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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 10 September

Instrumentation and Methods for Astrophysics

An X-ray Data Primer: What I Wish I Knew When Starting X-ray Astronomy

Nicholas P. Lee, Jonathan C. McDowell, Evan D. Tingle et al. (+1 more)

This guide is intended for astronomers new to X-ray astronomy. It provides a brief overview of the data products typically encountered by the user and highlights analysis considerations usually not discussed in more formal introductions to the discipline. In X-ray and $\gamma$-ray astronomy the primary data set is an event list (a table of individually detected photons with position, arrival time, and an instrumental energy estimate) rather than the image or visibility array familiar from other wavelength bands. We describe the files a user typically encounters, including: event lists, the aspect solution, spectra, instrumental responses, exposure maps, lightcurves, source lists, and calibration databases. These data are generally photon-limited and follow Poisson rather than Gaussian statistics. Combined with the coarse energy resolution of X-ray instruments, this means physical models must be fitted by "forward-folding"; we outline this technique and the systematic uncertainties introduced by calibration. Additional topics include: point spread function morphology, cosmic and instrumental backgrounds, pileup, contamination, binning conventions, the Chandra X-Ray Observatory focal plane, and sub-pixel event repositioning. This primer is intended to be generalized, not specific to any telescope or science subject area, although examples draw on Chandra. It was inspired by interactions with the astronomical community over several conferences and through the Chandra X-ray Center (CXC) HelpDesk.
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All authors Nicholas P. Lee, Jonathan C. McDowell, Evan D. Tingle, Karla M. Guardado

Instrumentation and Methods for Astrophysics

Astrophysics in the Era of Artificial Intelligence powered by Large Language Models

A. R. Rao

In recent times there is considerable unease about the way Artificial Intelligence (AI) powered by large language models is used to do astrophysics, and, assuming that these AIs will get far better in future, several alarming situations are also discussed. In a “white paper,” Hogg argues that extreme cases like allowing AI to write all astrophysics papers or strictly controlling AI are not good choices and posits that it is difficult to adopt moderate policies. I examine the impact of AI on astrophysics by making two rather extreme assumptions: first, that the modern astrophysicist has become increasingly preoccupied with the administrative task of publication over the act of physical discovery (astrophysicists are busy writing papers and have stopped doing astrophysics); and second, that while AI possesses the capacity to synthesize literature and generate manuscripts, they lack the intrinsic ability to perform original astrophysical inquiry (AI can write papers but cannot do astrophysics). I provide some plausible reasons for adopting these assumptions, but, more importantly, extrapolate the implications of these assumptions to argue that AI can have a very positive impact on astrophysics. By situating AI as agents of publication rather than discovery, the focus of the human researcher can be directed towards fundamental astrophysics, leading to very positive growth in the field.
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Earth and Planetary Astrophysics

OSIRIS-REx Returned a Pristine Sample of Asteroid Bennu: Takeaways from the Mission's Contamination Control and Knowledge Program

Jason P. Dworkin, Scott A. Sandford, Nicole G. Lunning et al. (+81 more)

NASA's OSIRIS-REx mission had the objective of delivering a pristine sample from asteroid (101955) Bennu to Earth for scientific analysis–where "pristine" signifies the absence of foreign materials that could affect sample measurements. OSIRIS-REx returned 121.6 g of regolith in September 2023; this study documents the systematic investigation of suspected contaminants encountered during the mission's sample analysis phase. Most suspected contaminants did not originate from the spacecraft or sample curation. Some were introduced during laboratory analyses, reinforcing the importance of procedural blanks and a strategic approach to sharing samples across laboratories with different analytical targets. Several suspected contaminants, such as phosphate and sodium fluoride particles, were ultimately identified as indigenous to Bennu, highlighting the critical role of contamination knowledge in preventing the dismissal of valuable scientific data. We find that the returned sample meets the definition of pristine, except for an isolated 1.24% (by mass) that escaped the sample container and was thereby contaminated with spacecraft particulates. These findings demonstrate the effectiveness of systematically applied contamination science and engineering practices and provide lessons and approaches to help maximize the scientific integrity of future planetary sample return missions.
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All authors Jason P. Dworkin, Scott A. Sandford, Nicole G. Lunning, Kevin Righter, Charles C. Lorentson, Daniel P. Glavin, Kathie L. Thomas-Keprta, Loan Le, Catherine M. Corrigan, Timothy J. McCoy, Edward B. Bierhaus, Jose C. Aponte, Angel Mojarro, Hannah L. McLain, Eric T. Parker, Denise K. Buckner, Frédéric Seguin, Radford L. Perry, Heather V. Graham, Havishk Tripathi, Pierre Haenecour, Piers Koefoed, Kun Wang, Cody Schultz, Takahiro Hiroi, Ralph E. Milliken, Simon J. Clemett, Bumsoo Kim, Christopher J. Snead, Eve L. Berger, Michael Liss, Jessica J. Barnes, Sandra Freund, Zoe A. Wilson, Ryan D. Dubisher, Natasha V. Almeida, Kimberly K. Allums, Erika H. Blumenfeld, Joseph E. Aebersold, Rachel C. Funk, Carla P. Gonzales, Julia L. Plummer, Maritza Montoya, Daniel J. Rohmer, Erika V. Rivera, Jannatul Ferdous, Gabriel C. Garcia, Melissa Rodriguez, Jose L. Ponce, Ronald Bastien, Wayland D. Connelly, Jemma Davidson, Marghaleray Amini, Vivian Lai, Dominique Weis, Josh Wimpenny, Jan Render, Gregory A. Brennecka, Yoshihiro Furukawa, Toshiki Koga, Yoshinori Takano, Hiroshi Naraoka, Yasuhiro Oba, Kenneth J. Domanik, Yao-Jen Chang, Zoe Zeszut, Thomas J. Zega, George D. Cody, Conel M. O'D. Alexander, Ian A. Franchi, Monica M. Grady, Danielle N. Simkus, Jamie E. Elsila, Philippe Schmitt-Kopplin, Allison A. Baczynski, Katherine H. Freeman, Amy E. Hofmann, Aaron S. Burton, Lindsay P. Keller, Sara S. Russell, Anjani T. Polit, Francis M. McCubbin, Harold C. Connolly Jr., Dante S. Lauretta

Earth and Planetary Astrophysics

Steepening Optical Slopes in Exoplanet Transmission Spectra with Charged Hazes

Masayuki Inai, Kazumasa Ohno and Shota Notsu

Observations of exoplanetary atmospheres have revealed the ubiquity of aerosols, yet their microphysics remain largely uncertain. Haze charging is a key microphysical process in aerosol-rich Solar System atmospheres, but it has been ignored in exoplanetary haze models. Here we develop a microphysical framework that includes haze charging for exoplanet atmospheres and investigate its effects on transmission spectra. Electrostatic repulsion suppresses coagulation, maintaining smaller particle radii and higher mixing ratios in the upper atmospheres. We find that particle charging steepens the optical spectral slopes when vertical mixing is weak. This behavior arises from the combination of reduced particle sizes and a steepened vertical gradient in haze opacity. Furthermore, we find distinct spectral responses to charging for different haze analogs, owing to the different contributions of scattering and absorption. For absorption-dominated materials such as soot, particle-size reduction has little impact on opacity profiles, leading to only minor charging-induced spectral changes. By contrast, scattering-dominated materials such as tholin and diamond show a stronger spectral signature of particle charging because of the strong dependence of scattering opacity on particle size. While previous studies have invoked haze formation under vigorous vertical mixing as a mechanism for producing super-Rayleigh optical slopes, we demonstrate that highly charged scattering haze can produce such slopes even under weak-to-moderate vertical mixing. Our results highlight haze charging as a previously neglected microphysical process that can affect particle growth and leave observable signatures in transmission spectra, providing a quantitative framework for assessing atmospheric electrical conditions.
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Solar and Stellar Astrophysics

