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Physics Astrophysics

astro-ph Watch Astrophysics

Tuesday 30 June

Astrophysics of Galaxies

The Sc, Ti, and V Abundance Discrepancy: Testing High-Mass IMF Variation and Massive-Star Rotation

Soonchul Choi, Eda Gjergo, Youngman Kim et al. (+1 more)

Scandium, titanium, and vanadium can be synthesized primarily in massive stars. Yet many of the current Galactic chemical evolution models under-produce these elements at early epochs. Motivated by evidence that the initial mass function varied in the past on the Galactic disc, we examine how assumptions about massive-star rotation and the initial mass function affect the inferred evolution of Sc, Ti, and V. We compute a grid of one-zone Galactic chemical evolution models that varies the initial rotational velocity of massive stars and the high-mass slope of the initial mass function. We compare the resulting [X/Fe] vs [Fe/H] for X= Sc, Ti, and V tracks and cross-element correlations with Galactic abundance data. We find that adopting rotating massive-star yields with an initial rotational velocity of 300 km/s brings the model trends closer to metal-poor observations, especially for halo stars ([Fe/H] $< -2$), and improves the joint behavior of Sc, Ti, and V. Variations of the high-mass slope of the initial mass function produce a secondary modulation. The remaining tensions, most apparent at solar to super-solar metallicities, motivate future work with a more complete treatment of the enrichment physics and model uncertainties.
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All authors Soonchul Choi, Eda Gjergo, Youngman Kim, Toshitaka Kajino

Solar and Stellar Astrophysics

Formation and Eruption of Filament Channel in Solar Active Region 12975: Insights from Observations and Simulations of Magnetic Field Evolution

Dinesh Mishra, P. Vemareddy and Brajesh Kumar

We studied the magnetic field evolution of active region (AR) 12975 using a time-dependent magnetofrictional (TMF) model. This AR produced two consecutive CMEs associated with M-class flares on March 28, 2022. The AR exhibited a simple bipolar configuration, with new bipolar flux emerging from March 27. These emerging flux regions evolved through shear motions, forming a filament-channel that ultimately erupted on March 28 at 12:00 UT. The simulation, initialized at 12:00 UT on March 26, is driven by electric fields derived from a time-series of photospheric vector-magnetograms. It reproduces the observed coronal evolution, including the gradual development of a sigmoidal, twisted flux rope (FR) over approximately 50 hours. The modeled temporal evolution of magnetic energy and helicity within the computational domain is consistent with the observed injection of both quantities. Furthermore, the ratio of current-carrying to total relative helicity reaches 0.23 at the time of observed eruption, however the torus-unstable regime is attained when the helicity ratio reaches 0.32, approximately 7 hr after the observed eruption. Notably, the FR forms adjacent to pre-existing magnetic fields, and a substantial portion of the coronal structure does not belong to the FR system. Consequently, the derived helicity thresholds vary and deviate from the proposed value of 0.29. While reproducing filament formation with high morphological accuracy, this study underscores the quantitative challenges involved in modeling and evaluating the eruptive behavior of different ARs.
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Astrophysics of Galaxies

Probing IMF Variations in High-Redshift Early-Type Galaxies with SHARP

F. La Barbera, G. De Lucia, F. Ditrani et al. (+9 more)

The stellar initial mass function (IMF), which describes the distribution of stellar masses at birth, is a fundamental ingredient in shaping galaxy evolution. Recent observations indicate that the IMF varies between galaxies, depending on their mass, morphology, and stellar content. In local early-type galaxies (ETGs), spectroscopy, dynamics, and lensing reveal bottom-heavy IMFs in dense central regions, with radial gradients toward a Milky Way-like distribution in the outskirts. Yet, the chemical enrichment of massive ETGs implies a dominant role of massive stars during their early formation phases. These findings can be reconciled if the IMF evolves over cosmic time – initially more top-heavy to enable rapid enrichment, and later dominated by long-lived, low-mass stars. Directly measuring the IMF at z>1 is therefore essential to test such time-dependent IMF scenarios, including variations in the dwarf-to-giant and stellar mass-to-light ratios. To date, no direct observational confirmation of these IMF variations – or of their physical origin – has been obtained. The SHARP spectrograph on the E-ELT, with unprecedented spatial resolution and sensitivity compared to facilities such as JWST, and broader spectral coverage than other E-ELT instruments, will enable spatially resolved spectroscopy of IMF-sensitive features in high-redshift ETGs up to z~3, providing unique insights into the origin of the non-universal IMF in massive galaxies.
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All authors F. La Barbera, G. De Lucia, F. Ditrani, F. Fontanot, P. Franzetti, A. Gallazzi, A. Gargiulo, M. Longhetti, P. Saracco, C. Tortora, A. Vazdekis, S. Zibetti

High Energy Astrophysical Phenomena

JWST Medium-Resolution Infrared Spectroscopy of SN 2022acko: Tracing Molecule Formation in the Nebular Phase

K. Medler, T. Mera, C. Ashall et al. (+28 more)

The Type II supernova (SN II) SN 2022acko was the first to be spectroscopically observed by the James Webb Space Telescope ($\textit{JWST}$). Here, we analyze SN 2022acko's second and third $\textit{JWST}$ spectra obtained at $+259$ and $+368$ d. We identify strong features associated with hydrogen along with Intermediate-Mass and Iron-Group Elements (IM/IGEs). The medium-resolution mode of $\textit{JWST}$/MIRI uniquely enables the isolation of emission features, allowing us to determine the structure of SN 2022acko, directly coupling the spectroscopic features and the explosion mechanism. We find that IMEs display peak velocities of $~ 300$ km s$^{-1}$, significantly larger than the $~ 100$ km s$^{-1}$ measured for H, He, and IGEs. We suggest a bipolar outflow best explains this ejecta distribution, although Rayleigh-Taylor instabilities may also contribute. Additionally, we find a bulk velocity offset of $~ 97.4^{+86.3}_{-42.3}$ km s$^{-1}$ in the ejecta which we associate with the natal kick of a neutron star. CO emission is also detected while no SiO or dust signatures are observed. We fit the CO first-overtone and fundamental bands with MOFAT and find a clumped distribution is required with a CO mass increasing from $1.55\times10^{-4}$ M$_{\odot}$ at $+259$ to $2.47\times10^{-4}$ M$_{\odot}$ at $+368$ d. This CO mass is approximately an order of magnitude lower than that of SN 2024ggi. As the first $\textit{JWST}$ nebular-phase study of a low-mass SN II, this work shows that such events form substantially less molecules than more massive SNe II, with dust formation likely occurring on longer timescales, if at all.
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All authors K. Medler, T. Mera, C. Ashall, P. Hoeflich, E. Baron, M. Shahbandeh, J. M. DerKacy, E. Fereidouni, C. M. Pfeffer, S. Shiber, P. Brown, C. Burns, A. Cikota, T. de Jaeger, A. Do, D. O. Jones, L. Galbany, W. B. Hoogendam, E. Hsiao, K. Krisciunas, S. Kumar, J. Lu, P. Mazzali, N. Morrell, M. Phillips, B. Shappee, M. D. Stritzinger, N. Suntzeff, M. Tucker, L. Wang, Y. Yang

