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Physics Astrophysics

astro-ph Watch Astrophysics

Thursday 9 October

Instrumentation and Methods for Astrophysics

Fisher Matrix for Beginners

David Wittman

The Fisher information matrix is used widely in astronomy (and presumably other fields) to forecast the precision of future experiments while they are still in the design phase. Although many sources describe the mathematics of the formalism, few sources offer simple examples to help the beginner. This pedagogical document works through a few simple examples to develop conceptual understanding of the applications.
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Astrophysics of Galaxies

Accretion-Regulated Type Transitions in Changing-Look AGNs: Evidence from Two-Epoch Spectral Analysis

Yu-Heng Shen, Kai-Xing Lu, Wei-Jian Guo et al. (+6 more)

The changing-look active galactic nucleus (CL-AGN), an extraordinary subpopulation of supermassive black holes, has attracted growing attention for understanding its nature. We present an analysis of the spectral properties of 203 low-redshift CL-AGNs ($z<0.35$) using two-epoch spectra from SDSS DR16 and DESI DR1 with time baseline ranging from $\sim$1000 to 8000 days, based on spectral fitting and decomposition. The sample consists of 11.3% Type 1.0, 26.6% Type 1.2, 43.1% Type 1.5, and 19% Type 1.8/2.0 AGNs. The total sample is divided into two datasets: Dataset A (110 objects) with minor spectral type variations, likely general AGN variability, and Dataset B (93 objects) showing significant type transitions and characteristic turn-on or turn-off behavior. Our results reveal clear optical continuum and emission-line variability, showing both bluer-when-brighter and redder-when-brighter trends. A strong correlation between the broad H$\beta$/[O~iii] ratio and broad H$\alpha$ luminosity ($L_{\rm H\alpha}$), ${\rm log(H\beta/[O~III])}=(0.63\pm 0.07){\rm log}(L_{\rm H\alpha})-(26.49\pm2.96)\pm0.48$ for Dataset B, as well as the correlation between H$\beta$/[O~iii] and Eddington ratio ($L_{\rm bol}/L_{\rm Edd}$), ${\rm log(H\beta/[O~III])}=(0.59\pm 0.08){\rm log}(L_{\rm bol}/L_{\rm Edd})+(1.02\pm0.15)\pm0.53$ for Dataset B, suggests that accretion rate variations drive changes in ionizing flux within the broad-line region, thereby triggering AGN type transitions. These findings underscore the critical role of supermassive black hole accretion processes in refining the AGN unification model. Future work should investigate potential connections between stellar evolution in outer accretion disk and the observed scatter in these correlations.
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All authors Yu-Heng Shen, Kai-Xing Lu, Wei-Jian Guo, Sha-Sha Li, Hai-Cheng Feng, Zhang Yue, Wen-Zhe Xi, Jian-Guo Wang, Jin-Ming Bai

High Energy Astrophysical Phenomena

Event Horizon Telescope Pattern Speeds in the Visibility Domain

Nicholas S. Conroy, Michi Bauböck, Vedant Dhruv et al. (+5 more)

The Event Horizon Telescope is preparing to produce time sequences of black hole images, or movies. In anticipation, we developed an autocorrelation technique to measure apparent rotational motion using the image-domain pattern speed $\Omega_p$. Here, we extend this technique to the visibility domain and introduce the visibility amplitude pattern speed $\Omega_{\mathrm{VA}}$. We show that in the Illinois v3 library of EHT source models, $\Omega_{\mathrm{VA}}$ depends on the source inclination, black hole mass, black hole spin, accretion state (MAD or SANE), and baseline length, and then provide approximate fits for this dependence. We show that $\Omega_{\mathrm{VA}}$ is particularly sensitive to baseline length for MAD (strongly magnetized) models, and that the slope of this dependence can be used to constrain black hole spin. As with $\Omega_p$, models predict that $\Omega_{\mathrm{VA}}$ is well below the Keplerian frequency in the emission region for all model parameters. This is consistent with the idea that $\Omega_{\mathrm{VA}}$ measures an angular phase speed for waves propagating through the emission region. Finally, we identify the information that would be provided by space-based millimeter VLBI such as the proposed BHEX mission.
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All authors Nicholas S. Conroy, Michi Bauböck, Vedant Dhruv, Daeyoung Lee, Chi-kwan Chan, Abhishek V. Joshi, Cora Prather, Charles F. Gammie

Earth and Planetary Astrophysics

Constraining exoplanet interiors using observations of their atmospheres

Tim Lichtenberg, Oliver Shorttle, Johanna Teske et al. (+1 more)

Astronomical surveys have identified numerous exoplanets with bulk compositions that are unlike the planets of the Solar System, including rocky super-Earths and gas-enveloped sub-Neptunes. Observing the atmospheres of these objects provides information on the geological processes that influence their climates and surfaces. In this Review, we summarize the current understanding of these planets, including insights into the interaction between the atmosphere and interior based on observations made with the James Webb Space Telescope (JWST). We describe the expected climatic and interior planetary regimes for planets with different density and stellar flux and how those regimes might be observationally distinguished. We also identify the observational, experimental, and theoretical innovations that will be required to characterize Earth-like exoplanets.
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All authors Tim Lichtenberg, Oliver Shorttle, Johanna Teske, Eliza M.-R. Kempton

Astrophysics of Galaxies

Measuring the Temperature of Extremely Hot Shock-Heated Gas in the Major Merger MACS J0717.5+3745 With Relativistic Corrections to the Sunyaev-Zel'dovich Effect

Benjamin J. Vaughan, Jack Sayers, Locke Spencer et al. (+10 more)

