Instrumentation and Methods for Astrophysics · Cross-listed from physics.med-ph
Retinal hazards and glare from space mirrors
Salvador Bará
Projects of orbital mirrors reflecting sunlight towards Earth raise reasonable concerns regarding photochemical and thermal retinal hazards and detrimental effects on visual performance (disability glare). This paper addresses these issues based on some current eye safety and glare standards. Telescopic observations of single mirrors appear to pose a significant risk of photochemical retinal hazard. The risk is higher for vulnerable populations. Unaided eye viewing of a mirror keeps the retinal risks low, both photochemical and thermal; however, disability glare may be unacceptably high, affecting awareness and response in critical visual operations. The simultaneous presence of several mirrors in the visual field of the observer, seen with the unaided eye or through optical instruments, will significantly increase all types of hazards. The kind and severity of their combined effects will depend on the angular distance between them. Additional information is needed to evaluate the effects of the transient flashes of light during mirror slewing operations.
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Astrophysics of Galaxies
The extreme Disturbed Galaxy Cluster Sample (eDGeS): Spectroscopy and Dynamical Analysis of the eROSITA-Selected Merging Galaxy Cluster Candidate 1eRASS J025859.4-193727
Anish S. Aradhey, Eleazar R. Carrasco, Alfredo Zenteno et al. (+7 more)
Addressing open questions such as the effect of
galaxy cluster mergers on the
evolution of
galaxies and the self-interaction cross-section of dark matter requires the construction of a large, diverse sample of disturbed
galaxy clusters. One contribution to such a sample is the extreme Disturbed
Galaxy Cluster Sample (eDGeS), an ongoing spectroscopic study of massive disturbed and merging
galaxy clusters selected from complementary surveys. Here, we present our first results from the eROSITA-selected subsample (eDGeS-eROSITA): a dynamical state analysis for the merging cluster candidate 1eRASS J025859.4-193727. We present the first spectroscopic
redshift measurements for 76
galaxies in the direction of the cluster, confirming 51 as cluster members. The cluster displays a line-of-sight velocity dispersion of $\sigma_{\rm{cl}}=808^{+59}_{-66}~\rm{km~s^{-1}}$ and a dynamical mass of $M_{200}=4.47^{+0.94}_{-0.93} \times 10^{14}~M_{\rm{Sun}}$. While the cluster shows no evidence for substructure along the line of sight, the projected distribution of member
galaxies reveals three subclusters, only one of which appears associated with the cluster's X-ray contours. Phase-space analysis reveals a large fraction of recently infallen member
galaxies. Together, this evidence suggests a cluster merger along the plane of the sky. Assuming that the two most massive subclusters are on outgoing (incoming) trajectories after their first pericentric passage, a two-body Monte Carlo model predicts that the two subclusters collided $0.50^{+0.20}_{-0.22}~\rm{Gyr}$ ($1.24^{+0.96}_{-0.38}~\rm{Gyr}$) ago.
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All authors Anish S. Aradhey, Eleazar R. Carrasco, Alfredo Zenteno, Rogério Monteiro-Oliveira, Facundo A. Gómez, Konstantina Boutsia, Esra Bulbul, Guillermo Damke, Amelia Ramirez, Hector Cuevas
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Relativistic Stellar Oscillations from Ultralight Dark Matter
Shanae Oishi, Christopher Reyes and Jeremy Sakstein
Ultra-light dark matter, composed of
bosons behaving as classical waves, can resonantly excite stellar oscillations. In this work, we investigate this phenomenon in relativistic
stars, showing that $\ell=0$ fluid modes can be excited. We derive a framework for calculating the mode amplitude and apply it to
neutron stars to predict the associated surface temperature fluctuations; the resulting signal lies beyond current observational sensitivities. We discuss prospects for extending this approach to other compact objects.
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Astrophysics of Galaxies
Honoring Paris Pişmiş' Legacy: Uniform Astrophysical Properties of 14 Understudied Clusters from Gaia DR3
Seliz Koç, Neslihan Alan, Furkan Akbaba et al. (+1 more)
Open clusters are fundamental tracers of the chemical and dynamical
evolution of the Galactic disc. This study presents a systematic characterisation of 14 understudied open clusters from the Pismis catalogue, selected for a well-defined stellar sequence in Gaia DR3 and spanning a wide range of ages and distances. Using high-precision Gaia DR3 astrometry, we provide a high-fidelity modernisation of these historical discoveries while testing our analytical framework across diverse stellar populations. Membership probabilities were determined via the unsupervised UPMASK
algorithm using Gaia DR3 positions, proper motions, and parallaxes. To ensure high sample purity, the member samples entering the isochrone fits were restricted to P >= 0.90, with astrophysical parameters calculated through membership-weighted likelihoods. Fundamental properties – age, distance, reddening, and
metallicity – were derived using a
Bayesian Nested Sampling approach to isochrone fitting, chosen for its robustness against the parameter degeneracies typical of dense Galactic fields. The 14 systems exhibit a broad range of properties, with ages from approximately 11 Myr to 1.5 Gyr and distances spanning approximately 690 to 5445 pc. These refined, uniform parameters reconcile historical observations with the precision era of modern astrophysics, providing a homogeneous baseline for systems that large-scale automated surveys recover only partially. A direct cross-match against widely used automated catalogues shows that they typically contain only about a third of the members identified here, and substantially less in the most crowded fields, underscoriecific analysis. This workcontributes to a more complete census of the Galactic disc and sets out a reproducible, per-cluster licable to the manycomparable low-latitude systems still to be characterised.
