields, the high B tail can extend up to 10^6 G with extremely low probabilities where the filling factors are less than about 10^-6. We propose that observations of
flares using spectropolarimetry can verify whether the anomalous broadening is from
magnetic structures in
flare ribbons.
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All authors Thomas Gomez, Adam Kowalski, Cole Tamburri, Graham Kerr, Jackson White
Astrophysics of Galaxies
From THESAN-ZOOM to JWST: Predicting ionizing photon escape and the rise of UV-bright reionization sources
Zebedee Summerfield, William McClymont, Sandro Tacchella et al. (+14 more)
Understanding the sources and
evolution of
cosmic reionization remains a central challenge in astrophysics, with the escape of ionizing Lyman-continuum (LyC)
photons from early
galaxies representing a major uncertainty. In this work, we use more than 35,000
galaxy realisations from the THESAN-ZOOM cosmological radiation-hydrodynamic simulations to identify indirect diagnostics of the LyC
photon escape fraction ($f_\mathrm{esc}$) and the LyC
photon escape rate ($\dot{N}_\mathrm{ion,esc}$) across the
redshift range $z=3-16$. We train random forest regression models using these diagnostics to predict both quantities. We present four models: two trained with the full set of simulation-derived indicators to predict $f_\mathrm{esc}$ and $\dot{N}_\mathrm{ion,esc}$, and two restricted to observables accessible to JWST photometric surveys. We find the 10-to-100$\,$Myr
star-formation rate ratio ($\mathrm{SFR}_{10} / \mathrm{SFR}_{100}$) and the gas-to-
stellar mass ratio ($M_\mathrm{gas} / M_*$) to be the strongest diagnostics of $f_\mathrm{esc}$, suggesting a strong relationship between ionizing
photon escape and gas clearing through bursty
star formation. In contrast, rest-frame UV ($1500 \, \r{A}$) absolute magnitude ($M_\mathrm{UV}$) dominates $\dot{N}_\mathrm{ion,esc}$ prediction. Motivated by the strong predictive power of $M_\mathrm{UV}$, we combine observed UV luminosity functions with derived $\dot{N}_\mathrm{ion,esc} - M_\mathrm{UV}$ relations to construct histories of reionization. These are consistent with observational constraints, avoiding the recently reported crisis in the ionizing
photon budget. Our analysis suggests that the bulk of reionization occurred rapidly after $z \approx 8$, driven by UV-bright
galaxies, with the $M_\mathrm{UV} < -17$ populations providing the dominant contribution.
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All authors Zebedee Summerfield, William McClymont, Sandro Tacchella, Aaron Smith, Rahul Kannan, Enrico Garaldi, Ewald Puchwein, Xuejian Shen, Josh Borrow, A. Lola Danhaive, Laura Keating, Gabriel Maheson, Parth Mehrotra, Charlotte Simmonds, Amanda Stoffers, Mark Vogelsberger, Oliver Zier
High Energy Astrophysical Phenomena
Linear Gravitational Wave Memory Through the Window of Core-Collapse Supernovae
Colter J. Richardson, Anthony Mezzacappa, Haakon Andresen et al. (+1 more)
Low-frequency gravitational waves ($\lessapprox$ 50 Hz) from core-collapse
supernovae are becoming more important for current and future gravitational wave studies. This frequency region is dominated by the global morphology of the explosion and the anisotropic emission of
neutrinos from the event. This paper serves as a brief review of both theory and detection (prospects) for gravitational waves in the low-frequency region. We discuss the generation of the linear gravitational wave
memory sourced from
neutrino emission and show results from an example 15 $M_{\odot}$
Solar metallicity progenitor. We also discuss the detection of the linear gravitational wave
memory in current detectors, utilizing a combination of a linear predictive filter and matched templating. Finally we will discuss detection prospects in future detectors such as
Cosmic Explorer, Einstein
Telescope, the
Laser Interferometer Space
Antenna, and the Lunar Gravitational-wave
Antenna.