The conversion of gravitational potential to kinetic energy results in an intracluster medium (ICM) gas with a characteristic temperature near 10 keV in the most massive galaxy clusters. X-ray observations, primarily from Chandra and XMM-Newton, have revealed a wealth of information about the thermodynamics of this gas. However, two regimes remain difficult to study with current instruments: superheated gas well above 10 keV generated by shocks from major mergers, and distant systems strongly impacted by cosmological dimming. Relativistic corrections to the Sunyaev-Zel'dovich effect (rSZe) produce a fractional spectral distortion in the cosmic microwave background at submillimeter and millimeter wavelengths that could offer a complementary probe of both high-temperature and high-redshift ICM gas. Here we describe multiband measurements of the rSZe, including observations from the Fourier Transform Spectrometer on the Herschel-SPIRE instrument, that constrain the ICM thermodynamics of the major merger MACS J0717.5+3745. Within the seven observed lines of sight, we find an average temperature of $T_{\mathrm{rSZe}}=15.1^{+3.8}_{-3.3}$ keV which is consistent with the values obtained from X-ray measurements of the same regions, with $T_{\mathrm{Chandra}}=18.0^{+1.1}_{-1.1}$ keV and $T_{\mathrm{XMM}}=13.9^{+0.9}_{-0.9}$ keV. This work demonstrates that the rSZe signal can be detected with moderate spectral resolution submillimeter data, while also establishing the utility of such measurements for probing superheated regions of the ICM.
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All authors Benjamin J. Vaughan, Jack Sayers, Locke Spencer, Nicholas Swidinsky, Ryan Wills, Michael Zemcov, Derek Arthur, Victoria Butler, Richard M. Feder, Daniel Klyde, Lorenzo Lovisari, Adam Mantz, Emily M. Silich

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

Distinguishing between Black Holes and Neutron Stars within a Population of Weak Tidal Measurements

Michael Müller and Reed Essick

We study the ability of tidal signatures within the inspiral of compact binaries observed through gravitational waves (GWs) to distinguish between neutron stars (NSs) and black holes (BHs). After quantifying how hard this measurement is on a single-event basis, we investigate the ability of a large catalog of GW detections to constrain the fraction of NS in the population as a function of mass: $f_{\mathrm{NS}}(m)$. Using simulated catalogs with realistic measurement uncertainty, we find that $> O(200)$ events will be needed before we can precisely measure $f_{\mathrm{NS}}$, and catalogs of $> O(100)$ events will be needed before we can even rule out the possibility that all low-mass objects are BHs with GW data alone (i.e., without electromagnetic counterparts). Therefore, this is unlikely to occur with advanced detectors, even at design sensitivity. Nevertheless, it could be feasible with next-generation facilities like Cosmic Explorer and Einstein Telescope.
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Astrophysics of Galaxies

LATIS Data Release: $\sim4200$ Spectra of $z \sim 2-3$ Galaxies, Redshifts, and Intergalactic Medium Tomography Maps

Andrew B. Newman, Gwen C. Rudie, Guillermo A. Blanc et al. (+8 more)

We present the data release of the Ly$\alpha$ Tomography IMACS Survey (LATIS), one of the largest optical spectroscopic surveys of faint high-redshift galaxies. The survey provides 7408 optical spectra of candidate $z \sim 2-3$ galaxies and QSOs in the Canada-France-Hawaii Telescope Legacy Survey D1, D2 (COSMOS), and D4 fields. The $R \sim 1000$ spectra were obtained using the Inamori Magellan Areal Camera and Spectrograph (IMACS) at the Magellan Baade telescope, with typical integrations of 12 hr. From these spectra, we measured 5575 high-confidence spectroscopic redshifts, of which 4176 are at $z > 1.7$, thereby substantially increasing the number of public spectroscopic redshifts at $z \approx 2-3$ in COSMOS and the other survey fields. The data release includes Ly$\alpha$ transmission fluctuations measured in $4.7 \times 10^5$ pixels, which were used to create 3D maps of the intergalactic medium (IGM) transmission spanning 1.65 deg$^2$ and $z = 2.2-2.8$ at a resolution of 4 $h^{-1}$ cMpc. These are the largest such maps to date and provide a novel tracer of large-scale structure in legacy fields. We also provide ancillary data, including mock surveys. The LATIS data will enable a variety of community studies of galaxy evolution, environments, and the IGM around cosmic noon.
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All authors Andrew B. Newman, Gwen C. Rudie, Guillermo A. Blanc, Daniel D. Kelson, Nima Chartab, Enrico Congiu, Victoria Pérez, Mahdi Qezlou, Simeon Bird, Brian C. Lemaux, Olga Cucciati

Astrophysics of Galaxies

The Distribution of Quenched Galaxies in the Massive z = 0.87 Galaxy Cluster El Gordo

Rachel Honor, Seth Cohen, Timothy Carleton et al. (+27 more)

El Gordo (ACT-CL J0102$-$4915) is a massive galaxy cluster with two major mass components at redshift $z=0.87$. Using SED fitting results from JWST/NIRCam photometry, the fraction of quenched galaxies in this cluster was measured in two bins of stellar mass: $9<\log{({M_*}/\mathrm{M}_{\odot})}<10$ and $10\leq\log{({M_*}/\mathrm{M}_{\odot})}<12$. While there is no correlation between the quenched fraction and angular separation from the cluster's overall center of mass, there is a correlation between the quenched fraction and angular separation from the center of the nearest of the two mass components for the less-massive galaxies. This suggests that environmental quenching processes are in place at $z\sim1$, and that dwarf galaxies are more affected by those processes than massive galaxies.
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All authors Rachel Honor, Seth Cohen, Timothy Carleton, Steven Willner, Maria del Carmen Polletta, Rogier Windhorst, Dan Coe, Christopher Conselice, Jose Diego, Simon Driver, Jordan D'Silva, Nicholas Foo, Brenda Frye, Norman Grogin, Nimish Hathi, Rolf Jansen, Patrick Kamieneski, Anton Koekemoer, Reagen Leimbach, Madeline Marshall, Rafael Ortiz III, Nor Pirzkal, Massimo Ricotti, Aaron Robotham, Michael Rutkowski, Russell Ryan, Payaswini Saikia, Jake Summers, Christopher Willmer, Haojing Yan

