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Physics Astrophysics

astro-ph Watch Astrophysics

Saturday 10 January

Astrophysics of Galaxies

Evaluating the efficacy of a data cube treatment procedure for kinematic analyses: application to NGC 3115 and NGC 4699

R. B. Menezes, L. D. B. Sonoda, Patrícia da Silva et al. (+5 more)

Data cubes have been increasingly used in astronomy. These data sets, however, are usually affected by instrumental effects and high-frequency noise. In this work, we evaluate the efficacy of a data cube treatment methodology, previously proposed by our research group, for analyses focused on the stellar and gas kinematics. To do that, we used data cubes of the central regions of the galaxies NGC 3115 and NGC 4699, obtained with the Integral Field Unit of the Gemini Multi-Object Spectrograph. For each galaxy, we analysed three data cubes: non-treated, filtered (with the Butterworth spatial filtering) and filtered and deconvolved (with the Richardson-Lucy deconvolution). For each data cube, we performed a dynamical modelling, using Jeans Anisotropic Models, to obtain, among other parameters, the masses of the central supermassive black holes. Both for NGC 3115 and NGC 4699, the values of the parameters provided by the dynamical modelling from the non-treated, filtered and filtered and deconvolved data cubes were compatible, at the 1-$\sigma$ level. However, the use of the Butterworth spatial filtering decreased the uncertainty of the parameters. The additional use of the Richardson-Lucy deconvolution decreased even more the uncertainty of the parameters. The complete data treatment procedure resulted in decreases of 41% and 45% in the uncertainties of the supermassive black hole masses in NGC 3115 and NGC 4699, respectively. These results indicate that our treatment procedure not only does not compromise analyses of data cubes focused on the stellar or gas kinematics, but actually improves the quality of the results.
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All authors R. B. Menezes, L. D. B. Sonoda, Patrícia da Silva, A. T. Monteiro, T. V. Ricci, R. G. Bravo, D. D. V. Gueter, V. C. Parro

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

Limits of vacuum-template subtraction for LISA massive black hole binary sources in realistic environments

Lorenz Zwick

We investigate the impact of gravitational wave (GW) dephasing due to gas accretion on the subtraction of massive black hole (MBH) binary signals over 4 yr of LISA data in the context of the global-fit. Based on state of the art predictions for the population of merging MBHs, we show that imperfect subtraction with vacuum waveform templates leaves a GW residual with an SNR of $3.2^{+5.4}_{-1.9}\times \sqrt{f_{\rm Edd} \langle \dot n \rangle/(20\, {\rm yr}^{-1})}$, where $f_{\rm Edd}$ is the typical Eddington ratio and $\langle \dot n \rangle$ the mean merger rate of LISA MBH binaries. We characterize the dependence of the residual on key population hyper-parameters and provide a simple fitting function. {Finally, we consider the distinguishability of the residual as a stochastic signal by comparing with Bayesian power-law sensitivity curves, while discussing several additional detection and mitigation strategies. Overall, our analysis indicates that the residual is unlikely to be confidently distinguishable from instrumental noise while nevertheless being likely to bias the inference of other signals.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Kerr-Newman-de Sitter black holes in $f(R)$ gravity with constant curvature: horizon structure and extremality

Alikram N. Aliev and Göksel Daylan Esmer

The theory of $f(R)$ gravity with constant curvature (i.e. constant scalar curvature) admits rotating and charged black hole solutions obtained from the Kerr-Newman-(A)dS metrics of general relativity through appropriate rescalings of the metric parameters. In this paper, we focus on the Kerr-Newman-de Sitter case and present a unified analytic treatment of the horizon structure and its physical properties, allowing for a transparent comparison between general relativity and $ f(R)$ gravity with constant curvature. We solve the quartic equation determining the horizon locations and derive closed analytic expressions for the horizon radii. Focusing on extremal configurations, we obtain analytic formulas for the squared rotation parameter $ a^2 $ and the inverse square of the curvature radius $ l^{-2} $ as functions of the horizon location and the electric charge. For generic values of these parameters, the extremality conditions are non-universal, reducing to the familiar Kerr-Newman bound only in the limit of vanishing background curvature. We identify an ultra-extremal configuration in which $ a^2 $ attains its maximal value at zero charge and decreases monotonically to zero as the charge approaches its limiting value, while $ l^{-2 }$ increases correspondingly. As an illustrative example, we show that black holes with charge $ q=M/2 $ necessarily possess a minimum rotation, which emerges naturally as an intersection point in our analytic description of $ a^2 $ and $ l^{-2 }$, when embedded in a universe characterized by a critical value of $ l^{-2} $ (equivalently, the scalar curvature or the cosmological constant). Finally, we demonstrate that when the mass satisfies $ M^2= (a^2+q^2)(1-a^2/l^2)$, the quartic horizon equation factorizes, leading in the extremal regime to a chiral-like horizon structure that allows only the outer-cosmological horizon merger.
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Cosmology and Nongalactic Astrophysics

Impact of a negative cosmological constant on the reconstruction of dark energy in light of DESI BAO data

Hao Wang and Yun-Song Piao

An anti-de Sitter vacuum, corresponding to a negative cosmological constant (NCC), might coexist with one evolving positive dark energy component at low redshift and is hinted by the latest DESI observations. In this paper, we use two methods, redshift-binned and Gaussian Process-based reconstructions to investigate the effect of a NCC on the equation of state (EOS) $w(z)$ of evolving dark energy (DE) component. We find that a NCC is slightly preferred in both the two reconstructions by up to $\simeq1\sigma$. Although the degeneracy between the EOS of evolving DE component and NCC weakens the constraint on the reconstructed $w(z)$, this degeneracy leads to the phantom divide $w=-1$ more consistent with the 1$\sigma$ posterior of $w(z)$.
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Cosmology and Nongalactic Astrophysics · Cross-listed from physics.pop-ph

