Astrophysics of Galaxies
The First Empirical Calibration of the MIR Abundance Diagnostic Ne$_{23}$ with JWST
Noah S. J. Rogers, Evan D. Skillman, Danielle A. Berg et al. (+10 more)
Large surveys of
galaxies in the local and high-
redshift Universe have, traditionally, relied on the intensity of rest-optical emission lines from metal ions in the Interstellar Medium (ISM) to indirectly estimate the O/H abundance in the gas. However, these optical strong line diagnostics are also sensitive to the electron gas temperature ($T_e$), resulting in large systematic uncertainties that inherently limit their utility as
metallicity tracers, especially in
dust-obscured and metal-rich environments. To this end, we provide the first empirical calibration of Ne$_{23}$, a novel abundance diagnostic using the mid-infrared (MIR) $T_e$-insensitive [Ne II]$\lambda$12.81$\mu$m and [Ne III]$\lambda$15.56$\mu$m fine-structure lines. We present new JWST/MIRI MRS observations of ten H II regions with optical measurements of $T_e$ and O/H from the CHAOS project, and we analyze MIRI observations of eight low-
metallicity galaxies with similarly high-fidelity direct O/H. We measure Ne$_{23}$ from 1D MIR spectra extracted from apertures matched to the ground-based spectroscopy used to obtain O/H, a method that is unfeasible from MIR spectra acquired on prior space-based observatories. From these nebulae, Ne$_{23}$ is strongly correlated with O/H over 1.5 dex in 12+log(O/H). We calibrate the O/H-Ne$_{23}$ relation from the empirical data, finding a scatter of just 0.06 dex in O/H at fixed Ne$_{23}$. The O/H-Ne$_{23}$ relation presented here provides a means to reliably estimate 12+log(O/H) from JWST/MIRI MRS observations of ionized nebulae out to z$\approx$0.8, enabling new chemical abundance surveys of highly-attenuated regions and in the metal-rich ISM.
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All authors Noah S. J. Rogers, Evan D. Skillman, Danielle A. Berg, Karla Z. Arellano-Córdova, Richard W. Pogge, Alessandra Aloisi, Leslie K. Hunt, Anne E. Jaskot, Matilde Mingozzi, Ryan J. Rickards Vaught, Karin M. Sandstrom, O. Grace Telford, Macarena G. del Valle-Espinosa
Astrophysics of Galaxies
Beyond Cloud-9: The case for discovering more HI-rich failed halos
Jorge Moreno, Coral Wheeler, Francisco J. Mercado et al. (+8 more)
HI-rich starless
halos, should they exist, hold great promise for elucidating dark matter
halo structure. Yet realizing this potential demands reliable theoretical predictions for their properties and abundances. Indeed, the recent identification of Cloud-9 as a strong HI-rich starless
halo candidate in the nearby universe makes such predictions timely. This Letter examines HI-rich ($M_\mathrm{HI} \geq 10^6\,M_\odot$) starless (isolated/central)
halos at $z=0$ across three cosmological simulations: FIREbox, Recal-EAGLE and NIVARIA-LG. All three successfully produce such objects, with $M_\mathrm{HI}$ extending up to $\sim\!1$–$2$ dex above Cloud-9, but with number densities that vary by a factor of $\sim30$. These populations span different regions of the $M_\mathrm{HI}$–$M_\mathrm{gas}$–$M_{200}$ space: NIVARIA-LG produces objects with higher $M_\mathrm{HI}$ and $M_\mathrm{gas}$ values ($\gtrsim 10^7$ and $\gtrsim 10^8\,M_\odot$), while FIREbox predicts they lie within extremely narrow ranges of $M_\mathrm{gas} \sim(1.1$–$1.6)\times10^8\,M_\odot$ and $M_{200} \sim(7.8$–$8.6)\times10^9\,M_\odot$. Recal-EAGLE and NIVARIA-LG exhibit a strong $M_\mathrm{gas}-M_{200}$ correlation, with similar slopes but different normalizations. The simulations predict numerical Cloud-9 analogs – though similarities in the shapes of their HI column-density profiles may be driven by FAST's modest beam; halving it already reveals differences. Collectively, these inter-simulation discrepancies make a compelling case for discoveries beyond Cloud-9: a statistical sample of well-resolved HI-rich starless
halos is needed to discriminate amongst competing predictions.
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All authors Jorge Moreno, Coral Wheeler, Francisco J. Mercado, M. Katy Rodriguez Wimberly, Pratik J. Gandhi, Jenna Samuel, Robert Feldmann, James S. Bullock, Andrew Wetzel, Michael Boylan-Kolchin, Philip F. Hopkins
High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Chiral-Transport-Induced Collective Modes in Strong Magnetic Fields and Their Implications for Neutron Star Phenomenology
Sota Hanai
In this thesis, we study the collective modes induced by the chirality of elementary particles in magnetized media and their implications for
neutron star phenomenology. We theoretically predict that the
chiral magnetic wave can arise in
quark matter inside
neutron stars, resulting in the emergence of novel types of seismic oscillations and associated gravitational waves in the context of asteroseismology. We also investigate the response to dynamical electromagnetic fields and find that a dynamical screening, distinct from the conventional Landau damping, occurs due to the
chiral anomaly.
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High Energy Astrophysical Phenomena · Cross-listed from nucl-th
Outer-crust equations of state for neutron stars
P.S. Koliogiannis and N. Paar
The equation of state of the outer crust of
neutron stars is sensitive to
nuclear mass predictions and provides a direct connection to the properties of
nuclei throughout the nuclide map, including those beyond experimental reach. We quantify the impact of contemporary
nuclear mass models on the composition and thermodynamic properties of the outer crust and assess the consequences for crust-dominated
neutron-
star configurations near the minimum-mass limit. We constructed four outer-crust equations of state based on the relativistic energy density functional and machine-learning mass model tables. The
equilibrium composition of cold catalysed matter in $\beta$-
equilibrium was obtained by minimising the Gibbs free energy per nucleon, and the resulting equations of state were implemented in
neutron-
star structure calculations. The different mass inputs lead to variations in the
equilibrium nuclide sequence, distinct last bound
nuclei, and moderate shifts in the
neutron-drip density. In contrast, the associated thermodynamic properties, as well as the minimum-mass
neutron-
star configurations, remain closely aligned across the four outer-crust equations of state. The model dependence of the outer crust is primarily reflected in the detailed nuclide composition and in the precise location of
neutron drip. Nevertheless, the considered outer-crust equations of state yield closely consistent predictions for the relevant
neutron-
star observables, providing a reliable input for
stellar modelling.