High Energy Astrophysical Phenomena · Cross-listed from nucl-th

Effect of Finite-Temperature $\beta$-Decay Rates on the Rapid Neutron Capture Process

Yukiya Saito, Ante Ravlić, Pranav Nalamwar et al. (+1 more)

$\beta$-decay is known to play an essential role in the rapid neutron capture process ($r$-process) during $(n, \gamma) \leftrightarrow (\gamma, n)$ equilibrium and freeze-out when the neutron-rich nuclei decay back to stability. Recent systematic theoretical studies on $\beta$-decay at finite temperature indicated that under hot conditions ($T\sim10$~GK), a significant acceleration of $\beta$-decay rates is expected, especially for nuclei near stability. This corresponds to the early stage of the $r$-process. In this study, we investigate the effect of the $\beta$-decays in finite temperature using the rates calculated with the finite-temperature proton-neutron relativistic quasiparticle random-phase approximation (FT-PNRQRPA). We explore a variety of astrophysical conditions and find that the effect on the abundance pattern is significant in hot and moderately neutron-rich conditions such as are expected in magnetorotational supernovae. Accelerated $\beta$-decay rates also increase the heating rate in the early phase, resulting in an additional modification of the final abundance pattern.
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All authors Yukiya Saito, Ante Ravlić, Pranav Nalamwar, Rebecca Surman

Earth and Planetary Astrophysics

Understanding Exoplanet Habitability: A Bayesian ML Framework for Predicting Atmospheric Absorption Spectra

Vasuda Trehan, Kevin H. Knuth and M. J. Way

The evolution of space technology in recent years, fueled by advancements in computing such as Artificial Intelligence (AI) and machine learning (ML), has profoundly transformed our capacity to explore the cosmos. Missions like the James Webb Space Telescope (JWST) have made information about distant objects more easily accessible, resulting in extensive amounts of valuable data. As part of this work-in-progress study, we are working to create an atmospheric absorption spectrum prediction model for exoplanets. The eventual model will be based on both collected observational spectra and synthetic spectral data generated by the ROCKE-3D general circulation model (GCM) developed by the climate modeling program at NASA's Goddard Institute for Space Studies (GISS). In this initial study, spline curves are used to describe the bin heights of simulated atmospheric absorption spectra as a function of one of the values of the planetary parameters. Bayesian Adaptive Exploration is then employed to identify areas of the planetary parameter space for which more data are needed to improve the model. The resulting system will be used as a forward model so that planetary parameters can be inferred given a planet's atmospheric absorption spectrum. This work is expected to contribute to a better understanding of exoplanetary properties and general exoplanet climates and habitability.
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High Energy Astrophysical Phenomena

Low-Frequency Gravitational Waves in Three-Dimensional Core-Collapse Supernova Models

Colter J. Richardson, Anthony Mezzacappa, Kya Schluterman et al. (+5 more)

We discuss the low-frequency gravitational wave signals from three state-of-the-art three-dimensional core-collapse supernova models produced with the Chimera supernova code. We provide a detailed derivation of the gravitational wave signal sourced from the anisotropic emission of neutrinos and provide the total (fluid sourced and neutrino sourced) gravitational waves signal generated in our models. We discuss the templatablity of this low-frequency signal, which is useful for future work involving matched filtering for signal detection and parameter estimation. Errata: The neutrino-induced gravitational waveforms presented were computed incorrectly. They were underestimated by a factor of $4\pi$. While the results are impacted, the original conclusions are not. In fact, they are only reinforced. The corrected versions of Figs. 5–7, 11–16, and 19 are given here. The captions of Figs. 5–7, 11, 12, 16, and 19 are not modified. The captions of Figs. 13, 14, and 15 are corrected to the fit parameters for the corrected waveforms. The corrected versions of Tables I–III are given here. There is no correction to the caption. Finally the authors would like to acknowledge Lella et al. [90] for pointing out the discrepancy between our computed neutrino-induced waveforms and theirs, which prompted us to investigate the discrepancy and which led to the discovery of our error.
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All authors Colter J. Richardson, Anthony Mezzacappa, Kya Schluterman, Haakon Andresen, Eric J. Lentz, Pedro Marronetti, Daniel Murphy, Michele Zanolin

Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc

Constraining the Cosmological Evolution of Post-Newtonian Parameters with Gravitational Wave Signals from Compact Binary Inspirals

Oliver Pitt and Timothy Clifton

Gravitational waves from compact binary inspirals offer a new opportunity to constrain the cosmological time dependence of gravitational coupling parameters, due to the high precision of the observations themselves as well as the significant cosmological redshifts at which such systems exist. We calculate theory-independent equations of motion for compact objects in a binary system, implementing a new approach to sensitivities, and subsequently determine the gravitational wave signal that one should expect to measure from their inspiral. Expressions for the wave phase and amplitude are derived in terms of post-Newtonian gravitational coupling parameters, radiative flux parameters, and compact body sensitivities. These results complement recent attempts to gain theory-independent constraints on the time-evolution of gravitational coupling parameters from cosmological probes, and represent a new opportunity to constrain modified gravity with gravitational wave data.
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Astrophysics of Galaxies

The CEERS Photometric and Physical Parameter Catalog

Isa G. Cox, Jeyhan S. Kartaltepe, Micaela B. Bagley et al. (+35 more)