Astrophysics of Galaxies

Chemical evolution of the Milky Way disc with radial gas flows: a Lagrangian approach

Fiorenzo Vincenzo

Chemical abundance patterns result from the interplay between gas accretion, star formation, and radial mixing of gas and stars. Disentangling these processes is crucial to recover the mechanisms shaping the formation and evolution of galaxies. We model the chemical evolution of the Galactic disc in the presence of radial gas flows, to assess their impact on the [O/Fe]-[Fe/H] abundance patterns and on the radial gradients of [Fe/H] and [O/H]. We develop fast, semi-analytic solutions for the gas surface mass density and the abundances of alpha-elements and iron, accounting for radial gas flows and chemical enrichment from core-collapse and Type Ia supernovae. The model follows a Lagrangian approach, using the method of characteristics, reducing the solutions to one-dimensional integrals. We apply our model to the Milky Way disc assuming a two-infall scenario. When radial gas flows are present, the chemical abundances of the gas at a given radius result from its whole inward journey in the disc, reflecting the star formation and accretion experienced at every radius it crossed. The integrated stellar mass along the characteristic is lower than the local value by up to an order of magnitude at v = 1.5 km/s. Models with mild flows of v = 1.5 km/s reproduce simultaneously the observed [O/Fe]-[Fe/H] distribution across the disc, the present-day stellar surface-density profile, and the [Fe/H] and [O/H] gradients, improving also the agreement with the observed age-abundance relations. The stellar mass formed per Type Ia supernova sets the [O/Fe] ratio and departs from its in-situ value by up to ~50 per cent, making the alpha-enhancement the quantity on which radial flows leave their strongest signature. Following the gas along its trajectory is essential to recover the correct enrichment history even for models with mild radial gas inflows. The code is made publicly available.
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Astrophysics of Galaxies

Deep Extragalactic VIsible Legacy Survey (DEVILS): Morphologically-selected galaxy merger fractions and their direct comparison to close-pair samples

Melissa F. Fuentealba-Fuentes, Luke J. M. Davies, Aaron S. G. Robotham et al. (+4 more)

Galaxy mergers are a central driver of galaxy evolution across cosmic time, and thus, quantifying their frequency is critical for constraining hierarchical models of galaxy formation. Motivated by the need to robustly quantify these fractions and their evolution, we build on our previous close-pair analysis by exploring morphological identification techniques within the Deep Extragalactic VIsible Legacy Survey (DEVILS), using the D10 (COSMOS) field, which covers an area of $1.47$ deg$^2$. While close-pairs trace the early stages of galaxy interactions, morphological methods probe more advanced phases of the merging process, including systems with disturbed structures and post-merger remnants. We present galaxy merger fractions over the redshift range $0.2 < z < 0.9$ using visual classification and automated identification based on non-parametric statistics: concentration ($C$), asymmetry ($A$), smoothness ($S$), Gini ($G$), and $M_{20}$, applied to HST/ACS imaging. To enhance the detection of subtle structural perturbations, we measure asymmetry on unsharp-masked images. We find relatively little overlap between visually and automatically identified samples, which highlights their distinct sensitivities and limitations. Moreover, galaxy merger fractions derived from morphological disturbances are consistently higher than those from close-pair counts at all redshifts. This potentially reflects how each method probes different stages of the merger process, with distinct observability timescales, as well as the fact that morphologically disturbed galaxies, at a given redshift, are typically the later-stage descendants of close-pairs from earlier epochs. This comparison allows us to examine systematic differences between identification techniques and assess how they impact the observed evolution of the galaxy merger fraction.
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All authors Melissa F. Fuentealba-Fuentes, Luke J. M. Davies, Aaron S. G. Robotham, Sabine Bellstedt, Claudia D. P. Lagos, Michael J. I. Brown, Malgorzata Siudek

High Energy Astrophysical Phenomena

Photoionization of the Composite Nebula Surrounding NGC 5408 X-1: Implications for Beamed Emission

Jing Guo, Hua Feng, Roberto Soria et al. (+4 more)

NGC 5408 X-1 is one of the best studied ultraluminous X-ray sources (ULXs) and is surrounded by a photoionized nebula. Previous optical spectroscopy established the presence of strong Balmer, [O III], and He II $\lambda4686$ emission from the nebula, but the powering engine remains uncertain. In this work, we present new integral-field observations of NGC 5408 X-1, supplemented by archival long-slit spectroscopy and Hubble Space Telescope (HST) imaging, and confirm the presence of a composite nebula, with a small He III region centered on the ULX and a large, shell-like H II region. We also confirm that the broad He II emission is point-like and most likely associated with the ULX binary system. Photoionization simulations with Cloudy show that the ULX spectral energy distribution (SED), with a total luminosity of $2.4 \times 10^{40}\ {\rm erg\ s^{-1}}$ obtained by fitting the optical/UV/X-ray data, overpredicts both the luminosity and size of the He III region. Instead, adopting the same SED shape with a reduced luminosity of $1.0 \times 10^{39}\ {\rm erg\ s^{-1}}$ together with a blackbody of temperature $30000\ {\rm K}$ and luminosity $1.3 \times 10^{39}\ {\rm erg\ s^{-1}}$ successfully reproduces both the He III and H II regions in terms of their luminosities and sizes. Such a dual-component ionizing spectrum is consistent with HST measurements of the ULX in the optical and UV, while being a factor of 24 lower than the inferred isotropic X-ray luminosity. This implies that the EUV and X-ray emission from the ULX may be mildly beamed toward our line of sight, consistent with the picture of supercritical accretion.
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All authors Jing Guo, Hua Feng, Roberto Soria, Fuyan Bian, Jianfeng Wu, Lian Tao, Jesús M. Corral-Santana