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High Energy Astrophysical Phenomena
Energy-Dependent Polarization Angle Variability as a Robust Diagnostic for Blazar Flaring Mechanisms
Haocheng Zhang, Benjamin de Jonge, Manel Errando et al. (+2 more)
Identifying the physical mechanism driving blazar
flares remains a central challenge in high-energy astrophysics. We show that the energy dependence of the standard deviation of the polarization angle variability ($\sigma_\text{PA}$) provides a powerful and robust discriminator of blazar flaring mechanisms. Using particle-in-
cell-integrated polarized radiative transfer simulations, we perform to-date the most rigorous statistical analyses of polarization variability. We demonstrate that
magnetic reconnection and magnetized
turbulence imprint qualitatively distinct energy dependence of $\sigma_\text{PA}$ that directly reflect their different
magnetic field
evolution and particle transport. Reconnection predicts higher $\sigma_\text{PA}$ with higher
photon energy till the synchrotron spectral peak, whereas
turbulence produces nearly flat $\sigma_\text{PA}$ across the synchrotron spectral component. These trends are resilient to realistic observational limitations. Applying our results to optical and IXPE data of Mrk~421 and 1ES~1959+650, we find strong evidence for reconnection-driven
flares embedded in a turbulent blazar zone. Energy-dependent $\sigma_\text{PA}$ emerges as a decisive new probe of particle acceleration in relativistic jets.
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All authors Haocheng Zhang, Benjamin de Jonge, Manel Errando, Xiaocan Li, Fan Guo
Earth and Planetary Astrophysics
The effect of spectral resolution on biosignature detection via reflected light observations of the Earth through time
Samantha Gilbert-Janizek, Jacob Lustig-Yaeger and Joshua Krissansen-Totton
NASA's Habitable Worlds Observatory (HWO) will search for biosignatures on Earth-like
exoplanets using reflected light spectroscopy. A critical instrument design parameter is resolving power, which must balance biosignature detectability against exposure time and detector noise constraints. We assess the resolving power needed to detect and characterize key biosignature gases and habitability indicators including O$_2$, O$_3$, H$_2$O, CH$_4$, CO$_2$ and CO across atmospheres representing the Archean, Proterozoic, and Phanerozoic Earth. We combine analytical detectability calculations spanning spectral resolutions ($\lambda/\Delta{\lambda}$) $R=20$-$5000$ with atmospheric
retrievals using the rfast radiative transfer model and pyEDITH exposure time calculator for realistic wavelength-dependent noise modeling. In the visible ($0.4$-$1.0$ $\mu$m), the nominal resolution $R_{Vis}=140$ is sufficient for detecting O$_2$ in Phanerozoic-like atmospheres. Higher resolutions could theoretically reduce exposure times for low-O$_2$ Proterozoic atmospheres, but require $>10\times$ reductions in dark current and could increase H$_2$O detection exposure times by $\sim 2\times$, penalizing the foundational habitability constraint that anchors downstream biosignature searches. The most efficient path for low-O$_2$ atmospheres may instead be indirect inference via O$_3$, whose Hartley-Huggins bands are detectable at $R_{UV}\sim 7$. In the near-IR ($1.0$-$1.7$ $\mu$m), $R_{NIR}\geq40$ is necessary to avoid a degeneracy between CO$_2$ and CO that could produce false positive detections of abundant CO. The nominal $R_{NIR}=70$ is sufficient for characterizing all Earth-through-time cases. These results support HWO's current baseline resolution choices and provide actionable guidance for finalizing spectrometer requirements while maintaining technological feasibility for the search for life on
exoplanets.
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Cosmology and Nongalactic Astrophysics
Testing Scale-Dependent Modified Gravity with DESI DR1
D. Gonzalez, G. Niz, A. Aviles et al. (+42 more)
The Dark Energy Spectroscopic Instrument (DESI) provides an unprecedented opportunity to test deviations from general relativity (GR) that introduce a new physical scale within its
redshift range. Using the connection between a Yukawa-like potential and the Hu-Sawicki $f(R)$ model, we place strong constraints on the range of a hypothetical fifth force mediated by a massive scalar field. We analyze the power spectrum measurements from DESI Data Release 1 using a baseline EFT model that employs the fkpt approach for the loop integrals. We find no evidence for deviations from GR and obtain the constraint $\log_{10} |f_{R_0}| < -4.59$ (95% C.L.). This corresponds to an upper bound at
redshift zero on the scale at which corrections to GR become important, $\lambda < 17.81$ Mpc, or equivalently, a lower bound on the mass of the additional gravitational mediator of $m_\phi > 3.60 \times 10^{-31}$ eV. We find that the modified
gravity parameter $f_{R_0}$ is largely orthogonal to the cosmological parameters in the model, such that no additional projection effects relative to the GR case are introduced in this Full-Shape analysis. Furthermore, a second modified
gravity parameter, the power index $n$, which modulates the time-variation of the associated mass, is found to be consistent with previous analyses that fixed it to unity. Adding DESI BAO data or other cosmological probes does not significantly change these results. The conclusions remain similar if the background
evolution is described by evolving dark energy instead of a cosmological constant. Additionally, we test the robustness of the baseline model by varying the maximum wavenumber used in the Full-Shape analysis and analyzing the DESI targets separately. Finally, we analyze the degeneracies between the modified-
gravity parameters and the sum of
neutrino masses.