Plasma Heating and Energization in Hot-Onset Flare Precursor Events

H. Da, J. F. Drake and M. Swisdak

Recent observations of solar flares have revealed a distinct 'hot onset' phase preceding the impulsive phase, characterized by elevated plasma temperature (>10 MK), a steady increase in emission measure, and the absence of detectable nonthermal emission. The standard flare model attributes the formation of hot flare plasma to chromospheric evaporation driven by energy deposition from nonthermal electrons, and therefore does not naturally explain why thermal heating precedes nonthermal emission. Motivated by recent observations of guide-field evolution in two-ribbon flares and by large-scale MHD simulations, we investigate hot-onset energization using simulations of magnetic reconnection with the kinetic macroscale model kglobal initialized with a spatially non-uniform guide field. Because the efficiency of electron non-thermal energy production from Fermi acceleration decreases with guide-field strength, the evolving guide field produces two distinct energization regimes. During the initial high-guide-field phase, the bulk electron temperature rises to approximately twice its initial value, while non-thermal particle production remains weak. Upon entering the low-guide-field regime, energetic particle production is significantly enhanced, with the population of high-energy electrons growing rapidly. These findings provide a self-consistent physical explanation for the hot onset, demonstrating that the macroscopic evolution of the guide field naturally bridges the hot-onset and impulsive phases of solar flares without requiring a separate trigger mechanism.
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Instrumentation and Methods for Astrophysics · Cross-listed from quant-ph

Path-Degenerate Quantum Interferometry for Loss Resilience in Gravitational-Wave Detectors

Jonas Rittmeyer, Niels Boettner, Farid Khalili et al. (+2 more)

Optical decoherence degrades quantum correlations in squeezed states of light, severely limiting the quantum-nondemolition (QND) sensitivity of gravitational-wave detectors. Here, we propose the path-degenerate quantum interferometry scheme that obviates the need for entire optical subsystems—including additional filter cavities, auxiliary parametric amplifiers, and Faraday isolators—thereby drastically reducing spatial mode mismatches while inherently integrating variational output, a long-standing theoretical proposal to further deepen the QND regime. We experimentally demonstrate a core aspect of this scheme, achieving a shot-noise-preserving signal enhancement that directly counteracts the detrimental effects of readout loss. By delivering an improved signal-to-quantum-noise ratio solely through the consolidation and reduction of currently considered optical subsystems, our approach offers a highly optimized route toward enhanced quantum-noise reduction in upcoming LIGO upgrades and next-generation gravitational-wave observatories.
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All authors Jonas Rittmeyer, Niels Boettner, Farid Khalili, Mikhail Korobko, Roman Schnabel

Astrophysics of Galaxies

NOEMA probes the [CII] and dust content in a 2175Å UV Bump Galaxy at $z=7.1$

Katherine Ormerod, Renske Smit, Joris Witstok et al. (+5 more)

The detection of the $2175$Å UV bump at $z>6$ challenges existing models of dust formation, suggesting rapid formation of small carbonaceous dust grains within the first billion years of cosmic time. We present the results of the first direct attempt at linking far-infrared (FIR) observations to the UV bump within the Epoch of Reionisation (EoR), through NOEMA observations of GNWY-7379420231 at $z=7.108$, a galaxy exhibiting the strongest known UV bump feature at $z>4$. We detect the [CII] 158$\mu$m emission line at 5.1$\sigma$ at $z_\mathrm{[CII]} = 7.1078 \pm 0.0005$, in excellent agreement with the redshift derived from the [OIII] $\lambda 5007$Å line. The {\cii} luminosity implies $\mathrm{SFR}_\mathrm{[CII]}=16.2^{+5.8}_{-5.5}M_\odot \mathrm{yr}^{-1}$, consistent with short timescale SFR tracers such as dust corrected $\mathrm{SFR}_\mathrm{H\alpha}=18.0\pm3.9 M_\odot \mathrm{yr}^{-1}$ and $\mathrm{SFR}_\mathrm{10~Myr}=20.5^{+3.8}_{-5.0}M_\odot \mathrm{yr}^{-1}$ from SED fitting. The dust continuum is not detected suggesting an obscured SFR of $\mathrm{SFR}_\mathrm{IR} < 32 ~M_\odot \mathrm{yr}^{-1}$ and a dust mass of $M_\mathrm{d} < 5.3\times10^6 ~M_\odot$ $(M_\mathrm{d}/M_\star<2\%)$. Finally, the [CII]-derived dynamical mass of $\log_{10}(M_\mathrm{dyn}/M_\odot)=8.95^{+0.51}_{-0.66}$ and stellar mass of $\log _{10}\left(\mathrm{M}_{\star} / \mathrm{M}_{\odot}\right) = 8.39_{-0.09}^{+0.13}$ suggest a gas-rich moderately massive galaxy. Taken together these results rule out GNWY-7379420231 being a heavily dust obscured or massive galaxy, but rather a `normal' EoR galaxy with a recent upturn in star-formation. Our results suggest efficient shattering of larger dust grains in the diffuse, turbulent ISM and/or fortunate line of sight alignment are needed to explain the UV bump properties of GNWY-7379420231.
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All authors Katherine Ormerod, Renske Smit, Joris Witstok, Anna de Graaff, Michael V. Maseda, Irene Shivaei, Andrew J. Bunker, Gareth C. Jones

High Energy Astrophysical Phenomena

Hidden structures in the UHE sky: unveiling potential sources via spectral signatures

Mateus Zeferino Rennó and Cainã de Oliveira

The search for the origin of ultrahigh-energy cosmic rays (UHECRs) typically relies on identifying directional excesses in the particle flux. While this approach is well established, it cannot detect localized spectral features, which could provide constraints on the sources of UHECRs if measured. In this work, we propose a complementary metric for directional searches, based on a functional $\mu_E$ of the energy spectrum in a given arrival direction. We demonstrate that $\mu_E$ mathematically decouples the flux normalization of a sky region from the spectral shape, providing a distinct probe for direction-dependent spectra. To assess the statistical significance of this metric, we derive a generalization of the Li-Ma significance formula for energy-weighted metrics. Using a maximum-likelihood analysis within an exploratory Monte-Carlo model, we show that $\mu_E$ can enhance discovery potential by identifying hard-spectrum regions that are not apparent in standard particle-flux maps, thereby providing a complementary probe of potential UHECR sources.
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Cosmology and Nongalactic Astrophysics

Probabilistic characterization of blending with LSST and application to cluster lensing cosmology

Manon Ramel, Cyrille Doux, Marine Kuna et al. (+9 more)