Matière noire et (ou) gravitation modifiée : une approche historique et épistémologique

Benoit Famaey and Jonathan Freundlich

The current standard model of cosmology assumes that the majority of matter in the Universe is made of dark matter, and that the latter is fundamentally different from ordinary matter. Dark matter can in principle explain the rotation of galaxies, the gravitational lensing from galaxy clusters or the appearance of the cosmic microwave background, the oldest light in the Universe. But does dark matter really exist? Here, we review the history of this concept and its implications for the formation and evolution of galaxies. We also consider the questions that remain, the limitations of the model, and present alternative theories, in particular modifications to the gravitional law that would – perhaps – make it possible to do without it.
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Cosmology and Nongalactic Astrophysics

A Universal Bilinear Model for the Dependence of Void Asymmetry Distributions on $\Omega_{m}$ and $\sigma_{8}$

Geonwoo Kang and Jounghun Lee

$Aims$: We present a new independent diagnostics based on void properties, by which the matter density parameter ($\Omega_{m}$) and amplitude of initial density field ($\sigma_{8}$) can be constrained. This diagnostics utilizes coherent rotation of void galaxies, which can be observed as redshift asymmetry in opposite sides bisected by the projected spin axes of hosting voids. $Methods$: Identifying the voids and their member galaxies in the AbacusSummit of cosmological simulations and searching for their projected spin axes with an iterative method, we numerically determine the void asymmetry distributions both in real and redshift spaces for three different classes of the background cosmologies: the $\Lambda$CDM, the $w$CDM and the $w_{0}w_{a}$CDM. $Results$: It is discovered that the void asymmetry distributions in real and redshift spaces are well approximated by the generalized Gamma models characterized by the scale and shape parameters for all of the $33$ background cosmologies considered. It turns out that the initial conditions affect only the scale parameter of the void asymmetry distributions that exhibits an almost linear dependence on each of $\Omega_{m}$ and $\sigma_{8}$ with being insensitive to $w$. Developing a bilinear model for the dependence of void asymmetry distributions on $\Omega_{m}$ and $\sigma_{8}$, we show that its coefficients are universal constants over the three cosmological classes. $Conclusions$: Given that the void asymmetry distributions in redshift space are readily measurable properties, our universal model for the scale parameter of the void asymmetry distributions will in principle complement the standard cosmological diagnostics to break the $\Omega_{m}$-$\sigma_{8}$ degeneracy, regardless of $w$.
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Astrophysics of Galaxies

AstroSat UV Deep Field IV. An Extended UV disk around a massive spiral galaxy at z=0.67

Pushpak Pandey, Kanak Saha and Sanchayeeta Borthakur

Extended ultraviolet (XUV) emission in nearby disk galaxies supports the inside-out growth scenario through low-efficiency star formation in their outer regions. However, such detections have largely been limited to the local Universe ($z \sim 0$) due to the need for deep, high-resolution UV imaging. We report the detection of a clumpy XUV disk in a massive, isolated spiral galaxy ($\log(M_*/M_\odot) \approx 11.04$) at $z=0.67$, observed with AstroSat/UVIT. The intrinsic rest frame FUV surface brightness profile, corrected for the instrument PSF, shows a more extended disk than its optical and IR counterparts. The XUV disk reaches nearly twice the optical radius and includes a large UV-bright low surface brightness (LSB) region ($S_{LSB}/S_{K80}\approx15,\ \mu_{FUV}-\mu_K\approx0.8$), consistent with the Type II XUV definition. Additionally, the detection of UV clumps without optical counterparts supports a Type I classification, suggesting gravitational instabilities and recent star formation. These features point to recent cold gas accretion onto the outer disk. From the asymmetric light profile, we estimate a gas accretion rate of $\sim11\ M_\odot$ yr$^{-1}$, providing evidence of active disk growth at intermediate redshift.
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High Energy Astrophysical Phenomena

A binary merger product as the direct progenitor of a Type II-P supernova

Zexi Niu, Ning-Chen Sun, Emmanouil Zapartas et al. (+16 more)

Type II-P supernovae (SNe II-P) are the most common class of core-collapse SNe in the local Universe and play critical roles in many aspects of astrophysics. Since decades ago theorists have predicted that SNe II-P may originate not only from single stars but also from interacting binaries. While ~20 SNII-P progenitors have been directly detected on pre-explosion images, observational evidence still remains scarce for this speculated binary progenitor channel. In this work, we report the discovery of a red supergiant progenitor for the Type II-P SN 2018gj. While the progenitor resembles those of other SNe II-P in terms of effective temperature and luminosity, it is located in a very old environment and SN 2018gj has an abnormally short plateau in the light curve. With state-of-the-art binary evolution simulations, we find these characteristics can only be explained if the progenitor of SN 2018gj is the merger product of a close binary system, which developed a different interior structure and evolved over a longer timescale compared with single-star evolution. This work provides the first compelling evidence for the long-sought binary progenitor channel toward SNe II-P, and our methodology serves as an innovative and pragmatic tool to motivate further investigations into this previously hidden population of SNe II-P from binaries.
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All authors Zexi Niu, Ning-Chen Sun, Emmanouil Zapartas, Dimitris Souropanis, Yingzhen Cui, Justyn R. Maund, JeffJ. Andrews, Max M. Briel, Morgan Fraser, Seth Gossage, Matthias U. Kruckow, Camille Liotine, Zhengwei Liu, Philipp Podsiadlowski, Philipp M. Srivastava, Elizabeth Teng, Xiaofeng Wang, Yi Yang, Jifeng Liu