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All authors Colter J. Richardson, Anthony Mezzacappa, Haakon Andresen, Michele Zanolin
Earth and Planetary Astrophysics
Hydrogen and Helium Dissolution, Outgassing, and Loss in Evolving Sub-Neptune Magma Oceans: Examining Demographic Features and Radius Evolution
Yao Tang, Jonathan J. Fortney, Laura K. Schaefer et al. (+1 more)
Sub-Neptunes' molten interiors are expected to accommodate large quantities of volatiles, potentially altering their radius
evolution. Previous studies have examined this effect in isolation with simplified
evolution modeling, often assuming idealized interior and atmospheric conditions. To address this limitation, we introduce SEAMIST, a unified
evolution model for sub-Neptunes and super-Earths that self-consistently combines, for the first time, interior structure, cooling, rock/iron solidification, boil-off, photoevaporation, H/He dissolution, and atmospheric composition. SEAMIST considers both a partially soluble case, in which hydrogen partitions into the magma ocean with a fraction set by mantle-envelope boundary conditions, and a fully miscible case, in which hydrogen may fully dissolve into the magma ocean at high temperatures. We identify a novel catastrophic boil-off mechanism, triggered by a positive feedback between hydrogen outgassing and mass loss that can operate billions of years after disk dispersal. In partially soluble models, the impact of H/He dissolution on radius
evolution is modest. This contrasts with previous expectations, as we find that increasing hydrogen abundance from outgassing enhances mass-loss efficiency, counterbalancing volatile replenishment from the rock/iron interior. Fully miscible hydrogen, in contrast, significantly enhances envelope survival especially around low-mass
stars. Overall, at intermediate to low masses, mass-radius curves from partially soluble models match observed distributions. The fully miscible case predicts a pronounced radius peak and excess
planets around low
stellar masses that appear inconsistent with current observations, although it reproduces the observed radius “cliff" near 4$R_\oplus$ at higher masses. Our results suggest that high
metallicity may explain the cliff, although alternatives cannot be entirely ruled out.
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All authors Yao Tang, Jonathan J. Fortney, Laura K. Schaefer, Peter Gao
Astrophysics of Galaxies
Nebular_AGN: A CIGALE module for fitting active galactic nucleus emission lines
Hao Zhang, Patrice Theule, Veronique Buat et al. (+3 more)
Aims. The increasing discovery of high-
redshift AGNs in recent years imposes more stringent requirements on spectral analysis tools for deriving the properties of AGNs and their host
galaxies from emission-line diagnostics. To address this need, we develop a new module for the popular SED-fitting tool Code Investigating
GALaxy Emission (CIGALE), the [nebular_AGN] module, which enables the efficient and flexible simulation and fitting of emission lines originating from the broad-line regions (BLRs) and narrow-line regions (NLRs) of AGNs, and allows the estimation of the physical properties of these regions. Methods. We use the spectral synthesis code Cloudy to construct the database for the new module. Based on the X-ray and
accretion disk continua implemented in CIGALE, we generate the incident radiation fields of the models. We then adopt the AGN geometry and
dust settings implemented in CIGALE to define a flexible set of physical parameters for the gas clouds, thereby producing a comprehensive database for the [nebular_AGN] module. Results. We
benchmark the [nebular_AGN] module using a
quasar composite spectrum, an empirical
metallicity calibration, and observational data from X-ray-selected AGNs. Our module can approximately reproduce the majority of
quasar emission-line profiles, cover the key emission-line ratios observed in AGN samples, and provide an assessment of their physical properties. For specific combinations of parameters, the
metallicity derived by our module is consistent with the empirical formula. We further compare our models with other photoionization models used to simulate AGN NLR emission, and perform a line-sensitivity study to identify the most effective diagnostic lines for each parameter in our module. Finally, we confirm that the
dust attenuation law plays an important role in SED fitting.
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All authors Hao Zhang, Patrice Theule, Veronique Buat, Denis Burgarella, Estelle Pons, Mederic Boquien
Earth and Planetary Astrophysics · Cross-listed from cs.CV
Improving Lunar Topography with Deep Learning Schrödinger Bridges
Matthew Repasky, Erwan Mazarico, Michael K. Barker et al. (+3 more)
Increasing the resolution of planetary topography models can enable a better understanding of surface processes and geomorphology; however, existing analytical super-resolution methods are expensive and difficult to apply at large scales. Generative models provide the tools to learn complex relationships within data and can be applied at scale due to hardware accelerators and parallelization. We present a
diffusion-based Schrödinger Bridge (SB) generative modeling approach for lunar topography super-resolution, connecting the distribution of low-resolution topography to that of high-resolution topography, incorporating physically-constraining optical imagery. Our approach is inspired by existing Shape-from-Shading methods, which improve a priori low-resolution topography by using optical images at the target resolution. We train SBs on a novel
dataset of rendered lunar topography, emulating optical imagery from the Lunar Reconnaissance Orbiter Narrow Angle Camera. The result is a flexible approach for topography super-resolution which can provide pixel-level uncertainties in the reconstruction.