Astrophysics of Galaxies

An Acceleration is Worth a Hundred Thousand Phase Space Measurements

Thomas Donlon II, Sukanya Chakrabarti and Elena D'Onghia

It is now possible to directly measure the accelerations that arise from the distribution of (dark) matter in the Milky Way. These acceleration-based measurements of the local dark matter density are now becoming competitive with estimates obtained through traditional kinematic techniques such as Jeans modeling. While classical methods can now draw on the positions and velocities of many millions of stars, recent acceleration-based studies have used fewer than 100 sources, yet achieve comparable precision. A key limitation of kinematic approaches is their reliance on assumptions of dynamical equilibrium and symmetry; direct acceleration measurements do not inherently suffer from this constraint. We find that, for the specific problem of estimating the local dark matter density, a single direct acceleration measurement can provide information comparable to $\sim$10$^5$ stars. We test the theoretical performance of direct acceleration techniques and Jeans modeling in estimating the local dark matter density using hydrodynamical N-body simulations of a MW-like galaxy, both in isolation and including a Sagittarius-like dwarf to generate disequilibrium. In the equilibrium scenario, Jeans modeling requires one thousand times more sources to achieve the same precision as the direct acceleration approach. This confirms that the per-source information advantage is intrinsic, and does not require disequilibrium to manifest. However, in the perturbed disk, the acceleration-based approach outperforms the Jeans analysis regardless of how many stars are available, due to significant bias in the result inferred from kinematics alone. Our results support earlier findings that non-equilibrium dynamics in the Galactic disk cause Jeans-based methods to systematically overestimate the local dark matter density; we show that this issue may also be present in other types of kinematic studies.
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Earth and Planetary Astrophysics

Formation and evolution pathways of planets. I. Comparison between theory and observations

Yasuhiro Hasegawa, Renyu Hu and Amine Bouzerzour

Discoveries of numerous exoplanets by various methods enable detailed characterization including bulk density. Formation and evolution pathways of planets can thus be probed in the mass-radius and mass-density diagrams. We develop a framework to identify dominant processes shaping parameter space in these diagrams by integrating previous studies. These include interior structure models, gas accretion/retention recipes, and photoevaporative and collisional mass losses. We find that the distribution of planets in the diagrams is diversified by two evolution processes: photoevaporative and collisional mass losses, and the properties of planets before experiencing these processes are consistent with predictions of standard core accretion. In particular, collisional mass growth and loss move planets to the parameter space, which is otherwise occupied by water-dominated (i.e., nearly pure water) planets, gathering non-necessity of invoking such planets. A potentially high abundance of water-rich planets are possible with the ice-to-rock ratio capped at $1/3$, similar to solar system comets. We propose a new classification scheme and apply to observed exoplanets. The classification scheme recovers four canonical planet types widely used in the literature and is expended to eight classes in total due to evolution processes. We divide formation and evolution pathways into four stages (core formation, gas accretion, collisional mass growth and loss, and photoevaporation) and trace how planets populate in the mass-radius and mass-density diagrams with time. We apply the framework to habitable zone planets and discuss possible predictions. This work emphasizes the importance of precise mass and radius measurements, especially for small-sized, potentially habitable planets.
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High Energy Astrophysical Phenomena

A New Relativistic Model for Spectral Formation in Accretion-Powered X-ray Pulsars: Pulse Profiles and Phase-Averaged Spectra

Ethan J. Gibson and Peter A. Becker

We develop a new analytical model describing the radiative and dynamical structure of an accretion-powered X-ray pulsar, including relativistic effects and a detailed representation of the rotational and magnetic geometry of the neutron star and the two accretion columns. The model provides for the first time a simultaneous calculation of both the phase-averaged spectrum and the pulse profile for an accretion-powered X-ray pulsar. The X-ray continuum spectrum is calculated using the analytical model of Becker & Wolff (2022), which assumes a conical accretion column geometry. The trajectory of the radiation escaping from the two columns is tracked through the curved spacetime using the Schwarzschild metric. The angular distribution of the radiation escaping from the surfaces of the columns (the beaming pattern) is represented using a set of "laser-like" emission directions, with associated amplitudes, called weight coefficients, that each contribute "sub-profiles" to the observed pulse profile. The sub-profiles provide basis functions that are used to fit the observed pulse profile. This yields a set of weight coefficients that determine the beaming pattern of the emission from the accretion column. We use the new model to analyze NuSTAR data for Her X-1, allowing the determination of the temperature, accretion rate, and magnetic field strength, as well as the rotational inclination angle and the latitudes of the two magnetic poles. The method also yields the beaming pattern of the emission, hence providing for the first time a self-consistent phenomenological description of the physical and radiative structures of the two accretion columns.
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Monday 29 June

Earth and Planetary Astrophysics · Cross-listed from eess.SP

Earth-baseline VLBI restores the observability of a lunar surface station in joint orbit-and-clock determination

