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Physics Astrophysics

astro-ph Watch Astrophysics

Friday 20 March

Earth and Planetary Astrophysics

An Enriched Methane D/H Ratio in the Interstellar Object 3I/ATLAS

Nathan X. Roth, Martin Cordiner, Stefanie Milam et al. (+15 more)

Interstellar objects are interlopers from other planetary systems, and their volatile compositions provide a glimpse into planet formation around their host star. We present near-infrared spectra of the coma of interstellar object 3I/ATLAS measured with the James Webb Space Telescope. Our results demonstrate an unexpectedly high D/H = $(3.33\pm0.31)\%$ for methane and represent an exceedingly rare detection of deuterated organic molecules in an interstellar object. This D/H ratio exceeds any other value for methane measured in the solar system, and is a factor of $14\pm2$ higher than that measured in comet 67P/Churyumov-Gerasimenko by the Rosetta spacecraft, the only other comet for which CH$_3$D has been detected. Both 3I/ATLAS and 67P/Churyumov-Gerasimenko show a higher degree of methane dueteration compared to water, consistent with trends seen in other solar system bodies and the nearby interstellar medium, where deuteration in organics exceeds that of water by up to an order of magnitude. The D/H ratio in methane itself is observationally unconstrained in extrasolar sources to date, but the enriched ratio in 3I/ATLAS is similar to those measured in methanol and formaldehyde toward primitive environments. The elevated D/H ratio for methane in 3I/ATLAS is consistent with the hypothesis that its ices formed in a cold, low metallicity interstellar or protostellar environment under a high cosmic ray irradiation rate (Cordiner et al. 2026).
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All authors Nathan X. Roth, Martin Cordiner, Stefanie Milam, Geronimo Villanueva, Steven Charnley, Nicolas Biver, Dominique Bockelee-Morvan, Dennis Bodewits, Jacques Crovisier, Maria N. Drozdovskaya, Davide Farnocchia, Kenji Furuya, Michael S.P. Kelley, Marco Micheli, John W. Noonan, Cyrielle Opitom, Megan E. Schwamb, Cristina A. Thomas

Astrophysics of Galaxies

Beyond compactness: a structural-dynamical-evolutionary manifold for the stellar-to-dynamical mass ratio in ultra-compact massive galaxies

Chiara Spiniello

Ultra-compact massive galaxies (UCMGs) exhibit elevated stellar-to-dynamical mass ratios when dynamical masses are estimated using standard virial prescriptions. This discrepancy has been interpreted as non-homology driven by their compactness. This study investigates how the stellar-to-dynamical mass ratio depends on compactness (C), velocity dispersion ($\sigma_*$), stellar population properties (age, metallicity, and [Mg/Fe]), and star formation histories (SFHs). The analysis is based on a homogeneous sample of 482 UCMGs from the INSPIRE and E-INSPIRE surveys, extending to smaller sizes than previously analysed samples. I first derive the compactness-mass relation assuming a constant virial coefficient (K=5). I then correct stellar masses for IMF variations and recompute stellar-to-dynamical mass ratios using an empirical prescription where the virial coefficient varies with radius and stellar mass. Finally, I test modulation by stellar kinematics and population properties, including the degree of relicness (DoR), quantifiying the extremeness of the SFH. A statistically significant anti-correlation between compactness and the IMF-corrected stellar-to-dynamical mass ratio is recovered under a constant virial coefficient, but the relation flattens when a structure-dependent K is adopted. The data define a structural-dynamical manifold in the logC-log$\sigma_*$ space. Velocity dispersion sets the dominant axis of variation, and the corresponding plane accounts for ~62% of the variance in stellar-to-dynamical mass ratio. The stellar-to-dynamical mass ratio in UCMGs is governed primarily by the depth of the gravitational potential traced by $\sigma_*$, rather than C alone. At fixed size, systems with higher velocity dispersion show lower stellar-to-dynamical mass ratios. Non-homology therefore reflects coupled dynamical and evolutionary processes rather than purely geometric compactness.
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High Energy Astrophysical Phenomena

Accurate and efficient simulation-based inference for massive black-hole binaries with LISA

Alice Spadaro, Jonathan Gair, Davide Gerosa et al. (+7 more)

We develop an accurate simulation-based inference framework for high-mass ($\gtrsim\!10^7 \rm{M_\odot}$) black-hole binaries observable by LISA. The method is implemented within the DINGO gravitational-wave parameter-estimation code, extending its application from ground-based detectors to the LISA band. We train a normalizing-flow model using aligned-spin higher-mode waveform models and a low-frequency approximation of the detector response at fixed reference time. After sampling, we importance-sample to the true posterior based on the underlying likelihood and prior. We validate performance on simulated signals spanning the signal-to-noise regimes relevant for LISA observations and benchmark our new DINGO implementation against standard methods. We report robust agreement in the inferred posterior distributions up to signal-to-noise ratios of $\sim\!500$. At higher signal-to-noise ratios of $\sim\!1000$, we observe a reduction in sampling efficiency, while still yielding unbiased and tightly localized posteriors that can be used as a starting point for follow-up with traditional methods. The trained flow can generate 20 thousand posterior samples in less than a minute, establishing DINGO as a promising neural inference framework for rapid full-parameter estimation of massive black-hole binaries in the LISA band. The proposed approach allows for straightforward generalizations, including a time-dependent detector response, non-stationary noise artifacts such as gaps and glitches, and low-latency parameter estimations.
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All authors Alice Spadaro, Jonathan Gair, Davide Gerosa, Stephen R. Green, Riccardo Buscicchio, Nihar Gupte, Rodrigo Tenorio, Samuel Clyne, Michael Pürrer, Natalia Korsakova

Astrophysics of Galaxies

Isolated or Dynamical? Tracing Black Hole Binary Formation through the Population of Gravitational-Wave Sources

Manuel Arca Sedda, Lavinia Paiella, Cristiano Ugolini et al. (+5 more)

The population of binary black hole (BBH) mergers observed by the LIGO-Virgo-KAGRA (LVK) collaboration offers a window into the cosmic evolution of compact binaries and their formation. We employ the semi-analytic population-synthesis code B-POP to model BBHs assembled through isolated binary evolution and dynamical interactions in young, globular, and nuclear star clusters. Our framework incorporates star formation history, metallicity evolution, and single and binary stellar evolution to quantify their impact on the observable properties of the BBH population and on the relative contribution of distinct formation channels. Our models are characterized by a merger rate, $\mathcal{R} = 17.5-24.1\mathrm{Gpc}^{-3}\mathrm{yr}^{-1}$, broadly consistent with LVK constraints. Moreover, the predicted distributions of primary mass, mass ratio, and effective inspiral spin parameter are compatible with those inferred from current LVK observations. Our primary-mass distribution is dominated by isolated binaries at $m_1 < 20$ M$_\odot$, while dynamically assembled first- and higher-generation mergers dominate at larger masses. As a consequence, the sub-population of mergers with $m_1 > 45$ M$_\odot$ exhibits a nearly flat mass-ratio distribution and distinctive spin properties. We leverage our models to explore how: (i) the fraction of stars in isolated binaries and the fraction of stellar mass bound in clusters regulate the merger rate; (ii) common-envelope physics shapes the primary-mass distribution and its redshift evolution; (iii) the inclusion of stellar-collision products enhances the formation of higher-generation mergers; and (iv) the natal spin distribution influences the effective spin. Using our models to assess possible origins of selected GW events, we illustrate how the complexity of the underlying astrophysical processes can hinder the possibility to draw definitive conclusions.
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All authors Manuel Arca Sedda, Lavinia Paiella, Cristiano Ugolini, Filippo Santoliquido, Benedetta Mestichelli, Ilaria Usai, Filippo Simonato, Marica Branchesi

Solar and Stellar Astrophysics

Hide and Seek with Gaia. Detectability of Predicted Thin-Disc Metal-Rich RR Lyrae Binaries in Gaia DR3 and DR4

Giuliano Iorio, Pranav Nagarajan, Alexey Bobrick et al. (+8 more)