We present the Cosmic Evolution Early Release Science Survey (CEERS) catalog, including space-based photometry, photometric redshifts, and physical parameters for more than 80,000 galaxies. The imaging used for this catalog comes from the CEERS survey, which has NIRCam coverage over ~100 sq. arcmin of the Extended Groth Strip (EGS) in seven filters from 1.15$\mu$m to 4.44$\mu$m. Alongside these data, we also include ancillary HST imaging in seven filters from 0.435$\mu$m to 1.6$\mu$m. We used Source Extractor with hot and cold detection settings to extract photometry. We derive photometric redshifts using the spectral energy distribution (SED) modeling code, LePHARE, and estimate their accuracy using spectroscopically confirmed galaxies out to $z\sim10$, with $\sigma_{NMAD}$ ranging from 0.035-0.073, depending strongly on galaxy magnitude and redshift. We compute stellar masses, star formation rates, and E(B-V) using three different SED fitting codes with different templates and assumptions about the galaxy star formation histories. All of these measurements, as well as the full mosaics in all filters, and redshift probability distribution functions, are made available via the CEERS DR1.0 data release.
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All authors Isa G. Cox, Jeyhan S. Kartaltepe, Micaela B. Bagley, Steven L. Finkelstein, Caitlin Rose, Ali Ahmad Khostovan, Katherine Chworowsky, Olivier Ilbert, Anton M. Koekemoer, Henry C. Ferguson, Pablo Arrabal Haro, Bren E. Backhaus, Mark Dickinson, Adriano Fontana, Yuchen Guo, Andrea Grazian, Norman A. Grogin, Santosh Harish, Nimish P. Hathi, Benne W. Holwerda, Kartheik G. Iyer, Lisa J. Kewley, Allison Kirkpatrick, Dale D. Kocevski, Rebecca L. Larson, Jennifer M. Lotz, Ray A. Lucas, Fabio Pacucci, Casey Papovich, Laura Pentericci, Pablo G. Pérez-González, Nor Pirzkal, Swara Ravindranath, Rachel S. Somerville, Jonathan R. Trump, Stephen M. Wilkins, Guang Yang, L. Y. Aaron Yung

Astrophysics of Galaxies · Cross-listed from physics.plasm-ph

Nonlinear evolution of perturbatively driven kinetic instabilities far from marginal stability

Emma G. Devin and Vinícius N. Duarte

Kinetic instabilities develop when a system's distribution function deviates from thermal equilibrium in such a way that allows free energy from that distribution to drive resonant modes. These instabilities occur in many systems, such as fusion and astrophysical plasmas, neutral fluids, and self-gravitating systems. Motivated by the case of Alfvénic instabilities driven by minority populations of energetic particles in tokamak plasmas, we consider a kinetic instability in the presence of sources and sinks and with perturbative drive far from its instability threshold, where a theoretical description of the time evolution has not yet been established. In cases with steady-state saturation levels, we find that the mode first evolves linearly, driven by the positive distribution gradient, then undergoes a fast, strongly nonlinear transition where the distribution function slope is completely flattened around the resonance. The system then evolves in a weakly nonlinear regime driven by the balance of the wave drive and dissipation until reaching saturation. The strongly nonlinear transition is sufficiently fast that it can be treated as occurring instantaneously, and by considering a time-local approximation for the distribution after the flattening has occurred, we find a closed-form analytical solution for the mode amplitude in the weakly nonlinear phase. A compact piecewise-continuous solution for the entire time evolution of the mode amplitude is therefore constructed. This result is shown to agree closely with nonlinear kinetic simulations and is derived within a framework common to other physical systems such as galactic discs and viscous fluids.
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Solar and Stellar Astrophysics

Planetary Nebula Evolution for Single Stellar Models. The Formation of Neutral Spikes

Guillermo Garcia-Segura, Arturo Manchado, Jesus A. Toala et al. (+2 more)

Two-dimensional hydrodynamical simulations are presented from the formation up to the late evolution of planetary nebula, for 6 different stellar models from 1 to 5 Mo. The hydrodynamical models use stellar evolution calculations as inner boundary conditions and updated values for the number of ionizing photons. Special emphasis is placed on the formation of neutral spikes, as recently observed by the James Webb Space Telescope. The results indicate that neutral spikes can be detected either at the formation of planetary nebulae or in their decline. In the first case, the temporal window decreases with the mass of the model, ranging from 3,000 years in the 1 Mo case to 0 for 5 Mo. In the second case, only the 1.5, 2.0, and 2.5 Mo cases allow us to detect the neutral spikes for most of the remaining time.
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All authors Guillermo Garcia-Segura, Arturo Manchado, Jesus A. Toala, Martin A. Guerrero, Alberto J. Castro-Tirado

Solar and Stellar Astrophysics

JWST imaging of omega Centauri: II. Evidence for a split white dwarf cooling sequence in the near-infrared

M. Scalco, M. Salaris, L. R. Bedin et al. (+11 more)

We present a detailed analysis of the white dwarf cooling sequence (WD CS) in omega Centauri based on combined Hubble Space Telescope (HST) and JWST observations. Our analysis confirms the previously reported split - based on HST observations in ultraviolet filters - in the upper part of the WD CS, consistent with the presence of two distinct WD populations, and extends it to a significantly fainter and cooler limit (down to ~8000 K), corresponding to cooling ages of about 1 Gyr. We used artificial star (AS) tests and cooling models to confirm that the split is evidence of two WD populations with different masses and progenitors: one sequence of canonical WDs produced by the He-normal progenitors, and one sequence of low-mass WDs originated from the cluster He-rich component. We show that the fraction of WDs from the He-rich component in the outer regions is smaller than that found in the innermost regions. We also studied the kinematics of WDs and showed that in the outer regions, the velocity distribution of WDs from He-rich progenitors is slightly radially anisotropic, while that of canonical WDs is slightly tangentially anisotropic. Both the radial variation of the fraction of WDs from the He-rich population and the difference between their velocity distribution and that of canonical WDs are consistent with spatial and kinematic differences previously found for He-rich and He-normal main-sequence (MS) stars and in general agreement with models predicting that He-rich stars form more centrally concentrated than He-normal stars.
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All authors M. Scalco, M. Salaris, L. R. Bedin, S. Blouin, E. Vesperini, P. Bergeron, M. Libralato, M. Griggio, A. Burgasser, D. Nardiello, A. Bellini, J. Anderson, R. Gerasimov, D. Apai

High Energy Astrophysical Phenomena

Neutrino diagnostics of hadron-quark phase transition in Neutron Stars

Yossef Zenati, Conrado Albertus Torres, Joseph Silk et al. (+1 more)