Chakshu Baweja

Lunar positioning, navigation, and timing (PNT) is moving from concept to hardware, ESA's Moonlight/LCNS, NovaMoon reference stations, LunaNet, and Coordinated Lunar Time, all reducing to one estimation core: fix the orbits and clocks of the lunar infrastructure and tie them to an Earth/inertial frame. We ask which measurements make a surface station's absolute position observable, and prove the answer. In a snapshot batch fit, the internal observables (station-to-satellite and inter-satellite ranging plus clock-sync) constrain only relative geometry and leave a six-dimensional rigid-body datum defect: three translations and three rotations of the cluster. The clocks are fully observable, so the defect is purely positional, and closing it needs a tie to the Earth frame. Two such ties exist and are not interchangeable. An indirect tie (Earth-to-satellite ranging through the constellation) reaches the station only when the satellite geometry is rich; a direct tie (an Earth-baseline VLBI delay to the station beacon) fixes it regardless. This gives a conditional design law, not a single number: VLBI restores absolute observability when the constellation cannot supply it, and merely sharpens the bound when it can. For a sparse three-satellite constellation the station lies in the null space of the Fisher information until VLBI is added, reaching a Cramer-Rao bound of 20.1 m; for a rich six-satellite constellation VLBI tightens the bound from 23.2 m to 9.7 m. A single-epoch baseline informs at most two of three axes, so the datum closes at three non-collinear Earth stations. The Gauss-Newton estimator attains the bound (efficiency 1.02), with a 91x median station-error improvement in the sparse regime. The FIM/CRLB engine is validated against NumPy and published closed forms; the lunar application stays modelled, every figure deterministic and reproducible.
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High Energy Astrophysical Phenomena

Understanding Pulsar Wind Nebulae with the SKA

Joseph D. Gelfand, C.-Y. Ng, B. Posselt et al. (+9 more)

Produced by the interaction between the “pulsar wind” powered by the rotational energy of a neutron star and its surroundings, the study of pulsar wind nebulae (PWNe) provides vital insight into the physics of neutron star magnetospheres and ultra-relativistic outflows. Spatially-resolved studies of the continuum and polarized radio emission of these sources are vital for understanding the production of $e^\pm$ in the magnetospheres of neutron stars, the acceleration of these particles (and potentially baryons) to $\gtrsim10^{15}~{\rm eV}$ energies, and their propagation within the PWN and in the surrounding interstellar medium. The significant improvements in sensitivity, dynamic range, timing capabilities offered by the Square Kilometer Array have the potential to greatly improve our understanding of the origin of some of the highest energy particles produced in the Milky Way.
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All authors Joseph D. Gelfand, C.-Y. Ng, B. Posselt, Mallory S. E. Roberts, Subir Bhattacharyya, Shi Dai, Rene Breton, Benjamin Stappers, Andrea Possenti, Jason Hessels, Yifan Sun, Moaz Abdelmaguid

High Energy Astrophysical Phenomena

SN 2023rve: A Type II Supernova with No Nebular Oxygen

Melissa Rosowsky, Stefano Valenti, Aravind P. Ravi et al. (+21 more)

We report on multiband photometric and spectroscopic observations of SN 2023rve, a nearby Type II supernova (SN II) discovered in galaxy NGC 1097 (D=15.4 $\pm$ 3.2 Mpc). Nearby SNe II provide constraints on late-stage evolution and progenitor mass loss, particularly the role of circumstellar material (CSM) in shaping SN II observables. SN 2023rve peaks with an absolute V-band magnitude of -17.1 and declines at a rate of 0.90 $\pm$ 0.02 mag/50 days during the plateau. The bolometric light curve implies a $^{56}$Ni mass of $0.0064 M_\odot$. Using hydrodynamic light-curve modeling, we infer an intermediate-mass progenitor ($\sim14-18 M_\odot$), a low explosion energy of 0.27$\times10^{51}$ ergs, and a dense CSM component with radial extent of $2900 R_\odot$ and density parameter of $10^{18}$ g cm$^{-1}$. This supports growing evidence that enhanced pre-SN mass loss influences the diversity of SNe II. The nebular spectra of SN 2023rve show narrow He I lines and an absence of [O I] lines unprecedented among Type II SNe. Comparison with other SNe II shows that only two other known objects, both with higher velocities, lack oxygen signatures at similar epochs, <10% of the sample. The lack of oxygen emission combined with low explosion energy, a long plateau, and a small synthesized nickel mass may be consistent with partial fallback of material onto the compact remnant. We also discuss alternative explanations for the suppressed oxygen emission, including dust formation, oxygen-calcium mixing, and ongoing CSM interaction.
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All authors Melissa Rosowsky, Stefano Valenti, Aravind P. Ravi, Yize Dong, Nicolas Meza Retamal, K. Azalee Bostroem, David J. Sand, Griffin Hosseinzadeh, Jeniveve Pearson, Anders Jerkstrand, Darshana Mehta, Jennifer E. Andrews, Moira Andrews, Joseph Farah, Emily Hoang, D. Andrew Howell, Daryl Janzen, Saurabh W. Jha, Michael Lundquist, Curtis McCully, Megan Newsome, Estefania Padilla Gonzalez, Manisha Shrestha, Giacomo Terreran

Cosmology and Nongalactic Astrophysics

Square Kilometer Array Synergies for the Epoch of Reionization and Cosmic Dawn

Anirban Chakraborty, Tirthankar R. Choudhury, Kanan K. Datta et al. (+15 more)

Synergies with other instruments will be essential in making, verifying, and interpreting a detection of the cosmic 21-cm signal from the Epoch of Reionization (EoR) and Cosmic Dawn (CD) with the Square Kilometer Array (SKA) telescope. Such synergies can (i) provide prior information about galaxies and the intergalactic medium (IGM) during the EoR/CD; (ii) pave the road to a first 21cm detection by mitigating foregrounds and systematics through cross-correlations; and (iii) give complimentary physical insights into the galaxy – IGM connection. Here we review the current state of synergies and discuss what observations will best compliment SKA-low EoR/CD observations.
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All authors Anirban Chakraborty, Tirthankar R. Choudhury, Kanan K. Datta, Pratika Dayal, Jiten Dhandha, Samuel Gagnon-Hartman, Sambit K. Giri, Adelie Gorce, Caroline Heneka, Anne Hutter, Barun Maity, Suman Majumdar, Andrei Mesinger, Kana Moriwaki, Chandra Shekhar Murmu, Yuxiang Qin, Shintaro Yoshiura, Erik Zackrisson

Earth and Planetary Astrophysics · Cross-listed from cs.LG

Physics-informed Conditional Normalizing Flows for Angles-only Cislunar Orbit Determination

Walther Litteri and Massimiliano Vasile

Generative Astrodynamics is advanced in this work by extending generative modelling to an orbit determination problem in the cislunar environment. The task is formulated as conditional density estimation, aiming to infer the probability distribution of the initial state from angles-only measurements over short observation arcs. A normalising flow is trained on perturbed topocentric observations from Near Rectilinear Halo Orbits, enabling a flexible and potentially multimodal posterior representation. Given new measurements, the learned density is sampled to generate statistically consistent and physics-informed state hypotheses. These estimates are refined via nonlinear least-squares minimisation, providing a competitive warm start for classical algorithms.
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Cosmology and Nongalactic Astrophysics