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All authors D. Gonzalez, G. Niz, A. Aviles, C. Garcia-Quintero, H.E. Noriega, J. Aguilar, S. Ahlen, D. Bianchi, D. Brooks, T. Claybaugh, A. de la Macorra, A. de Mattia, P. Doel, S. Ferraro, J. E. Forero-Romero, E. Gaztañaga, S. Gontcho A Gontcho, G. Gutierrez, C. Hahn, K. Honscheid, D. Huterer, M. Ishak, R. Joyce, S. Juneau, R. Kehoe, D. Kirkby, M. Landriau, L. Le Guillou, M. E. Levi, M. Manera, A. Meisner, R. Miquel, S. Nadathur, W.J. Percival, I. Pérez-Ràfols, G. Rossi, L. Samushia, E. Sanchez, D. Schlegel, H. Seo, J. Silber, D. Sprayberry, G. Tarlé, B. A. Weaver, R. Zhou
High Energy Astrophysical Phenomena
Eccentricity as a signature of hierarchical subsolar-mass mergers in collapsar disks
Jiaxi Wu, Elias R. Most, Nils L. Vu et al. (+4 more)
In this work, we investigate gravitational-wave signatures of a proposed subsolar-mass merger scenario resulting from fragmentation inside a collapsar
accretion disk. This scenario has gained recent interest with the electromagnetic transient AT2025ulz, a possible superkilonova counterpart candidate to the sub-threshold gravitational wave event S250818k. One prediction of fragmentation is the formation of multiple smaller
neutron-
star fragments, some of which might merge hierarchically. Such mergers are expected not only to produce individual electromagnetic counterparts, but also, because of their repeated capture and merger dynamics, to impart kicks to the system and thereby drive orbital eccentricity. By performing numerical relativity simulations of hierarchical subsolar-mass compact-object mergers modeled as black holes in a disk-like geometry consistent with this scenario, we demonstrate the build-up of potentially large eccentricity for the final merger, of order $e \simeq 0.6$ initially, and show that, because of the short lifetime of the system, a substantial part of this eccentricity , up to $e\simeq 0.1$, can survive until the final
neutron star – black hole merger in the general case. As a result, future detections of eccentricities in potential subsolar-mass gravitational-wave candidate events would be a strong indicator for a hierarchical formation scenario. In the extreme case, where we observe repeated mergers to lead to the formation of a
solar-mass
neutron star, the expected binary parameters can be in a regime similar to those of the eccentric
neutron star – black hole merger event GW200105.
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All authors Jiaxi Wu, Elias R. Most, Nils L. Vu, Nils Deppe, Lawrence E. Kidder, Kyle C. Nelli, William Throwe
Earth and Planetary Astrophysics
The tale of the 3 planets: 3D cloud feedback enhances the spectral diversity of warm Jupiters
Nishil Mehta, Vivien Parmentier, Xianyu Tan et al. (+14 more)
JWST has shown a large diversity in warm Jupiter spectra, despite only small variations in the planetary parameters. However, the main driver of this diversity remains unclear. We aim to identify the mechanisms responsible for the spectral difference of three warm Jupiter-size
exoplanets observed by JWST: whereas WASP-80b appears mostly cloud-free, both WASP-107b and WASP-69b have spectra dominated by clouds. We model each
planet using the same framework, ADAM (formerly SPARC/MITgcm), which solves for the interactions among cloud transport, radiative transfer, and atmospheric circulation in 3D. We investigate the role of three condensate species, Na$_2$S, KCl, and MgSiO$_3$, and four particle sizes (0.1, 1, 5, and 10 $\mu$m). Clouds settle deeper in the atmosphere of the higher-
gravity planet WASP-80b than in WASP-107b, reproducing their spectral difference naturally. For WASP-107b, three clouds can reproduce the NIRCam observations: 5 $\mu$m Na$_2$S, 1 $\mu$m KCl, and 5 $\mu$m MgSiO$_3$ models. However, these cannot match the scattering slope observed at shorter wavelengths in NIRISS and the possible silicate feature in the MIRI bandpass, suggesting a multi-modal distribution of clouds. Our model predicts that small silicate particles should be homogeneously distributed and thus cannot account for the difference between the two limb spectra in the MIRI bandpass. Finally, applying the same model to WASP-69b does not yield a partially cloudy dayside solution that fits the emission spectra, as proposed in a previous study. Coupling among 3D circulation, clouds, and radiative transfer can enhance the spectral diversity of warm Jupiter
exoplanets, particularly through changes in cloudiness with
gravity. The combination of multi-phase, wide-wavelength coverage and models that couple clouds, circulation, and radiative transfer is key to advancing our understanding of these new objects.
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All authors Nishil Mehta, Vivien Parmentier, Xianyu Tan, Elspeth K. H. Lee, Tristan Guillot, Matthew M. Murphy, Thomas P. Greene, Thomas G. Beatty, Taylor J. Bell, Jonathan J. Fortney, Michael R. Line, Sagnick Mukherjee, Kazumasa Ohno, Everett Schlawin, Anastasia Triantafillides, Luis Welbanks, Lindsey S. Wiser
Instrumentation and Methods for Astrophysics
Bayesian component separation and power spectrum estimation for 21 cm intensity mapping data cubes
Geoff G. Murphy, Philip Bull, Mario G. Santos et al. (+2 more)
Foreground removal remains an ongoing challenge in
radio cosmology, and increasingly sensitive experiments necessitate more robust analysis techniques. In this work, we model simulated data from a single-dish intensity mapping experiment, and use the Gibbs sampling and Gaussian constrained realisation (GCR) techniques to draw samples from the posterior probability distribution of the model parameters. This allows for a separation of the foregrounds and 21 cm signal at the map level, as well as recovery of the 1-dimensional HI power spectrum to within statistical uncertainties. Despite the model consisting of over 2 million free parameters in the example presented here, these methods allow us to sample from the
Bayesian posterior at a rate of $<30$ seconds per iteration. This framework is also resilient to frequency channel flagging (e.g. due to RFI excision), with the GCR steps effectively in-painting the missing data with statistically-consistent model realisations. The power spectrum is recovered accurately in the presence of strong foreground contamination and RFI flagging – the estimate falling within $2\sigma$ of the true model in our example, similar to the commonly-used transfer function correction method. Statistical realisations of foreground and HI maps are also recovered, with associated uncertainties available from the full joint posterior distribution of all parameters.