Earth and Planetary Astrophysics

High-order expansions of multi-revolution elliptic Halo orbits in the elliptic restricted three-body problem

Xiaoyan Leng and Hanlun Lei

Multi-revolution elliptic Halo (ME-Halo) orbits are a special class of symmetric and periodic solutions within the framework of the elliptic restricted three-body problem (ERTBP). During a single period, an M:N ME-Halo orbit completes $M$ revolutions around a libration point and the primaries revolve N times around each other. Owing to the repeated configurations, ME-Halo orbits hold great promise as nominal trajectories for space mission design. However, a major challenge associated with ME-Halo orbits lies in their mathematical description. To this end, we propose a novel method to derive high-order analytical expansions of ME-Halo orbits in the ERTBP by introducing two correction terms into the equations of motion in the y- and z-directions. Specifically, both the coordinate variables and correction terms are expanded as power series in terms of the primary eccentricity, the in-plane amplitude, and the out-of-plane amplitude. High-order approximations are constructed using a perturbation method, and their accuracy is validated through numerical analysis. Due to the inherent symmetry, ME-Halo orbits can be classified into four distinct families: southern/northern and periapsis/apoapsis groups. The analytical approximations developed in this study not only provide high-accuracy initial guesses for the numerical computation of ME-Halo orbits, but also offer new insights into the dynamical environment near collinear libration points in the ERTBP, thereby advancing practical applications in mission design.
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Instrumentation and Methods for Astrophysics · Cross-listed from cs.CL

Spec-o3: A Tool-Augmented Vision-Language Agent for Rare Celestial Object Candidate Vetting via Automated Spectral Inspection

Minghui Jia, Qichao Zhang, Ali Luo et al. (+5 more)

Due to the limited generalization and interpretability of deep learning classifiers, The final vetting of rare celestial object candidates still relies on expert visual inspection–a manually intensive process. In this process, astronomers leverage specialized tools to analyze spectra and construct reliable catalogs. However, this practice has become the primary bottleneck, as it is fundamentally incapable of scaling with the data deluge from modern spectroscopic surveys. To bridge this gap, we propose Spec-o3, a tool-augmented vision-language agent that performs astronomer-aligned spectral inspection via interleaved multimodal chain-of-thought reasoning. Spec-o3 is trained with a two-stage post-training recipe: cold-start supervised fine-tuning on expert inspection trajectories followed by outcome-based reinforcement learning on rare-type verification tasks. Evaluated on five rare-object identification tasks from LAMOST, Spec-o3 establishes a new State-of-the-Art, boosting the macro-F1 score from 28.3 to 76.5 with a 7B parameter base model and outperforming both proprietary VLMs and specialized deep models. Crucially, the agent demonstrates strong generalization to unseen inspection tasks across survey shifts (from LAMOST to SDSS/DESI). Expert evaluations confirm that its reasoning traces are coherent and physically consistent, supporting transparent and trustworthy decision-making. Code, data, and models are available at https://github.com/Maxwell-Jia/spec-o3.
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All authors Minghui Jia, Qichao Zhang, Ali Luo, Linjing Li, Shuo Ye, Hailing Lu, Wen Hou, Dongbin Zhao

High Energy Astrophysical Phenomena

Ruling Out Compact Jets as the Dominant Source of Radio Emission in Radio-quiet, High Eddington-ratio Active Galactic Nuclei

Jeremiah D. Paul and Richard M. Plotkin

The origin of core radio emission in radio-quiet active galactic nuclei (AGNs) is still actively debated. General relativistic magnetohydrodynamics simulations often predict the launching of moderately large-scale jets from super-Eddington accretion flows, but this prediction seems at odds with observations indicating most high/super-Eddington AGNs appear radio quiet. Here, we use the ratio of radio to X-ray luminosities as a multiwavelength diagnostic to probe the origin of radio emission in a sample of 69 radio-quiet, high/super-Eddington AGNs with black-hole masses $M_{\rm BH} \sim 10^{5}-10^{9}~M_\odot$. With this wide dynamic range in $M_{\rm BH}$, we adapt existing formalisms for how jetted radio emission and accretion-powered X-ray emission scale with black hole mass into the super-Eddington regime. We find that the radio/X-ray luminosity ratios observed across this $M_{\rm BH}$ range are inconsistent with a jet-dominated model for radio emission. We discuss how our results may instead be consistent with a corona-dominated radio emission origin with a contribution from outflows at higher accretion rates.
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Instrumentation and Methods for Astrophysics

Brahe: A Modern Astrodynamics Library for Research and Engineering Applications

Duncan Eddy and Mykel J. Kochenderfer

Brahe is a modern satellite dynamics library for research and engineering applications. The representation and prediction of satellite motion is the fundamental problem of astrodynamics. Current research and applications in space situational awareness, satellite task planning, and space mission operations require accurate and efficient numerical tools to perform coordinate transformations, model perturbations, and propagate orbits. While the core algorithms for predicting and modeling satellite motion have been known for decades, there is a lack of modern, open-source software that implements these algorithms in a way that is accessible to researchers and engineers. brahe is designed to address these challenges by providing a modern, open-source astrodynamics library that is quick-to-deploy, composable, extensible, and easy-to-learn.
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Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Cosmological Dynamics on a Novel $f(Q)$ Gravity Model with Recent DESI DR2 Observation