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All authors Seliz Koç, Neslihan Alan, Furkan Akbaba, Olcay Plevne
High Energy Astrophysical Phenomena
Lepto-hadronic modeling of blazars associated with well-reconstructed high-energy neutrino events
Leonard Pfeiffer, Margot Boughelilba, Simone Garrappa et al. (+3 more)
The association of active galactic
nuclei (AGN) with high-energy
neutrinos has been studied through population and individual source analyzes, but whether these associations reflect physical processes or chance coincidences remains open. Blazars, AGN with relativistic jets aligned with the line of sight, spatially consistent with IceCube high-energy events, offer a natural framework to address this question. Combining multifrequency observations with physically motivated emission models allows us to assess whether these sources can plausibly account for the detected
neutrinos. We study six blazars with single gamma-ray counterparts to well-reconstructed IceCAT-1 high-energy events, accounting for the improved localization expected from IceCAT-2, and compile their multifrequency spectral energy distributions (SEDs). We model these sources within a lepto-hadronic framework, exploring their parameter space to reproduce the observed emission while favoring solutions that maximize
neutrino production. The SEDs can be reproduced with compact emission regions close to the broad-line region with moderate Doppler factors. The emission is generally leptonic-dominated, with subdominant contributions from hadronic cascades, except for one source where the gamma-rays are hadronic-dominated. For four, the energy density of the relativistic particles is close to equipartition with the
magnetic field. The predicted
neutrino detection rates reach up to $~5x10^{-2}$ per year, mostly compatible with one observed IceCube event under Poisson statistics. While these blazars are unlikely to significantly contribute to the diffuse
neutrino flux, their properties are consistent with being possible counterparts to individual
neutrino events, driven by contributions of external
photon fields to the hadronic interaction rate, even for sources where these fields have previously been considered as non-significant.
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All authors Leonard Pfeiffer, Margot Boughelilba, Simone Garrappa, Sara Buson, Massimiliano Lincetto, Annette Bremer
Solar and Stellar Astrophysics
Energy redistribution during 2D oscillatory reconnection
Luiz A. C. A. Schiavo, Jordan Talbot, Gert J. J. Botha et al. (+4 more)
Magnetic reconnection is a fundamental energy release mechanism in solar and space
plasmas. However, the distribution of released
magnetic energy among kinetic and internal (thermal) energy during time-dependent reconnection remains largely unexplored. This work aims to study energy conversion in magnetohydrodynamics via oscillatory reconnection (OR) at a 2D
magnetic null point. Using a shock-capturing code, we identify three families of shocks: termination shocks, slow-mode deflection shocks, and Petschek-like shocks (even with uniform resistivity). We measure the time-dependent reconnection rate, finding a peak of $R \approx 0.1$, consistent with a fast reconnection regime. For the first time, we track the energy conversion pathways between
magnetic, kinetic and internal energy across the time-dependent reconnecting system. We find energy exchange is strongly region dependent, with shock locations dominating over the
diffusion region. In the classical incompressible steady-state reconnection models, the
magnetic energy is fully converted into internal and kinetic energy. In contrast, we find that in compressible time-dependent reconnection, the interchange between kinetic and internal energy dominates the system (due to the inclusion of
plasma compressibility).
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All authors Luiz A. C. A. Schiavo, Jordan Talbot, Gert J. J. Botha, Ben Snow, Daniel Johnson, Madeleine L. Combrinck, James A. McLaughlin
Astrophysics of Galaxies
Extreme Enrichment at Cosmic Dawn: Three FeII-Strong Quasars at z > 6 from the JWST Aether survey
Anniek J. Gloudemans, Emanuele Paolo Farina, Roberto Decarli et al. (+22 more)
We present three outliers on the
quasar main sequence at z>6, as revealed by JWST/NIRSpec IFU observations from the Aether survey, a program targeting ~200
quasars at
cosmic dawn. The
quasars, J0216-5226, J0320-3521, and J1429+5447, exhibit exceptionally strong FeII emission and weak H$\beta$ and [OIII] lines, indicating rapid chemical enrichment within the first Gyr of
cosmic history. Their FeII strengths ($R_{\rm{FeII},\lambda4570} \equiv \rm{EW}_{\rm{FeII}}/\rm{EW}_{\rm{H}\beta}$) range between ~2.5-3.6, placing them among the top ~3% of SDSS
quasars at ($0\lesssim z\lesssim 1$). The H$\alpha$ emission lines of J0216-5226 and J1429+5447 imply black hole masses of $\sim1-7\times10^9$ M$_{\odot}$ with $\lambda_{\rm{Edd}}\sim0.1-0.6$, comparable to typical high-z
quasars, although virial black hole masses may be systematically overestimated in strong FeII emitters. In contrast, J0320-3521 hosts a lower mass black hole of $\sim0.2-2\times10^9$ M$_{\odot}$, suggesting possible super-Eddington rate
accretion with $\lambda_{\rm{Edd}}$~0.5-6.0. The IFU data of J0320-3521 reveal a distinct emission-line region at a projected distance of ~1.5 kpc, consistent with either an interacting companion or ionized gas associated to the
quasar. We further identify a complex environment around J1429+5447, including two candidate companion
galaxies or extended ionized gas structures. These
quasars with bright emission-line regions, J0320-3521 and J1429+5447, are
radio-loud sources, while J0216-5226 remains undetected in
radio ($R_{5\rm{GHz,} \,3\sigma}\lesssim4$). Together, these results confirm previous findings that highly enriched, rapidly growing black holes were already in place at
cosmic dawn. Despite the small sample size, our results further highlight the diversity in environment and
radio-jet properties among
quasars that otherwise share the same extreme region of the
quasar fundamental plane.
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All authors Anniek J. Gloudemans, Emanuele Paolo Farina, Roberto Decarli, Klaudia Protušová, Fabrizio Arrigoni Battaia, Eduardo Bañados, Aaron J. Barth, Silvia Belladitta, Manuela Bischetti, Hyunseop Choi, Dominika Ďurovčíková, Anna-Christina Eilers, Simona Gallerani, Thales A. Gutcke, Luca Ighina, Brian C. Lemaux, Federica Loiacono, Yoshiki Matsuoka, Chiara Mazzucchelli, Silvia Onorato, Hyewon Suh, Fabian Walter, Feige Wang, Julien Wolf, Jinyi Yang
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Deep Learning Detection of Beyond-General-Relativity Deviations in Gravitational-Wave Signals: A Detection-Threshold Study with Real LIGO Noise
Muhammad Adnan Shahzad
We study machine-learning detection of controlled beyond-General-Relativity (beyond-GR) deviations in gravitational-wave signals, using both synthetic aLIGO-PSD noise and real LIGO H1 detector strain. Three deviation families are applied to General-Relativistic inspiral-merger-ringdown waveforms: amplitude modulation, phase modulation, and frequency modulation, each parameterized by a dimensionless strength coefficient $\beta$. A hybrid classifier combining a one-dimensional convolutional neural network with ten hand-crafted waveform statistics is trained on GR and modified waveforms and tested on a deviation type excluded from training. The central result is a quantitative detectability curve as a function of $\beta$. Using the real GW150914 strain as a template and real H1 detector noise, we find a detection threshold at $\beta \approx 0.25$, with accuracy rising smoothly from chance at $\beta \leq 0.2$ to perfect classification at $\beta \geq 0.5$. The threshold value is specific to the quadratic-in-time modulation form adopted here and should not be interpreted as a generic constraint on beyond-GR parameters. We nevertheless argue that the negative result at small $\beta$ is informative: it establishes a quantitative limit on machine-learning-only beyond-GR searches in real detector noise, in the absence of matched-filter signal extraction.