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All authors Geoff G. Murphy, Philip Bull, Mario G. Santos, Zheng Zhang, Steven Cunnington
Cosmology and Nongalactic Astrophysics
Predicted number counts and clustering of Hi galaxies from future radio surveys
Ainulnabilah Nasirudin, Philip Bull and Isabelle Ye
The 21cm emission line from neutral hydrogen (HI) contained within
galaxies provides a way to make accurate spectroscopic
redshift determinations at
radio frequencies. Large arrays such as SKA-MID will have the sensitivity required to catalogue millions of HI
galaxies. The expected number counts and clustering properties of the
galaxies are still quite poorly understood however, leading to uncertainties in the predicted performance of cosmological surveys. We use three different simulated
galaxy catalogues to predict the properties of the HI
galaxy distribution, along with estimates of the error on these predictions due to modelling uncertainty. The simulations are S$^3$-SAX (semi-analytic models based on the Millennium dark matter-only simulation); GAEA (an updated semi-analytic model partially calibrated on hydrodynamical simulations); and IllustrisTNG (a hydrodynamical simulation). We present predictions for
galaxy number counts as a function of sensitivity and
redshift, and use these to forecast the cosmological performance of a proposed SKA-MID cosmological survey. The simulated predictions differ by a factor of $\sim 2$ in the number counts and around 10% in the bias at $z \sim 0.1$, yielding around 20% differences in forecast cosmological uncertainties. These differences become significantly larger at $z \gtrsim 0.4$. We also model a 'medium-deep' SKA HI
galaxy survey at $z \lesssim 0.07$ by fitting a
halo occupation distribution (HOD) model to angular correlation functions measured from multiple $20^\circ \times 20^\circ$ sub-fields of IllustrisTNG. This provides clustering predictions and uncertainty estimates that can be used in future forecasts.
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Cosmology and Nongalactic Astrophysics
Bayesian power spectrum estimation with modelling of systematic effects in delay-fringe rate space
Sohini Dutta, Philip Bull, Jacob Burba et al. (+3 more)
Observing the Epoch of Reionisation using 21cm
radio interferometry has proven to be a challenging task. Extraction of the extremely faint redshifted signal is complicated by the presence of bright foregrounds,
radio frequency interference (RFI), and systematic artefacts. We discuss the challenge of accounting for systematic effects, particularly cable reflections, that appear in the visibility data obtained from 21cm interferometers. Cable reflections cause attenuated copies of the foreground signal to appear outside the 'foreground wedge' region in which foreground contamination is supposed to be localised. We build on the hydra-pspec Gibbs sampler to implement a model of the systematics as a multiplicative effect in delay-fringe rate space. We include this model in the inference of the joint posterior distribution, in addition to the 21cm signal, its power spectrum, and foregrounds. This allows the systematics contribution to be marginalised, rather than filtering it out and causing additional signal loss. We demonstrate the method on simulated visibility data for a single baseline, showing that the 21cm delay power spectrum can be recovered well regardless of the location of the systematics in delay-fringe rate space. Our implementation is suitable for modelling other multiplicative factors on the visibilities, e.g. residual gain errors.
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All authors Sohini Dutta, Philip Bull, Jacob Burba, Michael J. Wilensky, Zheng Zhang, Ainulnabilah Nasirudin
High Energy Astrophysical Phenomena · Cross-listed from nucl-th
C.A. Bertulani
This is a brief overview of the connection between
neutron skin thickness in finite
nuclei and the equation of state of
neutron-rich matter, with applications to
neutron stars. Multiple experimental probes are discussed, including dipole polarizability, parity-violating electron scattering, heavy-ion fragmentation, quasi-free scattering, and ultraperipheral collisions. A consistent picture emerges from
Bayesian analyses combining experimental data and energy density functionals, providing constraints on the
symmetry energy and its slope.
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Earth and Planetary Astrophysics
Oxygen and nitrogen isotopologues on cold COCONUTS-2b observed with MIRI/MRS
H. Kühnle, E. C. Matthews, P. Mollière et al. (+12 more)
Linking the composition of gas
giant planets to their formation paths has long been a goal in
exoplanet science. Especially, cold gas
giants with temperatures below $\sim$500K have been out of reach for detailed atmospheric characterization. With JWST, however, we can reach high signal-to-noise (S/N) spectra for such cool worlds and can can measure not only their main trace gas abundances, but even their isotopic content unlocking new possibilities in linking them to their formation paths. In this study, we present the spectrum of one of the coldest planetary-mass companions COCONUTS-2b ($\mathrm{T_{eff}}\approx$480K, separation of $\sim$6400 au from its M
dwarf host
star) obtained with the Mid-InfraRed Instrument Medium Resolution Spectrometer (MIRI/MRS). Combining the MIRI and archival Gemini/FLAMINGOS-2 data sets, we aim to characterize the chemical composition and physical structure of its frigid atmosphere, setting the stage to uncover insights on the formation of COCONUTS-2b. For the first time on a MIRI/MRS data set, we use the full spectral resolution of MIRI/MRS and perform atmospheric
retrievals to unlock the search for faint absorption features by rare molecules and isotopologues. The latter are identified using a leave-one-out analysis and Bayes factor comparison. We robustly detect three isotopologues, namely $^{15}$NH$_3$, H$_2^{18}$O and H$_2^{17}$O in the atmosphere of COCONUTS-2b. We find the first clear evidence of oxygen isotopes in water in a cold companion. This data set demonstrates the capability of MIRI/MRS to characterize such cold planetary-mass companion's atmospheres with respect to their compositional and isotopic content. In the future, the constrained elemental and isotope ratios provide a unique avenue in comparing with the host
star's abundances and eventually in tracing formation scenarios.