Cosmological Concordance in an Especially Opaque Universe: A Tentative Cosmological Detection of Physical Neutrino Mass in $\Lambda$CDM

James M. Sullivan, Roger de Belsunce and Mikhail M. Ivanov

The measurement of the sum of neutrino masses is among the primary promises of precision cosmology, achievable by combining complementary early- and late-Universe probes. However, these datasets currently exhibit mild-to-strong disagreements within $\Lambda$CDM and its simplest extensions, giving rise to multiple tensions, including the Hubble tension, the preference for "negative" neutrino mass, and indications of evolving dark energy. It has recently been shown that these tensions can be alleviated by adopting a higher value of the optical depth to reionization parameter, $\tau$, when large-scale cosmic microwave background (CMB) polarization data are ignored. We extend this proposal and show that an especially high prior on $\tau = 0.11 \pm 0.006$ simultaneously addresses all three of these tensions, significantly reducing the need for new physics beyond $\Lambda$CDM. We determine the "concordance" value of $\tau$ by requiring physical neutrino mass and consistency of the Hubble constant, $H_0$, inferred from the CMB and that preferred by the Dark Energy Spectroscopic Instrument (DESI) baryon acoustic oscillation (BAO) and full-shape measurements. Within this high-$\tau$ Universe, we obtain the first $2\sigma$ detection of a positive neutrino mass, $\Sigma m_{\nu} = 0.10^{+0.04}_{-0.05}$~eV at 68% C.L., while restoring cosmological concordance between datasets within $\Lambda$CDM. In particular, low-redshift distance predictions are consistent with DESI BAO observations and the inferred dark-energy equation-of-state parameters are consistent with a cosmological constant, both with and without supernovae data. The concordance power of our $\tau$ prior further motivates new measurements of $\tau$, e.g., through large angular scale CMB polarization observations with the LiteBIRD, CLASS, or proposed PICO experiments. (Abridged)
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Instrumentation and Methods for Astrophysics

SAOImageDS9: An Essential Tool for Astronomical Exploration

Antonella Fruscione, Kenny Glotfelty, William Joye et al. (+1 more)

SAOImageDS9 (DS9) is an open-source, cross-platform application for the visualization and analysis of astronomical data. Developed at the Smithsonian Astrophysical Observatory, DS9 evolved from an example implementation of reusable imaging components into one of the most widely used astronomical display environments. It has remained useful because it supports many astronomical file formats and coordinate systems, can work directly with event data and image cubes, provides interactive region-based analysis, and can communicate with external tools through command-line and messaging interfaces. DS9 is used in research, mission operations, and education across a range of wavelengths and at both ground- and space-based observatories. This paper summarizes the historical development of DS9, its principal capabilities, and its impact on the astronomical community, and concludes with an appendix describing the internal architecture that has supported its long-term sustainability.
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All authors Antonella Fruscione, Kenny Glotfelty, William Joye, Jonathan McDowell

High Energy Astrophysical Phenomena

Energy-Resolved Limits on Orbital X-ray Polarization Modulation in Cygnus X-1

Sohee Chun, Bert Vander Meulen, Kun Hu et al. (+1 more)

Reflection off the companion star and its focused stellar wind is predicted to modulate the X-ray polarization of black hole X-ray binaries at half the orbital period ($P_{\rm orb}/2$), with an energy-dependent amplitude. We test this prediction against all publicly available IXPE observations of Cygnus X-1, comprising 26 time bins of up to one day from 12 observation IDs spanning 2022-2024. Since the normalized Stokes parameters correlate linearly with the spectral hardness ratio in all three energy bands (2-4, 4-6, and 6-8 keV), we employ a simultaneous harmonic regression that decouples spectral variability from orbital modulation at both $P_{\rm orb}/2$ and $P_{\rm orb}$, complemented by direct fitting of 3D Monte Carlo radiative transfer stellar companion and wind-scattering templates. After removing the spectral hardness trend, neither approach reveals statistically significant orbital modulation: permutation tests yield $p > 0.01$ in all bands, with 99% confidence upper limits of 0.25%, 0.63%, and 1.96% on the $P_{\rm orb}$ amplitude and 0.42%, 0.97%, and 2.78% on the $P_{\rm orb}/2$ amplitude in the 2-4 keV, 4-6 keV, and 6-8 keV bands, respectively. The best-fit stellar companion and wind-scattering amplitude scaling factors in the three bands of $A = 0.67 \pm 0.85$, $0.97 \pm 0.62$, and $-1.06 \pm 1.11$ are consistent with a null result. These non-detections are sensitivity-limited, as the predicted stellar companion and wind-scattering RMS amplitudes in the three bands of $\approx$0.10%, $\approx$0.33%, and $\approx$0.49% lie below the statistical noise floor of $\sim$0.18%, $\sim$0.38%, and $\sim$1.01%. We quantify the additional exposure required to detect the predicted signal and constrain the wind physics.
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All authors Sohee Chun, Bert Vander Meulen, Kun Hu, Henric Krawczynski

High Energy Astrophysical Phenomena

Multipolar Magnetic-Field Inference for PSR J0740+6620 with Neural-Network-Accelerated NICER Pulse-Profile Modeling

Farhana Taiyebah, Constantinos Kalapotharakos, Greg Olmschenk et al. (+6 more)