S. A. Kadam, D. Revanth Kumar and Santosh Kumar Yadav

In this article, we investigate the cosmological viability of a modified symmetric teleparallel gravity model within the $f(Q)$ framework. We derive observational constraints on the model parameters by performing a Markov Chain Monte Carlo analysis using a combined dataset consisting of cosmic chronometers, PantheonPlus SH0ES, and DESI BAO DR2. Our analysis yields the best-fit values for the model parameters $m=-0.386 \pm 0.090$ and $n=-1.055 \pm 0.047$, along with the cosmological parameters at present: $H_0 = 73.19 \pm 0.25$, $q_0 = -0.51 \pm 0.6$, and $\omega_{0} = -0.73 \pm 0.3$, at 68% CL. Furthermore, we examine the physical behavior of the model, focusing on the effective equation of state and deceleration parameter. Our findings indicate that the model experiences a transition from the early deceleration phase to the late-time cosmic acceleration, and the transition occurs at a redshift $z_{tr} = 0.573$. We also analyse the $om(z)$ diagnostic, which reflects a positive slope, supporting the behavior of the equation of state parameter in the quintessence region.
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Solar and Stellar Astrophysics

Simulations of Electron Beam Interactions in Brown Dwarf Atmospheres

Anna Zuckerman, J. Sebastian Pineda, David Brain et al. (+2 more)

Over two decades ago, the first detection of electron cyclotron maser instability (ECMI) radio emission from a brown dwarf confirmed the presence of aurorally precipitating electrons on these objects. This detection established that brown dwarfs can exhibit magnetic activity that is planetary and auroral, rather than stellar in nature. This discovery motivated ongoing observational searches for the corresponding optical, ultraviolet (UV), and infrared (IR) auroral emission expected based on solar system analogs. The continuing nondetection of such auroral emission indicates important differences exist between auroral processes on brown dwarfs and solar system planets. In this work, we implement a Monte Carlo simulation of monoenergetic electron beams interacting with brown dwarf atmospheres, as a step towards understanding the physics of brown dwarf auroral emission. We detail the algorithm and underlying assumptions, and validate against previously published Jovian results (Hiraki et al. 2008). Our results agree well with literature, with some discrepancy from our updated interaction cross sections. We demonstrate the applicability of our simulation across the range of surface gravities and effective temperatures of radio-emitting brown dwarfs. We present an analytic parameterization of interaction rates based on our finding that atmospheric column density governs the interaction profiles. We apply this parameterization to calculate the total volumetric interaction rates and energy deposition rate for representative electron beam energy spectra enabling future predictions for spectra of aurorally emitting brown dwarfs. Simulations of high energy electron interactions with substellar hydrogen-dominated atmospheres will guide observational searches for multi-wavelength auroral features beyond the solar system.
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All authors Anna Zuckerman, J. Sebastian Pineda, David Brain, James Mang, Caroline Morley

High Energy Astrophysical Phenomena

Radio Morphing: Fast computation of inclined air shower radio emission

Simon Chiche, Olivier Martineau-Huynh, Matias Tueros et al. (+1 more)

The preparation of the next-generation of large-scale radio experiments requires running a large number of simulations to explore multiple detector configurations over vast areas and develop novel methods for the reconstruction of air shower parameters. While Monte Carlo simulations are accurate and reliable tools, they are too computationally expensive to explore the full parameter space of these new detectors within a reasonable timescale, and faster and more efficient methods are needed. We introduce a new version of Radio Morphing, a semi-analytical tool designed to simulate the radio emission of any cosmic-ray induced air shower with zenith angle $\theta>60^{\circ}$, at any desired antenna position, from the simulation data of a few reference showers at given positions. This version incorporate refined scaling laws of the radio emission with the shower zenith angle, a novel interpolation method, the implementation of the charge-excess mechanism and the possibility to enable shower-to-shower fluctuations. We present the latest performances of Radio Morphing, tuned for a GRAND-like detector, which now provides an estimation of air shower radio signals four orders of magnitude faster than standard Monte Carlo simulations, while keeping an accuracy on the peak amplitude better than $17\%$ on unfiltered traces, better than $13\%$ in the [50 - 200] MHz band, and below $\sim 10\%$ in the [30 - 80] MHz band.
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All authors Simon Chiche, Olivier Martineau-Huynh, Matias Tueros, Krijn D. de Vries

High Energy Astrophysical Phenomena

In-ice Radio Signatures of Cosmic Ray Particle Cascades

Simon Chiche, Simona Toscano and Krijn D. de Vries

To detect ultra-high-energy neutrinos, experiments such as the Askaryan Radio Array and the Radio Neutrino Observatory in Greenland target the radio emission induced by these particles as they cascade in the ice. This is done by, amongst others, using deep in-ice antennas at the South Pole or in Greenland. A crucial step toward this goal is the characterization of the in-ice radio emission from cosmic-ray-induced particle showers. These showers form a primary background for neutrino searches, but can also be used to validate the detection principle and provide calibration signals for in-ice radio detectors. In this work, we use the Monte-Carlo framework FAERIE to perform the first characterization of cosmic ray signals with simulations that incorporate both their in-air and in-ice emissions. We investigate cosmic ray signatures such as their radiation energy, timing, polarization and frequency spectrum and quantify how they depend on shower properties. These results provide key guidelines for cosmic-ray identification and cosmic-ray/neutrino discrimination in future in-ice radio experiments.
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High Energy Astrophysical Phenomena

Radio Signatures of Cosmic-Ray Particle Showers in Deep In-Ice Antennas

Simon Chiche, Krijn D. de Vries and Simona Toscano

To detect ultra-high-energy neutrinos, experiments such as ARA and RNO-G target the radio emission induced by these particles as they cascade in the ice, using deep in-ice antennas at the South Pole or in Greenland. In this context, it is essential to first characterize the in-ice radio signature from cosmic-ray-induced particle showers, which constitute a primary background for neutrino detection, and represent the fist in-situ detection of in-ice particle cascades with radio antennas. This characterization will help validate the detection principle and assist in calibration. To achieve this goal, we used FAERIE, the "Framework for the simulation of Air shower Emission of Radio for in-Ice Experiments", that combines CoREAS and GEANT4 to simulate the radio emission of cosmic ray showers deep in the ice. Using this tool, we analyze in-ice radio signatures of cosmic-ray showers, including polarization, timing, and radiation energy, as well as their dependence on shower parameters. These insights will facilitate the first cosmic-ray detections and improve cosmic-ray/neutrino discrimination.
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Astrophysics of Galaxies