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All authors H. Kühnle, E. C. Matthews, P. Mollière, P. Patapis, Z. Zhang, E. Nasedkin, D. Gasman, N. Whiteford, H. S. Wang, M. Ravet, G. Chauvin, M. Bonnefoy, D. Barrado, A. M. Glauser, S. P. Quanz
Cosmology and Nongalactic Astrophysics
Mujic{\Lambda}: Reconstructing Initial Conditions from Incomplete Redshift Surveys with Projected Optimization
Chenze Dong, Benjamin Horowitz, Adrian E. Bayer et al. (+1 more)
In this paper, we introduce Mujic{\Lambda} (Mapping the Universe with Jax-based Initial Condition Reconstr{\Lambda}ction), an optimization-based framework for reconstructing initial conditions from realistic
galaxy spectroscopic
redshift surveys. Unlike standard optimization-based approaches, Mujic{\Lambda} augments the L-BFGS
algorithm with a projection operator and rank-order matching to enforce Gaussianity of the initial conditions and substantially improve robustness to incomplete survey geometries. We validate Mujic{\Lambda} on a mock lightcone catalog derived from semi-analytic models applied to the Millennium simulation. We construct a differentiable forward model that incorporates a fast particle-mesh simulation at megaparsec resolution and a comprehensive treatment of observational effects and survey incompleteness. Mujic{\Lambda} reaches good agreement with the true density field down to the scale of the forward model, while maintaining consistency with the Gaussian prior through the projection step. It also broadly recovers the
cosmic web classification, underscoring its value for deciphering environmental information in
galaxy evolution studies. Beyond its key role in next-generation constrained simulations, the methodology offers a practical way to generate initial guesses and speed up field-level inference, especially for upcoming large-scale
galaxy surveys.
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All authors Chenze Dong, Benjamin Horowitz, Adrian E. Bayer, Khee-Gan Lee
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
A positive definite formulation of vacuum decay with reduced symmetry
José R. Espinosa, Ryusuke Jinno, Thomas Konstandin et al. (+2 more)
The Euclidean bounce for
vacuum decay enjoys an $O(4)$
symmetry that is lost in the presence of
impurities than can catalyze the decay. We present a formulation for the calculation of the tunneling decay action, that is explicitly positive definite, for
impurities whose effects are spherically symmetric so that the bounce
symmetry is reduced to $O(3)$. The action constructed can be regarded as a generalization of the tunneling potential method, which implicitly assumed $O(4)$
symmetry. We show that the action obtained reduces to the tunneling potential for $O(4)$-symmetric cases and provide analytic examples with $O(3)$
symmetry and arbitrary wall thickness.
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All authors José R. Espinosa, Ryusuke Jinno, Thomas Konstandin, Shogo Matake, Taiga Miyachi
Earth and Planetary Astrophysics
The Influence of the Fractal Dimension on Dust Evolution in Protoplanetary Disks
J. E. Schöll, C. P. Dullemond and C. Dominik
Context: During the first stages of
dust coagulation in protoplanetary disks, the
dust aggregates are expected to have a high degree of porosity. Most models of
dust growth, however, do not take this into account. The reason for this is the technical complexity of this problem. Furthermore, the coagulation/fragmentation kernel for colliding porous or fractal
dust aggregates is not well understood. Aims: We wish to explore the effect of aggregate porosity on the
evolution of the
dust population in protoplanetary disks, with an emphasis on the fragmentation and the bouncing barrier. Methods: We use the DustPy code, and implement porosity as a prescribed function of particle mass with the fractal dimension as a free parameter. In this way, we parameterize the ill-constrained physics of colliding porous/fractal aggregates, and we can explore the effect of different porosity prescriptions. We take into account the effect of porosity on the
dust dynamics, while neglecting its effect on the collision outcomes. Results: We find that larger particle masses are reached for lower fractal dimensions. The maximum Stokes numbers that are reached do not depend on the fractal dimension in the case of fragmentation-limited growth and decrease with decreasing fractal dimension in the case of bouncing-limited growth. Furthermore, particle growth is slower for smaller fractal dimensions in our models. Conclusions: The
dust evolution is strongly influenced by the fractal dimension. Although larger masses are reached for smaller fractal dimensions, the particles are still much smaller than planetesimals. Under the assumption that the bouncing/fragmentation velocity does not depend on the fractal dimension or filling factor, fractal growth is not beneficial for the streaming instability to occur in the case of fragmentation-limited growth and even disadvantageous in the case of bouncing-limited growth.
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Solar and Stellar Astrophysics
Coronal Diagnostics Via Modelling Periodic-Beaded Stripes of Solar Radio Bursts
Chuanyang Li, Yao Chen, Bing Wang et al. (+11 more)
Using high-resolution data from the Chashan Broadband
Solar radio spectrometer at meter wavelengths (CBSm) of the Chinese Meridian Project-Phase II (CMP-II), Li et al. (2025) identified a novel fine spectral structure of
solar radio bursts, termed periodic beaded stripes, and proposed a generation mechanism. Here we report additional events and develop a quantitative method to determine the physical conditions in the emission region. Periodic stripes tend to occur in the post-phase of
flares and are associated with complex
magnetic configurations. They repeat on sub-second timescales and show $\sim$0.1 s bead-like modulations, often accompanied by low-frequency absorptions. Modeling the chained stripes with linear kinetic theory of the double
plasma resonance (DPR) instability constrains the source-region
magnetic field to 0.2-1.7 G and the
plasma density to (1-7) $\times 10^8$ cm $^{-3}$. The former follows the drift of individual stripes, and the latter tracks the overall trend. This study summarizes the key properties of periodic beaded stripes and establishes a quantitative DPR-based framework for coronal diagnostics.
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All authors Chuanyang Li, Yao Chen, Bing Wang, Yutong Li, Xiangliang Kong, Hao Ning, Sulan Ni, Shuwang Chang, Zichuan Li, Yang Gao, Zhe Cui, Li Deng, Jingye Yan, Fabao Yan
High Energy Astrophysical Phenomena
Status of the KM3NeT real-time analysis framework
Martina Marconi
Multi-messenger astronomy requires real-time systems capable of rapidly responding to external alerts and sharing significant detections with partner observatories. KM3NeT, a deep-sea Cherenkov
neutrino telescope in the Mediterranean Sea, is actively contributing to these efforts through a dedicated real-time analysis framework. It comprises two detectors - ARCA, optimised for TeV-PeV
neutrinos, and ORCA, for GeV-TeV
neutrinos - both also sensitive to MeV
neutrinos from core-collapse
supernovae, providing a wide field of view and an almost continuous duty cycle. The framework performs low-latency event reconstruction and classification, follows up external alerts from the multi-messenger community, monitors for core-collapse
supernova neutrino bursts, and autonomously identifies and distribute
cosmic neutrino alerts. Now in advanced commissioning, the KM3NeT real-time alert system represents a major step toward rapid, coordinated multi-messenger observations.