RR Lyrae stars (RRLs) are classical tracers of old stellar populations, yet growing evidence suggests the presence of a metal-rich ([Fe/H]>-0.5), intermediate-age (2-7 Gyr) sub-population in the Milky Way disc. Binary evolution, particularly stable mass transfer, has been proposed as a viable formation channel, predicting that most metal-rich, intermediate-age (<9 Gyr) RRLs should reside in binaries with orbital periods of ~900-2000 days. However, no genuine RRL binaries have been robustly identified, including in the Gaia DR3 astrometric binary catalogues, despite Gaia being sensitive to the predicted orbital-period range. We investigate whether the lack of detections in Gaia DR3 reflects an intrinsically low binary fraction or instead arises from observational biases. We analyse a carefully selected sample of 100 Gaia DR3 RRLs designed to trace the metal-rich population with thin-disc kinematics and compare them with predictions from binary evolution models. We generate realistic Gaia observation mocks, including variability-induced astrometric biases, and assess the detectability of binaries and the posterior constraints on the hidden binary fraction using astrometric quality indicators, such as RUWE, and a robust Bayesian inference. While current uncertainties prevent a definitive rejection of a high fraction of hidden binaries, our results reveal tensions between existing binary evolution predictions and the Gaia DR3 non-detections. This suggests either the presence of unaccounted systematics in the modelling of Gaia observations or the need to revise assumptions in binary evolution models. We predict that Gaia DR4 will significantly improve the binary detectability and provide powerful new constraints on the post-interaction binary populations.
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All authors Giuliano Iorio, Pranav Nagarajan, Alexey Bobrick, Kareem El-Badry, Elena Pancino, Vasily Belokurov, HanYuan Zhāng, Valentina D'Orazi, Cecilia Mateu, Sara Rastello, Mark Gieles

Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph

Inverse Electroweak Baryogenesis

Jacopo Azzola, Oleksii Matsedonskyi and Andreas Weiler

We propose a mechanism for baryogenesis in which the baryon asymmetry is generated as an equilibrium response of weak sphalerons in a region where electroweak sphaleron transitions remain unsuppressed, $h/T\lesssim 1$. A nonzero equilibrium baryon density arises in the presence of an approximately conserved global charge, carried either by new states with nonzero hypercharge, or by Standard Model fields themselves. The required global charge asymmetry is generated during a phase transition that changes the strength of electroweak symmetry breaking, but need not coincide with the final electroweak phase transition. In particular, the mechanism can operate during an inverse electroweak phase transition, where baryon number is produced behind the advancing wall, in contrast to conventional electroweak baryogenesis. Because baryon production is decoupled from a direct first-order electroweak phase transition, the scenario can be realized at parametrically higher temperatures than standard electroweak baryogenesis, thereby weakening current experimental constraints. This framework provides a qualitatively distinct route to electroweak baryogenesis, with different parametric dependence, phase-transition dynamics, and phenomenological signatures.
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Solar and Stellar Astrophysics

Cyclic light variations and accretion disk evolution in the LMC eclipsing binary OGLE-LMC-DPV-062

R.E. Mennickent, G. Djurašević, J.A. Rosales et al. (+4 more)

Many intermediate-mass close binaries exhibit photometric cycles longer than their orbital periods, likely related to accretion-disk variability. Previous studies indicate that historical light curves (LC) provide key constraints on disk evolution and may help trace mass-transfer changes in these systems. We investigate the short- and long-term variability of the eclipsing system OGLE-LMC-DPV-062, with special emphasis on the long cycle. Our aims are to clarify the role of the accretion disk in these modulations, particularly on timescales of hundreds of days, and to determine the evolutionary state of the system in order to better understand its stellar components. We analyzed 32.3 years of photometric time series from OGLE in the I and V bands, and from MACHO in the BM and RM bands. Using data from multiple epochs, we modeled the accretion disk at 20 equally spaced phases of the long cycle. To solve the inverse problem, we applied an optimized simplex algorithm to derive the best-fitting parameters of the stars, orbit, and disk. The MESA code was used to assess the evolutionary stage of the system and predict its past and future evolution. We find an orbital period of 6.904858(15) d and a long cycle of 229.7 d. The orbital solutions reproduce the LC, but the quasi-conservative mass-transfer scenario yields rates too high to be compatible with the observed orbital-period stability. We find consistency with the observed orbital-to-long-period ratio under the magnetic dynamo hypothesis. The normalized mass-transfer rate follows the long cycle, reaching a maximum at minimum brightness. At that phase, the inner disk edge thickens, obscuring a larger fraction of the gainer star. Disk variability occurs mainly in its vertical extent, with a standard deviation of 69% of the mean value at the inner border, whereas changes in outer radius and temperature are smaller, 7% and 5%, respectively.
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All authors R.E. Mennickent, G. Djurašević, J.A. Rosales, J. Garcés, J. Petrović, D.R. G. Schleicher, I. Soszyński

High Energy Astrophysical Phenomena

The impact of gamma-ray propagation effects on indirect dark matter searches

Ignacio Martínez López, Rafael Alves Batista, Miguel A. Sánchez-Conde et al. (+1 more)

In this work, we investigate dark matter (DM) detection in the context of weakly interacting massive particles (WIMPs). Upon annihilation, WIMPs generate cascades of secondary particles through various channels, many of which culminate in the production of gamma rays. As these gamma rays travel toward Earth, their spectra are reshaped by interactions with the intervening medium. While current models typically account for attenuation via pair production on the extragalactic background light, they often neglect the fate of the resulting electrons and positrons, specifically subsequent inverse Compton scattering of these secondary particles, which can regenerate high-energy gamma rays. Here, we revisit the predicted gamma-ray fluxes from WIMP annihilation by performing a more detailed treatment of propagation effects. We show that for distant sources and annihilation channels such as $\tau^+\tau^-$, the full treatments can significantly alter the observed gamma-ray flux, by up to a factor of three orders of magnitude for heavy WIMPs. This has an impact on current dark matter limits derived without taking into account propagation effects, depending on the considered WIMP mass and annihilation channel. Our study demonstrates the importance of a detailed propagation treatment for indirect dark matter searches, and the need to account for such effects in order to obtain accurate, more reliable dark matter signal predictions and exclusion limits.
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All authors Ignacio Martínez López, Rafael Alves Batista, Miguel A. Sánchez-Conde, Antonio Juan Rubio-Montero

Instrumentation and Methods for Astrophysics

Searching for Fast Astronomical Transients in Archival Photographic Plates

Ivo Busko

Fast astronomical transients were observed by the VASCO Project (Villarroel et al 2020) in photographic sky surveys conducted in the 1950s. Those searches analyzed the Palomar Observatory Sky Survey (POSS-I and POSS-II) digitized plates. In this article, we present a preliminary report on a similar but independent search using archival plates taken at the Hamburg Observatory with the Großer Schmidtspiegel 1.2-m Schmidt camera, also from the mid-1950s. These plates were digitized by the APPLAUSE Archive, which provides both images and tables of detected objects. By analyzing pairs of plates taken in rapid sequence (about 30 minutes apart) of the same sky regions, we find evidence of transients similar to those previously reported by the VASCO Project for POSS plates. While the analysis is ongoing, one notable result is that our findings independently confirm that these transients exhibit systematically narrow full width at half maximum (FWHM) compared to stellar point spread functions. This provides further support for their interpretation as sub-second optical flashes, consistent with reflections from flat, rotating objects in orbit around Earth.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc

Nonlinear tails in the Kerr black hole ringdown

Siyang Ling and Sam S. C. Wong

Power law tails induced by nonlinearities of General Relativity (“sourced” or “nonlinear” tails) were recently shown to dominate the late time waveform of Schwarzschild black hole ringdowns. We extend the analytical results regarding such nonlinear tails from Schwarzschild to Kerr black holes by studying the Teukolsky equation. Using a far field approximation to the radial Green's function, we analytically derived the tail power law for spin-weight $s \neq 0$, harmonic mode $(\ell m)$ and source decay $r^{-\beta}$. Specifically, we found a $t^{-\ell-\beta-s}$ tail for $\beta \leq 1$ or $\beta \geq \ell - s + 2$, and a $t^{-2\ell-3}$ Price tail for $2 \leq \beta \leq \ell - s + 1$. Our numerical tests were in exact agreement with these analytic results. We also demonstrate the dynamical formation of such nonlinear tails for a massless scalar by numerically solving the Teukolsky equation. In all numerical results, Kerr black hole nonlinear tails have the same power laws as that for Schwarzschild black holes, as expected from the Minkowski nature of the spacetime in the far field region.
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High Energy Astrophysical Phenomena