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Astrophysics of Galaxies
From observing strategies to velocity dispersion bias: forward modeling unresolved binaries in ultra-faint dwarf galaxies
Xiaowei Ou, Andrew B. Pace, Nitya Kallivayalil et al. (+9 more)
Ultra-faint dwarf
galaxies (UFDs) in the Milky Way are ideal probes of low-mass
galaxy formation and dark matter because they are highly dark-matter dominated. In the lowest-mass systems, however, unresolved binary orbital motion complicates dynamical mass estimates by inflating measured velocity dispersions and biasing the interpretation of the inferred masses. We develop a flexible forward-modeling pipeline, the Binary Observation Simulator, to generate mock multi-epoch radial-velocity observations of binary populations in dwarf
galaxies and to quantify how binary-induced biases depend on both
galaxy properties and observing strategy. We generate mock samples spanning true velocity dispersion of $\sigma_{\rm true}\sim0.75$-$3.5$ km/sec, binary fractions of $0.1$-$0.9$, and multi-epoch baselines of up to $10$ yr. We find that, while multi-epoch monitoring reduces the binary-induced bias, residual contamination remains significant for low-mass
halos: even a $10$-yr baseline can leave $\sim10$-$120\%$ relative bias for systems with $\sigma_{\rm true}\lesssim1$ km/sec. We also note that small sample sizes ($\lesssim20$) introduce substantial
stochastic scatter in the recovered dispersions, sometimes masking the expected improvement from longer observational baselines. Applying the framework to the real $\sim17$-yr Bootes I observing record reproduces the literature velocity dispersions, yields an empirical correction conditioned on that cadence, and shows that redistributing the same observations onto half the number of
stars would have removed roughly half of the residual binary bias. These results emphasize that robust dispersion estimates for the faintest dwarfs require forward modeling of both binary populations and survey cadence.
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All authors Xiaowei Ou, Andrew B. Pace, Nitya Kallivayalil, Amery Gration, Christopher T. Garling, Nathan R. Sandford, Lina Necib, Niusha Ahvazi, Andres Almeida, Kaia R. Atzberger, Yanbo Pan, Jack T. Warfield
Astrophysics of Galaxies
Characterizing the hierarchical structure of filaments I. On the origin of the length-mass (L-M) scaling relation
Rahul Patel, Daniel Seifried and Alvaro Hacar
Aims. Filamentary structures in molecular clouds are widely recognized as fundamental components of
star formation. Observations report a length-mass relation of the form $L \propto M^\alpha$ with $\alpha \simeq 0.5$. We characterize this relation in simulated molecular clouds and investigate the influence of hierarchical fragmentation and spatial resolution. Methods. We apply a two-step filament identification method to high-resolution 3D hydrodynamical and magnetohydrodynamical simulations from the SILCC-Zoom project, combining the Rolling Hough Transform with dendrogram-based segmentation for hierarchical decomposition. We analyze the resulting structures across multiple spatial resolutions. Results. The identified structures span column densities of $\sim 10^{21}$–$\sim 10^{23}\,\mathrm{cm}^{-2}$. Across multiple resolutions and, separately, the full hierarchical decomposition at the highest resolution, the ensemble exhibits a sub-linear $L-M$ relation close to $L \propto M^{0.5}$. When individual structures are traced across resolutions, the slopes remain sub-linear ($\alpha \simeq 0.45$–$0.70$), consistent with the
geometric prediction $L \propto M^{0.5}$ of a fragmentation-driven random walk. In contrast, decomposing individual structures at the highest resolution yields a wide range of slopes ($\alpha \simeq 0.2$–$3$), peaking at $\alpha<1$. A simple toy model shows that this diversity arises from differences in the internal column-density distribution and segmentation geometry. Conclusions. Taken together, these results indicate that the average sub-linear length-mass relation with $\alpha \simeq 0.5$ is a robust property of the hierarchical structure and fragmentation occurring in molecular clouds.
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Astrophysics of Galaxies
Star clusters as tracers of the perturbed southern outer disk of the Large Magellanic Cloud
Matías Chiarpotti, Andrés E. Piatti, Denis M.F. Illesca et al. (+1 more)
The complex interaction history between the Large and Small Magellanic Clouds (L/SMC) has left significant imprints on their structural and chemical
evolution. In this work, we use a sample of 70
star clusters located in the southern outer disk of the LMC ($R > 5^{\circ}$) to trace the magnitude of these tidal perturbations. Using deep $g,i$ photometry from the SMASH DR2 survey and the Automated Stellar Cluster Analysis (ASTeCA) code, we provide a homogeneous determination of cluster ages,
metallicities, and heliocentric distances. Our results show a population with ages ranging from 1.02 to 3.34 Gyr and
metallicities between -0.70 and -0.07 dex. We find that clusters at greater heliocentric distances are predominantly located toward the western regions, facing the SMC. Analysis of the vertical distribution reveals an oscillatory variation in the mean height ($\langle Z \rangle$) relative to the LMC mid-plane and an increase in intrinsic vertical dispersion ($W$) toward the West. These
geometric features are consistent with a corrugated disk structure induced by recent tidal encounters with the SMC. Chemically, the clusters follow the age-
metallicity relationship typical of the LMC and are well-represented by a bursting-type formation model. The lack of chemically distinct clusters suggests that while the interaction was sufficient to dynamically deform and corrugate the outer disk, it did not lead to significant cluster capture from the SMC. We conclude that the southern outer disk remains structurally and chemically part of the LMC, despite being heavily perturbed by tidal forces.