Generalized Bondi Accretion Flow with and without Outflow

Dongho Han and Myeong-Gu Park

The properties of accretion flows are affected by the angular momentum of the accreting gas. M.-G. Park found that the mass accretion rate, specifically, decreases significantly as the gas angular momentum increases. However, R. Narayan & A. C. Fabian found the decrease modest. We investigate global solutions for rotating polytropic flows in a much wider parameter space to understand their general properties within the slim disk approximation and a viscosity description suitable for both low- and high-angular-momentum flows. We find that the mass accretion rate for flows with a small Bondi radius decreases steeply as the gas angular momentum increases, while for those with a large Bondi radius, it decreases gradually. Therefore, the decrease of mass accretion rate due to gas rotation can be significant or mild depending on the Bondi radius. We further investigate global solutions of accretion with outflows using the ADIOS model of R. D. Blandford & M. C. Begelman. Stronger outflows in general slightly increase the mass inflow rate at the outer boundary, but the actual mass accreted into the black hole decreases by orders of magnitude. Stronger outflows also weaken the dependence of the mass accretion rate on the gas angular momentum when the viscosity parameter {\alpha} is small. The intricate dependence of the mass inflow rate at the outer boundary and the mass accretion rate into the black hole on gas angular momentum will have interesting implications for the growth of black holes and their energy output.
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Instrumentation and Methods for Astrophysics

NASA Decadal Astrobiology Research and Exploration Strategy (NASA-DARES 2025) White Paper – Habitable Worlds Observatory Living Worlds Science Cases: Research Gaps and Needs

Niki Parenteau, Giada Arney, Eleanora Alei et al. (+28 more)

Executive Summary: The Habitable Worlds Observatory (HWO) is the first astrophysics flagship mission with a key cross-divisional astrobiology science goal of searching for signs of life on rocky planets beyond our solar system. The Living Worlds Working Group under the Science, Technology, and Architecture Review Team (START) was charged with investigating how HWO could characterize potentially habitable exoplanets orbiting stars in the solar neighborhood, search for signs of life, and interpret potential biosignatures within a false positive and false negative framework. In particular, we focused on (1) identifying biosignatures that have spectral features in the UV-Vis-NIR wavelength range and defining their measurement requirements, (2) determining additional information needed from the planet and planet system to interpret biosignatures and assess the likelihood of false positives, and (3) assembling current knowledge of likely HWO target stars and identify which properties of host stars and systems are most critical to know in advance of HWO. The Living Worlds atmospheric biosignatures science case is considered one of the key drivers in the design of the observatory. An additional 10 astrobiology science cases were developed that collectively revealed key research gaps and needs required to fully explore the observatory parameter space and perform science return analyses. Investment in these research gaps will require coordination across the Science Mission Directorate and fall under the purview of the new Division-spanning astrobiology strategy.
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All authors Niki Parenteau, Giada Arney, Eleanora Alei, Ruslan Belikov, Svetlana, Berdyugina, Dawn Cardace, Ligia F. Coelho, Kevin Fogarty, Kenneth Gordon, Jonathan Grone, Natalie Hinkel, Nancy Kiang, Ravi Kopparapu, Joshua Krissansen-Totton, Emilie LaFleche, Jacob Lustig-Yaeger, Eric Mamajek, Avi Mandell, Taro Matsuo, Connor Metz, Mark Moussa, Stephanie Olson, Lucas Patty, Bill Philpot, Sukrit Ranjan, Edward Schwieterman, Clara Sousa-Silva, Anna Grace Ulses, Sara Walker, Daniel Whitt

Cosmology and Nongalactic Astrophysics

Exploring the internal structure of a neutron star and the associated magnetic fields aided by the mass-radius relationship

Abriana Lyda and Prajwal MohanMurthy

Neutron stars exhibit magnetic fields and densities far beyond those achievable in terrestrial laboratories, offering a natural probe of strongly interacting matter under extreme conditions. Using observationally anchored mass-radius relations and a density profile consistent with established equations of state, we construct a piecewise model that explicitly integrates the neutron-drip line, nuclear-saturation, the electron-dominated halo, and core-crust interfaces. The resulting structure reproduces the stiffness and curvature behavior across the nuclear-pasta regime reported in the literature, validating our treatment of the crust-core transition. From this model, we derive updated moments of inertia, crustal mass fractions, and the effective number of neutrons contributing to the star's magnetic moment. Comparing these quantities with spin-down inferred magnetic dipole moments indicates that the observed magnetic fields of particularly millisecond pulsars can be sustained entirely by the crustal neutron polarization, requiring alignment of only about $\lesssim5.5\%$ ($99\%$ C.L.) of the neutrons in the crust. This finding supports a crust-confined magnetic-field origin for non-magnetar neutron stars, consistent with magneto-thermal evolution studies, and provides a quantitative framework for connecting neutron-star observables to its underlying structure.
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Friday 9 January

Astrophysics of Galaxies

Collision between molecular clouds IV: The role of feedback and magnetic field in head on collisions