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All authors Matthew Repasky, Erwan Mazarico, Michael K. Barker, Stefano Bertone, Terence J. Sabaka, Yao Xie
Cosmology and Nongalactic Astrophysics
Impact of non-Gaussian likelihood on cosmological constraints from the thermal Sunyaev–Zel'dovich power spectrum: a simulation-based inference analysis
Licong Xu, Íñigo Zubeldia, James Alvey et al. (+2 more)
The thermal Sunyaev–Zel'dovich (tSZ) power spectrum is a sensitive probe of cosmology and cluster astrophysics, but its statistics are non-Gaussian because the signal receives a significant contribution from rare, massive, low-
redshift galaxy clusters. As a result, a Gaussian likelihood fails to describe the statistics of its power spectrum on large scales. We use simulation-based inference (SBI) to test the accuracy of the standard Gaussian power-spectrum likelihood for a Planck-like tSZ analysis. Using
halo-based simulations of full-sky Compton-$y$ maps, we train neural posterior and likelihood
estimators and compare the resulting constraints with those from a Gaussian likelihood assumption. Using only multipoles $\ell < 1000$, we find that the Gaussian likelihood assumption gives unbiased cosmological constraints, while the SBI-based inference shows a mild broadening of the posterior distributions for the amplitudes of residual foregrounds. This suggests that the Gaussian likelihood assumption is sufficiently accurate for cosmological inference for a Planck-like tSZ analysis, while SBI provides a useful validation tool to model non-Gaussian likelihoods beyond analytic approximations.
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All authors Licong Xu, Íñigo Zubeldia, James Alvey, Boris Bolliet, Anthony Challinor
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
A Supernova Constraint on F-theory
Sebastian Vander Ploeg Fallon, James Halverson, Liam McAllister et al. (+1 more)
We study constraints on the
quantum chromodynamics (QCD)
axion in F-theory, a strongly coupled limit of string theory. We build models of QCD from compactifications to four dimensions on
elliptic fibrations over toric threefolds $B_3$, characterized by an integer $N=h^{1,1}(B_3)$. The QCD
axion mass increases with $N$, and we find that models with sufficiently high $N$ are inconsistent with observations of the
neutrino burst from
supernova 1987A, disfavoring large regions of the
moduli space. Specifically, at least $95\%$ of models with $N \ge 8,791$ – a regime that arguably contains the vast majority of known F-theory
topologies – have a QCD
axion mass $m_{QCD}>15~meV$ and are thus constrained. This limit is independent of cosmology. We only consider weakly-curved threefolds, where $\alpha'$ corrections are plausibly negligible.
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All authors Sebastian Vander Ploeg Fallon, James Halverson, Liam McAllister, David J. E. Marsh
Solar and Stellar Astrophysics
Research on the Flat Field Measurement Method of Coronagraph
Yulong Feng, Xuefei Zhang, Hongfei Liang et al. (+4 more)
The
solar corona has an extremely low density, and its brightness is only about one millionth of that of the photosphere. High-dynamic-range imaging of its faint structure is therefore essential for studying coronal heating, coronal mass ejections, and space weather. Quantitative coronagraph imaging requires flat-field measurement and calibration, which underpin intensity calibration, small-scale feature detection, and long-term cyclic analysis. This paper analyzes the coronagraph imaging chain and the origins of flat-field errors, including optical aberrations, stray light, and pixel-response non-uniformity, and summarizes the resulting calibration requirements of next-generation coronagraphs. On this basis, ground-based and space-based flat-fielding methods are systematically reviewed: the ground-based methods include integrating-sphere uniform light sources, opal glass/diffuser plates, clear-sky and thin-cloud backgrounds, and
solar-disk scanning, while the space-based methods include internal light sources and diffuser plates, attitude-roll and off-corona offset observations, and multi-phase statistical self-consistent flat-fielding. Their accuracy, resource cost, and applicability are compared. The review shows that no single method is simultaneously high-precision, easy to update, and engineer-friendly; a hierarchical, multi-method calibration framework is therefore recommended. Finally, a new method is proposed in which lithographically generated structured light fields, combined with
Fourier-optics and machine-learning inversion, are used to estimate the pixel-response function. Preliminary experiments show that this method achieves a lower residual error than the integrating-sphere and opal-glass methods, providing a high-precision reference for future wide-band, high-resolution coronagraph calibration.