Probing the statistical correlation of optical tidal disruption events with high-energy neutrinos

D.A. Langis, I. Liodakis, K.I.I. Koljonen et al. (+1 more)

High-energy (HE) neutrinos have been observed by the IceCube (IC) Neutrino observatory for over a decade. Nevertheless, the astrophysical origin and the responsible mechanisms producing these HE neutrinos are still a mystery, with many astrophysical phenomena as potential emitters. A plethora of previous studies have attempted to study the correlation between HE neutrinos and active galactic nuclei, finding inconclusive results. Tidal disruption events (TDEs) have been proposed as candidate HE neutrino emitters, yet there is only one prior statistical study for the correlation of the two due to the limited number of observed TDEs. For this reason we used TDECat, an optical TDE repository, to investigate the potential association of TDEs with IceCube HE neutrino events. We implemented a spatio-temporal algorithm, where the temporal constraint is based on the transient nature of TDEs. We also simulated two sets of TDEs, correlated differently with neutrinos, to further study their statistical correlation. Despite the individual cases of TDE AT2019dsg and AT2021lo, we find no statistical association between optical TDEs and HE neutrinos. We find jetted TDE Sw J2058+05 to be spatio-temporally associated with a neutrino event. However, a $\gamma$-ray-flaring, flat-spectrum radio quasar is also within the neutrino's sky error region. Although our findings indicate no statistical correlation between optical TDEs and HE neutrinos, this correlation should be further studied in the future. Upcoming surveys such as the Legacy Survey of Space and Time, coupled with next-generation neutrino observatories, such as KM3NET and IceCube-Gen2, will expand both TDE and HE neutrino populations, clarifying their potential correlation.
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All authors D.A. Langis, I. Liodakis, K.I.I. Koljonen, P.M. Kouch

Earth and Planetary Astrophysics

Radiating Bondi Flows II: Giant Planet Accretion Models

Avery Bailey, Kaitlin Kratter and Andrew Youdin

In the core accretion model of giant planet formation, the late stages of runaway growth are regulated by the hydrodynamic infall of gas from the protoplanetary disk. For a subset of planet-disk pairings, this scenario is analogous to the classical Bondi problem, which has motivated a Bondi-like parameterization of accretion in some population synthesis models. Existing models and the associated classical Bondi rate however, are predicated upon an adiabatic equation of state. In reality, the planet and its associated accretion shock supply a luminosity that substantially heats the accretion flow. In Paper I of this series, we demonstrate that such radiative feedback can dramatically suppress accretion by orders of magnitude. Here we quantify this effect under realistic planet-forming conditions. We find that for planets forming in an unperturbed disk, accretion is suppressed by 1-2 orders of magnitude interior to $\sim 10$ AU. For planets that open a gap, this feedback is less dramatic and the effect is $\sim$ 1 order in magnitude. We investigate the effect of various assumptions regarding dust opacities, shock efficiency, and planet radius and find this radiative suppression mechanism to be fairly insensitive to these effects. We also perform full time-dependent simulations demonstrating that the associated adverse entropy profiles are accurate and stable to convection. A simple and flexible set of open-source tools are provided to incorporate this radiative feedback into existing accretion models and population synthesis frameworks.
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High Energy Astrophysical Phenomena

SN 2024iss: A Multi-Wavelength Exposé of a Type IIb Supernova with an Early-Time Ultraviolet Spectrum and Shock Breakout Constraints

Rujula Yete, Wynn Jacobson-Galan, Ferdinand Ferdinand et al. (+49 more)

We present multi-wavelength observations and a comprehensive analysis of the nearby (D$\sim$14 Mpc) Type IIb supernova (SN IIb) 2024iss. Observations of SN2024iss include an early ZTF detection at $\sim$40 minutes after first light and the earliest Hubble Space Telescope UV spectrum for a SN IIb to date at 7 days after first light. With the bolometric light curve and He-star models, we estimate an ejecta mass range of $\sim 1.1-3.3~M_{\odot}$ and a $^{56}\textrm{Ni}$ mass of $0.11 \pm 0.01~M_{\odot}$. We fit shock-cooling emission models to the first peak in the light curve and estimate a progenitor radius of $100-320~R_{\odot}$ and a H-rich envelope mass of $0.07-0.46~M_{\odot}$. We also compared optical/UV spectra to binary progenitor model spectra, which indicate a stripped H-rich envelope mass of $0.19-0.28~M_{\odot}$. We use early-time X-ray detections to calculate CSM densities that are consistent with a progenitor mass-loss rate of $5\times10^{-4}~M_{\odot}$ ($v_w = 100~$km/s), corresponding to a period of significant mass ejection in the final ~2-5 years before core collapse. In the UV spectrum, we observe strong Mg II emission extending to $\sim15,000 ~$km/s as well as weak P-Cygni profiles of iron-group elements (e.g., Fe, Ti, Al, Ni) present in the outer SN ejecta during the end of shock cooling phase. We find that the overall spectroscopic evolution of SN2024iss is comparable to other SNe IIb, but that the increased brightness following the initial light curve peak is likely influenced by SN ejecta-CSM interaction. Finally, optical/NIR nebular spectroscopy of SN2024iss at $\sim 260-412~$ days reveals multi-peaked forbidden line profiles of O I and Mg I] indicative of inner ejecta asymmetry and/or clumping. We demonstrate the utility of a rich, multi-wavelength dataset for constraining the progenitor systems and explosion dynamics of SNe IIb.
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All authors Rujula Yete, Wynn Jacobson-Galan, Ferdinand Ferdinand, Luc Dessart, Mansi Kasliwal, Kyle Davis, Anthony Piro, Victoria Villar, Igor Andreoni, Katie Auchettl, Kenneth Chambers, Ryan Chornock, Michael Coughlin, David Coulter, Richard Dekany, Ryan Foley, Ori Fox, Lluís Galbany, Christa Gall, Anjasha Gangopadhyay, Jared Goldberg, Gowri Govindaraj, Xinze Guo, Mark Huber, Joahan Jaimes, Jenna Karcheski, Ravjit Kaur, Charles Kilpatrick, Russ Laher, Natalie LeBaron, Chien-Cheng Lin, Raffaella Margutti, Yen-Chen Pan, Kishore Patra, Haille Perkins, Priscila Pessi, Oleksandra Pyshna, Armin Rest, Sara Romagnoli, Steve Schulze, Huei Sears, Aidan Sedgewick, Matthew Siebert, Avinash Singh, Jesper Sollerman, Niharika Sravan, Samaporn Tinyanont, Richard Wainscoat, Qinan Wang, Daniel Warshofsky, Yuhan Yao, Yossef Zenati

Instrumentation and Methods for Astrophysics

DETECT: A Pipeline to Quantify Detection Thresholds in Rubin for Nearby Targets Embedded in Bright Host Galaxies

Tobias Géron, Maria R. Drout, W. V. Jacobson-Galán et al. (+1 more)