Tabassum S. Tanvir and Michael Y. Grudić

We systematically investigate how cloud-cloud collisions influence star formation, emphasizing the roles of collision velocity, magnetic field orientation, and radiative feedback. Using the first cloud-cloud collision simulations that model individual star formation and accretion with all stellar feedback mechanisms, we explore the morphological evolution, star formation efficiency (SFE), fragmentation, stellar mass distribution, and feedback-driven gas dispersal. Our results show that cloud collisions substantially enhance the rate and timing of star formation compared to isolated scenarios, though the final SFE remains broadly similar across all setups. Lower collision velocities facilitate prolonged gravitational interaction and accumulation of gas, promoting sustained star formation characterized by elongated filamentary structures. Conversely, high-velocity collisions induce rapid gas compression and turbulent motions, leading to intense but transient episodes of star formation, which are curtailed by feedback-driven dispersal. The orientation of the magnetic field markedly affects collision outcomes. Parallel fields allow gas to collapse efficiently along magnetic lines, forming fewer but more massive stars. In contrast, perpendicular fields generate significant magnetic pressure, which stabilizes the shock-compressed gas and delays gravitational collapse, resulting in more distributed and less massive stellar fragments. Radiative feedback from massive stars consistently regulates star formation, halting further gas accretion at moderate efficiencies (10-15%) and initiating feedback-driven dispersal. Although the cloud dynamics vary significantly, the stellar mass function remains robust across scenarios-shaped modestly by magnetic orientation but only weakly influenced by collision velocity.
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Instrumentation and Methods for Astrophysics

Incorporating Wavefront Error, Wavefront Sensing and Control, and Sensitivities into Exposure Time Calculations for Future Space Missions with the Error Budget Software (EBS)

Sarah Steiger, Pin Chen and Laurent Pueyo

A primary goal of NASA's Habitable Worlds Observatory (HWO) mission concept is to explore the Habitable Zones (HZ) of ~100 stellar systems and acquire spectra of ~25 terrestrial-type planets (with planet/star flux ratios on the order of 1E-10) which places tight constraints on the performance of observatory systems. In particular, coronagraph instrumentation needs to be matured for higher throughput, deeper contrasts, and better broadband performance, while also considering their sensitivity and ability to mitigate the impact of telescope instability and wavefront error (WFE), which can have a profound impact on exo-Earth imaging. The success of various proposed HWO mission architectures is often represented by the estimated exo-Earth candidate yield. Computation of the minimum exposure time to achieve the required signal-to-noise on a given target, using an exposure time calculator (ETC), is a key part of yield estimation. The impacts of coronagraph sensitivity, WFE, and wavefront sensing and control (WFS&C) have been well studied in the context of developing error budgets for missions and instruments such as the Roman Coronagraph Instrument, but there is currently no easily accessible way to incorporate the effects of these key parameters into calculating exposure times for HWO. To address this, we developed the Error Budget Software (EBS) - an open-source tool that synthesizes sensitivity, WFE, and WFS&C information for a variety of temporal and spatial scales and directly interfaces with the open-source yield code EXOSIMS to produce exposure times. We demonstrate how EBS can be used for mission error budgeting using the example of the Ultrastable Observatory Roadmap Team (USORT) observatory design. This includes both single and multi-variate parameter explorations using EBS where we identify trends between raw contrast and wavefront error, and detector noise and energy resolution.
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High Energy Astrophysical Phenomena

The Role of Interferometric Phase in Measuring Black Hole Photon Rings

Sol Gutiérrez-Lara, Daniel C. M. Palumbo and Michael D. Johnson

The Event Horizon Telescope (EHT) captured the first images of a black hole using Very Long Baseline Interferometry (VLBI). In the near future, extensions of the EHT such as the Black Hole Explorer (BHEX) will allow access to finer-scale features, such as a black hole's ”photon ring.” In the Kerr spacetime, this image structure arises from strong gravitational lensing near the black hole that results in a series of increasingly demagnified images of each emitting region that exponentially converge to a limiting critical curve. Exotic black hole alternatives, such as wormholes, can introduce additional photon rings. Hence, precisely characterizing multi-ring images is a promising pathway for measuring black hole parameters, such as spin, as well as exploring non-Kerr spacetimes. Here, we examine the interferometric response of multi-ring systems using a series of 1) simple geometric toy models, 2) synthetic BHEX and EHT observations of geometric models, and 3) semi-analytic accretion models with ray-tracing in the Kerr spacetime. We find that interferometric amplitude is more sensitive to the shape of the photon ring, while interferometric phase is more sensitive to its displacement, which is most sensitive to black hole spin. We find that for models similar to Messier 87* (M87*), the relative displacement of the first strongly lensed image from the weakly lensed direct image is approximately $1\,\mu {\rm as}$ per unit dimensionless spin, yielding an expected phase signature on a 25 G$\lambda$ baseline of $\sim44^\circ$ per unit spin.
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Astrophysics of Galaxies

Star formation quenching precedes morphological transformation in COSMOS-WEB's richest galaxy groups