Next-generation galaxy surveys, like the Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST), will deliver unprecedented depth and sky coverage, enabling precise measurements of cosmic probes such as weak lensing and galaxy clustering. However, increased imaging depth leads to significant blending of galaxy images, particularly in dense fields like galaxy clusters. This blending, exacerbated by atmospheric blurring in ground-based observations, contaminates galaxy property measurements and causes source confusion. To simultaneously capture these effects, we develop a probabilistic framework introducing the blending entropy, a metric quantifying the ambiguity in matching detected objects to true galaxies or external reference sources. Using simulated data from the DESC Data Challenge 2 (DC2), we characterize blending in LSST data and quantify its impact on cluster lensing cosmology around cosmoDC2 halos. We demonstrate that imposing a blending entropy threshold of $S_b<0.2$ effectively filters out highly blended objects (around 25%), which are especially prevalent near the survey's magnitude limit and are associated with higher errors in shape measurements and photometric redshifts. Applying this cut substantially reduces blending-induced biases in cluster lensing profiles and mass estimates, thereby mitigating systematic errors in cosmological parameters—most notably reducing tension in $\sigma_8$ estimates. Our method is readily generalizable to other static probes and offers a practical path forward for real data analyses, particularly when leveraging overlapping high-resolution datasets from spaced-based missions such as Euclid or the Roman Space Telescope, where these external datasets can act as reference catalogs to improve the identification of blended sources in LSST data.
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All authors Manon Ramel, Cyrille Doux, Marine Kuna, Michel Aguena, Céline Combet, Shuang Liang, Constantin Payerne, Camille Avestruz, Alex I. Malz, Marina Ricci, Nikolina Šarčević, the LSST Dark Energy Science Collaboration

Instrumentation and Methods for Astrophysics

A Proliferated Space Architecture for Time-Domain Astrophysics

Daniel Kocevski, Eric Burns, Thomas Barclay et al. (+58 more)

Time-Domain and Multi-Messenger Astrophysics (TDAMM) is entering a discovery-rich but follow-up-limited era, creating an urgent need for responsive, multiwavelength space-based capabilities. The Hydra constellation is a concept for a proliferated space architecture for time-domain astrophysics. The constellation would act as a disaggregated observatory composed of coordinated, relatively low-cost spacecraft that collectively provide capabilities traditionally concentrated within a single large mission. The architecture would combine persistent wide-field gamma-ray monitoring, wide-field and focused X-ray observations, and rapid-response ultraviolet, optical, and infrared imaging and spectroscopy. The constellation would both discover high-energy transients and respond to external alerts from gravitational-wave detectors, neutrino observatories, and ground- and space-based surveys, using low-latency communications, automated event prioritization, and community coordination frameworks to rapidly assign observing resources. A proliferated architecture would offer operational advantages over a single larger mission, including simultaneous observations of multiple targets, graceful degradation following individual spacecraft failures, recurring technology refresh, and opportunities for commercial, international, and philanthropic contributed nodes to join the network. The constellation would address fundamental questions concerning cosmic accelerators, the origin and evolution of the elements, the behavior of matter at extreme density, and the nature of dark energy through gravitational-wave standard sirens. This white paper presents the Hydra concept description that was submitted to NASA's ASTRA initiative for consideration by the Cosmic Origins Program Analysis Group (CoPAG) and Physics of the Cosmos Program Analysis Group (PhysPAG).
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All authors Daniel Kocevski, Eric Burns, Thomas Barclay, Nicholas E. White, Massimiliano Galeazzi, Brendan O'Connor, Amy Lien, Chris Fryer, Hallie Fausey, Fe McBride, Neil Cornish, Dheeraj Pasham, Kip Kuntz, Anya Nugent, Scott Porter, Tzu-Ching Chang, Adam Lidz, Alexander van der Horst, Sylvain Guiriec, Ed Cackett, Dieter Hartmann, Brad Cenko, C. Michelle Hui, Tyler Parsotan, Michael W. Coughlin, Eliza Neights, Zorawar Wadiasingh, Catherine Grant, Oindabi Mukherjee, Francesco Longo, Eric Bellm, Alec Habig, George Younes, Kim Page, Shivam Kumar Sharma, Oliver J. Roberts, Rachel Hamburg, Rahul Gupta, Colleen A. Wilson-Hodge, William Cleveland, Breann Sitarski, Vikas Chand, Raffaella Margutti, Adam Goldstein, Ryan J. Foley, Vidushi Sharma, Yi-Jung Yang, Elisabetta Bissaldi, M. Coleman Miller, T. A. Pritchard, D. J. Sand, Tomas Ahumada, Judith Racusin, Noah Franz, Kate D. Alexander, Brenna Mockler, D. Andrew Howell, Elisa Quintana, Chin-Ping Hu, Igor Andreoni, Boyan Hristov

High Energy Astrophysical Phenomena

Probing Lorentz Invariance Violation in Cosmogenic Neutrino Propagation with KM3-230213A

Rodrigo Sasse, Rodrigo Guedes Lang and Rita de Cássia dos Anjos

We investigate superluminal Lorentz invariance violation (LIV) in the neutrino sector using cosmogenic neutrino fluxes generated with ultrahigh-energy cosmic-ray propagation models. Standard fluxes are calculated with CRPropa 3.2 and subsequently modified using a prescription based on LIV-induced neutrino splitting. Superluminal LIV suppresses the flux at the highest energies while producing an enhancement at PeV - EeV energies. We use the KM3-230213A event as a benchmark to evaluate the sensitivity of current observations to these spectral modifications. Although the available statistics do not allow a formal constraint, the predicted fluxes are particularly sensitive to coefficients in the range $10^{-24} \mathrm{eV}^{-1} \lesssim \delta_{\nu,1} \lesssim 10^{-22}\,\mathrm{eV}^{-1}$, with the results strongly depending on the assumed cosmic-ray source properties. Intermediate coefficients can enhance the expected event rate within the reconstructed energy range of KM3-230213A, whereas larger coefficients may overproduce neutrinos in energy intervals constrained by IceCube and the Pierre Auger Observatory. These results identify a region of observational sensitivity to LIV and provide testable predictions for future neutrino telescopes.
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High Energy Astrophysical Phenomena

Which Type Ia supernova observables best indicate the ages of their progenitor stars?

Young-Lo Kim, Chul Chung, Young-Wook Lee et al. (+3 more)

Type Ia supernovae (SNe Ia) observables, such as the light-curve shape and the colour, are expected to contain information about the progenitor star. In this work, we explore this information, with a particular focus on the age of the SN Ia progenitor star. For this, we construct the SN Ia progenitor age distribution (SPAD) and compare it to the observed distributions of light-curve shape (x1) and the colour (c) parameters in a volume-limited SN Ia sample. We find that SPAD and the x1 distribution share a common shape: a young/high-x1 peak and an old/low-x1 bump in the tail, and this shape varies systematically with redshift. In contrast, this behaviour is not evident in the c distribution. We then examine the correlation of the local age at the SN Ia explosion site, used as a proxy for the progenitor age, with x1 and c. The local age and x1 are well correlated (the linear correlation coefficient ~ -0.71), whereas the local age and c show no significant correlation (the coefficient ~ 0.08). Furthermore, we find that the x1 distribution systematically evolves with the local age. Lastly, we demonstrate that an empirical mapping approach based on SPAD successfully reproduces the observed x1 distribution across different redshift bins. Taken together, our results suggest that the light-curve shape distribution indicates progenitor age at the population level more robustly than the colour does. In particular, younger progenitors are more likely to have higher-x1 SNe Ia. We discuss an application for creating a more homogeneous sample of SNe Ia in terms of progenitor age across a wide redshift range without the Malmquist bias, thereby improving the accuracy of cosmological constraints derived from SNe Ia.
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All authors Young-Lo Kim, Chul Chung, Young-Wook Lee, Seunghyun Park, Junhyuk Son, Suk-Jin Yoon