We investigate the multipolar surface magnetic-field structure of the high-mass millisecond pulsar PSR J0740+6620 using the 32-bin bolometric NICER pulse profile of Dittmann et al. (2024). Building on the neural-network surrogate framework of Olmschenk et al. (2025), we model the emitting regions as open-field-line footpoints of an offset dipole plus axisymmetric quadrupole static vacuum field, rather than as prescribed geometric hotspots. We fix the stellar mass, radius, observer inclination, and hotspot temperature ratio to the Dittmann et al. (2024) maximum-likelihood values and explore the resulting 11-dimensional magnetic-field space. To make this feasible, we train convolutional neural-network surrogates on $5.12\times10^7$ synthetic bolometric light curves and use them in a parallel ensemble Markov Chain Monte Carlo calculation on 4000 CPU cores, accelerating likelihood evaluations by a factor of $\gtrsim 400$. We perform independent inferences for two calibrated temperature-weight prescriptions, Tw=1.31 and Tw=1.41, encoding the relative bolometric weight associated with the hotspot temperature difference. The posteriors, posterior-predictive light curves, and maximum-likelihood values are very similar, indicating weak sensitivity to this choice. The offset model reproduces the observed double-peaked profile and yields broad, multimodal posteriors, reflecting both the background-dominated data and degeneracies of the multipolar parameterization. The hotspot-density map shows that pulse phases constrain the approximate azimuthal placement of the emission, while latitude, surface extent, and morphology remain weakly constrained. A restricted zero offset run is disfavored within the adopted field basis. This work extends neural-network-accelerated magnetic-field inference to PSR J0740+6620 and motivates future energy-dependent, force-free, and joint X-ray/$\gamma$-ray extensions.
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All authors Farhana Taiyebah, Constantinos Kalapotharakos, Greg Olmschenk, Wendy F. Wallace, Soumi De, Abu Bucker Siddik, Diane Oyen, Thibault Lechien, Zorawar Wadiasingh

Cosmology and Nongalactic Astrophysics

Testing cosmological structure formation in a Unified Dark Matter-Energy model with fast transition

Diogo Castelão, Alberto Rozas-Fernández and Ismael Tereno

Unified Dark Matter-Energy models (UDM), a class of models where dark matter and dark energy exist as a single cosmological fluid, are an alternative approach to $\Lambda$CDM. In this work we focus on a model with a fast transition between dark matter-like and dark energy-like behaviour. The epoch and rapidity of the transition are the key features to enable the formation of structure in this model. We have studied its viability using CMB and Weak Lensing data with nested sampling inference methods. We found that the preferred region of the parameter space is the one with early and fast transition models, where it also lies the model's $\Lambda$CDM limit. Our study confirms that this UDM model is able to form cosmological structure compatible with the data used.
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Instrumentation and Methods for Astrophysics

SHARPing accretion and outflows in young stellar objects in star forming regions of the outer Galaxy and beyond

Juan Manuel Alcala', Alessio Caratti o Garatti, Linda Podio et al. (+5 more)

As part of the science book of SHARP, we present here the science case of star-disk interaction of low-mass (\Mstar$\leq$2\Msun) young stellar objects (YSOs), in low-metallicity (Z$<$ 0.2 \Zsun) star forming regions (SFRs) and supermassive star clusters, using the SHARP instrument mounted on the ESO-ELT. Extreme adaptive optics (AOs), with a spatial resolution a factor $\sim$3 better than JWST, as well as sensitive multiplexing capabilities, uniquely offered by SHARP, are essential to efficiently survey the whole area of low-Z SFRs and massive clusters in the outer Milky Way (MW) Galaxy and in the Magellanic Clouds (MCs). Using the SHARP exposure time calculator (ETC) we demonstrate that SHARP can achieve the required signal-to-noise, both for the continuum and emission lines, to investigate accretion and outflows in YSOs in distant (d$>$5\,kpc) SFRs, including those relatively embedded. SHARP will be able to observe very faint YSOs ($H\sim$\,24\,mag), allowing us extending studies to very low-mass YSOs in distant SFRs. The performance of SHARP in terms of sensitivity and spatial resolution in the NIR will provide significant insights into the evolution of protoplanetary disks in low-metallicity and massive environments: studies of accretion, jets/winds and photo-evaporation processes, down to the very low-mass ($\sim$0.2\,\Msun) regime in the MCs, and down to substellar YSOs in SFRs of the outer MW Galaxy (d\,$\lesssim$\,10\,kpc), will be possible. SHARP will also be able to observe jets/outflows in targets that are several magnitudes fainter than those reachable with current instruments, and will facilitate studies in low metallicity environments of wide binaries and multiple systems, with separations of $\sim$1600\,au, at a distance $\sim$50\,kpc scale, and of $\sim$150\,au, in regions of the outer MW Galaxy (d $\sim$10\,kpc).
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All authors Juan Manuel Alcala', Alessio Caratti o Garatti, Linda Podio, Mario Giuseppe Guarcello, Loredana Prisinzano, Rosaria Bonito, Paolo Franzetti, Fedor Getman

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

Scalarization and descalarization in hyperbolic encounters of black holes

Frederick C.L. Pardoe and Helvi Witek

We use numerical relativity to study the scalar field evolution sourced by hyperbolic encounters of black holes in quadratic scalar Gauss-Bonnet gravity. In this theory, single black holes are known to acquire a scalar hair through scalarization for certain values of their mass and spin. We work in the decoupling limit and evolve the scalar field on top of a background metric. Seeding binary black holes with an initial scalar field, we find that configurations which initially cannot sustain a scalar hair temporarily scalarize during an encounter and thereby exhibit dynamical scalarization. This is possible for both positive and negative couplings between the scalar field and curvature in black hole binaries with zero and non-zero initial spins, respectively. Furthermore, we find that the change in the spin magnitude of black holes during certain hyperbolic encounters can lead to permanent spin-induced scalarization (or descalarization), which we refer to as spin-up (de)scalarization.
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Instrumentation and Methods for Astrophysics

Deep Learning for Astrophysics: An Open Textbook from the NASA Cosmic Origins AI/ML Science and Technology Interest Group

Yuan-Sen Ting, Digvijay Wadekar, Phill Cargile et al. (+21 more)

Recent community assessments identify education as a principal barrier to adopting modern machine learning in astronomy. We present Deep Learning for Astrophysics, a freely available textbook at https://deeplearning4astro.com, curated from the NASA Cosmic Origins Artificial Intelligence and Machine Learning Science and Technology Interest Group (AI/ML STIG) lecture series. The book collects 23 chapters by 17 lecturers across six parts, moving from computational foundations and deep-learning architectures through generative modeling, simulation-based inference, reinforcement learning, and large-language-model agents to the practice of AI-laden science. Many include executable notebooks using astronomical data.
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All authors Yuan-Sen Ting, Digvijay Wadekar, Phill Cargile, Carol Cuesta-Lazaro, André Curtis-Trudel, Gregory Green, Ryan McClelland, Daniel Muthukrishna, Tri Nguyen, Helen Qu, Tomasz Rozanski, Anna Scaife, Jesse Thaler, Licia Verde, Francisco Villaescusa-Navarro, John F. Wu, Duo Xu, Siyu Yao, Alex Gagliano, Siddharth Mishra-Sharma, Andrew K. Saydjari, Georgios Valogiannis, Peter Kurczynski, Swara Ravindranath