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All authors Yulong Feng, Xuefei Zhang, Hongfei Liang, Yu Liu, Mingzhe Sun, Tengfei Song, Mingyu Zhao
Earth and Planetary Astrophysics
Tidal locking as a negative feedback on Earth-like planetary dynamos: Consequences for magnetic shielding and habitability
J. P. Hidalgo and D. R. G Schleicher
We investigate how
tidal locking affects the
magnetic field generation and magnetospheric protection of Earth-like
planets orbiting the habitable zone of M
dwarfs. While the role of
stellar activity has been widely studied, the impact of
tidal locking on the planetary dynamo remains largely unexplored. We develop a framework that couples the
stellar wind with two distinct dynamo paradigms: direct rotational scaling of a dipolar field, and energy-flux scaling where the local Rossby number governs the
magnetic geometry, capturing a rapid transition from a dipolar to a multipolar configuration. We employ a Constant Time Lag model to capture the continuous
tidal spin-down of the
planets, evaluating two distinct planetary interiors: a highly dissipative Modern Earth and a less dissipative, rapidly rotating Early Earth. We find that
tidal locking acts as a severe negative feedback on planetary magnetism across both paradigms, where the dipolar field frequently collapses before full
tidal synchronization is reached. At the inner boundary, nearly all the
planets are rapidly locked and the intrinsic
magnetic fields are significantly attenuated. The outer boundary provides a favorable environment only for early M
dwarfs ($M_\star \gtrsim 0.32~M_\odot$) hosting Early Earth. Here, the combination of non-synchronous rotation and residence outside the sub-Alfvénic regime provides atmospheric protection likelihoods of $97-100\%$. For mid-to-late M
dwarfs, the combination of inevitable
tidal locking and a sub-Alfvénic environment results in a total collapse of the
magnetic shield, reducing the likelihood of atmospheric protection to essentially zero across the entire habitable zone.
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High Energy Astrophysical Phenomena
Spectral Softenings, Composition Bump, and Anisotropy Transition: A Consistent Picture of Cosmic-Ray Origin Below the Knee
Xulin Dong, Yuhua Yao, Shuwang Cui et al. (+1 more)
Recent DAMPE measurements of individual
cosmic-ray components, including carbon, oxygen, and iron, reveal distinct spectral softenings below the knee. The energy spectrum, mass composition, and anisotropy together provide key probes of
cosmic-ray origin and propagation. By incorporating the individual elemental spectra reported by DAMPE, we derive a more complete $\langle \ln A\rangle$ distribution, which smoothly connects to the higher-energy $\langle \ln A\rangle$ measurements from LHAASO and exhibits a pronounced bump-like feature. This feature indicates a transition from the conventional
Galactic cosmic ray source population to a nearby-source-dominated regime. We show that a spatially dependent propagation model with a nearby-source contribution can consistently reproduce the observed spectra, mass composition, and anisotropy. This suggests a unified picture in which
Galactic cosmic rays below the knee arise from multiple source populations jointly constrained by these observables. Leveraging the precise component-resolved spectra from DAMPE, we further predict the transition energies in the anisotropy phase and amplitude for different mass components. Future component-resolved anisotropy measurements by LHAASO will provide a crucial test of this scenario.
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All authors Xulin Dong, Yuhua Yao, Shuwang Cui, Yiqing Guo
High Energy Astrophysical Phenomena
Pulse profile modelling of accreting millisecond pulsars with disc occultation and its impact on parameter inference
Ying-Han Mao, Bas Dorsman, Anna L. Watts et al. (+3 more)
Pulse profile modelling is a relativistic ray-tracing technique used to infer
neutron star mass, radius, and surface hotspot properties from X-ray pulsations. Pulse profile modelling has been widely applied to rotation-powered millisecond
pulsars, where the local environment is relatively empty. Application to accreting millisecond
pulsars is complicated by the geometry of the local
accretion flow, including disc occultation of surface emission. In this work, we extend an established pulse profile modelling code, X-PSI, to incorporate
accretion disc occultation in accreting millisecond
pulsar pulse profile modelling. We quantify how disc occultation depends on system geometry and evaluate its impact on parameter inference. We find that disc occultation is primarily governed by the viewing inclination and can significantly reshape pulse profiles at moderate to high inclinations. Using synthetic
Neutron Star Interior Composition Explorer
datasets, we investigate parameter recovery for two representative hotspot configurations. For hotspots close to the rotational poles, statistically acceptable fits can yield posteriors that deviate noticeably from the true parameters. In contrast, in a case with hotspots located closer to the equator we find more reliable parameter recovery. We further find that neglecting disc occultation can introduce spurious posterior modes with comparable statistical support, potentially affecting the interpretation of inferred
neutron star parameters, suggesting that this effect should be included in accreting millisecond
pulsar pulse profile modelling.