High Energy Astrophysical Phenomena

Long-term X-ray spectral analysis of Cygnus X-1 using AstroSat

H Lalthantluanga, Akash Garg, Ranjeev Misra et al. (+2 more)

We performed a spectral analysis of long-term observations (2016-2019) of the black hole binary Cygnus X-1 using AstroSat, covering its hard, intermediate, and soft states. During soft states, we found that a typical spectrum fitted with a single Comptonization, a thermal disc, and an iron line yields poor fits and unphysically small disk radii (R_in < 1 R_g). While adding a relativistic disk component (kerrbb) improved the fit but required high color factors (f_col ~ 3.35-5.08), indicating additional Comptonization. We therefore adopted a dual-Comptonization model with hot (optically thin) and warm (optically thick) coronae. This provided consistent good fits across all soft and hard states of Cygnus X-1. The spectral evolution reveals the critical role of dual Comptonization in shaping the broadband emission of Cygnus X-1.
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All authors H Lalthantluanga, Akash Garg, Ranjeev Misra, Vanzarmawii Chhangte, Lalthakimi Zadeng

Cosmology and Nongalactic Astrophysics

The Role of Big Bang Nucleosynthesis in Joint Cosmological Analyses

Mehmet Akharman, Nicholas DePorzio, Cara Giovanetti et al. (+1 more)

We perform joint Baryon Acoustic Oscillation (BAO) + Big Bang Nucleosynthesis (BBN) and BAO+BBN+Cosmic Microwave Background (CMB) analyses with Planck CMB and DESI DR2 BAO data, explicitly marginalizing over BBN nuisance parameters for the first time with these data combinations and paying particular attention to the impact of BBN on these results. We find in our fiducial analyses $h=0.6833^{+0.0048}_{-0.0053}$ ($\Lambda$CDM, BAO+BBN), $h=0.6823^{+0.0027}_{-0.0026}$ ($\Lambda$CDM, BAO+BBN+CMB), as well as $h=0.6791^{+0.0069}_{-0.0075},N_{\rm{eff}}=2.974^{+0.098}_{-0.099}$ ($\Lambda$CDM+$N_{\rm{eff}}$, BAO+BBN), and $h=0.6838^{+0.0052}_{-0.0054},N_{\rm{eff}}=3.065^{+0.078}_{-0.076}$ ($\Lambda$CDM+$N_{\rm{eff}}$, BAO+BBN+CMB). We demonstrate how investigator choices can impact results of joint analyses involving BBN. We provide recommendations for the treatment of BBN in light of recent work, and demonstrate a pipeline that accurately accounts for prediction uncertainties in BBN.
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All authors Mehmet Akharman, Nicholas DePorzio, Cara Giovanetti, Hongwan Liu

Astrophysics of Galaxies

Unified modelling of broad and narrow optical-UV emission lines from massive black holes: interpreting high-redshift JWST observations

Adele Plat, Michaela Hirschmann, Emma Curtis-Lake et al. (+10 more)

JWST is uncovering a large population of active galactic nuclei (AGN) at high redshift, motivating the extension of models calibrated on local sources to a broader range of physical conditions. We present a consistent suite of broad- and narrow-line photoionisation models based on ionising spectra that vary with black-hole mass and Eddington ratio, spanning sub- to super-Eddington accretion. For the broad-line region (BLR), we investigate the detectability of low-mass accreting black holes. At z=6, broad H{\alpha} may be detectable down to $M_{BH}\approx10^{5.7} M\odot$ for a BH accreting at the Eddington limit under favourable assumptions. We derive line-to-accretion-luminosity corrections, with hydrogen and helium recombination lines providing more robust tracers than metal lines. We also explore which changes in black-hole properties and BLR conditions can contribute to the large H{\alpha} equivalent widths, elevated Balmer decrements, and weak high-ionisation lines observed in some high-redshift sources, finding that variations in BLR structure can substantially modify the emergent spectrum. For the narrow-line region (NLR), H{\alpha} and [O III] {\lambda}5007 are among the most promising tracers of low-mass accreting black holes, probing $M_{BH}\approx10^{5.5} M\odot$ at the Eddington limit. Many classical diagnostic diagrams miss low-metallicity AGN; we identify alternative UV and optical diagnostics that more robustly separate AGN from Pop. II and Pop. III stellar photoionisation over the conditions explored. Nevertheless, NLR line ratios are driven primarily by metallicity and ionisation parameter, with only a weak dependence on black-hole mass and Eddington ratio. Looking ahead, these models are intended for Bayesian interpretation of JWST spectra and connection to cosmological simulations through physically motivated priors.
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All authors Adele Plat, Michaela Hirschmann, Emma Curtis-Lake, Anna Feltre, Stephane Charlot, Steven L. Finkelstein, Lorenzo Napolitano, Fabio Pacucci, Norbert Pirzkal, Sandra Raimundo, Anthony Taylor, Alba Vidal-Garcia, L. Y. Aaron Yung

Astrophysics of Galaxies

BAQARO: Tracing Stochastic Black Hole Growth Histories and Quasar Lightcurves in a Cosmological Context

Elia Pizzati, Joseph F. Hennawi and Joop Schaye

How supermassive black holes (BHs) assemble their mass and power the luminous quasars we observe across cosmic time remain central open questions in galaxy evolution. We present BAQARO, a semi-empirical framework for BH growth. Built on subhalo merger trees extracted from the FLAMINGO-10k simulation, the model links BH growth histories to those of their host subhalos through prescriptions that capture both average trends and stochastic variability. BAQARO is constrained by the bolometric quasar luminosity function, the clustering of UV-luminous quasars, and the conditional Eddington ratio distribution function. With six free parameters controlling BH seeding, the coupling between gas accretion and halo growth, and the stochasticity and temporal coherence of accretion, the model reproduces the available observational constraints over $0 \lesssim z \lesssim 7$. Using emulators, we perform Bayesian inference and quantify the constraining power of each observable. Our main findings are: (i) BH accretion is well described by the assembly of cold gas reservoirs in halos, without requiring an explicit dependence on cosmic time. (ii) BHs rapidly assemble their mass at high redshift through stochastic episodes of super-Eddington accretion. (iii) These episodes are radiatively inefficient and persist for timescales of $\sim1\,\mathrm{Myr}$, imprinting observable signatures on quasar lightcurves, proximity zones, and clustering measurements. (iv) The merger growth channel is always subdominant, but becomes increasingly important at $z \lesssim 1$, particularly for massive BHs. BAQARO growth histories and quasar lightcurves provide a flexible framework for interpreting the rapidly expanding landscape of quasar observations, from high-$z$ accretion probed by JWST to low-$z$ mergers constrained by pulsar timing arrays.
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Astrophysics of Galaxies

Galaxies in the first two billion years: Earlier formation and quenching with surface-density modulated star formation and feedback

Akash Vani, Mohammadreza Ayromlou, Guinevere Kauffmann et al. (+1 more)