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All authors Matías Chiarpotti, Andrés E. Piatti, Denis M.F. Illesca, Roberto Butrón
Astrophysics of Galaxies
Sub-arcsecond imaging of HCN and CN in the Orion Bar. UV-driven warm Nitrogen chemistry in dense environments
M. Zannese, J. R. Goicoechea, S. Cuadrado et al. (+3 more)
Rotationally excited HCN and CN lines, due to their high critical densities, are often used as tracers of gas densities. ALMA, with its high spectral and spatial resolution, provides unique access to the spatial morphology and kinematics of HCN and CN emission to study the substructures of the molecular cloud edges. We present new sub-arcsecond imaging of HCN 4-3 and CN 3-2 lines to probe the density structure in the Orion Bar. We study their spatial distribution and compare them to other existing tracers inside the PDR. We complemented these data with multiple J lines observed with the IRAM 30m and Herschel
telescopes to study HCN and CN excitation near the dissociation front (DF). We find that HCN and CN emission are more spatially extended toward the more UV-shielded cloud than C2H and H2. However, they both peak very close to the DF, in disagreement with previous lower-angular-resolution observations. This morphology can be explained by the enhanced UV-driven chemistry. In dense and irradiated environments, HCN is efficiently formed via H2+CN. Hence, its emission can also probe warmer gas near the DF. CN emission is observed in the atomic PDR, not accounted by stationary gas-phase chemistry due to the very low H2 abundances. We interpret this as photoprocessing of CN-bearing PAHs. We derive high densities near the DF when comparing observations with RADEX and Meudon PDR Code models. Finally, we do not find evidence of small-scale high-density clumps and argue that the observed density gradient could explain the variation of excitation between the different tracers. We resolve two velocity components in HCN emission: 10.5 km/s (velocity of the Bar) and 11.5 km/s. The very structured emission of HCN observed in this redshifted emission component is more compatible with the signature of the propagation of a UV-induced shock compressing the gas than clumps.
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All authors M. Zannese, J. R. Goicoechea, S. Cuadrado, J. Pety, M. Gerin, E. Chapillon
Solar and Stellar Astrophysics
Extragalactic Multi-Band Exploration of Red Supergiants (EMBERS): Pipeline, Source Classification, and Bolometric Properties of 101,219 Red Supergiants from James Webb Space Telescope Imaging
Aswin Suresh, Charles D. Kilpatrick, Wen-fai Fong et al. (+6 more)
The
evolution of red supergiants (RSGs), especially in their final stages before exploding as hydrogen-rich Type II
supernovae (SNe), remains poorly understood, owing to small samples of well-characterized
stars in the Local Group. We present the largest population study of RSGs to date using $\sim10^5$
stars with bolometric parameters inferred from archival James Webb Space
Telescope/Near-Infrared Camera (NIRCam) imaging of 15
galaxies within 20 Mpc. We also present jwst123, a newly-developed general-purpose NIRCam reduction and photometry pipeline, and its application to our set of 15
galaxies. We build a simulation-based parameter inference framework to rapidly fit multi-band photometry of $\sim1.5$ million luminous
stars in milliseconds per source. Using clustering in the effective temperature ($T_{\rm eff}$)-luminosity ($\log L/L_{\odot}$)-dust optical depth ($\tau_V$) phase space, we introduce a novel method to select RSGs with high completeness and purity. Leveraging the scale of our catalog, we find that the dustiest RSGs prefer metal-rich hosts, and RSG luminosities correlate with host specific
star formation rate, suggesting that environment shapes RSG
evolution. While most selected RSGs agree with theoretical stellar
evolution tracks, we identify a new population of 1,669 RSGs that are heavily dust-enshrouded ($\tau_V>4$), overluminous ($\log(L/L_{\odot})>5.55$), or anomalously cool ($T_{\rm eff}<3000\,{\rm K}$), including analogs of known SN progenitors. Our catalog provides a population-scale baseline for understanding massive stellar
evolution and connecting field RSGs to dusty progenitors of Type II SNe.
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All authors Aswin Suresh, Charles D. Kilpatrick, Wen-fai Fong, Maria R. Drout, Daichi Hiramatsu, Luca Izzo, Wynn V. Jacobson-Galán, Armin Rest, Samaporn Tinyanont
Solar and Stellar Astrophysics
A Grid of Contribution Functions to Help the Interpretation of Time-resolved Observations of Brown Dwarfs
Myrla Phillippe, Theodora Karalidi, Elena Manjavacas et al. (+4 more)
We present a grid of thermal emission contribution functions and their corresponding atmospheric spectra model for cloudy and cloud-free brown dwarfs, spanning effective temperatures $T_{\rm eff} \in [500, 2000]$ K, surface gravities $\log g = [3.5, 5.5]$ [cgs], sedimentation efficiencies $f_{\rm sed} = 1, 2, 3, 4$ and 8, and eddy
diffusion coefficients $\log K_{\rm zz} = [6, 11]$. We use temperature-pressure profiles from the Sonora Diamondback models in conjunction with the picaso radiative transfer code and the cloud modeling code virga, to explore how different atmospheric parameters influence the vertical distribution of emitted radiation for atmospheres in chemical
equilibrium. We confirm that cloud opacity significantly impacts atmospheric emission depth in prominent molecular features such as CH$_4$, H$_2$O, CO, NH$_3$, CO$_2$, and atomic features Na and K. The atmospheric emission depth varies most notably in the $J$-band, and at mid-resolution spectra in the Na and K doublets. Our analysis highlights pressure-wavelength differences between cloudy and cloud-free atmospheres for characterizing L, L/T transition, and T-type brown dwarfs and demonstrates how contribution functions can guide targeted spectroscopic investigations. To facilitate observational planning, we provide an accessible database and web-based application that enable the community to compare observational data with our model grid of spectra and contribution functions with a wavelength range of 0.5 - 30 $\mu$m.