We investigate neutrino signatures of a hadron-quark phase transition (HQPT) in neutron stars (NS) leading to quark star (QS) formation. We use representative hadronic and quark equations of state i.e. DD2 and MIT bag model along with a phenomenological neutrino emission model including the dominant leptonic and hadronic processes. Rather than aiming at a fully consistent hydrodynamical simulation, our goal is to identify generic temporal diagnostics that may arise when deconfinement occurs during the evolution of a compact star. We identify characteristic diagnostic features that may emerge in the neutrino light curve on $\simeq 10-50$ ms timescales. These include an enhanced peak-to-plateau ratio, a delay tracing the central density evolution, and a transient spectral hardening. After standard MSW flavor conversion, these temporal and spectral signatures remain potentially detectable for Galactic events under optimistic assumptions with detectors such as IceCube and Hyper-Kamiokande. Our results suggest possible temporal and spectral diagnostics of quark deconfinement in future Galactic neutrino bursts.
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All authors Yossef Zenati, Conrado Albertus Torres, Joseph Silk, M.Ángeles Pérez-García

Cosmology and Nongalactic Astrophysics

Inferring cosmological parameters from galaxy and dark sirens cross-correlation

Giona Sala, Alessandro Cuoco, Julien Lesgourgues et al. (+3 more)

The number of observed gravitational wave (GW) events is growing fast thanks to rapidly improving detector sensitivities. GWs from compact binary coalescences like Black Holes or Neutron Stars behave like standard sirens and can be used as cosmological probes. To this aim, generally, the observation of an electromagnetic counterpart and the measurement of the redshift are needed. However, even when those are not available, it is still possible to exploit these "dark sirens" via statistical methods. In this work, we explore a method that exploits the information contained in the cross-correlation of samples of GW events with matter over-density tracers like galaxy catalogues. Contrary to other currently employed dark-sirens methods, this approach does not suffer from systematic errors related to the incompleteness of the galaxy catalogue. To further enhance the technique, we implement tomography in redshift space for the galaxy catalogue and luminosity distance space for the GWs. We simulate future data collected by the array of currently existing detectors, namely LIGO, Virgo, and Kagra, as well as planned third-generation ones such as the Einstein Telescope and Cosmic Explorers. We cross-correlate these data with those from upcoming photometric galaxy surveys such as Euclid. We perform a sensitivity forecast employing a full-likelihood approach and explore the parameter space with Monte Carlo Markov Chains. We find that with this method, third-generation detectors will be able to determine the Hubble constant $H_0$ with an error of only 0.7%, which is enough to provide decisive information to shed light on the Hubble tension. Furthermore, for the other cosmological parameters, we find that the GWs and galaxy surveys information are highly complementary, and the use of both significantly improves the ability to constrain the underlying cosmology.
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All authors Giona Sala, Alessandro Cuoco, Julien Lesgourgues, Konstantinos-Rafail Revis, Lorenzo Valbusa Dall'Armi, Santiago Casas

Earth and Planetary Astrophysics

The polar debris disc around 99 Herculis: A potential signpost for polar circumbinary planets

Jeremy L. Smallwood, William DeRocco, Zhizhen Qin et al. (+1 more)

The nearby binary star system 99 Herculis (99 Her) is host to the only known polar-aligned circumbinary debris disc. We investigate the hypothesis that the narrow structure of this circumbinary disc is sculpted by the gravitational influence of one or more unseen polar circumbinary planets. We first establish the theoretically viable parameter space for a sculpting planet by considering dynamical stability and clearing mechanisms, including the chaotic zone, Hill radius, diffusion, and polar alignment timescales. We then use $N$-body simulations to test three specific architectures: a single planet interior to the disc, a single planet exterior, and a two-planet system bracketing the disc. Our simulations demonstrate that single-planet models are insufficient to reproduce the observed morphology, as they can only truncate one edge of the disc while leaving the other dynamically extended. In contrast, the two-planet shepherding model successfully carves both the inner and outer edges, confining the debris into a narrow, stable polar ring consistent with observations. We conclude that the structure of the 99 Her debris disc is most plausibly explained by the presence of two shepherding, polar circumbinary planets. We present a specific, testable model for this unique system, which elucidates the pivotal role of planetary bodies in sculpting the architecture of debris discs.
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All authors Jeremy L. Smallwood, William DeRocco, Zhizhen Qin, Antranik A. Sefilian

Solar and Stellar Astrophysics

The Sonora Substellar Atmosphere Models VI. Red Diamondback: Extending Diamondback with SPHINX for Brown Dwarf Early Evolution

C. Evan Davis, Jonathan J. Fortney, Aishwarya Iyer et al. (+5 more)

We extend the Sonora Diamondback brown dwarf evolution models to higher effective temperatures to treat the evolution of younger, higher mass objects. Due to an upper temperature limit of $T_\mathrm{eff}=$2400 K in the original Sonora Diamondback model grid, high mass objects ($M\geq$ 0.05 $M_\mathrm{\odot}=$ 52.4 $M_\mathrm{J}$) were limited to ages of $\gtrsim$ 100 Myr. To include the early evolution of brown dwarfs at $T_\mathrm{eff}>$ 2400 K, we use existing and new SPHINX cloud-free model atmosphere calculations of temperature structures of M-type atmospheres. These atmospheres range from $T_\mathrm{eff}$ 2000–4000 K, log($g$) 3.0–5.5, and metallicity [M/H] $-$0.5 to $+$0.5. This combination of Diamondback and SPHINX atmospheres, with a transition across $T_\mathrm{eff}$ 2000–2400 K, allows us to calculate evolution tracks, and infrared photometry and colors, for ages $>$ 1 Myr and masses from above the hydrogen burning minimum mass down to planetary masses. The Hayashi phase of massive brown dwarf evolution (ages $<$ 10–100 Myr) at low surface gravity leads to nearly constant $T_\mathrm{eff}$ values, at effective temperatures much lower than would be obtained from simply extrapolating backwards from evolution tracks at older ages.
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All authors C. Evan Davis, Jonathan J. Fortney, Aishwarya Iyer, Sagnick Mukherjee, Caroline V. Morley, Mark S. Marley, Michael Line, Philip S. Muirhead