Solar and Stellar Astrophysics

Coherent and Incoherent Emission from the Ordered Magnetospheres of Low-Mass Stars, UCDs, and Massive Stars

Francesco Cavallaro, Paolo Leto, Barnali Das et al. (+15 more)

Massive early-type (B/A) stars and ultracool dwarfs (UCDs) represent two distinct regimes in which ordered, large-scale magnetospheres are observed. In rapidly rotating massive stars, incoherent radio emission is explained by the centrifugal breakout (CBO) mechanism: plasma confined within the rigidly rotating magnetosphere accumulates beyond the co-rotation radius, where centrifugal forces trigger breakout events and magnetic reconnection, generating non-thermal electrons that produce incoherent gyro-synchrotron emission. Empirically, the radio luminosity correlates with the power released by CBO events, establishing a clear link between stellar rotation, magnetic confinement, and radio output. In UCDs, persistent non-thermal radio emission exhibits similar luminosity trends to those of massive magnetic stars, despite the absence of strong stellar winds. This similarity suggests that a CBO-like process may also operate in these fully convective, low-mass objects, though the plasma source and acceleration mechanisms remain uncertain. In both classes, coherent electron cyclotron maser emission (ECME), characterized by strong polarization and rotational modulation, is observed, indicating common magnetospheric processes analogous to planetary auroral emission. The Square Kilometre Array (SKA) will be able to deeply observe about 70% of the sky. We expect to observe $\sim 1000$ UCDs, enabling better statistical analysis of their emission and a test of the CBO hypothesis.
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All authors Francesco Cavallaro, Paolo Leto, Barnali Das, Corrado Trigilio, Grazia Umana, Cristobal Bordiu, Filomena Bufano, Carla S. Buemi, Joseph R. Callingham, Laura Driessen, Adriano Ingallinera, Sara Loru, Stanley Owocki, Simone Riggi, Alan C. Ruggeri, Giovanni Sabatini, Matt E. Shultz, Alessio Traficante

High Energy Astrophysical Phenomena

Magnetar Formation from Accretion Induced Collapse of White Dwarfs

Luís Felipe Longo Micchi, Patrick Chi-Kit Cheong and David Radice

We aim to characterize the post-collapse evolution of accretion-induced collapse (AIC) remnants of rapidly rotating, magnetized white dwarfs, focusing on their rotational, magnetic, and thermal structure, as well as the development of instabilities and their energy content. We perform nine axis-symmetric general-relativistic neutrino magnetohydrodynamic (MHD) simulations of collapsing, rapidly rotating, magnetized white dwarfs. The simulations follow the system from collapse through bounce and up to $\sim$1 s post-bounce. The simulations are performed by the conformally flat general relativistic neutrino MHD code Gmunu. The collapse produces a rapidly rotating proto-magnetar surrounded by a persistent accretion disk lasting at least $\sim 1$ s after bounce. The remnant mass and spin span 1.15–1.45 $M_{\odot}$ and 2.9–4.9 kHz, respectively, with stronger initial magnetic fields generally leading to lower rotation rates. During the first $\sim 10$ ms, the proto-magnetar exhibits global oscillations that drive both gravitational-wave emission and coherent modulation of the poloidal magnetic field energy. The magnetic energy evolution, normalized to its bounce value, follows an approximately universal behavior across all models. The remnant interior remains strongly magnetized ($\gtrsim 10^{13}$ G) and hot ($\gtrsim 20$ MeV) up to 1 s after bounce, with maxima of both quantities co-located in the inner $\sim 10$ km. The magnetic field topology shows surface poloidal fields of ${\sim}10^{12}$ G and toroidal fields of ${\sim}10^{14}$ G, with strong toroidal components extending into the equatorial region. When the magnetic energy exceeds the rotational energy ($\sim 10^{52}$ erg), the remnant core becomes unstable, leading to episodic magnetic flux expulsion, mass ejection, and flare-like activity in which magnetic energy is released and thermalized in the surrounding material.
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Cosmology and Nongalactic Astrophysics

The Limits of Photometric Dynamics: Benchmarking Cluster Relaxation Diagnostics

Alisson P. Costa, Andre L. B. Ribeiro, Zhonglue L. Wen et al. (+1 more)

Galaxy clusters are key probes of cosmology and structure formation, yet their dynamical classification traditionally relies on spectroscopic redshifts, which do not scale efficiently with survey size. As large photometric surveys such as LSST become available, photometric redshifts offer an attractive alternative, but their impact on velocity-based diagnostics remains poorly constrained. We quantify the sensitivity of two Gaussianity diagnostics - the Anderson-Darling (AD) test and Gaussian mixture modeling (Mclust) - to different photometric redshift error prescriptions. Propagating Gaussian and Student-t uncertainties through SDSS photometric velocity distributions, we assess how the error model affects recovery of cluster dynamical states established by the independent $\Gamma$ morphological proxy. Using 1672 SDSS clusters with pre-existing $\Gamma$, we perform Monte Carlo resampling under Gaussian and Student-t errors, the latter mimicking heavy-tailed uncertainties and catastrophic outliers, plus a spectroscopic control experiment with mock photometric redshifts from spectroscopic data. Under Gaussian errors, relaxed clusters are recovered in ~95% of realizations, while unrelaxed ones in only ~5%, revealing a strong bias toward relaxed classifications. Student-t errors drop relaxed recovery to ~60-70% and raise unrelaxed to ~30-45%, though still incomplete. Paired Wilcoxon tests confirm these differences are significant. This has direct implications for large photometric surveys: dynamical studies based primarily on photometric data may significantly underestimate disturbed cluster fractions without robust spectroscopic calibration, outlier mitigation, and validation with realistic mock catalogs.
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All authors Alisson P. Costa, Andre L. B. Ribeiro, Zhonglue L. Wen, Flavio R. Morais-Neto