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All authors Myrla Phillippe, Theodora Karalidi, Elena Manjavacas, Natalia Oliveros-Gomez, Daniel Apai, Jonathan Fernandez, Kieran M. Manjrawala
Instrumentation and Methods for Astrophysics
Gravitas: A Browser-Based Astrophysics Laboratory for Prediction, Measurement, and Discovery
Carl Ziegler
Astronomy students are often asked to reason about systems that cannot be handled in a laboratory, evolve over inaccessible timescales, or reveal themselves only through indirect measurements. Gravitas is a free, browser-based astrophysics environment designed to turn those limitations into opportunities for experimentation. Its version 1.0.0 release combines a configurable gravitational sandbox with 59 ready-to-run scenarios and 22 guided investigations comprising 636 steps and roughly 15-19 hours of structured work. Students can build and alter systems, change reference frames, measure distances, angles, periods, energies, forces, and orbital elements, and observe simulated systems through transit, radial-velocity, astrometric, rotation-curve, stellar-
evolution, and gravitational-wave displays. Guided activities use a predict-test-measure-revise-explain cycle, retain the student's evidence, and export a report for submission. Instructor guides, answer keys, short classroom routes, lecture and embed modes, reproducible share links, Spanish localization, keyboard-accessible navigation, and offline operation lower the practical barrier to adopting the simulation in introductory astronomy and physics courses. A public dashboard reports 243 scientific checks across 25 areas and names the sources and tolerances behind them. This article describes the learning experiences available in Gravitas, illustrates several ways it can be used from a brief demonstration to a full laboratory exercise, and states the scientific scope and limitations of the models. The aim is not to replace quantitative calculation or observation, but to give students a place where they can make a prediction, change one thing, measure what follows, and build an explanation from their own evidence.
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Solar and Stellar Astrophysics
Mapping Molecular Ion Distributions in a Diverse Sample of Protoplanetary Disks
Deryl E. Long, L. Ilsedore Cleeves, Charles J. Law et al. (+10 more)
Observations of ionization-tracing molecules in protoplanetary disks suggest that their ionization environments are diverse due to varying degrees of
cosmic ray modulation, stellar activity, and environmental differences that alter the impact of ionizing radiation. To better understand ionization chemistry in disks, we present the largest survey of resolved observations of molecular ions to date. Using new and archival ALMA observations we detect HCO+, H13CO+, N2H+, and DCO+ toward seven protoplanetary disks (AS 209, DM Tau, GM Aur, HD 163296, LkCa 15, MWC 480, and V4046 Sgr). We compare distributions of ions to continuum features and find no robust relationships between the two. The observations do, however, reveal distinctions between Herbigs and T-Tauris and hint at a dichotomy between two types of T-Tauri ionization environments. The Herbig sources exhibit unique centrally-peaked N2H+ J = 4-3 emission, which we speculate could be tracing either a highly ionized surface layer or a zone of CO destruction, possibly due to their strong UV fields. Three T-Tauri sources in our sample exhibit bright, radially coincident rings in all optically thin molecular ion lines. We speculate that these radially coincident ion rings are evidence of a global change in ionization, possibly at the edge of a T-Tauriosphere. While it is not yet clear what factors most strongly influence the distribution of ion emission, this survey more than doubles the number of resolved ion observations in disks and points to potential distinctions in ion emission morphology related to the central
star and environment.
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All authors Deryl E. Long, L. Ilsedore Cleeves, Charles J. Law, Fred C. Adams, Dana E. Anderson, Sean M. Andrews, Edwin A. Bergin, Jane Huang, A. Meredith Hughes, Chunhua Qi, Kamber R. Schwarz, Jacob B. Simon, David Wilner
Cosmology and Nongalactic Astrophysics
Monitoring the power spectrum of magnetic field fluctuations across the simulated intracluster medium
T. Bartalesi, F. Vazza, S. Ettori et al. (+2 more)
Thanks to the current and forthcoming
radio interferometers, Faraday rotation measure maps extend out to the outskirts of
galaxy clusters. Interpreted through models of the
magnetic power spectrum, these maps can provide stringent constraints on the properties of the
magnetic field of the intracluster medium (ICM). Our goal is to ascertain how the
magnetic power spectrum varies with the environment and dynamics of the ICM in a post-merger
galaxy cluster formed in a state-of-the-art non-radiative cosmological magneto-hydrodynamic simulation. We divide the simulated cluster into cubic subboxes with side length 950 kpc and compute the kinetic and
magnetic power spectra in each. Starting from a "dynamo-only" functional form proposed in previous works to describe
magnetic fluctuations amplified by the small-scale dynamo, we introduce an additional Kolmogorov-like component to account for the contribution of unamplified
magnetic field patches. We fit this extended model to the
magnetic power spectrum of each subbox individually using a Markov chain Monte Carlo method and examine scatter plots of the inferred parameters versus the local ICM properties evaluated in the corresponding subboxes. The extended model reproduces the
magnetic power spectrum data well in most subboxes, whereas the "dynamo-only" model fits these data well only in subboxes not too far from the center. The inferred parameters exhibit substantial subbox-to-subbox variations that correlate significantly with the local ICM density and clumpiness. These correlations suggest that the
magnetic power spectrum is closely linked to the local ICM environment, and may help observers in the interpretation of Faraday Rotation data.
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All authors T. Bartalesi, F. Vazza, S. Ettori, C. Nipoti, P. Dominguez-Fernandez
Astrophysics of Galaxies
MSA-3D: A Diversity of Dust Attenuation Profiles Across the Epoch of Thin Disk Emergence
Ivana Barišić, Tucker Jones, Naveen Reddy et al. (+13 more)
We present spatially resolved measurements of dust attenuation and
star formation in 18 main-sequence
star-forming
galaxies at z$\sim$1 from the MSA-3D survey, obtained by mapping the Balmer emission lines at $\sim$1 kpc resolution with JWST/NIRSpec's MSA in a slit-stepping strategy. We investigate the diversity of radial attenuation profiles, and how the spatial variation affects attenuation and
star formation rates (SFR) derived from single-aperture measurements. We find a notable diversity among radial attenuation profiles: some
galaxies exhibit centrally peaked attenuation, but the majority exhibit flat or even positive radial profiles, with large variation at a fixed stellar mass. This diversity may reflect different evolutionary pathways shaped by various mechanisms such as disk settling, merging, and internal processes. We examine possible biases arising from single-aperture and integrated measurements and find that, while they can under- or over-estimate attenuation and SFRs for individual
galaxies, the sample-averaged trends remain roughly unchanged, with the derived SFRs consistent with the
star-forming main sequence, and a small scatter. From our sample, we find a median stellar-to-nebular reddening ratio f = E(B-V)$_{\rm star}$/E(B-V)$_{\rm gas}$ of 0.88 with an interquartile range of 0.51-0.96, suggesting relatively uniform dust distributions even in intermediate-mass
galaxies (stellar masses $\sim 10^9$-$10^{10.5}~M_{\odot}$). Our results highlight the importance of spatially resolved attenuation measurements for accurately tracing
star formation and understanding the evolving dust geometry in
galaxies during a critical epoch of morphological transformation.