Earth and Planetary Astrophysics

The ExoGRAVITY survey: A K-band spectral library of giant exoplanet and brown dwarf companions

J. Kammerer, T. O. Winterhalder, S. Lacour et al. (+106 more)

Direct observations of exoplanet and brown dwarf companions with near-infrared interferometry, first enabled by the dual-field mode of VLTI/GRAVITY, provide unique measurements of the objects' orbital motions and atmospheric compositions. Here, we compile a homogeneous library of all exoplanet and brown dwarf K-band spectra observed by GRAVITY thus far. We re-reduced all the available GRAVITY dual-field high-contrast data and, where companions are detected, extract their ~2.0-2.4 $\mu$m K-band contrast spectra. We then derived stellar model atmospheres for all employed flux references, which we used to convert the companion contrast into companion flux spectra. Solely from the resulting GRAVITY spectra, we extracted spectral types, spectral indices, and bulk physical properties for all companions. Finally, and with the help of age constraints from the literature, we also derived isochronal masses for most companions using evolutionary models. The resulting library contains R ~ 500 GRAVITY spectra of 39 substellar companions from late M to late T spectral types, including the entire L-T transition. Throughout this transition, a shift from CO-dominated late M- and L-type dwarfs to CH4-dominated T-type dwarfs can be observed in the K-band. The GRAVITY spectra alone constrain the objects' bolometric luminosity to typically within $\pm$0.15 dex. The derived isochronal masses agree with dynamical masses from the literature where available, except for HD 4113 c for which we confirm its previously reported potential underluminosity. Medium-resolution spectroscopy of substellar companions with GRAVITY provides insight into the carbon chemistry and the cloudiness of these objects' atmospheres. It also constrains these objects' bolometric luminosities which can yield measurements of their formation entropy if combined with dynamical masses, for instance from Gaia and GRAVITY astrometry.
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All authors J. Kammerer, T. O. Winterhalder, S. Lacour, T. Stolker, G.-D. Marleau, W. O. Balmer, A. F. Moore, L. Piscarreta, C. Toci, A. Mérand, M. Nowak, E. L. Rickman, L. Pueyo, N. Pourré, E. Nasedkin, J. J. Wang, G. Bourdarot, F. Eisenhauer, Th. Henning, R. Garcia Lopez, E.F. van Dishoeck, T. Forveille, J. D. Monnier, R. Abuter, A. Amorim, M. Benisty, J.-P. Berger, H. Beust, S. Blunt, A. Boccaletti, M. Bonnefoy, H. Bonnet, M. S. Bordoni, W. Brandner, F. Cantalloube, P. Caselli, W. Ceva, B. Charnay, G. Chauvin, A. Chavez, A. Chomez, E. Choquet, V. Christiaens, Y. Clénet, V. Coudé du Foresto, A. Cridland, R. Davies, R. Dembet, J. Dexter, A. Drescher, G. Duvert, A. Eckart, C. Fontanive, N. M. Förster Schreiber, P. Garcia, E. Gendron, R. Genzel, S. Gillessen, J. H. Girard, S. Grant, J. Hagelberg, X. Haubois, G. Heißel, S. Hinkley, S. Hippler, M. Houllé, Z. Hubert, L. Jocou, M. Keppler, P. Kervella, L. Kreidberg, N. T. Kurtovic, A.-M. Lagrange, V. Lapeyrère, J.-B. Le Bouquin, D. Lutz, A.-L. Maire, F. Mang, E. C. Matthews, P. Mollière, C. Mordasini, D. Mouillet, T. Ott, G. P. P. L. Otten, C. Paladini, T. Paumard, K. Perraut, G. Perrin, O. Pfuhl, D. C. Ribeiro, Z. Rustamkulov, D. Ségransan, J. Shangguan, T. Shimizu, M. Samland, D. Sing, J. Stadler, O. Straub, C. Straubmeier, E. Sturm, L. J. Tacconi, S. Udry, A. Vigan, F. Vincent, S. D. von Fellenberg, F. Widmann, J. Woillez, S. Yazici, the GRAVITY Collaboration

Astrophysics of Galaxies

Metals versus Non-metals: Chemical Evolution of Hydrogen and Helium Isotopes in the Milky Way

James W. Johnson, Miqaela K. Weller and Ryan J. Cooke

Star formation drives changes in the compositions of galaxies, fusing H and He into heavier nuclei. This paper investigates the differences in abundance evolution between metal and non-metal isotopes using recent models of Galactic chemical evolution appropriate for the thin disk epoch. A strong degeneracy arises between metal yields from stellar populations and the mean Galactocentric radial velocity of the interstellar medium (ISM). Similar metallicities arise when increases (decreases) in metal yields are combined with increases (decreases) to the gas flow velocity. A similar degeneracy exists between metal yields and the rate of gas ejection from the ISM. We demonstrate that this degeneracy can be confidently broken with precise measurements of the hydrogen (D/H) and helium ($^3$He/$^4$He) isotope ratios in the Galactic ISM. At fixed O/H, higher metal yields lead to higher D/H and lower $^3$He/$^4$He. Measurements available to date are not sufficiently precise or numerous to draw confident conclusions. A detailed inventory of non-metal isotopes in the Milky Way would provide critical empirical constraints for stellar and galactic astrophysics, as well as a new test of Big Bang Nucleosynthesis. We forecast that only $\sim$4 additional measurements of $^3$He/$^4$He within $\sim$$3$ kpc of the Sun are required to measure the primordial $^3$He/$^4$He ratio at $\sim$30% precision. In parallel, empirical benchmarks on metal yields also have the power to inform stellar models, since absolute yield calculations carry factor of $\sim$$2-3$ uncertainties related to various complex processes (e.g., rotational mixing, convection, mass loss, failed supernovae).
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Astrophysics of Galaxies