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Instrumentation and Methods for Astrophysics
IQUEYE at Gemini South: instrument, science commission, and first results
Tomas Cassanelli, Pascual Marcone-Puga, Giampiero Naletto et al. (+7 more)
The Italian
quantum eye (IQUEYE) is a fast
photon counter based on the single
photon avalanche diode detectors and capable of preserving a ~0.5 ns/h accuracy
photon time of arrival. IQUEYE was originally developed for intensity interferometry experiments, but now its scientific scope has been extended towards ultra fast astronomy, including optical
pulsars, millisecond
pulsars and the enigmatic fast
radio bursts. IQUEYE's capabilities are mainly restricted by the number of
photons detected, a quantity that scales with the collector size of an optical
telescope. Through the visitor instrument program at Gemini South (Cerro Pachón, Chile) we brought IQUEYE to the 8.1-m dish, reaching an order magnitude sensitivity increased from previous operations. At Gemini South we installed IQUEYE to observe
giant pulse emitters, millisecond
pulsars, and transitional millisecond
pulsars for over 40 hours in the span of a week.
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All authors Tomas Cassanelli, Pascual Marcone-Puga, Giampiero Naletto, Luca Zampieri, Paolo Ochner, Michele Fiori, Alessia Spolon, Susana B. Araujo Furlan, Albert Wai Kit Lau, Ryan Mckinven
Solar and Stellar Astrophysics
SPHEREx Ultracool Dwarf spectrophotometric Atlas (SUDA): Atmospheric and Fundamental Parameters of Ultracool Dwarfs
Zhijun Tu, Shu Wang, Haomiao Huang et al. (+2 more)
We present the SPHEREx Ultracool
Dwarf spectrophotometric Atlas (SUDA), a homogeneous sample of 1675 field ultracool
dwarfs with continuous 0.75–5~$\mu$m spectrophotometry from SPHEREx Quick Release 2 (QR2). Using the SAND and ATMO2020++ atmospheric grids, we derive atmospheric parameters, compute bolometric luminosities ($L_{\rm bol}$), and combine $T_{\mathrm{eff}}$ and radii with evolutionary tracks to estimate masses, ages, and evolutionary $\log g$. For sources at 1700–2500~K, spectroscopic $\log g$ is systematically lower than evolutionary $\log g$, with a median offset of $\sim$1.05~dex, likely driven primarily by cloud-related model uncertainties. We further construct an empirical atlas by binning the measurements in $T_{\mathrm{eff}}$ and evolutionary $\log g$, producing 57 spectrophotometric templates spanning $T_{\mathrm{eff}}\simeq700$–3000~K. Molecular indices trace a coherent atmospheric sequence: H$_2$O and CH$_4$ indices strengthen toward lower $T_{\mathrm{eff}}$, while CO and CO$_2$ indices increase below $\sim$1500~K and turn over near $\sim$1000~K. Model comparisons indicate that CO$_2$ index is more sensitive to
metallicity than
gravity at $T_{\mathrm{eff}}\sim800$–1200~K. SUDA provides a reference sample linking 0.75–5~$\mu$m spectrophotometric morphology to atmospheric and evolutionary trends in ultracool
dwarfs.
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All authors Zhijun Tu, Shu Wang, Haomiao Huang, Xiaodian Chen, Jifeng Liu
Astrophysics of Galaxies
Dust enrichment from core-collapse supernovae and extinction curves in the high-redshift universe
Koki Otaki, Raffaella Schneider, Simone Bianchi et al. (+4 more)
Recent JWST observations have revealed that some
galaxies at $z \gtrsim 7$ generally exhibit relatively flat ultraviolet (UV) attenuation curves and a weak UV bump. These features suggest that the first
dust grains formed rapidly, possibly originating from core-collapse
supernovae (SNe). We investigate the time
evolution of grain size distributions and extinction curves in the early phase of
dust enrichment for different parameters of progenitor
stars, rotation velocities,
metallicity, and interstellar medium densities, including the effect of the reverse shock. We model a single starburst system assuming an initial mass function. Extinction curves are calculated from the grain size distribution for each
dust species. The total
dust-to-
stellar mass ratio at $30 \,\mathrm{Myr}$ is $M_\mathrm{dust}/M_\star \sim 10^{-3}$ before the passage of the reverse shock, but we find it to be at most $M_\mathrm{dust}/M_\star \sim 10^{-5}$ due to the destruction effect of the reverse shock. This effect destroys grains smaller than $\sim 10\,\mathrm{nm}$ and makes amorphous carbon the dominant species, resulting in a flatter extinction curve with a wide bump at $2500\,\mathrm{\mathring{A}}$ compared to the no-reverse shock models. We find that our models are consistent with the observed attenuation curve and emissivity of high-
redshift galaxies and show that the reverse shock processing significantly affects
dust enrichment and grain properties such as extinction curves and emissivity in
supernova yields for high-
redshift galaxies.