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All authors Ivana Barišić, Tucker Jones, Naveen Reddy, Matthew Malkan, Ryan Sanders, Alaina Henry, Ayan Acharyya, Kevin Bundy, Juan M. Espejo Salcedo, Karl Glazebrook, Themiya Nanayakkara, Danail Obreschkow, Namrata Roy, Takafumi Tsukui, Benedetta Vulcani, Xin Wang
Cosmology and Nongalactic Astrophysics
A Global Overview of Starobinsky Inflation beyond slow-roll with CMB-BAO data
Tarun, Tanmoy Modak and Björn Malte Schäfer
We perform a global analysis of the Starobinsky inflation using most recent CMB data from ACT and SPT together with DESI BAO measurements. By directly solving the equations of motion, we find relatively stronger constraints on the model parameters than those obtained under the slow-roll approximation from the baseline $\Lambda$CDM parameters $A_s$ and $n_s$. We translate these constraints into limits on the reheating temperature. We also discuss the dependence of the prior choices of the model parameters. Further, the correlation of the model parameters with the BAO parameter $r_d h$ is also studied. We further investigate the impact of the global analysis on the dimension-six $R^3$ modified Starobinsky model, deriving constraints on its additional parameters. Finally, we also provide parameter limits on the effective inflationary Hubble slow-roll (HSR) and potential slow-roll (PSR) parametrization.
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Astrophysics of Galaxies
Reconstructing the Projected Dark Matter Field across 0.1-100 Mpc Scales from the SDSS Survey
Kunyao Zhao, Yingjie Peng, Dingyi Zhao et al. (+16 more)
Dark matter sets the gravitational environment in which
galaxies form and evolve, but cannot be observed directly. We present a conditional
diffusion model that reconstructs the projected dark matter density field from the
galaxy stellar-mass density field for direct application to
galaxy surveys. The model is trained on CAMELS and validated on the independent IllustrisTNG300-1 simulation.
Halo masses inferred from the reconstructed projected-aperture measurements agree well with the corresponding true values, with a scatter below 0.2 dex. On 100 kpc scales, reconstructed surface densities show a typical scatter of ~0.3 dex in the regime most relevant for observations. We apply the model to SDSS
galaxies with $M_\star\ge10^9\,M_\odot$ in a contiguous low-
redshift region. Averaging over 100
stochastic realizations, we reconstruct and publicly release a projected dark matter field covering $90\times90\,(h^{-1}\mathrm{Mpc})^2$ with a pixel size of $0.097\,h^{-1}\mathrm{Mpc}$. This pixel area corresponds to the characteristic projected area of
halos with masses of ~$10^{10.6}\,h^{-1}\,M_\odot$. The map reveals the multiscale projected
cosmic web, including cluster-scale overdensities, filaments and voids. Projected-aperture masses are statistically consistent with SDSS group-catalog masses, while the derived
halo mass function broadly matches mock-catalog expectations. The reconstructed projected potential places Coma in one of the deepest wells and near a convergence region of the inferred projected acceleration field, suggesting that the reconstruction retains both local overdensities and coherent large-scale projected gravitational structure. This work shows that
diffusion-based dark matter reconstruction can be applied to real
galaxy surveys, enabling
halo-mass- and spatially resolved dark-matter-environment-based studies of
galaxy evolution in SDSS and future wide-area surveys.
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All authors Kunyao Zhao, Yingjie Peng, Dingyi Zhao, Xiaohu Yang, Luis C. Ho, Kai Wang, Jing Dou, Zeyu Gao, Qiusheng Gu, Yukun Liu, Roberto Maiolino, Houjun Mo, Alvio Renzini, Canpo Su, Bitao Wang, Yu-Chen Wang, Bingxiao Xu, Feng Yuan, Xingye Zhu
Earth and Planetary Astrophysics
JWST Reveals Refractory-Rich Water Ice in Interstellar Comet 3I/ATLAS: Evidence for a Continuum of Grain Properties across Protoplanetary Disks
Silvia Protopapa, Michael S. P. Kelley, Martin A. Cordiner et al. (+12 more)
We present JWST/NIRSpec PRISM observations of the interstellar comet 3I/ATLAS obtained on 2025 August 6 (Epoch 1), 2025 December 22 (Epoch 2), and 2026 April 1 (Epoch 3), spanning eight months around perihelion at heliocentric distances of 3.3, 2.4, and 5.7 au, respectively. The spectra reveal a broad 3 $\mu$m absorption band together with H$_2$O, CO$_2$, and CO gas emission. Unlike previously reported water-ice-rich Solar System comae, the strong 3 $\mu$m absorption is accompanied by weak or absent 1.5 and 2.0 $\mu$m water-ice bands. Spectral modeling indicates that the observations are best reproduced by submicron- to micron-sized water-ice-bearing aggregates containing refractory material. Compared with Epoch 1, the Epoch 3 spectrum favors the presence of a second population of larger, micron-sized, ice-rich aggregates and exhibits a subtle Fresnel-like structure near 3.1 $\mu$m, consistent with crystalline water ice. The observations can be explained by either crystalline water ice at both epochs, with the spectral
evolution arising primarily from changes in grain size and refractory mixing, or an
evolution from an amorphous-like to crystalline state. The spectral properties of 3I bridge those of water-ice-bearing Solar System comae and several spectral classes of mid-sized trans-Neptunian objects, suggesting that the icy building blocks of planetesimals formed in different protoplanetary disks may span a continuum in the physical state of water ice, ranging from pure ice grains to water-ice-bearing aggregates with varying refractory content at submicron-to-micron scales, with 3I extending toward the refractory-rich end of this continuum.