JWST has revealed massive, UV-bright, compact, and in some cases quenched galaxies in the first two billion years of cosmic history, challenging current galaxy formation models. We develop an extended L-Galaxies semi-analytic model, run on the MillenniumTNG dark-matter-only simulation, and follow galaxy evolution over $0 \le z \lesssim 15$. The model ties the star formation efficiency and the coupling of stellar feedback energy to the local cold gas surface density, making star formation efficient and feedback ineffective in dense gas. We include dissipative gas-rich mergers and disc instabilities in stellar and gaseous discs. All parameters are calibrated simultaneously against stellar mass functions and quenched fractions at $z\simeq0-4$ and UV luminosity functions at $z\simeq11-12$ with a new parallelised Markov chain Monte Carlo framework. The model reproduces the stellar mass function up to $z\approx 11$ and increases the abundance of massive and UV-bright galaxies at $z\gtrsim9$ by up to two orders of magnitude over the legacy version. Although the AGN feedback prescription is unchanged, the enhanced bulge growth and black hole fuelling make massive quenched galaxies at $z\simeq3-8$ two orders of magnitude more abundant, while dissipative mergers produce compact remnants with UV size-luminosity relations matching observations at $z\simeq10-13$. At low redshift, galaxy sizes, cold-gas content, metallicities, radial profiles, and morphologies remain consistent with observations. Our results indicate that the tension between models and JWST observations at cosmic dawn can be substantially reduced by regulating star formation and feedback through the local gas surface density, without a modified initial mass function, non-standard cosmology, or new AGN physics.
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All authors Akash Vani, Mohammadreza Ayromlou, Guinevere Kauffmann, Volker Springel

Astrophysics of Galaxies

Resolved SED modelling with JWST and ALMA: the role of stellar mass surface density in regulating star formation in cosmic noon galaxies

Cheng-Lin Liao, Leindert A. Boogaard, Jacqueline A. Hodge et al. (+27 more)

We present kpc-scale ($0.2''-0.5''$) physical property maps of 35 main-sequence galaxies at $z \approx 0.5-3.7$, with stellar masses of $\log(M_*/M_\odot) \sim 9.7-11.7$ and star formation rates of $\mathrm{SFR} \sim 1.4-280\,\mathrm{M_\odot\,yr^{-1}}$, selected from the ALMA Spectroscopic Survey (ASPECS) in the Hubble Ultra Deep Field. Leveraging the unique HST, JWST (NIRCam and MIRI), and ALMA observations, we perform spatially resolved spectral energy distribution (SED) modeling across the UV-to-FIR regime. We find that incorporating MIRI and/or ALMA data reduces the overestimation of dust luminosity (by up to $\sim0.8$ dex), while ALMA observations further mitigate the age-dust degeneracy. In the absence of such data, restricting the SED model library based on the observed unresolved colors can partially mitigate these biases. The stellar masses ($M_{*}$) derived from resolved and unresolved modeling are consistent within $\sim0.05$ dex, suggesting that mass discrepancies (attributed to outshining) are less significant for cosmic noon main-sequence galaxies when rest-frame near-infrared (NIR; e.g., $\sim1-3\,\mu\mathrm{m}$) data are included. After normalization to the same reference, the composite SED of our sample closely resembles that of local starburst galaxies such as M82, suggesting similar dust attenuation and re-emission properties. Finally, we find that the molecular gas fraction and depletion time correlate with the effective stellar mass surface density ($\Sigma_{\rm eff,*} = M_{*}/2\pi R_{\rm eff,M_*}^2$) similarly to that observed in local galaxies. These results provide a first qualitative view of how the stellar gravitational potential influences gas regulation and star formation in galaxies beyond the local Universe.
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All authors Cheng-Lin Liao, Leindert A. Boogaard, Jacqueline A. Hodge, J. Li, E. da Cunha, P. Sharda, A. Battisti, C. Lagos, M. Kaasinen, I. Smail, M. Aravena, F. E. Bauer, R. K. Cochrane, L. Colina, P. Cox, R. Decarli, T. Díaz-Santos, R. Fernández Aranda, N. N. Geesink, H. Inami, B. Magnelli, J. Melinder, M. Neeleman, G. Östlin, G. Popping, D. A. Riechers, I. Shivaei, P. van der Werf, F. Walter, A. Weiss

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

Accretion onto a moving black hole for stiff equations of state

Elliott Ewell, Peter K. Harris, Thomas W. Baumgarte et al. (+1 more)

We revisit accretion of an asymptotically uniform fluid onto a moving Schwarzschild black hole, the relativistic analog of Bondi-Hoyle-Lyttleton accretion. Expanding on previous treatments, we focus on relativistic accretion of stiff fluids with adiabatic indices $\Gamma \geq 5/3$, which is particularly relevant for the treatment of primordial black holes captured by neutron stars. We perform numerical simulations to systematically explore the dependence of the steady-state accretion and drag rates on the asymptotic sound speed $a_\infty$ and relative speed $v_\infty$, and identify different regimes, both subsonic and supersonic, in which these rates either increase or decrease with respect to the spherical accretion rate for $v_\infty = 0$. We propose simple analytical approximations that capture the qualitative features observed in the dependence of the accretion and drag rates on $a_\infty$ and $v_\infty$.
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All authors Elliott Ewell, Peter K. Harris, Thomas W. Baumgarte, Stuart L. Shapiro