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All authors Koki Otaki, Raffaella Schneider, Simone Bianchi, Joris Witstok, Luca Graziani, Marco Limongi, Roberto Maiolino
Astrophysics of Galaxies
A Rare Eddington-Limited, Heavily Obscured Low-Mass Active Galactic Nucleus Likely Triggered by a Galaxy Merger
Shouyi Wang, Fan Zou, Chang-Hao Chen et al. (+7 more)
We report a detailed analysis of GAMA 376183, a powerful, heavily obscured active
galactic nucleus (AGN) hosted by a low-mass
galaxy ($M_\star \approx 10^{10}~M_{\odot}$) likely experiencing a
galaxy merger. The source was initially identified due to its remarkably strong [Ne v] $\lambda3426$ emission, exhibiting a rest-frame equivalent width (EW) of $\approx 48$ A. We present $\sim100$ ks
Nuclear Spectroscopic
Telescope Array follow-up observations, confirming its heavily obscured nature with a column density (in $\mathrm{cm^{-2}}$) of $\log N_\mathrm{H} = 23.3^{+0.4}_{-1.2}$ and an intrinsic $2$–$10$ keV luminosity (in $\mathrm{erg~s^{-1}}$) of $\log L_\mathrm{X,int} = 42.92^{+0.24}_{-0.20}$. GAMA 376183 thus represents one of the few known heavily obscured AGNs in low-mass
galaxies. Its estimated Eddington ratio is $\lambda_\mathrm{Edd}\approx0.8$, indicative of rapid black-hole growth. High-resolution optical images reveal a disturbed, likely merging morphology, while its multiwavelength spectral energy distribution indicates a recent starburst in its host
galaxy. These pieces of evidence suggest that the ongoing merger has triggered both the heavily obscured, Eddington-limited
accretion and the starburst, making GAMA 376183 a rare observed case in low-mass
galaxies. Overall, this unique source demonstrates that (i) [Ne v] can help identify heavily obscured low-mass AGNs, and (ii) the merger-driven coevolution framework established for massive
galaxies may also extend to low-mass
galaxies.
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All authors Shouyi Wang, Fan Zou, Chang-Hao Chen, W. N. Brandt, Elena Gallo, Bin Luo, Xue-Bing Wu, Yuming Fu, Dieu D. Nguyen, Shengxiu Sun
Astrophysics of Galaxies
Invariant manifolds in barred galaxy simulations. I. Material density waves
Toni Soler-Terricabras, Mercè Romero-Gómez and Santi Roca-Fàbrega
We investigate the dynamical origin and kinematic signatures of spiral structure in an N-body simulation of an isolated barred
galaxy, assessing whether invariant
manifold theory provides a consistent dynamical framework to disentangle the disc particle populations and to identify those that genuinely build, trace, and sustain the spiral arms. We compute the Jacobi energy of disc particles and classify them relative to the energies of the
equilibrium points, thereby isolating
manifold-compatible orbits. We analyse their spatial distribution and velocity structure to characterise spiral-related streaming motions. The Jacobi constant provides a physically motivated dynamical separator that reveals three distinct kinematic populations: (i) low-energy particles on nearly circular orbits populating most of the disc, (ii) high-energy particles associated with banana orbits, and (iii)
manifold-compatible particles originating near the bar and following transit orbits along the spiral arms. Only the
manifold-compatible population generates the prominent outward-migrating ridge observed in the R - v_phi plane and reproduces the characteristic spiral streaming pattern. In contrast, the low-energy population exhibits a global quasi-circular motion with small perturbations induced by the self-
gravity of the spiral structure. Our results demonstrate that the spiral arms are dynamically traced by the
manifold-compatible population, which forms the backbone of the structure and drives effective radial transport. The bulk of low-energy disc particles responds to the spiral perturbation similarly to the traditional density wave picture, enhancing the density contrast caused by the invariant-
manifold compatible particles. In this framework, barred spiral arms emerge as material structures sustained by
manifold-guided transport, with the surrounding disc behaving as a system of material density waves.
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Earth and Planetary Astrophysics
Shape and spin axis determination of the Tianwen-2 target asteroid (469219) Kamo'oalewa from lightcurve inversion
Roberto Bonamico, Josef Hanuš and Marco Delbo
Near-Earth asteroid (469219) Kamo'oalewa is an Earth quasi-satellite, temporarily trapped in a 1:1 orbital resonance with our
planet. Despite its dynamical relevance and the hypothesis that it may be a lunar ejecta fragment, its physical properties are still poorly constrained. In particular, no reliable models of its shape and
spin state have been published so far. The scientific interest in this object is further enhanced by its selection as the primary target of the Chinese Tianwen-2 mission, which aims to rendezvous with this asteroid and return samples of it to Earth. The aim of this work is to determine the shape and
spin axis orientation of Kamo'oalewa by means of photometric
telescope observations and lightcurve inversion. We analyzed lightcurves obtained during several apparitions using the well-established
algorithm, based on convex shape modeling. We derived a convex shape model and estimated the
spin pole orientation. In the preferred solution, the pole is located at ecliptic coordinates {\lambda}, {\beta} = (126,-16) degrees, with a sidereal rotation period of P~0.465 h. Conclusions. Our results provide the first direct constraints on the rotational state and morphology of Kamo'oalewa, information of key importance in preparation for the upcoming Tianwen-2 sample-return mission.
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Astrophysics of Galaxies
Radial Profiles of Binary Fraction in Elliptical Galaxies
Xiejin Li, Fenghui Zhang, Yinghe Zhao et al. (+4 more)
The radial profile of binary fraction may vary with environment and is of significant importance for studying the formation mechanisms of binary
stars and their dynamical
evolution within globular clusters (GCs) and
galaxies. However, existing studies remain limited to the Milky Way and its neighboring
galaxies. Leveraging the method proposed by Zhang et al. for estimating the variation of binary fraction from integrated spectral features, we analyze a sample of 513 elliptical
galaxies drawn from the Mapping Nearby
Galaxies at Apache Point Observatory (MaNGA) survey to measure their radial binary fraction profiles. Our results show that after accounting for the effect induced by radial variations in the
stellar population (SP), the median SP-subtracted binary fraction, $r_{\rm b,sub}^{\rm med}$, becomes approximately flat. For nearly all elliptical
galaxies in our sample, the variation in binary fraction relative to the
galaxy center at $1R_e$ is less than 5%. No clear correlation is found between the binary fraction gradient and the gradients of SP properties. Moreover, we also compare differences between ultraviolet (UV) upturn and non-UV upturn
galaxies. The overall binary fraction profiles and SP properties of the non-UV upturn
galaxies in our sample are comparable to those of the UV upturn
galaxies. This similarity may arise from the presence of residual
star formation (RSF) in the non-UV upturn systems.