The final stages of stellar evolution can be constrained by studying pre-SN variability. The incredible amount of data coming from the upcoming Rubin Legacy Survey of Space and Time (LSST) will be fundamental to this type of work. However, robustly measuring pre-SN variability can be hard, as even state-of-the-art image subtraction pipelines struggle when the target is embedded in a bright nearby galaxy. We developed Detection Efficiency and Threshold Estimation for Characterization of Transients (DETECT) to tackle this problem. It performs a series of source injection, image subtraction, and forced photometry to obtain reliable detection thresholds tailored to a specific location within a given host galaxy. We first validate the pipeline using simulated data from Rubin DP0 and then apply it to a sample of 15 targets found in Rubin DP1. We demonstrate that DETECT is capable of identifying pre-SN variability while calculating reliable upper limits and suppressing false positives for targets embedded in bright host galaxies. Most of the false positives in this work occurred when the signal-to-noise ratio (SNR) was between 5 and 10, while no false positives were found when the SNR was greater than 10. Finally, even though DETECT was originally developed in the context of pre-SN variability, it is broadly applicable to any situation where detections are uncertain and robust upper limits are needed.
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All authors Tobias Géron, Maria R. Drout, W. V. Jacobson-Galán, C. D. Kilpatrick

Earth and Planetary Astrophysics

Radiating Bondi Flows I: Dimensionless Framework and Constant Opacity Solutions

Avery Bailey, Andrew Youdin and Kaitlin Kratter

In this paper, we extend the foundational work of Bondi (1952) to include the effects of radiative feedback in gas-pressure-dominated environments. We construct steady-state spherically symmetric accretion solutions including radiative heating and cooling. Under the simplifying assumption of a constant opacity, the solutions are controlled by four dimensionless parameters: the adiabatic index $\gamma$, optical depth through the Bondi radius $\tau_B$, dimensionless luminosity at infinity $\tilde{L}_\infty$, and a characteristic dimensionless cooling time $\beta$. We present numerical solutions across the dimensionless parameter space $(\tau_B, \tilde{L}_\infty, \beta)\in [10^{-3}, 10^3]$. Contrary to radiation-pressure-dominated environments, radiative feedback primarily operates to suppress accretion – particularly at high $\tau_B$, $\tilde{L}_\infty$, and/or $\beta$. We also present analytic descriptions confirming the suppressive nature of this feedback and give the scalings for the accretion rate $\dot{M}\sim \tilde{L}_\infty^{-5/4}$ at large $\tilde{L}_\infty$, $\dot{M}\sim \tau_B^{-10/11}\beta^{-5/11}$ at large $\tau_B$, and $\dot{M}\sim (\tilde{L}_\infty\tau_B)^{-5/8}$ for large $\tilde{L}_\infty\tau_B$. We discuss the potential role of convection in these steady-state solutions, and the particular relevance to problems of planet formation where radiative heating is significant, but the system remains in the gas-pressure-dominated regime.
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Solar and Stellar Astrophysics

Radial Velocity Orbital Solutions for Candidate Black Hole and Neutron Star Binary Systems in the Gaia Data Release 3 Catalog

Joshua D. Simon, Casey Y. Lam, Kareem El-Badry et al. (+8 more)

We present spectroscopic followup observations of binary systems from the Gaia Data Release 3 (DR3) binary catalog that were selected to have large enough mass functions for their companions to be black holes or neutron stars. The selection includes 20 stars that are astrometric and/or spectroscopic binaries, as well as 11 stars with large accelerations both in the plane of the sky and along the line of sight but no DR3 orbital solution. We provide classifications for this entire sample, including radial velocity orbital solutions for 12 binaries. Apart from the previously published binaries Gaia BH1, Gaia BH2, and Gaia NS1, we show that the Gaia orbits are incorrect for all of the stars with candidate dark companions above 2 Msun. We suggest more conservative cuts on the significance and goodness of fit parameters that may be useful for identifying reliable orbital solutions in the tail of the binary star distribution. Although we find no new confirmed black hole or neutron star companions, one accelerating system has a minimum companion mass of 1.16 +/- 0.01 Msun that is likely to be a neutron star or an ultramassive white dwarf. The acceleration catalogs may therefore provide a largely unexplored source of additional wide binaries containing compact objects.
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All authors Joshua D. Simon, Casey Y. Lam, Kareem El-Badry, Henrique Reggiani, Sukanya Chakrabarti, Puragra Guhathakurta, Ian B. Thompson, Nidia Morrell, Daniel Huber, Benjamin J. Fulton, Lauren M. Weiss

Astrophysics of Galaxies

Probing Atomic Dark Matter with Stellar Streams in Milky Way-Mass Galaxies

Lucas S. Mandacarú Guerra, Stephanie O'Neil, Mariangela Lisanti et al. (+7 more)

We present the first detailed analysis of the effects of dissipative dark matter on stellar streams. As a concrete example, we generate a cosmological hydrodynamic zoom-in simulation of a Milky Way-mass galaxy, assuming that the dark matter consists of Cold Dark Matter (CDM) with a sub-component ($\sim6\%$) of Atomic Dark Matter (ADM). The ADM subcomponent behaves as collisional, efficiently dissipative gas and allows for the formation of dense compact objects that enhance the central density of satellite galaxies, making them more resistant to tidal disruption. We show that stellar streams with stellar mass $M_{\rm{tot}, \star} \gtrsim 10^{5.5} \ \text{M}_\odot$ form later and exhibit prolonged star formation throughout their evolution, as compared to their CDM counterparts. Changes to star formation history are reflected on the chemical tracks of the stellar stream stars, where the youngest have enhanced [Fe/H] and [Mg/Fe] in the presence of ADM. Furthermore, a population of low-mass satellites with high ADM mass fractions is identified at low pericenter distances, which may affect the population of streams at $M_{\rm{tot}, \star} \lesssim 10^{5.5} \ \text{M}_\odot$. The results of this study should generalize to other dark matter models that lead to inner-density enhancements in satellites, such as elastic self-interacting dark matter in the gravothermal collapse regime.
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All authors Lucas S. Mandacarú Guerra, Stephanie O'Neil, Mariangela Lisanti, Sandip Roy, Robyn Sanderson, Aritra Kundu, Arpit Arora, Lina Necib, Nora Shipp, Xuejian Shen

Astrophysics of Galaxies

The Pristine HeII Emitter near GN-z11: Constraining the Mass Distribution of the First Stars

Elka Rusta, Stefania Salvadori, Roberto Maiolino et al. (+6 more)

The properties of the first metal-free stars remain largely unknown, and so far, the only data-driven constraints on their mass distribution (IMF) come from near-field cosmology. Here, we interpret new observations of the C1 and C2 components of Hebe, the HeII emitter near the galaxy GN-z11. Using a locally calibrated model, we robustly confirm the pristine (PopIII) nature of both components, showing that the measured upper limits on metal lines can only be reproduced by galaxies with $>50\%$ of their stellar mass in PopIII stars. We find that C1 is consistent with a purely PopIII system and adopt a simple parametric approach to infer the implications for the PopIII IMF and stellar mass. The observed $\rm HeII/H_\gamma$ ratio excludes steep IMFs, favoring top-heavy distributions, especially for young stellar ages ($\leq 1$ Myr). Combined with the HeII luminosity, this implies a total PopIII stellar mass of $2 \cdot 10^4 < M_\star/M_\odot < 6 \cdot 10^5$. While degeneracies between IMF, stellar mass, and age remain, adopting the lower stellar masses predicted by simulations ($M_\star < 10^5\,M_\odot$) strengthens the preference for top-heavy IMFs. Combining these results with near-field constraints, which instead exclude the flattest IMFs, we define a data-driven range of viable PopIII IMFs, linking characteristic mass and slope. This work demonstrates that direct observations of high-$z$ PopIII systems can place independent constraints on the IMF of the first stars, opening a new window on their formation and properties.
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All authors Elka Rusta, Stefania Salvadori, Roberto Maiolino, Viola Gelli, Ioanna Koutsouridou, Stefano Carniani, Hannah Übler, Alessandro Marconi, Daniel Schaerer

Astrophysics of Galaxies

The search for Population III: Confirmation of a HeII emitter with no metal lines at z=10.6

Roberto Maiolino, Hannah Übler, Michele Perna et al. (+49 more)