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All authors Silvia Protopapa, Michael S. P. Kelley, Martin A. Cordiner, Stefanie N. Milam, Dennis Bodewits, Steven B. Charnley, Maria N. Drozdovskaya, Sara Faggi, Davide Farnocchia, Aurélie Guilbert-Lepoutre, Marco Micheli, Nathan X. Roth, Megan E. Schwamb, Darryl Z. Seligman, Geronimo L. Villanueva
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Lukewarm inflation and the QCD axion
Paulo B. Ferraz, António Torres Manso and João G. Rosa
We show that a late period of warm inflation, at temperatures just above the QCD scale, can dilute the abundance of the QCD
axion produced by the misalignment mechanism, thus avoiding the need to fine-tune the initial misalignment angle in scenarios with an
axion decay constant close to the GUT scale. We develop a concrete realization of this lukewarm inflation stage involving right-handed
neutrinos in 0.1 - 1 GeV mass range and an associated scalar sector, showing that coherent
axion oscillations are damped during this period. In this scenario, a previously generated large baryon asymmetry may also be diluted to yield the observed value, and lukewarm inflation is followed by an early-matter era dominated by the lightest right-handed
neutrino, before it decays into Standard Model states. This model can be tested via changes to the number of relativistic species and the induced small-scale enhancements of the primordial
curvature power spectrum, leading to primordial black holes and scalar-induced gravitational waves.
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High Energy Astrophysical Phenomena
Hydrodynamic Simulations of Eccentric Black Hole Encounters in AGN Discs
Andrew Imai, Henry Whitehead and Bence Kocsis
We investigate close encounters between stellar-mass black holes (BHs) in the gaseous discs of active galactic
nuclei (AGNs), during which binary black holes (BBHs) may form. We perform a suite of 483 2D adiabatic viscous hydrodynamic simulations within a shearing box prescription using the Eulerian grid code Athena++. We co-evolve the two embedded BHs with the gas. To probe the dependence of capture on non-circular initial conditions, we vary the initial radial separation $b$, the eccentricity $e$ of one of the stellar BHs around the central supermassive black hole, and the eccentric phase angle $\phi_e$. We consider eccentricities from $e=0$ to $e=0.1$ and compare them with the local disc aspect ratio $h=H/R_0\simeq0.005$. We find that small eccentricities shift the capture window in the parameter space. Eccentricities of order the disc aspect ratio, in particular $e\sim h$–$2h$, produce successful captures at initial separations that do not capture in the circular models. By contrast, systems with $e \gg h$ retain less gas before encounter and have lower capture fractions across the sampled parameter grid. We find that the first periapsis distance is a useful predictor of direct capture. Predicting direct capture for $r_{\rm p}<0.1r_H$ correctly classifies $92.7\%$ of Hill sphere encounters. The Hill sphere gas mass helps identify gas-poor failures, but provides no clear additional capture boundary within this suite, in which the initial disc density, temperature, and viscosity parameter are held fixed. Pre-encounter eccentricity modifies gas-assisted BBH formation through its combined effects on the first-encounter geometry and the gas reservoir available for orbital energy dissipation.
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Solar and Stellar Astrophysics
Coronal Mass Ejections from Young Suns: An Observational View through the Solar-Stellar Connection
Kosuke Namekata
Kepler and TESS have revealed that magnetically active
stars frequently produce
flares and superflares, raising the possibility that frequent, fast, and massive coronal mass ejections (CMEs) may affect planetary space weather environments. However, observational constraints on stellar CMEs remain extremely limited. Several diagnostics, including Doppler-shifted spectral lines, coronal dimming, and
radio bursts, have been explored mainly for cool dwarfs, while recent observations have begun to extend these searches to young solar-type
stars, which serve as important
benchmarks for the solar-stellar connection. The goal of this review is to summarize the current understanding and recent observational progress on CME signatures from young solar-type
stars, with a primary focus on Doppler-shift methods. It examines how these signatures resemble solar observations and models, what the inferred physical properties can tell us about the occurrence of stellar CMEs and their contribution to stellar mass loss, and how Doppler-shift signatures can be connected with multi-wavelength diagnostics. Comparisons with CME candidates from cool dwarfs and close binaries further place these signatures in the broader context of stellar CMEs in different stellar environments. These results have important implications for the space weather environments of young
planets, while also pointing to key directions for future observations and modeling.
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Earth and Planetary Astrophysics
Does HD 3167 Have Planets with Perpendicular Orbits?
Joshua N. Winn, Jack Lubin, Gu{\dh}mundur Stefánsson et al. (+5 more)
The two transiting
planets of HD 3167 were reported to follow nearly perpendicular paths, with the inner orbit aligned with the stellar equator and the outer orbit nearly polar. This interpretation depends critically on a challenging single-transit detection of the Rossiter-McLaughlin effect of the inner
planet. We observed three additional transits of the inner
planet with the Keck
Planet Finder and analyzed the new data together with two archival ESPRESSO transit
datasets. We do not confirm the previously reported low obliquity. Our analysis favors a projected obliquity of $-66^{+14}_{-12}$ degrees, consistent with coplanar orbits. However, because the best-fit projected rotation velocity is higher than expected, and because the obliquity uncertainty grows substantially when the most discrepant of the five transit
datasets is omitted, we regard the geometry of the HD 3167 system as still unsettled.
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All authors Joshua N. Winn, Jack Lubin, Gu{\dh}mundur Stefánsson, Haochuan Yu, Erik Petigura, Howard Isaacson, Andrew W. Howard, Fei Dai
Cosmology and Nongalactic Astrophysics
Generalised Visibility ILC: a new foreground mitigation strategy for interferometric HI intensity mapping in the low-redshift Universe
M. Ruiz-Granda, A. Mazumder, L. Wolz et al. (+3 more)
HI intensity mapping is a powerful probe of the large-scale matter distribution and of the underlying astrophysics and cosmology. However, its application is limited by the challenge of separating the faint neutral hydrogen (HI) signal from much brighter foreground emission. We present a new non-parametric foreground-cleaning method in visibility space for low-
redshift HI intensity mapping and apply it to interferometric MeerKAT and SKA-Mid-like simulations. Our newly-developed Generalised Visibility Internal Linear Combination (GVILC) method combines Principal Component Analysis (PCA) for foreground subspace identification, informed by a prior HI signal-plus-noise covariance
matrix, with a multi-dimensional ILC in visibility space to suppress foregrounds and recover the HI signal with reduced contamination. The number of modes to remove in the PCA is calculated using a data-driven statistical approach, leading to significant foreground residual suppression with limited HI signal loss. Moreover, GVILC in combination with foreground avoidance can prevent most of the signal loss, while simultaneously recovering modes that were initially contaminated by foregrounds. The mean squared error statistic shows that for both MeerKAT and SKA-Mid-like simulations, GVILC outperforms the foreground avoidance only strategy. We find that including a more realistic HI model with line broadening and spatial correlations between HI and continuum sources leads to increased signal loss after foreground removal, without affecting the number of modes removed by GVILC. This paper demonstrates that GVILC is an effective method to clean foreground contamination in HI intensity mapping with
radio interferometric data, enabling the recovery of cosmological information from previously inaccessible regions of
Fourier space.