That's so Retro: The Gaia-Sausage-Enceladus Merger Trajectory as the Origin of the Chemical Abundance Bimodality in the Milky Way Disk

James W. Johnson, Diane K. Feuillet, Ana Bonaca et al. (+1 more)

The Milky Way (MW) is thought to have experienced a $\sim$3:1 mass-ratio merger event near redshift $z\sim2$ with a significantly retrograde trajectory. This now-disrupted dwarf galaxy is commonly known as the Gaia-Sausage-Enceladus (GSE). In this paper, we investigate the impact of the GSE merger trajectory on metal abundances in the MW disk. We construct numerical models of Galactic chemical evolution (GCE) incorporating radial gas flows to account for angular momentum transport during the merger event. Unlike prograde trajectories, radial and retrograde mergers are generally accompanied by a major sinking event in which much of the interstellar medium falls toward the Galactic center. This effect leads to a net decrease in surface density across much of the disk. Ongoing Type Ia supernova explosions then drive a rapid decline in [$\alpha$/Fe] due to the lowered gas supply. Consequently, radial and retrograde trajectories increase (decrease) the number of low (high) [$\alpha$/Fe] stellar populations relative to prograde trajectories. If high [$\alpha$/Fe] stars form in sufficient numbers through other mechanisms, the effect of the retrograde trajectory can produce a bimodal [$\alpha$/Fe] distribution at fixed [Fe/H], as observed in the MW. In models dominated by low [$\alpha$/Fe] stellar populations, a bimodality does not arise because the retrograde trajectory cannot increase the number of high [$\alpha$/Fe] stars. More broadly, our results highlight the importance of gas dynamics in GCE models featuring major merger events.
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All authors James W. Johnson, Diane K. Feuillet, Ana Bonaca, Danielle de Brito Silva

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

Hydrodynamic models of reheating

Juan Pablo Elía, Lucas Cantarutti, Nahuel Mirón-Granese et al. (+1 more)

We develop a causal hydrodynamic model that provides an effective macroscopic description of the field-theoretic dynamics during the early stages of reheating. The inflaton condensate is treated as a homogeneous background coupled to a relativistic fluid that represents its inhomogeneous fluctuations. Within the divergence-type theory framework derived from kinetic considerations, the model captures essential dissipative and non-equilibrium effects while remaining stable and causal. We find that the coupling between the oscillating condensate and the fluid induces a parametric resonance in the tensor sector, leading to the amplification of the viscous stress tensor and the generation of gravitational waves with a characteristic spectral peak. The predicted spectrum agrees with lattice simulations performed with CosmoLattice. This hydrodynamic approach offers an effective bridge between microscopic field dynamics and macroscopic cosmological observables.
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All authors Juan Pablo Elía, Lucas Cantarutti, Nahuel Mirón-Granese, Esteban Calzetta

Astrophysics of Galaxies

A Vertically Orientated Dark Matter Halo Marks a Flip of the Galactic Disk

Ling Zhu, Runsheng Cai, Xi Kang et al. (+5 more)

Unveiling the 3D shape of the Milky Way's dark-matter halo is critical to understanding its formation history. We created an innovative dynamical model with minimal assumptions on the internal dynamical structures and accommodates a highly flexible triaxial DM halo. By applying the method to 6D phase-space data of K-giant stars from LAMOST + Gaia, we robustly determine the 3D dark-matter distribution of the Milky Way out to approximately $50$ kpc. We discover a triaxial, nearly oblate dark-matter halo with $q_{\rm DM} = Z/X= 0.92\pm0.08$, $p_{\rm DM} = Y/X= 0.8\pm0.2$ averagely within 50 kpc, where $Z$ axis is defined perpendicular to the stellar disk. The axes ratio $q_{\rm DM} > p_{\rm DM}$ is strongly preferred; the long-intermediate axis plane of the dark-matter halo is unexpectedly vertical to the Galactic disk, yet aligned with the `plane of satellites'. This striking configuration suggests that the Galactic disk (and the inner halo) has flipped, likely torqued by minor mergers, from an original alignment with the outer dark-matter halo and satellite plane, as supported by Milky Way analogues from Auriga and TNG50. By allowing $q_{\rm DM}(r)$ and $p_{\rm DM}(r)$ vary with radii, we find tentative evidence that the dark-matter halo is twisted, that it agrees alignment with the disk in the inner regions and transitions to a vertical orientation at $r\gtrsim 20$ kpc, supporting the disk flip scenario prediction. Such disk reorientation is non-trivial yet its physical mechanism is straightforward to comprehend and naturally originates a vertical satellite plane. Our findings offer a unified framework that links dark-matter halo orientation, satellite alignment, and disk evolution, reinforcing the internal consistency of the Milky Way in $\Lambda$CDM model.
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All authors Ling Zhu, Runsheng Cai, Xi Kang, Xiang-Xiang Xue, Chengqun Yang, Lan Zhang, Shude Mao, Chao Liu

Astrophysics of Galaxies

Multi-messenger Analysis of Supermassive Black Hole Binaries: The Joint-likelihood Approach

Maria Charisi, Stephen Taylor, Jessie Runnoe et al. (+2 more)

Supermassive black hole binaries (SMBHBs) formed in galaxy mergers are promising multi-messenger sources. They can be identified as quasars with periodic variability in electromagnetic (EM) time-domain surveys. The most massive of those systems can be detected by Pulsar Timing Arrays (PTAs) in the nanohertz frequency gravitational-wave (GW) band. We present a method to simultaneously analyze EM lightcurves and PTA observations as a multi-messenger data stream. For this, we employ a joint likelihood analysis, in which the likelihood of the EM data and the PTA likelihood are multiplied. We test this approach by simulating 208 binary signals that can be detected both by the Rubin Observatory in the nominal ten-year survey and by a PTA dataset with a ~30-year baseline, which resembles our expectations for a dataset of the International Pulsar Timing Array (IPTA) collaboration in ~2035. We compare our multi-messenger analysis with analyses that take into account the EM and PTA data separately. We find that the joint likelihood approach results in improved parameter estimation with smaller percent errors compared to the distinct analyses that consider only EM or PTA data separately. Among the SMBHB parameters, the binary total mass and the orbital inclination show the greatest improvement. We also compare our multi-messenger pipeline with an analysis, in which the EM constraints are used as priors to the PTA analysis. We demonstrate that the joint likelihood approach delivers tighter constraints on all binary parameters, with systematically higher values of Kullback-Leibler divergence, which measures the deviation of the posterior distribution from the prior.
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All authors Maria Charisi, Stephen Taylor, Jessie Runnoe, Caitlin Witt, Polina Petrov