We report the confirmation of a HeII$\lambda$1640 emitter located at 3 pkpc from the galaxy GN-z11, at z=10.6. The detection, based on JWST NIRSpec-IFU high-resolution spectroscopy, confirms a previous claim based on medium-resolution spectroscopy. The HeII$\lambda$1640 identification is further supported by the independent detection of H$\gamma$ obtained by Übler et al. (2026) at the same location. The HeII emission is spectrally resolved in two components separated by 120 km/s. The Equivalent Width of the HeII emission is extremely high ($>$20 A). No metal lines are detected. We argue that Population III stars are the most plausible explanation for the observed He II emission, with no satisfactory alternative from other classes of sources or mechanisms.
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All authors Roberto Maiolino, Hannah Übler, Michele Perna, Joris Witstok, Gareth C. Jones, Pablo G. Perez-Gonzalez, Kimihiko Nakajima, Elka Rusta, Stefania Salvadori, Sandro Tacchella, Piero Madau, James A. A. Trussler, Francesco D'Eugenio, Xihan Ji, Jan Scholtz, Stefano Carniani, Yuki Isobe, Harley Katz, Santiago Arribas, William M. Baker, Torsten Böker, Volker Bromm, Andrew J. Bunker, Stephane Charlot, Jacopo Chevallard, Mirko Curti, Emma Curtis-Lake, Daniel Eisenstein, Eiichi Egami, Andrea Ferrara, Luca Graziani, Kevin Hainline, Jakob M. Helton, Lucy Ivey, Benjamin Jonson, Maria Koller, Nimisha Kumari, Alessandro Marconi, Giovanni Mazzolari, Nicolas Laporte, Eleonora Parlanti, Robert Pascalau, Laura Pentericci, Pierluigi Rinaldi, Brant Robertson, Bruno Rodríguez Del Pino, Raffaella Schneider, Alessandra Venditti, Giacomo Venturi, Christopher N. A. Willmer, Callum Witten, Sandra Zamora

Astrophysics of Galaxies

GA-NIFS and JADES: Confirmation of pristine gas near GN-z11

Hannah Übler, Roberto Maiolino, Pablo G. Pérez-González et al. (+32 more)

According to the leading cosmological model, a first generation of stars called Population III (PopIII), condensed almost entirely out of hydrogen and helium, must have initiated the creation of all heavier chemical elements. We report the detection of ionised hydrogen (H$\gamma_{4342}$) with a signal-to-noise ratio of $S/N$=5.9 in a region about 3 pkpc (projected) north-east from the z~10.6 galaxy GN-z11, where line emission compatible with doubly ionised helium (HeII$_{1640}$) has been found. Our new JWST/NIRSpec-IFU G395H data confirm the authenticity of the previous detection at a redshift of $z_{\rm H\gamma}$=$10.5862$$\pm$$0.0003$. H$\delta$ is marginally detected ($S/N$$\sim$$2$). No metal lines are detected in our observations spanning $\lambda_{\rm rest}$=$0.25$-$0.45\mu$m. We derive a $3\sigma$ upper limit on the gas phase metallicity of 12+log(O/H)$<$7.0 ($Z_{\rm gas}$$<$$0.02$ $Z_\odot$). Through comparison with NIRCam imaging, we constrain a lower limit on the equivalent width of EW$_0$(H$\gamma$)$>$350Å. We compare our emission line constraints to model predictions and find them compatible with photoionisation by PopIII stars, possibly intermixed with next-generation (PopII) stars. We infer an upper limit on the dynamical mass of $M_{\rm dyn}$$\lesssim$$3$$\times$$10^8M_\odot$. Our data provide novel support for the presence of PopIII stars nearby GN-z11, 440 Myr after the Big Bang.
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All authors Hannah Übler, Roberto Maiolino, Pablo G. Pérez-González, Yuki Isobe, Gareth C. Jones, Nimisha Kumari, Stéphane Charlot, Elka Rusta, Stefania Salvadori, Kimihiko Nakajima, Michele Perna, Santiago Arribas, Andrew J. Bunker, Stefano Carniani, Francesco D'Eugenio, Bruno Rodríguez Del Pino, Elena Bertola, Torsten Böker, Jacopo Chevallard, Chiara Circosta, Giovanni Cresci, Mirko Curti, Emma Curtis-Lake, Daniel J. Eisenstein, Kevin Hainline, Benjamin D. Johnson, Eleonora Parlanti, Pierluigi Rinaldi, Brant Robertson, Jan Scholtz, Sandro Tacchella, Giacomo Venturi, Christopher N. A. Willmer, Joris Witstok, Sandra Zamora

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

White Dwarf Structure in $f(Q)$ Gravity

Rajasmita Sahoo

In this work, we investigate the equilibrium structure of white dwarfs within the covariant formulation of symmetric teleparallel $f(Q)$ gravity, in which gravity is described by the nonmetricity scalar $Q$ instead of spacetime curvature. We consider static and spherically symmetric stellar configurations composed of cold, fully degenerate electron matter and adopt a quadratic form of the gravitational Lagrangian, $f(Q)=Q+\alpha Q^{2}$, where $\alpha$ quantifies deviations from general relativity. The corresponding modified stellar structure equations are solved numerically in conjunction with the Chandrasekhar equation of state. We examine the impact of the parameter $\alpha$ on the internal structure and global properties of white dwarfs, including the radial profiles of the metric potentials, pressure, density, nonmetricity scalar, and enclosed mass, as well as the mass–radius relation. While negative values of $\alpha$ were explored, they lead to unstable or nonphysical configurations at high densities; therefore, the analysis is restricted to non-negative values of $\alpha$. Our results show that nonmetricity corrections produce significant deviations from the general relativistic predictions in the high-density regime. In particular, increasing $\alpha$ modifies the equilibrium configurations and leads to a reduction in the maximum mass relative to the Chandrasekhar limit, accompanied by corresponding changes in the stellar radius and interior profiles. For $\alpha = 5\times10^{18}\,\mathrm{cm^2}$, we obtain a maximum mass $M_{\max}=1.3519\,M_{\odot}$ and radius $R=2228.85\,\mathrm{km}$, which are consistent with the observational constraints of the ultra-massive white dwarf ZTF J1901+1458. These findings suggest that white dwarfs can provide a complementary astrophysical probe for testing the viability of $f(Q)$ gravity in the strong-field regime.
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Instrumentation and Methods for Astrophysics