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All authors M. Ruiz-Granda, A. Mazumder, L. Wolz, M. Remazeilles, D. Herranz, P. Vielva
Astrophysics of Galaxies
Galactic archaeology meets exoplanets: linking stellar birth radii to exoplanet demographics
M. L. L. Dantas, J. J. García-Delgado, I. Rebollido et al. (+1 more)
Stars observed in the solar vicinity were not necessarily born there. Radial mixing can redistribute stellar populations across the Galactic disc, decoupling their present-day locations from the environments in which they formed. We summarise a framework that combines Galactic chemical
evolution models with a generalised additive model to infer stellar birth radii. We apply it to 1327 predominantly thin-disc
planet hosts with homogeneous ages, Gaia DR3 astrometry, and SWEET-Cat atmospheric parameters. We find that giant-
planet systems preferentially trace metal-rich inner-disc birth environments, whereas rocky-only systems are less centrally concentrated; and no clear relation between radial displacement and detected
planet multiplicity.
Planet-host
stars that migrate towards the inner parts of the
Galaxy have systems with larger orbital separations; however, this may partly reflect the known dependence of planetary orbital properties on host-
star metallicity rather than a causal effect of Galactic stellar migration. These results illustrate how Galactic archaeology can complement
exoplanet demographics by linking planetary systems to their probable birth environments.
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All authors M. L. L. Dantas, J. J. García-Delgado, I. Rebollido, R. Smiljanic
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Probing Scalar-Induced First-Order Phase Transitions with the Diffuse Supernova Neutrino Background
Sudipta Das, Shamik Niyogi and Manibrata Sen
We investigate the possibility of probing a scalar-induced first-order phase transition (FOPT) inside core-collapse
supernovae through the diffuse
supernova neutrino background (DSNB). We consider a light scalar coupled to
neutrinos that is produced and thermalised in the proto-
neutron-
star core. This leads to two distinct
neutrino components: a
prompt contribution from thermally produced scalars and a delayed, spectrally narrow contribution from the decay of coherent scalar excitations due to the FOPT. We study the resulting DSNB signal at Super-Kamiokande, Hyper-Kamiokande, and DUNE, finding a strong dependence on the
neutrino mass ordering. The recent Super-Kamiokande data already constrain the scalar parameter space for inverted ordering and quasi-degenerate
neutrino masses, while future detectors can significantly improve this sensitivity. Our results demonstrate that DSNB measurements can provide a novel probe of finite-temperature scalar dynamics in core-collapse
supernovae.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Lukewarm inflation, primordial black holes and gravitational waves
Paulo B. Ferraz, António Torres Manso and João G. Rosa
We show that a secondary period of warm inflation, at temperatures parametrically below the GUT scale, may not only dilute any unwanted thermal relics formed after reheating but also significantly enhance the power spectrum of primordial
curvature perturbations on small scales. The latter is nearly scale-invariant over an exponentially large range of comoving scales, resulting in a
stochastic gravitational wave background with a nearly constant energy density over a broad range of frequencies and an associated population of sub-solar mass primordial black holes (PBHs). This scenario could, in particular, explain the NANOGrav signal if it persists at much higher frequencies with a comparable magnitude, up to a sharp cut-off, $f_{max}$. The associated PBH mass distribution may exhibit either a peak at a mass $M_*\propto f_{max}^{-2}$ or a broad plateaux above this mass threshold, depending on the spectral tilt. Moreover, in this scenario the NANOGrav signal is compatible with a significant fraction of dark matter in PBHs in the asteroid- and planetary-mass ranges.
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Solar and Stellar Astrophysics
A census of massive eclipsing binaries in the Whirlpool Galaxy
Cheyanne Shariat, Kareem El-Badry, Maude Gull et al. (+3 more)
We present a census of massive eclipsing binary (EB) candidates in the Whirlpool
Galaxy (M51), a face-on spiral
galaxy at 7.5 Mpc with $Z\sim Z_\odot$. Using 34 epochs of red-optical Hubble Space
Telescope (HST) photometry and a single epoch of broadband UV-optical photometry, we identify 173 massive EB candidates ($>5~{\rm M_\odot}$) with orbital periods $P_{\rm orb}$=1-30 days. The sample traces young stellar populations across the spiral arms of M51. Joint light-curve and spectral energy distribution fits for 136 systems yield binaries spanning $T_{\rm eff}=10{,}000$-$50{,}000$ K, $R=7$-$66~{\rm R_\odot}$, and masses of $5$-$120~{\rm M_\odot}$. We use detailed injection-recovery simulations to quantify the survey's completeness and infer intrinsic properties of the massive binary population. At the population level, we infer a close-binary fraction of $f_{\rm close}=27.4\pm7.1\%$ for $2\leq P_{\rm orb}/{\rm d}<20$ and $0.1\leq q\leq1$. Over the same period range, the intrinsic period distribution is consistent with being log-uniform, ${\rm d}N/{\rm d}\log P_{\rm orb}\propto P_{\rm orb}^{\pi}$ with $\pi=0.29\pm0.32$. These demographics broadly match those of massive-
star populations in the Milky Way, LMC, and SMC, with tentative evidence for a lower close-binary fraction at lower
metallicity. Across the $\sim0.2$-$1.1~Z_\odot$ range spanned by these
galaxies, the overall similarities suggest that the formation of close massive binaries depends only weakly on
metallicity. Our survey establishes EBs as a powerful tool for measuring massive-binary demographics beyond the Local Group and provides a rich panchromatic census of $\sim$100,000 luminous
stars and variables in M51.
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All authors Cheyanne Shariat, Kareem El-Badry, Maude Gull, Daniel R. Weisz, Charlie Conroy, Alessandro Savino