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All authors Ying-Han Mao, Bas Dorsman, Anna L. Watts, Tuomo Salmi, Juri Poutanen, Xiang-Dong Li
Earth and Planetary Astrophysics
A population view of transiting hot giant exoplanets: Tracing Fe and Ti chemistry with ESPRESSO and MAROON-X
Bibiana Prinoth, Vivien Parmentier, Stefan Pelletier et al. (+9 more)
Hot and ultra-hot Jupiters offer a unique laboratory to study atmospheric chemistry at the population level using ground-based high-resolution spectroscopy. Fe and Ti are key tracers of thermal and chemical structure, yet they exhibit different observational trends across the population. We present a homogeneous reanalysis of high-resolution transmission spectra of ten hot and ultra-hot Jupiters observed with VLT/ESPRESSO and Gemini-N/MAROON-X. We search for neutral Fe and Ti absorption and perform injection-recovery tests using models spanning a range of Ti-depletion levels and T-p profiles. For direct comparison across observations, we introduce the relative cross-correlation metric, $\Delta$Ti-Fe. We detect Fe in 7 and Ti in 4
planets above 5$\sigma$. Across the population, $\Delta$Ti-Fe decreases sharply towards lower
equilibrium temperatures. Under the assumption of equal Ti depletion across
planets, isothermal models fail to reproduce this trend, instead requiring a temperature-dependent depletion of Ti that increases toward cooler
planets, consistent with cold-trapping processes in cooler atmospheres. Models with inverted T-p profiles naturally reproduce the decline without invoking temperature-dependent depletion. There, Ti is converted into TiO in deeper, cooler layers and then removed from the gas phase through condensation, leading to strong suppression of the observable atomic Ti signal. Nevertheless, even in the gradient models, overall depletion of Ti relative to Fe is required to match the hottest
planets. Our results demonstrate that observable refractory chemistry is governed by the interplay of molecular partitioning, ionisation, condensation, and cold-trapping processes, as well as the vertical structure of ultra-hot Jupiter atmospheres. Additional observations will be necessary to distinguish between temperature-dependent cold-trapping and overall depletion.(abbrev.)
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All authors Bibiana Prinoth, Vivien Parmentier, Stefan Pelletier, Daniel Kitzmann, Julia V. Seidel, Adrien Simonnin, Valentin De Lia, Sydney Vach, Jens Kammerer, Matteo Brogi, Florian Debras, Michael R. Line
Astrophysics of Galaxies
GATOS XV: A JWST/MIRI survey of extended circumnuclear dust emission in nearby Seyfert galaxies
David J. Rosario, Houda Haidar, Steph Campbell et al. (+32 more)
The subarcsecond angular resolution and stable background of JWST has given us the first high-fidelity images of the arcsecond-scale environment around Active
Galactic Nuclei (AGNs) in the nearby Universe. With mid-infrared (MIR) surface brightness sensitivities that are much deeper than the best ground-based instruments, the Mid-InfraRed Instrument imager (MIRIM) now allows us to understand the structure and thermal properties of
dust using information over wavelengths of $5$-$25$ $\mu$m, almost all of the MIR range. We present a Cycle 1 JWST MIRIM survey of Seyfert
galaxies with the express aim of characterising AGN-heated
dust in the central few 100 pcs, and searching for signatures of
dust-laden
nuclear outflows. This paper outlines the motivation behind the programme, the data reduction and analysis techniques used to isolate the
nuclear and extended emission, and a comparison of the observed MIR structures with those seen in other phases (
stars, ionised and molecular gas, absorbing
dust). In concert with earlier studies that used these data, we conclude that resolved AGN-heated
dust is widespread in the Seyfert population, extending out to a few hundred pcs from the
nucleus and often displaying a higher surface-brightness compared to the more widespread
star-forming dusty circumnuclear disk. Even after accounting for contamination from emission lines in the MIRI filters, we find strong spatial correlations between MIR
dust emission and the AGN-ionised gas in the narrow-line region (NLR).