Advanced Virgo Plus for O5 – Design Report Overview

F. Acernese, A. Agapito, D. Agarwal et al. (+578 more)

This document presents an overview of the design, implementation, and expected performance of the Advanced Virgo Plus (AdV+) upgrades in view of the O5 observing run. Following the experience gained during the O4 commissioning and operations, the Virgo Collaboration has revised the upgrade strategy to address limitations associated with marginally stable recycling cavities. The O5 upgrade program combines elements from the original AdV+ Phase II project with new design solutions, including the implementation of stable recycling cavities, a major modification to the central interferometer layout, and a comprehensive renewal of critical subsystems. The planned upgrades are organized in two steps, targeting progressive improvements in operational stability, noise reduction, and detector sensitivity. Key developments include new vacuum infrastructures, suspensions, mirrors, optical configurations, quantum noise reduction systems, and high-power laser technologies. The resulting configuration is expected to significantly enhance the interferometer performance, enabling a substantial increase in astrophysical reach and scientific return during O5.
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All authors F. Acernese, A. Agapito, D. Agarwal, I.-L. Ahrend, L. Aiello, A. Ain, S. Albanesi, W. Ali, C. Alléné, A. Allocca, W. Amar, A. Amato, F. Amicucci, C. Amra, M. Andia, T. Andrić, S. Ansoldi, S. Antier, E. Z. Appavuravther, M. Arca Sedda, F. Arciprete, F. Armato, N. Arnaud, L. Asprea, M. Assiduo, S. Assis de Souza Melo, P. Astone, F. Attadio, F. Aubin, G. Avallone, S. Babak, S. Bagnasco, T. Baka, G. Balbi, G. Baldi, N. Baldicchi, G. Ballardin, B. Banerjee, M. Baratti, P. Barneo, F. Barone, M. Barsuglia, D. Barta, A. Basti, M. Bawaj, M. Bazzan, F. Beirnaert, M. Bejger, D. Belardinelli, C. Bellani, L. Bellizzi, D. Beltran-Martinez, I. Bentara, S. Bera, S. Bernuzzi, D. Bersanetti, T. Bertheas, A. Bertolini, G. Bevilacqua, V. Biancalana, A. Bianchi, F. Bianchi, A. Binetti, S. Bini, S. Biot, M. Bitossi, M.-A. Bizouard, G. Boileau, M. Boldrini, A. Bolliand, R. Bondarescu, F. Bondu, R. Bonnand, N. Borghi, V. Boschi, Y. Bothra, A. Boudon, A. Bozzi, C. Bradaschia, M. Branchesi, T. Briant, A. Brillet, M. L. Brozzetti, G. Bruno, F. Bucci, O. Bulashenko, T. Bulik, H. J. Bulten, R. Buscicchio, D. Buskulic, C. Buy, R. Cabrita, G. Cagnoli, E. Calloni, M. Canepa, G. Caneva Santoro, E. Capocasa, G. Capoccia, G. Capurri, G. Carapella, F. Carbognani, M. Carpinelli, G. Carullo, A. Casallas-Lagos, J. Casanueva Diaz, C. Casentini, R. Cavalieri, G. Cella, S. Cepic, P. Cerdá-Durán, E. Cesarini, W. Chaibi, E. Chassande-Mottin, S. Chaty, P. Chessa, F. Chiadini, A. Chincarini, M. L. Chiofalo, A. Chiummo, N. Christensen, G. Ciani, M. Cieślar, P. Ciecielag, M. Cifaldi, S. Clesse, F. Cleva, E. Coccia, E. Codazzo, P.-F. Cohadon, S. Colace, A. Colombo, L. Conti, I. Cordero-Carrión, S. Corezzi, L. A. Corubolo, A. Cozzumbo, J. R. Cudell, E. Cuoco, M. Cusinato, B. D'Angelo, S. D'Antonio, L. D'Onofrio, D. D'Urso, G. Dálya, S. Dall'Osso, T. Dal Canton, S. Dal Pra, S. Danilishin, V. Dattilo, A. Daumas, M. Davier, P. Davis, J. Degallaix, C. J. Delgado Mendez, S. Della Torre, W. Del Pozzo, A. Demagny, G. Demasi, A. Depasse, J. De Bolle, M. De Laurentis, F. De Lillo, F. De Marco, F. De Matteis, R. De Pietri, R. De Rosa, C. De Rossi, R. De Simone, C. Diaz, D. Diksha, J. Ding, M. Di Cesare, L. Di Fiore, M. Di Giovanni, T. Di Girolamo, S. Di Pace, I. Di Palma, D. Di Piero, F. Di Renzo, A. Domiciano De Souza, T. Dooney, O. Dorosh, M. Drago, M. Dubois, U. Dupletsa, H. Duval, P.-A. Duverne, M. Ebersold, H. Einsle, L. Errico, M. Esposito, F. Fabrizi, V. Fafone, M. Fays, E. Fenyvesi, T. Fernandes, S. Ferraiuolo, F. Fidecaro, P. Figura, A. Fiori, I. Fiori, R. Fittipaldi, V. Fiumara, R. Flaminio, J. A. Font, K. Franceschetti, F. Frappez, S. Frasca, F. Frasconi, A. Freise, O. Freitas, B. Gadre, S. Galaudage, B. Garaventa, J. García-Bellido, P. García Abia, J. Gargiulo, X. Garrido, F. Garufi, C. Gasbarra, F. Gautier, G. Gemme, A. Gennai, V. Gennari, Archisman Ghosh, S. Gkaitatzis, F. Glotin, S. Gomez Lopez, A. Goodwin-Jones, M. Gosselin, C. Gostiaux, R. Gouaty, A. Grado, M. Granata, V. Granata, G. Greco, A. C. Green, G. Grignani, C. Grimaud, D. Guerra, D. Guetta, G. M. Guidi, F. Gulminelli, Y. Guo, N. Gutierrez, M. Haney, S. Harikumar, T. Harmark, J. Harms, M. T. Hartman, B. Haskell, D. Hegde, H. Heitmann, G. Hemming, J. Heynen, S. Hild, D. Hofman, N. A. Holland, L. Honet, C. A. Hrishikesh, W.-F. Hsu, V. Hui, L. Iampieri, G. A. Iandolo, M. Ianni, G. Iannone, A. Ierardi, G. Iorio, P. Iosif, C. Jacquet, P.-E. Jacquet, T. Jacquot, J. Janquart, S. Jaraba, P. Jaranowski, G. Joubert, V. Juste, W. Kiendrebeogo, G. Koekoek, S. Koley, A. E. Koloniari, A. Koushik, A. Królak, E. Kraja, S. L. Kranzhoff, J. Kubisz, A. Lakhal, M. Lalleman, A. Lartaux-Vollard, L. Lavezzi, C. Lazarte, C. Lazzaro, P. Leaci, A. Lemaître, M. Lenti, M. Leonardi, M. Lequime, N. Leroy, N. Letendre, M. Lethuillier, S. Lexmond, M. Le Jean, T. G. F. Li, J.-P. Locquet, A. Longo, D. Lopez, M. Lopez Portilla, M. Lorenzini, V. Loriette, G. Losurdo, L. Lucchesi, D. Lumaca, L. Lunghini, A. Macquet, S. S. Madekar, S. Maenaut, R. Maggiore, M. Magnozzi, E. Majorana, N. Man, M. Mancarella, V. Mangano, M. Mantovani, M. Mapelli, S. Marchetti, C. Marinelli, F. Marion, S. Marsat, F. Martelli, M. Martinez, V. Martinez, A. Martini, L. Massaro, A. Masserot, S. Mastrogiovanni, G. Mastropasqua, T. Matcovich, L. Maurin, Q. Meijer, L. Mereni, G. Merino, M. Merzougui, B. Mestichelli, A. Miani, C. Michel, A. L. Miller, E. Milotti, V. Milotti, Y. Minenkov, Ll. M. Mir, L. Mirasola, C.-A. Miritescu, A. L. Mitchell, L. Mobilia, M. Montani, A. Moreso Serra, G. Morras, A. Moscatello, B. Mours, C. M. Mow-Lowry, L. Muccillo, F. Muciaccia, D. Nabari, S. Nadji, A. Nagar, D. Nanadoumgar-Lacroze, V. Napolano, I. Nardecchia, H. Narola, L. Naticchioni, L. Negri, A. Nemmani, S. Nissanke, F. Nocera, J. Novak, J. F. Nuño Siles, M. Oertel, G. Oganesyan, M. Orselli, A. Ouzriat, C. Périgois, L. Paiella, M. A. Palaia, P. P. Palma, C. Palomba, P. Palud, P. T. H. Pang, F. Pannarale, M. Panzeri, F. Paoletti, A. Paolone, L. Papalini, G. Papigkiotis, A. Paquis, A. Parisi, D. Pascucci, A. Pasqualetti, R. Passaquieti, D. Passuello, B. Patricelli, A. Perego, G. Perna, A. Perreca, J. Perret, S. Perriès, J. W. Perry, S. Peters, C. Petrillo, M. Piarulli, L. Piccari, M. Pichot, M. Piendibene, F. Piergiovanni, L. Pierini, G. Pierra, V. Pierro, M. Pietrzak, M. Pillas, L. Pinard, I. M. Pinto, M. Pinto, A. Placidi, E. Placidi, W. Plastino, R. Poggiani, E. Polini, J. Pomper, E. Porcelli, E. K. Porter, R. Poulton, M. Pracchia, T. Pradier, G. Principe, G. A. Prodi, P. Prosperi, P. Prosposito, P. Puppo, G. Quéméner, I. Rainho, A. Ramos-Buades, P. Rapagnani, M. Razzano, T. Regimbau, A. I. Renzini, B. Revenu, A. Revilla Peña, L. Ricca, F. Ricci, M. Ricci, A. Ricciardone, S. Rinaldi, F. Robinet, A. Rocchi, L. Rolland, R. Romano, A. Romero-Rodríguez, L. Rosa, D. Rosińska, S. Roy, D. Rozza, P. Ruggi, E. Ruiz Morales, P. Saffarieh, T. Sainrat, S. Sajith Menon, O. S. Salafia, L. Salconi, F. Salemi, M. Sallé, S. Salvador, A. Samajdar, N. Sanchis-Gual, F. Santoliquido, F. Sarandrea, A. Sasli, P. Sassi, B. Sassolas, S. Sayah, V. Scacco, S. Schmidt, K. Schouteden, M. Schulz, M. Scialpi, M. Seglar-Arroyo, J. W. Seo, V. Sequino, M. Serra, A. Sevrin, N. S. Shcheblanov, L. Silenzi, L. Silvestri, V. Sipala, L. Smith, S. Soares de Albuquerque Filho, V. Sordini, F. Sorrentino, F. Spada, V. Spagnuolo, P. Spinicelli, D. A. Steer, J. Steinlechner, S. Steinlechner, N. Stergioulas, P. Stevens, M. Suchenek, S. Sudhagar, J. Suresh, A. Svizzeretto, B. L. Swinkels, A. Syx, M. J. Szczepańczyk, P. Szewczyk, M. Tacca, M. Tagliazucchi, I. Takimoto Schmiegelow, N. Tamanini, E. N. Tapia San Martín, C. Taranto, A. Theodoropoulos, J. Tissino, P. Tiwari, E. Tofani, M. Toffano, A. Torres-Forné, I. Tosta e Melo, E. Tournefier, M. Trad Nery, A. Trapananti, R. Travaglini, F. Travasso, M. C. Tringali, G. Troian, A. Trovato, L. Trozzo, K. Turbang, M. Turconi, C. Turski, H. Ubach, M. Vacatello, M. Valentini, E. Vallejo-Pagès, S. Vallero, M. van Dael, E. Van den Bossche, J. F. J. van den Brand, C. Van Den Broeck, M. van der Kolk, M. van der Sluys, A. Van de Walle, J. van Dongen, H. van Haevermaet, J. V. van Heijningen, P. Van Hove, N. van Remortel, M. Vardaro, G. Vedovato, S. Venikoudis, P. Verdier, M. Vereecken, D. Verkindt, F. Vetrano, A. Veutro, A. Viceré, N. Villanueva Espinosa, J.-Y. Vinet, S. Viret, H. Vocca, M. Was, M. Wils, J. Woehler, I. C. F. Wong, T. Wouters, M. Wright, Z. Wu, N. Yadav, T. Zelenova, J.-P. Zendri, M. Zeoli, M. Zerrad, Y. Zhao, L. Zimmermann