Astrophysics of Galaxies

SUNRISE-3D: Sharp UNveiling of AGN feedback Regulation and its Impact on Star-formation at the cosmic noon Epoch

G. Vietri, S. Bisogni, E. Piconcelli et al. (+4 more)

To better understand the role of AGN-driven outflows as a mechanism for heating or sweeping up gas over distances comparable to the size of the galaxy in its evolution, and to explore their physical characteristics as a function of AGN and host galaxy properties, it is necessary to have a statistical sample of AGNs selected from a uniform sample of galaxies with spectroscopic coverage of key restframe optical emission lines. To assess the impact of AGN-driven outflows on their host galaxies, we need to derive the mass and energy carried by the outflows, as well as correlations of these quantities with both AGN and host galaxy properties, in order to reveal their effects on the galaxy population and constrain the physical mechanisms driving the outflows. The availability of adaptive-optics-assisted 3D spectroscopy with the ELT multi-IFU instrument SHARP/VESPER enables the construction of spatially resolved outflow property maps, providing instantaneous outflow rates across the entire field of view without assuming outflow geometry, and thus significantly reducing the uncertainties compared to methods based on longslit spectroscopy. Furthermore, combining these maps with resolved star formation rate (SFR) maps allows a direct comparison between outflow properties and star-formation activity across the galaxy, providing key insights into how AGN feedback regulates star formation down to sub-kpc scales. By applying this approach to a representative sample of galaxies at cosmic noon ($1.5 < z < 2.5$), spanning a wide range of stellar masses from low-mass systems ($M_\star = 10^{8-10}\,M_\odot$) to the massive end ($M_\star > 10^{10}\,M_\odot$), we aim to systematically investigate the interplay between AGN activity, outflows, and star formation in the galaxy population as a whole.
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All authors G. Vietri, S. Bisogni, E. Piconcelli, F. Ricci, P. Franzetti, A. Gargiulo, C. Mancini

Astrophysics of Galaxies

SMGPS: A study of Galactic HII regions with extended morphology

Athanaseus J.T. Ramaila, Mark A. Thompson, Oleg M. Smirnov et al. (+7 more)

We present a study of ionised hydrogen ($\textrm{H}\scriptstyle\mathrm{II}$) regions in the Galactic Plane using data from the SARAO MeerKAT Galactic Plane Survey (SMGPS). The SMPGS is a wide-field, wide-band 1.3 GHz radio continuum survey ($251^\circ \leq l \leq 358^\circ$ and $2^\circ \leq l \leq 61^\circ$ at $\quad |b| \leq 1^\circ.5$) that has enabled us to trace the diffuse emission enveloping recently formed massive stars. Our multifrequency synthesis images reveal faint and extended emission that was previously overlooked by $\textrm{H}\scriptstyle\mathrm{II}$ region surveys. We report the distances and Lyman-photon flux ($N_{\mathrm{Ly}}$) measurements for 1,327 Galactic $\textrm{H}\scriptstyle\mathrm{II}$ regions from which we characterise the spectral types for candidate ionising stars. The spectral types range from B2 to O4. The typical stellar spectral type responsible for ionisation is the B0, which constitutes about $\text{16%}$ of our catalogue, corresponding to a mean $\log(N_{\mathrm{Ly}}) = 47.5\ \mathrm{s}^{-1}$. Moreover, as a result of the lack of radio recombination line (RRL) velocity measurements for faint $\textrm{H}\scriptstyle\mathrm{II}$ regions, we identify the effective completeness limit at $\log(N_{\mathrm{Ly}}) \approx 47.6\ \mathrm{s}^{-1}$. The multiwavelength approach reveals that the physical radius at 1.3 GHz and in the mid-infrared are well correlated with a slope of $1.15 \pm 0.02$. We find clear power-law relations between $N_{\mathrm{Ly}}$ and physical radius, and an inverse correlation between electron density and radius ($n_{\rm e} \propto R^{-0.73}$). However, no significant correlation is observed between the $N_{\mathrm{Ly}}$ and Galactocentric distance, suggesting that the observed trends are governed primarily by local star-forming environments rather than large-scale Galactic gradients.
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All authors Athanaseus J.T. Ramaila, Mark A. Thompson, Oleg M. Smirnov, Sphesihle Makhathini, James O. Chibueze, Willice Obonyo, Chukwuebuka J. Ugwu, Cristobal Bordiu, Simone Riggi, Alessio Traficante

Astrophysics of Galaxies

Time-dependent adaptive mesh refinement solver for the Gross-Pitaevskii-Poisson equations

Iván Álvarez-Rios

This work presents a new numerical code for solving the time–dependent Gross–Pitaevskii–Poisson (GPP) system using adaptive mesh refinement (AMR). The code is designed to study the nonlinear dynamics of self–gravitating bosonic matter in three spatial dimensions under periodic boundary conditions. It combines high–order spatial discretization, explicit time integration, and dynamic refinement driven by the magnitude of the gravitational potential. The implementation is validated through a set of test problems in the nonlinear regime. These benchmarks demonstrate that the solver accurately preserves global conservation laws, resolves strong wave interference and phase singularities, and maintains consistency across refinement levels in highly dynamical scenarios.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Black holes in a bouncing universe

Iara Pintos, Daniela Pérez and Florencia L. Vieyro

Bouncing cosmologies offer an alternative to the standard $\Lambda$CDM model by avoiding the problem of the initial cosmological singularity by construction. In these models, the universe undergoes a contraction phase that begins in a nearly flat and dilute state, followed by a bounce, after which the universe transitions into the expanding phase described by the $\Lambda$CDM model. During contraction, most large-scale structures are expected to be erased. Black holes, however, as shown by several previous investigations, may persist through the bounce. The goal of this work is to analyze the evolution of a black hole population throughout the contraction, bounce, and expansion phases. Additionally, we investigate how the presence of black holes influences the properties of the background cosmological fluid. To this end, we develop a cosmological model involving two interacting fluids. Our findings indicate that the cosmological fluid alters its properties in a spacetime with fixed geometry.
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