Earth and Planetary Astrophysics

Next-Generation Improvements in Giant Exoplanet Evolutionary and Structural Models

Ankan Sur, Roberto Tejada Arevalo, Adam Burrows et al. (+1 more)

Many evolutionary models of giant exoplanets still rely on simplifying assumptions that are no longer adequate given detailed constraints from Jupiter, Saturn, and modern exoplanet observations. Here, we identify the key physical improvements required for next-generation planetary evolution models using our code, APPLE, which enables systematic emulation and extension of legacy studies. We quantify the effects of updated equations of state, helium rain, fuzzy cores, non-adiabatic and compositionally inhomogeneous envelopes, and improved atmospheric boundary conditions by first isolating the impact of each physical ingredient and then constructing combined baseline models for planets with masses between 0.3 and 4~$M_{\rm Jup}$ to assess their collective influence on planetary structure and observable properties. We find that the adoption of modern equations of state and realistic heavy-element distributions leads to systematic, but sometimes subtle, differences ($\sim 5$ to 10%) in radius evolution, while helium rain and the treatment of convection can significantly alter thermal histories and atmospheric compositions (by $\sim$ 5 to 20%). These updated physical processes must be incorporated into the next-generation exoplanet evolutionary models to achieve physically consistent interpretations of planetary observations.
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All authors Ankan Sur, Roberto Tejada Arevalo, Adam Burrows, Yi-Xian Chen

High Energy Astrophysical Phenomena · Cross-listed from hep-ph

Dark matter Simplified models in the Resonance Region

Mattia Di Mauro and Bohan Xie

The particle-physics nature of dark matter (DM) remains one of the central open questions in modern physics. A widely used framework to investigate DM properties is provided by simplified models (DMSimps), which extend the Standard Model with a DM particle and a mediator that connects the visible and dark sectors. Much of the DMSimps parameter space is already constrained by direct and indirect detection, collider searches, and the measured DM relic abundance. We show, however, that the resonant regime $m_{\rm DM}\simeq m_{\rm med}/2$ remains viable under current bounds and will be stringently tested by forthcoming experiments. Using a full Boltzmann treatment that allows for departures from kinetic equilibrium near resonance, we demonstrate that this regime can reproduce the observed relic density with couplings compatible with direct-detection limits. We also show that models with s-wave-dominated annihilation can explain the Fermi-LAT Galactic Center Excess with couplings consistent with relic-density and direct-detection constraints. Finally, we propose two minimal constructions that naturally realize $m_{\rm med} \approx 2m_{\rm DM}$, making the resonant scenario generic rather than fine-tuned.
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Solar and Stellar Astrophysics

Tracing Planetary Accretion in a 3 Gyr-old Hydrogen-Rich White Dwarf: The Extremely Polluted Atmosphere of LSPM J0207+3331

Érika Le Bourdais, Patrick Dufour, Carl Melis et al. (+7 more)

We report the detection of 13 heavy elements (Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni, Cu, and Sr) in the photosphere of LSPM J0207+3331, a ~3 Gyr old hydrogen-rich white dwarf with an effective temperature comparable to that of the Sun. Upper limits on carbon, obtained through the absence of molecular CH, suggest accretion from a carbon-volatile-depleted source. The accreted parent body exhibits slight deficits of Mg and Si relative to Fe but otherwise bulk Earth-like abundance patterns; a reasonable interpretation is that LSPM J0207+3331 is accreting a massive differentiated rocky body that had a core mass fraction higher than the Earth's. The high level of pollution indicates that substantial accretion events can still occur even after 3 Gyr of cooling. We also detect weak Ca II H & K line-core emission, making this only the second known isolated polluted white dwarf to exhibit this phenomenon and suggesting the presence of additional physical processes in or above the upper atmosphere. Our analysis also highlights the critical importance of including heavy elements in the model atmosphere structure calculations for highly polluted hydrogen-rich white dwarfs. Neglecting their contribution significantly impacts the inferred thermodynamic structure, leading to inaccuracies in derived stellar parameters. Finally, we show that the observed 11.3 microns infrared excess can be explained by a single silicate dust disk rather than a two-ring disk model.
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All authors Érika Le Bourdais, Patrick Dufour, Carl Melis, Beth L. Klein, Laura K. Rogers, Antoine Bédard, John Debes, Ashley Messier, Alycia J. Weinberger, Siyi Xu

Solar and Stellar Astrophysics

How precisely can we measure the ages of subgiant and giant stars?

Cheyanne Shariat, Kareem El-Badry and Soumyadeep Bhattacharjee

Precise stellar ages are fundamental to Galactic archaeology. However, obtaining reliable age estimates and uncertainties for field stars has been a long-standing challenge. We test the fidelity of ages from recent catalogs of giants and subgiants using wide binaries, whose components formed at the same time and thus should have consistent inferred ages. We find that subgiant ages based on spectroscopic metallicities from Xiang & Rix (2022) are generally consistent within their reported uncertainties, implying that fractional uncertainties of 5-10% are realistically achievable. In contrast, we find that published photometric subgiant ages underestimate true uncertainties by factors of 2-3. Spectroscopic age estimates for red giant and red clump stars also show reliable uncertainties, but are generally less precise (25-30%). These results demonstrate that accurate chemical abundance measurements are essential for precise subgiant ages and establish wide binaries as a powerful, model-independent benchmark for calibrating stellar age measurements in the era of large spectroscopic surveys.
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