Cosmology and Nongalactic Astrophysics

Galaxy sizes as complementary (zero-)bias tracers of local primordial non-Gaussianity

Nhat-Minh Nguyen, Kazuyuki Akitsu and Atsushi Taruya

The scale-dependent bias in halo and galaxy power spectra is a key signature of local primordial non-Gaussianity (local PNG), with PNG sensitivity scaling as $b_\phi/b_1$ – the ratio of their responses to long-wavelength primordial potential $b_\phi$ and late-time density fluctuations $b_1$. For number density fluctuations, these responses are closely tied by the universality relation, limiting the achievable ratio. We show that size density fluctuations strongly violate this relation, thus evading the limit. For galaxy-mass halos, sizes have a vanishingly small density response but a sizable, negative local PNG response, implying an effective $b_\phi/b_1$ that is large in magnitude and opposite in sign to that of number counts. This makes galaxy sizes complementary probes of local PNG from the same galaxy sample, without any sample split. For a DESI-like survey, a multi-tracer analysis combining galaxy numbers and sizes improves the local-PNG detection significance by a factor of $\sim\!3.6$. Due to the sign flip, the number-size cross power spectrum further provides a handle on systematics in the event of a detection.
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Cosmology and Nongalactic Astrophysics

Improved constraint on the Hubble constant from dark sirens with LIGO/Virgo/KAGRA O4a

V. Alfradique, C. R. Bom, G. Teixeira et al. (+1 more)

A new measurement of the Hubble constant $H_0$ is presented using the statistical dark siren method applied to a sample of seven well-localized gravitational-wave (GW) events from the fourth LIGO-Virgo-KAGRA (LVK) observing run and ten additional events from the first three runs. Galaxy catalogs from the DESI Legacy Imaging Survey (LS) are combined with a deep learning model to compute photometric redshift probability density functions. We extend our previous analysis by including the events GW230731_215307 and GW230927_153832, using sky maps from the fourth Gravitational-Wave Transient Catalog (GWTC-4), and introducing key methodological improvements: $r$-band luminosity weighting of host galaxies; an extended GW likelihood that incorporates information from the binary black hole component masses; and a consistent treatment of selection effects that accounts for the incompleteness of the magnitude-limited LS galaxy catalog. Using a total of 17 well-localized dark sirens (seven from the first part of the fourth observing run, O4a), we obtain $H_0 = 78.8^{+14.6}_{-12.2}$ km/s/Mpc without luminosity weighting and $H_0 = 78.2^{+12.0}_{-11.0}$ km/s/Mpc when applying $r$-band luminosity weighting. Finally, we combine the luminosity-weighted dark siren sample with the bright siren GW170817, including constraints on the jet viewing angle and corrections for the host galaxy peculiar velocity, to obtain a final constraint of $H_0 = 69.9^{+4.1}_{-4.0}$ km/s/Mpc, representing an improvement of approximately 11% in the uncertainty relative to the GW170817-only result.
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All authors V. Alfradique, C. R. Bom, G. Teixeira, A. Santos

Astrophysics of Galaxies

VINTERGATAN-GM: long-lived satellite planes induced by a massive GSE-like merger

R. Rodríguez-Cardoso, S. Roca-Fàbrega, Oscar Agertz et al. (+7 more)

Satellite galaxies in the Local Group tend to be distributed in thin, planar configurations, with many sharing coherent orbital motion. Galaxy formation simulations in $\Lambda$CDM have historically struggled to produce similar structures, leading to the so-called "planes of satellites problem". In this work, we investigate whether the emergence of such structures is connected to the mass of a major merger at $z\sim2$, analogous to the Gaia-Sausage-Enceladus (GSE) event in the Milky Way. We use the VINTERGATAN-GM suite of high-resolution zoom-in simulations, comprising five realizations of the same Milky Way-mass halo generated through targeted genetic modifications of a GSE progenitor. The GSE-like merger mass ratio is systematically varied from 1:10 to 1:2.1, while keeping the final dynamical mass and large-scale environment fixed. We find a clear and consistent trend: more massive GSE-like mergers lead to satellite populations that are both more planar and more kinematically coherent. In particular, simulations with merger mass ratios larger than 1:6 develop Kinematic Persistent Planes (KPPs), in which at least 40% of satellites co-orbit around a common axis over extended periods, comparable to those observed in the Milky Way. These structures arise when sufficiently massive mergers, accreted along the direction of maximum compression of the Lagrangian volume, produce flattened host halos with anisotropic velocity dispersions aligned with the merger direction. The merger aligns the host halo's minor axis with the direction of flattening of the surrounding cosmic web, and planes of satellites then emerge through two complementary processes: (i) satellites preferentially infall along the host's equatorial plane, and (ii) anisotropic dynamical friction in the non-spherical halo gradually reshapes their orbits toward this plane, generating coherent and long-lived planar configurations.
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All authors R. Rodríguez-Cardoso, S. Roca-Fàbrega, Oscar Agertz, Jesus Gallego, Justin Read, Andrew Pontzen, Martin P. Rey, I. Santos-Santos, M. Gámez-Marín, Jess Kocher

Cosmology and Nongalactic Astrophysics

SPT-3G D1: Maps of the millimeter-wave sky from 2019 and 2020 observations of the SPT-3G Main field