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All authors Xiejin Li, Fenghui Zhang, Yinghe Zhao, Cheng Li, Zhanwen Han, Yunkun Han, Xiaoyu Kang
Solar and Stellar Astrophysics
A short-period binary OGLE-BLG-ELL-006503 showing slow variations in brightness
S. M. Rucinski
Analysis of 28 years of OGLE project data for the 0.404 day period binary OGLE BLG ELL-006503 (V1231 Sco) shows a superposition of
tidal-interaction variations of about 0.07 magnitude in the I-band onto a time-scale 5-10 year, 0.15-0.17 magnitude brightness drift. Seasonal light-curves suggest that this long-term variability is driven by large photospheric spots (approx 0.3
stellar radii) that exhibit a tendency to orient themselves relative to the
tidal interaction line. The eclipse time O-C residuals reveal an orbital period change characterized by a timescale of approximately 2x10^6 years, suggesting a mild mass redistribution, potentially linked to global
magnetic fields reconfiguration.
Gaia parallax and absolute magnitude estimates indicate a system consisting of
solar-type
stars. The lack of eclipses and extreme spot activity suggest the binary may consist of late-type, tidally-deformed
stars rather than a typical W UMa-type system.
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Solar and Stellar Astrophysics
SRGA J115215.0$-$510656: an unusual long-period eclipsing dwarf nova with disc wind signatures
Nikita Rawat, David A. H. Buckley, John R. Thorstensen et al. (+9 more)
We present the first detailed optical study of the cataclysmic variable SRGA J115215.0$-$510656, based on new time-resolved photometric and spectroscopic observations complemented by long-baseline Transiting
Exoplanet Survey Satellite (TESS) data. The TESS light curve reveals deep, recurring eclipses consistent with a high-inclination geometry and an orbital period of 0.43567659(9)d. The eclipse morphology during outburst is consistent with a possible 'inside-out' type outburst and supports classification of the system as a U Gem-type
dwarf nova. By combining eclipse phase width and ellipsoidal modulation, we constrain the system geometry to a narrow locus in the $(q,i)$ plane, with allowed mass ratios $0.28 \lesssim q \lesssim 0.84$ and inclinations $i$ $\simeq$75$-$84$^{\circ}$. The persistence of single-peaked Balmer lines during outburst, together with strong He II emission and a flattened Balmer decrement, points towards emission arising in a disc wind or vertically extended regions above the disc. Absorption features from a late-type secondary
star (approximately K3) are detected, contributing roughly 30 per cent of the red optical flux. Comparison with main-sequence expectations suggests that the donor
star is moderately inflated, consistent with a mildly evolved secondary. With its long orbital period, modest outburst amplitude, and emission-line characteristics, SRGA J115215.0$-$510656 appears to be a rare and compelling example of a bright, long-period
dwarf nova whose optical properties are influenced by disc-wind processes during outburst.
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All authors Nikita Rawat, David A. H. Buckley, John R. Thorstensen, Christian Knigge, Yusuke Tampo, Stephen B. Potter, Anupam Bhardwaj, Simone Scaringi, Ilya A. Mereminskiy, Jeewan C. Pandey, Srinivas M Rao, Alexander A. Lutovinov
Solar and Stellar Astrophysics
Population synthesis of Be X-ray binaries in the Small Magellanic Cloud: Angular momentum recycling and stable mass transfer
Víctor López Oller, Boyuan Liu, Michela Mapelli et al. (+5 more)
Be X-ray binaries (BeXRBs) are key laboratories to constrain binary interaction processes such as mass transfer, angular-momentum transport, and natal kicks. The Small Magellanic Cloud (SMC), hosting a nearly complete and well-characterized BeXRB population, offers a unique opportunity to test these physical processes at low
metallicity. We aim to identify the combination of binary-
evolution parameters that simultaneously reproduces the observed number and the joint distribution of orbital period and optical magnitude of SMC BeXRBs. We performed an extensive grid analysis of binary population-synthesis models exploring different mass transfer efficiencies, angular-momentum transport prescriptions and Roche-lobe overflow stability criteria. We also considered the impact of natal kicks, and that of the propeller effect of rotating
magnetic fields of
neutron stars. Synthetic populations obtained with the binary population synthesis code $\texttt{sevn}$ are statistically compared to observations using likelihood-based methods applied to the orbital period and $V$-band magnitude distributions, together with requirements on the total number of systems. We find that models in which mass transfer via Roche-lobe overflow is assumed to be always stable and angular momentum is recycled back into the orbit through tides when the accretor approaches critical rotation provide the best match to observations. Our best-fitting models favor low natal kicks ($\lesssim 100\ \rm km\ s^{-1}$), a moderate mass transfer efficiency ($f_{\rm MT} \simeq 0.6$), a minimum Be threshold
spin close to critical rotation, and a strong suppression of
accretion onto
neutron stars due to the propeller effect. Specifically, the observable population is highly sensitive to the treatment of the propeller effect, which regulates the X-ray luminosity of wide, low-
accretion-rate systems.
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All authors Víctor López Oller, Boyuan Liu, Michela Mapelli, Stefano Rinaldi, Cecilia Sgalletta, Julia Bodensteiner, Giuliano Iorio, Rebekka Schupp
Cosmology and Nongalactic Astrophysics
Nonlinear Relativistic Effects on Cosmological Redshift Drift
Pierre Béchaz, Giuseppe Fanizza, Giovanni Marozzi et al. (+1 more)
Using a fully gauge-invariant approach, we compute for the first time in the literature relativistic effects on the
redshift drift up to second order in cosmological perturbation theory. This is achieved by employing a set of light-cone coordinates that simplify the description of light propagation in an inhomogeneous and anisotropic universe. We show that
redshift-space distortion occurs only as a second-order effect whereas, as known, it is not present among the linear perturbations. We then derive analytical expressions of the bispectrum for the leading-order perturbative contributions on sub-Hubble scales, providing some numerical evaluations. Our finding is that, at low
redshift and for large momenta, the non-linearities in the bispectrum are enhanced more than the squared power spectrum.
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All authors Pierre Béchaz, Giuseppe Fanizza, Giovanni Marozzi, Matheus R. Medeiros Silva