High Energy Astrophysical Phenomena

Time-Integrated Searches for Sub-TeV Neutrino Sources with IceCube-DeepCore

R. Abbasi, M. Ackermann, J. Adams et al. (+418 more)

We have developed techniques for a competitive sub-TeV time-integrated neutrino search and applied it to 11.1 years of IceCube-DeepCore data. The DeepCore subarray lowers the sensitivity of IceCube down to sub-TeV energies and is especially interesting for objects with soft spectra. Three studies were performed: a search for neutrino emission from AGN exhibiting high intrinsic X-ray flux, including NGC 1068, as identified by SWIFT/BAT; a search for neutrino emission from Galactic objects identified by Fermi-LAT as exhibiting a spectral shape consistent with neutral pion decay; and an all-sky search for neutrino point sources. Objects for this study were selected given their prospects for sub-TeV neutrino emission. No evidence for sub-TeV neutrino emission is found in any of the searches performed. Finally, for each catalog of objects, we use a statistical combination of the p-values via a binomial test to search for aggregated neutrino emission from a subset of the objects. Neither of the binomial tests yields significant results. For NGC 1068, assuming a power law spectrum with index 3.4, the 90% confidence level upper limit on per-flavor neutrino emission in the 30–400 GeV range is $\Phi_{\nu+\bar{\nu}}|_{\mathrm{1 TeV}} < 9.5 \times 10^{-11}$ TeV$^{-1}$ cm$^{-2}$ s$^{-1}$, a factor of two higher than the extrapolation of IceCube's measurement at higher energies. We additionally provide neutrino flux upper limits for a variety of spectra.
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All authors R. Abbasi, M. Ackermann, J. Adams, J. A. Aguilar, M. Ahlers, J.M. Alameddine, S. Ali, N. M. Amin, K. Andeen, C. Argüelles, S. Athanasiadou, S. N. Axani, R. Babu, X. Bai, A. Balagopal V., S. W. Barwick, V. Basu, R. Bay, J. J. Beatty, J. Becker Tjus, P. Behrens, J. Beise, C. Bellenghi, S. Benkel, S. BenZvi, D. Berley, E. Bernardini, D. Z. Besson, E. Blaufuss, L. Bloom, S. Blot, F. Bontempo, J. Y. Book Motzkin, C. Boscolo Meneguolo, S. Böser, O. Botner, J. Böttcher, J. Braun, B. Brinson, Z. Brisson-Tsavoussis, L. Brusa, R. T. Burley, D. Butterfield, K. Carloni, J. Carpio, N. Chau, Y. C. Chen, Z. Chen, D. Chirkin, S. Choi, A. Chubarov, B. A. Clark, D. A. Coloma Borja, A. Connolly, J. M. Conrad, D. F. Cowen, C. De Clercq, J. J. DeLaunay, D. Delgado, T. Delmeulle, S. Deng, P. Desiati, K. D. de Vries, G. de Wasseige, T. DeYoung, J. C. Díaz-Vélez, S. DiKerby, T. Ding, M. Dittmer, A. Domi, L. Draper, L. Dueser, D. Durnford, K. Dutta, M. A. DuVernois, T. Ehrhardt, L. Eidenschink, A. Eimer, C. Eldridge, P. Eller, E. Ellinger, D. Elsässer, R. Engel, H. Erpenbeck, W. Esmail, S. Eulig, J. Evans, P. A. Evenson, K. L. Fan, K. Fang, K. Farrag, A. Fattorini, A. R. Fazely, A. Fedynitch, N. Feigl, C. Finley, D. Fox, A. Franckowiak, S. Fukami, P. Fürst, J. Gallagher, E. Ganster, A. Garcia, M. Garcia, E. Genton, L. Gerhardt, A. Ghadimi, C. Glaser, T. Glüsenkamp, J. G. Gonzalez, S. Goswami, A. Granados, D. Grant, S. J. Gray, S. Griffin, S. Griswold, K. M. Groth, D. Guevel, C. Günther, P. Gutjahr, C. Ha, A. Hallgren, L. Halve, F. Halzen, L. Hamacher, M. Handt, K. Hanson, J. Hardin, A. A. Harnisch, P. Hatch, A. Haungs, J. Häußler, K. Helbing, J. Hellrung, B. Henke, L. Hennig, F. Henningsen, L. Heuermann, R. Hewett, N. Heyer, S. Hickford, A. Hidvegi, C. Hill, G. C. Hill, R. Hmaid, K. D. Hoffman, A. Hollnagel, D. Hooper, S. Hori, K. Hoshina, M. Hostert, W. Hou, M. Hrywniak, T. Huber, K. Hultqvist, K. Hymon, A. Ishihara, W. Iwakiri, M. Jacquart, S. Jain, O. Janik, M. Jansson, M. Jin, N. Kamp, D. Kang, W. Kang, A. Kappes, L. Kardum, T. Karg, A. Karle, A. Katil, M. Kauer, J. L. Kelley, M. Khanal, A. Khatee Zathul, A. Kheirandish, T. Kim, H. Kimku, F. Kirchner, J. Kiryluk, C. Klein, S. R. Klein, Y. Kobayashi, S. Koch, A. Kochocki, R. Koirala, H. Kolanoski, T. Kontrimas, L. Köpke, C. Kopper, D. J. Koskinen, P. Koundal, M. Kowalski, T. Kozynets, A. Kravka, N. Krieger, T. Krishnan, K. Kruiswijk, E. Krupczak, E. Kun, N. Kurahashi, C. Lagunas Gualda, L. Lallement Arnaud, M. J. Larson, F. Lauber, J. P. Lazar, K. Leonard DeHolton, A. Leszczyńska, C. Li, J. Liao, C. Lin, Q. R. Liu, Y. T. Liu, M. Liubarska, C. Love, L. Lu, F. Lucarelli, W. Luszczak, Y. Lyu, M. Macdonald, E. Magnus, Y. Makino, E. Manao, S. Mancina, A. Mand, I. C. Mariş, S. Marka, Z. Marka, L. Marten, I. Martinez-Soler, R. Maruyama, J. Mauro, F. Mayhew, F. McNally, K. Meagher, A. Medina, M. Meier, Y. Merckx, L. Merten, J. Mitchell, L. Molchany, S. Mondal, T. Montaruli, R. W. Moore, Y. Morii, A. Mosbrugger, D. Mousadi, E. Moyaux, T. Mukherjee, M. Nakos, U. Naumann, R. Neshat, L. Neste, M. Neumann, M. U. Nisa, K. Noda, A. Noell, A. Novikov, A. Obertacke, V. O'Dell, A. Olivas, R. Orsoe, J. Osborn, E. O'Sullivan, B. Owens, V. Palusova, H. Pandya, A. Parenti, C. Parisel, N. Park, V. Parrish, E. N. Paudel, L. Paul, C. Pérez de los Heros, T. Pernice, T. C. Petersen, J. Peterson, S. Pick, M. Plum, A. Pontén, V. Poojyam, B. Pries, R. Procter-Murphy, G. T. Przybylski, L. Pyras, C. Raab, J. Rack-Helleis, N. Rad, M. Ravn, K. Rawlins, Z. Rechav, A. Rehman, I. Reistroffer, E. Resconi, C. D. Rho, W. Rhode, L. Ricca, B. Riedel, A. Rifaie, E. J. Roberts, S. Rodan, M. Rongen, A. Rosted, C. Rott, T. Ruhe, L. Ruohan, D. Ryckbosch, J. Saffer, D. Salazar-Gallegos, P. Sampathkumar, A. Sandrock, G. Sanger-Johnson, M. Santander, S. Sarkar, M. Scarnera, M. Schaufel, H. Schieler, S. Schindler, L. Schlickmann, B. Schlüter, F. Schlüter, N. Schmeisser, T. Schmidt, F. Schmitt, A. Scholz, F. G. Schröder, S. Schwirn, S. Sclafani, D. Seckel, L. Seen, M. Seikh, S. Seunarine, P. A. Sevle Myhr, R. Shah, S. Shah, A. Sharma, S. Shefali, N. Shimizu, C. Silva, M. Shin, B. Skrzypek, R. Snihur, J. Soedingrekso, D. Soldin, P. Soldin, G. Sommani, D. Song, C. Spannfellner, G. M. Spiczak, C. Spiering, J. Stachurska, M. Stamatikos, T. Stanev, T. Stezelberger, T. Stürwald, T. Stuttard, G. W. Sullivan, I. Taboada, S. Ter-Antonyan, A. Terliuk, A. Thakuri, M. Thiesmeyer, W. G. Thompson, J. Thwaites, W. Tian, S. Tilav, K. Tollefson, J. A. Torres, S. Toscano, D. Tosi, K. Upshaw, A. Vaidyanathan, N. Valtonen-Mattila, J. Valverde, J. Vandenbroucke, T. Van Eeden, N. van Eijndhoven, L. Van Rootselaar, J. van Santen, J. Vara, F. Varsi, M. Velazquez, M. Venugopal, M. Vereecken, S. Vergara Carrasco, S. Verpoest, A. Vijai, J. Villarreal, C. Walck, A. Wang, E. H. S. Warrick, C. Weaver, P. Weigel, A. Weindl, J. Weldert, A. Y. Wen, C. Wendt, J. Werthebach, M. Weyrauch, N. Whitehorn, C. H. Wiebusch, D. R. Williams, L. Witthaus, J. Woodward, G. Wrede, X. W. Xu, J. P. Yanez, Y. Yao, E. Yildizci, S. Yoshida, F. Yu, S. Yu, T. Yuan, S. Yun-Cárcamo, A. Zander Jurowitzki, A. Zegarelli, S. Zhang, Z. Zhang, P. Zhelnin, P. Zilberman, C. Zilleruelo Cañas