W. Quan, E. Camphuis, C. Daley et al. (+92 more)

Maps of the sky in millimeter wavelengths contain rich information on cosmology through anisotropies of the cosmic microwave background (CMB). Creating multifrequency sky maps of anisotropies in the $I$, $Q$, and $U$ Stokes parameters is one of the first steps of CMB cosmology analyses. In this work, we describe the production and validation of a set of sky maps from the South Pole Telescope's third-generation camera, SPT-3G. The maps are from data taken in frequency bands centered at 95, 150, and 220 GHz and taken during the first two years, 2019 and 2020, of the SPT-3G Main survey, which covers $4\%$ of the sky. We applied high-pass filters to time series of individual detectors and binned the filtered time series samples into map pixels. After that, we calibrated and cleaned the maps to reduce known systematic errors. In addition, we searched for other systematic errors through null tests and mitigated a significant systematic error detected therein. The white noise levels of the full-depth maps of the $I$ Stokes parameter are $5.4$, $4.4$, and $16.2$ $\mathrm{{\mu}K}$-$\mathrm{arcmin}$ in the 95, 150, and 220 GHz bands, respectively, and $8.4$, $6.6$, and $25.8$ $\mathrm{{\mu}K}$-$\mathrm{arcmin}$ for $Q/U$. These maps are the deepest to date used for measurements of mid-to-high-$\ell$ primary temperature and $E$-mode polarization CMB anisotropies, and reconstructions of the CMB gravitational lensing potential. We make these maps and supporting data products publicly accessible.
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All authors W. Quan, E. Camphuis, C. Daley, N. Huang, Y. Omori, F. Guidi, E. Anderes, A. J. Anderson, B. Ansarinejad, M. Archipley, L. Balkenhol, D. R. Barron, K. Benabed, A. N. Bender, B. A. Benson, F. Bianchini, L. E. Bleem, S. Bocquet, F. R. Bouchet, M. G. Campitiello, J. E. Carlstrom, J. Carron, C. L. Chang, P. M. Chichura, A. Chokshi, T.-L. Chou, A. Coerver, T. M. Crawford, T. de Haan, K. R. Dibert, M. A. Dobbs, M. Doohan, D. Dutcher, C. Feng, K. R. Ferguson, N. C. Ferree, K. Fichman, A. Foster, S. Galli, A. E. Gambrel, A. K. Gao, F. Ge, S. Guns, N. W. Halverson, E. Hivon, G. P. Holder, W. L. Holzapfel, J. C. Hood, A. Hryciuk, T. Jhaveri, F. Kéruzoré, A. R. Khalife, L. Knox, K. Kornoelje, C.-L. Kuo, K. Levy, Y. Li, A. E. Lowitz, C. Lu, G. P. Lynch, T. J. Maccarone, A. S. Maniyar, E. S. Martsen, F. Menanteau, M. Millea, J. Montgomery, Y. Nakato, T. Natoli, A. Ouellette, Z. Pan, P. Paschos, K. A. Phadke, A. W. Pollak, K. Prabhu, S. Raghunathan, M. Rahimi, A. Rahlin, C. L. Reichardt, M. Rouble, J. E. Ruhl, A. C. Silva Oliveira, A. Simpson, J. A. Sobrin, A. A. Stark, J. Stephen, C. Tandoi, C. Trendafilova, J. D. Vieira, A. G. Vieregg, A. Vitrier, Y. Wan, N. Whitehorn, W. L. K. Wu, M. R. Young, J. A. Zebrowski

Cosmology and Nongalactic Astrophysics

Cosmological forecast from the full-sky angular power spectrum and bispectrum of 21cm intensity mapping

Rodrigo F. Pinheiro, André A. Costa and Yu Sang

We compute the full-sky angular power spectrum and bispectrum, along with their Fisher matrices, to forecast constraints on cosmological parameters for the BINGO and SKA1-MID Band 2 radio telescopes. This represents the first forecast analysis using the full-sky relativistic bispectrum in redshift space for these surveys. Our results show that the second-order velocity contribution, often neglected under the Limber approximation, accounts for approximately $24\%$ of the total signal at low redshifts, indicating that it must be included for accurate modeling. Using these forecasts, we find that while the bispectrum provides constraints comparable to the angular power spectrum for $\Lambda$CDM and ${\rm w}$CDM models, it becomes a powerful probe of dynamical dark energy. Restricting the analysis to linear scales, we show that the inclusion of the bispectrum yields a substantial improvement in the determination of the Chevallier-Polarski-Linder (CPL) parameters. In particular, the joint analysis of the bispectrum, power spectrum, and Planck CMB data improves constraints on ${\rm w}_0$ and ${\rm w}_a$ by over $70\%$, and the Hubble parameter $h$ by approximately $60\%$. These results underscore the importance of relativistic bispectrum for breaking parameter degeneracies and probing the nature of dark energy with upcoming large-scale structure surveys.
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Solar and Stellar Astrophysics

A New Multi-Constraint Potential Field Source Surface (PFSS) Extrapolation Model

C. Antonio, I. Chifu, R. Gafeira et al. (+1 more)

The Potential Field Source Surface (PFSS) model is the most used approach for extrapolating the global coronal magnetic field, offering efficiency and strong performance at large scales. However, PFSS assumes a potential coronal field, so it cannot account for distortions from electric currents. More advanced methods, such as nonlinear force-free field (NLFFF) models, can represent these effects but are much more computationally intensive. Recent observational techniques also allow 3D reconstruction of coronal loops, which trace solar magnetic field geometry. This work develops a new approach that constrains the PFSS model using 3D coronal loop information, improving agreement with observations while keeping efficiency. The model is based on PFSS field constraints from photospheric data but allows magnetic field deviations from the potential state within loop-influenced regions, maintaining control over divergence and force-freeness. We adapted NLFFF optimization to the PFSS framework, enabling multiple physical constraints. Our functional includes up to three terms: divergence-free, loop geometry, and force-free. The resulting Python algorithm was tested with synthetic loops, using Carrington rotation 2284 as the lower boundary. This method yields magnetic field solutions that better match the geometry of included loops and controls divergence and force-freeness. Our results show that 3D coronal loop information can be incorporated into PFSS, largely preserving computational efficiency even with many loops. This approach lets PFSS better reflect observed coronal structures without significant computational cost.
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All authors C. Antonio, I. Chifu, R. Gafeira, J.J.G. Lima

Instrumentation and Methods for Astrophysics

Theory of optical long-baseline interferometry on polarized sources

Guy Perrin

The effects of the polarization characteristics of beam trains in optical long-baseline interferometers are well known and have led to difficulties in measuring the spatial coherence of astronomical sources in the past. This has been overcome by designing symmetrical optical trains. With the advent of interferometers using large telescopes, observations of faint sources with high degrees of polarization have become even more possible. As in the radio domain, where radiation processes usually lead to high polarization rates, a description of coherence for polarized or unpolarized sources observed with non-polarization neutral interferometers is necessary. A theory of optical long-baseline interferometry fully taking into account the polarization characteristics of beam trains and those of the sources is presented in this paper, building on concepts developed for radio aperture synthesis. The concept of generalized Mueller matrix is introduced for the case of multi-aperture interferometers leading to a simple matrix relationship between the observed Stokes visibilities, as they are disturbed by the instrument polarization characteristics, and the object Stokes visibilities. This relationship is applied to the case of single-mode interferometers. The formalism also shows that classical complex visibilities (squared moduli, phases and closure phases) need to be debiased from polarization crosstalk, even when the source is not polarized as in this case ghost polarized visibilities are created.
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High Energy Astrophysical Phenomena

Numerically stable equations for the orbital evolution of compact object binaries

Max M. Briel and Jeff J. Andrews

The orbital and eccentricity evolution for compact object binaries through gravitational wave emission first derived by Peters and Mathews are used extensively throughout the gravitational wave community for calculating the orbital evolution and merger time of compact binaries. While improved calculations of the binary merger time have been the focus of several investigations since, the orbital evolution has not received the same attention. As the equations lack a closed form solution, a numerical integrator is required, but standard methods typically break when the point of merger is overstepped. We present a rewrite of Peters' equations in $\ln$-space, which allows common numerical solvers to converge. This leads to a more numerically robust and computationally efficient method for evolving compact binaries due to gravitational wave emission, reducing the number of function evaluations by 60% to 70% in our tests.
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