Z. Ghaffari, G. Gozaliasl, A. Biviano et al. (+26 more)

We analyzed the 25 richest galaxy groups in COSMOS-Web at z = 0.18-3.65, identified via the AMICO algorithm. These groups contain 20-30 galaxies with high (>75%) membership probability. Our study reveals both passive-density and active-density relations: late-type galaxies (LTGs) prefer higher central overdensities than early-type galaxies (ETGs) across all groups, and many massive LTGs exhibit colors typical of quiescent galaxies. We identify red sequences (RS) in 5 groups, prominently established at z < 1, with early emergence in the RS locus up to z ~ 2.2. This suggests group environments represent a transitional phase where star formation quenching precedes morphological transformation, contrasting with the classical morphology-density relation in rich clusters. In the central regions (~33 arcsec / 100 kpc from centers), we identified 86 galaxies: 23 (~27%) ETGs and 63 (~73%) LTGs. High-mass galaxies (M_star > 10^10.5 M_sun) undergo rapid quenching over ~1 Gyr, becoming predominantly spheroidal ETGs. This indicates morphological transformation accelerates in massive systems during peak cosmic star formation. Intermediate-mass galaxies (10^9 < M_star/M_sun < 10^10.5) show mild quenching, while low-mass galaxies (M_star < 10^9 M_sun) remain largely star-forming; here, environmental processes suppress star formation without destroying disks, suggesting group quenching operates on longer timescales than mass quenching. Overall, mass-dependent quenching dominates the high-mass end, while environment shapes lower-mass systems. The HLAGN fraction for both groups and field increases with redshift, peaking at z ~ 2, with groups consistently showing higher fractions. We suggest AGN feedback partially drives rapid quenching in high-mass galaxies, while mergers may trigger AGN activity.
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All authors Z. Ghaffari, G. Gozaliasl, A. Biviano, G. Toni, S. Taamoli, M. Maturi, L. Moscardini, A. Zacchei, F. Gentile, M. Haas, H. Akins, R. C. Arango-Toro, Y. Cheng, C. Casey, M. Franco, S. Harish, H. Hatamnia, O. Ilbert, J. Kartaltepe, A. H. Khostovan, A. M. Koekemoer, D. Liu, G. A. Mamon, H. J. McCracken, J. McKinney, J. Rhodes, B. Robertson, M. Shuntov, L. Yang

Astrophysics of Galaxies

CAMELS Environments: The Impact of Local Neighbours on Galaxy Evolution across the SIMBA, IllustrisTNG, ASTRID, and Swift-EAGLE Simulations

Xavier Sims, Daniel Anglés-Alcázar, Boon-Kiat Oh et al. (+6 more)

Internal feedback from massive stars and active galactic nuclei (AGN) play a key role in galaxy evolution, but external environmental effects can also strongly influence galaxies. We investigate the impact of environment on galaxy evolution, and its dependence on baryonic physics implementation, using Cosmology and Astrophysics with MachinE Learning Simulations (CAMELS) spanning a wide range of stellar and AGN feedback implementations in the SIMBA, IllustrisTNG, ASTRID, and Swift-EAGLE galaxy formation models. We show that satellite galaxies are significantly affected by the environment in all simulation models, with their gas fraction and star formation rate (SFR) suppressed in overdense regions compared to similar mass satellites in underdense environments at $z=0$. Central galaxies are less sensitive to environment but tend to show lower gas fraction and SFR in overdense regions at low stellar mass, transitioning to higher gas fraction and SFR for massive galaxies in higher-density environments. Halo baryon fraction ($f_{\rm B}$) and circumgalactic medium mass fraction ($f_{\rm CGM}$) at $z=0$ show clear environmental effects. In SIMBA, low-mass haloes in overdense regions have systematically lower $f_{\rm B}$ and $f_{\rm CGM}$ at fixed halo mass, while Swift-EAGLE haloes in overdense regions have systematically higher $f_{\rm B}$ and $f_{\rm CGM}$ across the full halo mass range, and IllustrisTNG and ASTRID show opposite trends at the low and high mass ends. Environmental effects can flip at higher redshift, with SFR and $f_{\rm B}$ increasing with local density in low-mass haloes before quenching at an increasing overdensity threshold. Our results demonstrate that the impact of environment on galaxy evolution depends significantly on galaxy formation model, and higher-density environments can either suppress or enhance star formation depending on galaxy mass and cosmic epoch.
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All authors Xavier Sims, Daniel Anglés-Alcázar, Boon-Kiat Oh, Daisuke Nagai, Jonathan Mercedes-Feliz, Isabel Medlock, Yueying Ni, Christopher C. Lovell, Francisco Villaescusa-Navarro

High Energy Astrophysical Phenomena

VLBI Observations of SN 2012au Reveal a Compact Radio Source a Decade Post Explosion

Mattias Lazda, Kenzie Nimmo, Maria R. Drout et al. (+13 more)

Three leading models have been put forth to justify the observed radio re-brightening associated with stripped-envelope supernovae (SESNe) years post-explosion: radiation from an emerging pulsar wind nebula (PWN), shock interaction with a dense circumstellar medium (CSM), or emission from off-axis, relativistic jets. SN 2012au is a particularly intriguing SESN in this regard as observations obtained $\gtrsim$ 6 years post-explosion have shown both (i) optical emission features consistent with a young PWN and (ii) a radio re-brightening. We present the results of our Very-Long-Baseline-Interferometric (VLBI) observations of SN 2012au performed between 8 to 13 years post core-collapse. Our VLBI observations reveal a luminous, steadily fading radio source that remains compact ($\leq1.4\times10^{17}~\mathrm{cm}$) and stationary ($\leq0.36c$) over the course of our campaign. Overall, we find that our VLBI measurements can be readily explained by a $\sim$decade-old PWN, potentially explained by shock interaction with specific CSM geometries, and are unlikely to be explained by emission from an off-axis, relativistic jet. Assuming a PWN origin, our observations require that the initial spin-down luminosity of the central pulsar be between $10^{36}~\mathrm{erg~s^{-1}}\leq\dot{E}_0\leq {4\times10^{42}}~\mathrm{erg~s^{-1}}$ and radio efficiency factor be $\eta_\mathrm{R}\geq {3\times10^{-7}}$ (both quoted at the $ {99.7\%}$ confidence interval). These results are consistent with independent inferences obtained using optical spectroscopy of SN 2012au, alongside inferences of known Galactic systems. If a PWN origin is confirmed, SN 2012au would represent the first extragalactic PWN emerging from a modern day SN, providing a novel opportunity to study the formation properties of a decade-old pulsar.
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All authors Mattias Lazda, Kenzie Nimmo, Maria R. Drout, Benito Marcote, Jason W.T. Hessels, Eli Wiston, Raffaella Margutti, Omar Ould-Boukattine, Tanmoy Laskar, Jacco Vink, Ryan Chornock, James K. Leung, Deanne L. Coppejans, Dan Milisavljevic, Juan Mena-Parra, Dan Patnaude