Cosmology and Nongalactic Astrophysics

Reconsidering the role of bright and dark gravitational-wave standard sirens for cosmology

Alberto Colombo, Sonia Triscari-Benimavò and Simone Mastrogiovanni

Gravitational-wave (GW) standard sirens have emerged as powerful probes of cosmic expansion. They are commonly divided into two classes: bright sirens, observed in coincidence with an electromagnetic (EM) counterpart, and dark sirens, detected without one. Bright sirens have often been considered the main avenue for precision cosmology; however, following the latest observing run of the LIGO-Virgo-KAGRA (LVK) collaboration, the estimates of merger rates of compact objects involving neutron stars (NSs) have decreased. In this Letter, we reconsider the role that bright and dark sirens will play in precision cosmology. We demonstrate that bright sirens, although detected in small numbers, will play a crucial role in achieving the precision needed to address the Hubble tension, primarily by breaking the degeneracy between the Hubble constant ($H_0$) and the matter density parameter ($\Omega_m$) inherent to dark sirens. Alternatively, we show that dark sirens alone can resolve the $H_0$ tension when supplemented with an external prior on $\Omega_m$. Furthermore, we present a self-consistent statistical framework for GW cosmology with bright and dark sirens, which have traditionally been treated as independent populations although they originate from the same underlying population of black holes (BHs) and NSs. Finally, we find that treating bright and dark sirens as independent populations will not significantly bias GW cosmology in the next LVK observing runs, but can lead to a biased reconstruction of the low-mass end of the mass spectrum.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Constraining Ultralight Scalars with Black Hole Binary Mergers in Galactic Nuclei

Majed Khalaf, Eric Kuflik, Alessandro Lenoci et al. (+2 more)

Ultralight scalars can form long-lived, macroscopic bound states around spinning black holes, known as superradiance clouds. These clouds provide an additional channel for energy dissipation during close encounters, enhancing the black hole binary formation and merger rates in dense environments such as galactic nuclei. We show that the rate of mergers with mass ratio below $3/10$ in the LIGO-Virgo-KAGRA GWTC-5 catalog can probe ultralight scalars in the mass range $[4\times 10^{-14},10^{-13}]$ eV, complementing existing strategies based on black hole spin measurements.
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All authors Majed Khalaf, Eric Kuflik, Alessandro Lenoci, Nicholas Chamberlain Stone, Ofri Telem

Astrophysics of Galaxies

Little Red Dots are Direct-Collapse Black Hole-Forming Galaxies

Daniel J. Whalen, Muhammad A. Latif, Konstantinos Topalakis et al. (+3 more)

"Little Red Dots" (LRDs) at $4 < z < 8$ are one of the most challenging discoveries by JWST to date because their distinctive V-shaped spectra and compact morphologies (100 - 200 pc) defy conventional astrophysical interpretation. Previous attempts to explain LRDs as compact stellar systems, heavily-cocooned black holes with differential flows, supermassive stars, or more exotic objects like 'black-hole stars' either cannot show how they formed, explain the origin of the dense shells needed for the absorption features in their spectra, or account for their observed abundances or inferred lifetimes. Here we show that LRDs are simply direct-collapse black hole galaxies in which the BH is still shrouded by the massive disk that created it. Our cosmological simulations yield spectra that are good matches to those of LRDs because high densities at the center of the disk trap X-rays from the BH and produce the observed Balmer absorption features while allowing UV, optical and reprocessed IR flux to partly escape. The host galaxy forms a dense 10$^8$ M$_{\odot}$ cluster of stars with a radius of 150 pc next to the BH, consistent with observations of LRDs. Our models reproduce a wide variety of LRD spectra from typical objects like RUBIES-EGS-42046 at $z = 5.28$ to those with the strongest Balmer breaks such as MoM-BH$^*$-1 at $z = 7.76$ and those at the highest redshifts like CAPERS-LRD-z9 at $z = 9.29$.
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All authors Daniel J. Whalen, Muhammad A. Latif, Konstantinos Topalakis, Fergus Cullen, Devesh Nandal, Sadegh Khochfar

High Energy Astrophysical Phenomena

Constraining dark matter using 20-year INTEGRAL/IBIS observations I: Primordial black holes

Jordan Koechler and Pedro De la Torre Luque

Primordial black holes (PBHs) in the asteroid-mass window remain a viable dark matter candidate. In the lower part of this mass range, Hawking evaporation produces electrons and positrons that generate diffuse hard X-ray emission through inverse Compton (IC) scattering on Galactic radiation fields. We present the first search for this signal using a combined spectral and morphological analysis of the 20-year INTEGRAL/IBIS observations. We construct a physically motivated model of the Galactic hard X-ray background, including IC emission from cosmic-ray electrons and unresolved accreting white dwarfs, and consistently incorporate the IC contribution from PBH evaporation. By exploiting both spatial and spectral information, we improve the separation between a possible PBH signal and astrophysical backgrounds compared to analyses based only on spectral data. We derive constraints on the PBH dark matter fraction over a broad mass range, including extended PBH mass functions and rotating PBHs. We assess the impact of uncertainties in cosmic-ray propagation and the Galactic dark matter density profile, finding that the propagation of low-energy electrons and positrons represents the main source of uncertainty in the predicted signal. Despite these limitations, our results provide competitive constraints over a wide range of PBH masses, highlighting the potential of hard X-ray observations as a complementary probe of evaporating PBHs.
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Astrophysics of Galaxies

Clustering-based halo mass assignment for high-redshift galaxies: method, validation, and application to JWST

Seunghwan Lim, Sandro Tacchella, Sara Saleh et al. (+7 more)

We present a clustering-based method for inferring halo masses of high-redshift galaxies, validated using the COLIBRE simulations combined with the HOMA empirical model, which assumes star formation to be proportional to halo accretion rate and is calibrated to JWST observations. Our approach matches the two-point correlation function of galaxies in stellar mass bins to reference halo clustering, establishing the stellar-to-halo mass relation over an optimal radial range 0.5 < r_p/cMpc < 1.0. Validation against true halo masses shows minimal bias, with scatter below 0.3 dex for volumes down to (50 cMpc)^3 and redshifts to z=12, even for photometric data. Cross-validation using the native COLIBRE population shows that the method is robust to the different galaxy-halo prescriptions. Survey volume dominates the error budget: field-to-field variations in the clustering amplitude vary by factors of 3 (2) for photometric (spectroscopic) samples, translating to 0.3-0.5 dex uncertainty in halo masses. Splitting the sample by properties such as SFR, colour, and age mitigates assembly bias, offering a key advantage over abundance matching. Application to JWST (JADES) samples at z=6 and 10 yields halo masses of log M_h/M_sun = 10.52_{-0.21}^{+0.12} and 9.91_{-0.34}^{+0.19} for M_UV < -17 galaxies, with linear biases of b_h = 4.2_{-0.41}^{+0.26} and 7.7_{-1.16}^{+0.77}, respectively. Current data cannot distinguish between star formation models. Our Roman Deep Tier forecasts indicate that at z=10, the inferred halo masses for M_UV < -21 galaxies differ by 0.5 dex between bursty and non-bursty models, but the expected number of pairs limits the constraining power. Our framework provides robust, empirically-calibrated halo masses essential for interpreting JWST observations and constraining galaxy formation during reionization.
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All authors Seunghwan Lim, Sandro Tacchella, Sara Saleh, Roberto Maiolino, Lily Whitler, Joop Schaye, Evgenii Chaikin, Carlos S. Frenk, Filip Huško, Alexander J. Richings