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All authors David J. Rosario, Houda Haidar, Steph Campbell, John Schneider, Chris Packham, Nancy A. Levenson, Almudena Alonso-Herrero, Richard I. Davies, Dan Delaney, Santiago García-Burillo, Erin K. S. Hicks, Sebastian F. Hönig, Mason Leist, Enrique Lopez-Rodriguez, Miguel Pereira-Santaella, Anelise Audibert, Enrica Bellocchi, Françoise Combes, Ismael García-Bernete, Peter Boorman, Andrew J. Bunker, Luis Colina, Tanio Diaz Santos, Fergus R. Donnan, Poshak Gandhi, Omaira González-Martín, Laura Hermosa Muñoz, Alvaro Labiano, Cristina Ramos Almeida, Claudio Ricci, Rogemar A. Riffel, Dimitra Rigopoulou, Daniel Rouan, Marko Stalevski, Lulu Zhang
High Energy Astrophysical Phenomena
Detecting classical nova-like explosions with LISA
Ethan McKeever, Shu Yan Lau, Hang Yu et al. (+1 more)
Gravitational waves from close binary white
dwarfs will form the bulk of measurements obtained by the
Laser Interferometer Space
Antenna (LISA). Previous studies have highlighted the importance of including the effects of steady-state mass transfer in waveform models as many individually resolvable white
dwarf binaries will be interacting during the LISA observation window. However, few studies have considered the effect of novae on gravitational wave observations and parameter estimations. We fill in this gap by analyzing the detectability of novae in these systems and the biases in physical parameters when these bursts are not considered. We model a nova burst as a rapid loss of mass from the accretor that suddenly shifts the gravitational wave frequency. We analytically predict the signal-to-noise ratios for direct detection of the nova and where bias from mismodeling becomes greater than the statistical uncertainty. We also consider comparison of two halves of future LISA data to detect bursts in a model agnostic way. Our work has implications for identifying and classifying individual nova events as well as constraining the
galactic nova rate throughout the entire
galaxy, a challenging task for optical surveys.
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All authors Ethan McKeever, Shu Yan Lau, Hang Yu, Neil J. Cornish
High Energy Astrophysical Phenomena
Transitions in the Mass-ratio and Spin Properties of Binary Black Holes in GWTC-5
Elizabeth Flanagan, Fabio Antonini, Thomas Callister et al. (+4 more)
We analyze the mass-ratio and effective-
spin ($\chi_{\rm eff}$) distributions of binary black hole mergers in the latest gravitational-wave catalog, GWTC-5, as a function of primary mass. Using hierarchical
Bayesian inference with flexible Gaussian-process population models, we identify four distinct mass regions separated by sharp transitions in both mass-ratio and
spin properties. Below $\sim15~M_{\odot}$, the population strongly favors equal-mass binaries and exhibits a narrow $\chi_{\rm eff}$ distribution peaked at positive values. In the range $18$-$30\,M_{\odot}$, the mass-ratio distribution becomes substantially flatter, while the $\chi_{\rm eff}$ distribution broadens, shifts to a peak consistent with zero, and shows tentative–but not statistically required–evidence for positive skewness. The region associated with the feature near $\simeq35~M_{\odot}$ returns to a narrow $\chi_{\rm eff}$ distribution consistent with
symmetry at zero and strongly favors equal-mass binaries. Above $\simeq 45~M_{\odot}$, both the mass-ratio and $\chi_{\rm eff}$ distributions broaden significantly. The inferred support of the
spin distribution converges toward the range expected for binaries containing remnants of previous black hole mergers, making the highest-mass region fully consistent with a
star cluster population of hierarchical mergers. The close correspondence between transitions in mass ratio and effective
spin suggests that different primary-mass ranges trace distinct formation channels, with isolated binary or triple
evolution likely dominating the lower-mass population and dynamical assembly becoming increasingly important at higher masses.
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All authors Elizabeth Flanagan, Fabio Antonini, Thomas Callister, Debatri Chattopadhyay, Fani Dosopoulou, Isobel Romero-Shaw, Jakob Stegmann