Solar and Stellar Astrophysics

The Energy-Duration Relationship in Astrophysical Self-Organized Criticality Systems

Markus J. Aschwanden and Alexandre Araujo

Scaling laws in astrophysical systems that involve the energy, the geometry, and the spatio-temporal evolution, provide the theoretical framework for physical models of energy dissipation processes. A leading model is the standard fractal-diffusive self-organized criticality (FD-SOC) model, which is built on four fundamental assumptions: (i) the dimensionality $d=3$, (ii) the fractal dimension $D_V=d-1/2=2.5$, (iii) classical diffusion $L \propto T^{(1/2)}$, and (iv) the proportionality of the dissipated energy to the fractal volume $E \propto V$. Based on these assumptions, the FD-SOC model predicts a scaling law of $T \propto E^k \propto E^{(4/5)} = E^{0.8}$. On the observational side, we find empirical scaling laws of $T \propto E^{0.81\pm0.03}$ by Peng et al.~(2023) and $T \propto E^{0.86\pm0.03}$ by Araujo & Valio (2021) that are self-consistent with the theoretical prediction of the FD-SOC model. However, cases with a small time range $q_T = \log{(T_{max}/T_{min})} \lapprox 2$ have large statistical uncertainties and systematic errors, which produces smaller scaling law exponents ($k \approx 0.3, ..., 0.6$) as a consequence. The close correlation of the scaling exponent $k$ with the truncation bias $q_T$ implies that the dispersion of k-values is an observational effect, rather than a physical property.
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Astrophysics of Galaxies

Spectral Signatures of Spinning Dust from Grain Ensembles in Diverse Environments: A Combined Theoretical and Observational Study

Zheng Zhang, Jens Chluba, Roke Cepeda-Arroita et al. (+1 more)

Recent observations of anomalous microwave emission (AME) reveal spectral features that are not readily reproduced by spinning dust models. We examine how dust grain distributions and environmental parameters determine the peak frequency and spectral width of AME spectral energy distribution (SED). Using Monte Carlo sampling and global sensitivity analysis, we find that AME features are dominantly controlled by three parameters: grain size, shape, and a phase-dependent environmental parameter. We also quantify the effects of SED broadening from ensembles of these dominant parameters, finding that the level of tension with observations is strongly phase dependent: Molecular Cloud (MC) is fully consistent, Dark Cloud (DC) shows minor deviations, and HII regions exhibit significant offsets in peak frequency. The discrepancy in HII echoes the observed depletion of small dust grains, particularly polycyclic aromatic hydrocarbons (PAHs), in HII regions. However, an observational HII region may still have AME originating from nearby non-HII clouds. In this case, model calculations for HII regions would be inappropriate. Reproducing MC and DC AME features requires ensemble variations in both grain size and environmental parameters are required to reproduce the observed spread in peak frequency and spectral width. We further propose moment expansion and emulation-based inference methods for future AME spectral analysis.
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All authors Zheng Zhang, Jens Chluba, Roke Cepeda-Arroita, José Alberto Rubiño-Martín

Earth and Planetary Astrophysics

Ultraviolet observations of atmospheric escape in exoplanets with the Habitable Worlds Observatory

Leonardo A. Dos Santos and Eric D. Lopez

Among the many recommendations of the Decadal Survey on Astronomy and Astrophysics 2020, we found that a priority area of research is to pave the pathways towards finding and characterizing habitable worlds. In this context, we aim to understand how planetary systems evolve through atmospheric escape, and develop techniques to identify potentially Earth-like worlds. Using the ultraviolet (UV) capabilities of the Habitable Worlds Observatory, we can use transit spectroscopy observations to determine what processes drive the evolution of exoplanets, how well can small exoplanets retain atmospheres, and search for Earth-like atmospheres. We advocate the development of a UV spectrograph that is capable of moderate- to high-resolution spectroscopy of point sources, access to key spectral features between 1000 and 3000 Angstrom, and UV detectors that are resilient to high count rates.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Temperature-Dependent CPT Violation: Constraints from Big Bang Nucleosynthesis

Gabriela Barenboim and Anne-Katherine Burns

In this study, we explore temperature-dependent CPT violation during Big Bang Nucleosynthesis (BBN) through electron-positron mass asymmetries parametrized by $b_0(T) = \alpha T^2$. The $T^2$ scaling naturally evades stringent laboratory bounds at zero temperature while allowing for significant CPT violation at MeV scales in the early universe \cite{ParticleDataGroup:2024cfk}. Using a modified version of the BBN code \faGithub \href{https://github.com/vallima/PRyMordial}{\,PRyMordial} with dynamically-solved chemical potentials and appropriate finite-mass corrections, we constrain electron-positron mass differences from observed abundances of Helium-4, Deuterium, and $N_{\rm eff}$. We find that $\alpha$ must be greater than or approximately equal to $10^{-6}$ GeV$^{-1}$ for keV-scale mass differences at BBN. All three observables show no simultaneous $1\sigma$ overlap, though pairwise combinations allow for constrained regions of parameter space. We present three toy models demonstrating how $b_0(T) \propto T^2$ arises from field-theoretic mechanisms, including temperature-driven phase transitions. These results provide the most stringent constraints on early-universe CPT violation in this regime, probing parameter space inaccessible to laboratory experiments.
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