Cosmology and Nongalactic Astrophysics

Impact of galaxy intrinsic alignments on non-Gaussian weak lensing statistics for modified gravity

Mehar Chawla, Christopher T. Davies, Joachim Harnois-Déraps et al. (+3 more)

Non-Gaussian weak lensing statistics improve the constraining power of cosmic shear data by harvesting information unavailable to two-point statistics, within and beyond the GR+$\Lambda$CDM scenario. Dark energy, total neutrino mass and deviations from GR have all been shown to be better measured with non-Gaussian lensing probes, in simplified conditions. Previous studies typically overlook the impact of secondary lensing signals, which can be large and therefore can significantly affect the conclusions. Here we investigate the impact on measurements of cosmological and modified gravity parameters in the presence of galaxy intrinsic alignments. We focus on the power spectra, lensing PDF, peaks and minima counts, void abundance and void profiles. These non-Gaussian statistics are measured from the MGLenS mock weak lensing maps, in which three cosmological parameters and one gravitational parameter are varied, either in the $f(R)$ or nDGP scenario, assuming Stage-IV lensing survey precision. These simulations are infused with the non-linear linear alignment model, allowing us to build emulators for each statistic with or without IA, and to study biases in full MCMC analyses. We show that in the absence of IA, lensing void profiles and abundance generally yield the highest Figure of Merit in the $S_8 - f_{R0}$ and $S_8 - H_0 r_{\rm c}$ planes, at times improving by an order of magnitude over two-point functions. When IA is unaccounted for, major parameter biases are observed in the cosmology sector, while the modified gravity sector is relatively unaffected. We find that these biases can generally be flagged from poor goodness-of-fit measurements, except for a few cases where IA can fully masquerade as a lower $\Omega_{\rm m}$ and lower $S_8$ cosmology.
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All authors Mehar Chawla, Christopher T. Davies, Joachim Harnois-Déraps, Baojiu Li, Joseph J. Mohr, Bipradeep Saha

Solar and Stellar Astrophysics

An unresolved extreme warm infrared excess toward a nearby low-mass star

Sahin Torlakcik

Gaia DR3 2981818948336660224 is a nearby low-mass star with a substantial warm mid-infrared excess. Identified in a Gaia-2MASS-WISE search, it lies at approximately 127 pc and has an AllWISE W3 signal-to-noise ratio of 33.1. We recover the emission in all 16 available cryogenic exposures over 1.26 d; removing any one exposure leaves the signal intact. The W3 emission is centred close to the propagated stellar position, and the known neighbour 6.1 arcsec away fails to reproduce its morphology. Nominal scene fits place 97-98 per cent of the W3 flux at the target position. This provides strong spatial support for association, although template uncertainty and a nearly coincident hidden source prevent a definitive decomposition. The excess can be described by a roughly 300-350 K component with L_IR/L_star ~ 0.022, assuming stellar association and retaining the weaker W4 detection. If produced by circumstellar dust, it falls in the extreme warm-debris regime around a dwarf with no established evidence of youth. Its origin remains unresolved. The repeatable excess and close spatial association make this a useful target for subarcsecond MIR imaging and spectroscopy to test the warm-dust interpretation.
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Instrumentation and Methods for Astrophysics

Continuous Learning of Gravity Field Irregularities Around Small Bodies via Neural Hamiltonian ODEs

Giacomo Acciarini and Dario Izzo

We propose to learn the unknown dynamics in the proximity of a small body directly from tracking data, representing them as a feed-forward neural network embedded in the system Hamiltonian. The equations of motion form a Neural Hamiltonian Ordinary Differential Equation, whose variational equations provide exact training gradients: estimation uses position and velocity arcs at realistic noise levels, without acceleration or potential labels, and a continual learning approach warm-starts the network as new data are acquired. The known part of the Hamiltonian carries whatever is available, from the central term and spin state to the constant-density model of the imaged shape. We assess the method against a normalized spherical harmonics expansion estimated from identical arcs through the same machinery, on scenarios built on the shapes of Itokawa, 67P, Bennu and Eros. The network remains usable inside the Brillouin sphere: it plans ballistic descents at Itokawa to \SI{4.6}{m} median touchdown error from tracking alone, against 5.1–\SI{48.9}{m} for harmonics of degree 4–12, and to \SI{0.9}{m} with the imaged shape as prior, a configuration that also recovers localised density anomalies invisible to any harmonics degree. The two representations are complementary, and we discuss their combined use across the phases of a small-body mission.
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Instrumentation and Methods for Astrophysics

A Framework for Evaluating Forward Contamination Risk for Bio-ISRU Microorganisms

Una Nattermann, Devon A. Stork, Tom Pedersen et al. (+9 more)

NASA planetary protection policy seeks to avoid inadvertent forward contamination of celestial bodies and backward contamination of Earth during space exploration. For Mars missions, it has historically focused on sterilization of landers and rovers. Current policy provides no framework for assessing the forward contamination risk of missions that deliberately include living organisms and must not be sterilized, such as a human crew, agriculture, or biotechnology for manufacturing and life support. We propose the PRIM (Propagation Restricted, Inert on Mars) framework to evaluate the forward-contamination risk posed by known organisms. Building on the biocontainment literature and probability-of-contamination model, PRIM bounds the ability of an organism released from a worst-case off-nominal event to sustain growth on the Martian surface at a probability under P_c <= 10^-4 using independent single-stressor propagation assays. We apply the PRIM framework to two engineered Mars biological in situ resource utilization (bio-ISRU) chassis organisms, using low water activity and carbon starvation to qualify them for low forward contamination risk even at high bioburden, and outline how to extend the assays to phototrophs and anaerobes. PRIM offers a path to flight-qualify living organisms for Mars based on laboratory assays rather than bioburden alone. This enables biological life support infrastructure for a sustained presence on Mars while keeping forward contamination risk demonstrably low.
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All authors Una Nattermann, Devon A. Stork, Tom Pedersen, Nathan D. Hicks, Jordan E. Mancuso, Keren Isaev, Max G. Schubert, Fatima R. Martin, Jonathan Liu, Harley Greene, Edward Sukarto, Erika A. DeBenedictis

Earth and Planetary Astrophysics

The Mysterious Inspiral of WASP-12b: Why Obliquity Tides Cannot Drive Orbital Decay

Caleb Lammers, Yubo Su and Joshua N. Winn

WASP-12b's orbit is decaying, for unknown reasons. The planet's period is shrinking more rapidly than can be attributed to equilibrium tides or dynamical tides in a main-sequence star. Planetary obliquity tides could be sufficiently dissipative to drive WASP-12b's inspiral, but would also damp the planet's obliquity, halting the decay. Millholland & Laughlin proposed that a nearby, low-mass planet ($\sim 10$ M$_\oplus$) is maintaining a large obliquity for WASP-12b, sustaining the dissipation. We re-evaluated this hypothesis, finding that the companion must be more massive than originally proposed ($\gtrsim 65$ M$_\oplus$) to absorb WASP-12b's orbital angular momentum. Radial velocity data allowed us to rule out a companion of this type. Any companions within $3$ AU have $K \lesssim 14$ m/s at $95$% confidence.
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