Astrophysics of Galaxies
Determining star formation histories and age-metallicity relations with convolutional neural networks
Enrique Galceran, Patricia Sánchez-Blázquez, Artemi Camps-Fariña et al. (+8 more)
We aim to develop a state-of-the-art tool to infer detailed
star formation histories (SFHs) and age-
metallicity relations from realistic observational data, while mitigating classical degeneracies and substantially reducing computational cost. In particular, we seek to exploit the complementarity of spectroscopic and photometric data to improve constraints on the spatially resolved SFH and
metallicity evolution of nearby
galaxies in the PHANGS collaboration. We construct and train a convolutional neural network (CNN) that combines convolutional layers,
attention mechanisms, and a shared latent space to jointly predict SFHs and
metallicities in 16 age bins. The network simultaneously processes integral-field spectroscopic data from PHANGS-MUSE and five-band photometric fluxes from PHANGS-HST. Training is performed on a
dataset of 165\,000 synthetic spectra and photometric measurements spanning a broad range of SFH shapes,
metallicity evolution,
dust attenuation, and signal-to-noise ratios representative of the observations. The CNN accurately recovers SFHs and age-
metallicity relations over a wide range of evolutionary scenarios. The inferred luminosity- and mass-weighted mean ages and
metallicities show negligible bias, with dispersions of $\sim0.12$ dex in age and $\sim0.03$ dex in
metallicity. When applied to real PHANGS-MUSE and PHANGS-HST data for NGC\,3627, the network produces smooth, spatially coherent maps of
stellar age and
metallicity that recover physically meaningful structures, including younger populations tracing the spiral arms and
star-forming regions. The CNN is approximately $5\times10^{3}$–$2\times10^{4}$ times faster than traditional full spectral fitting codes, providing a powerful and efficient alternative for the analysis of large spectro-photometric surveys.
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All authors Enrique Galceran, Patricia Sánchez-Blázquez, Artemi Camps-Fariña, Médéric Boquien, Ralf S. Klessen, Francesco Belfiore, Daniel A. Dale, Francesca Pinna, Ivan S. Gerasimov, Thomas G. Williams, Hsi-An Pan
High Energy Astrophysical Phenomena
Particle Acceleration, Coronal Neutrino Production, and the Diffuse Extragalactic Neutrino Background from Supermassive Black Holes
Rostom Mbarek
We present a generalized
neutrino luminosity function for
protons accelerated in the X-ray coronae of supermassive black holes in Seyfert-like
galaxies. A major uncertainty in assessing the diffuse
neutrino contribution of these systems is the underlying particle acceleration physics. We address this using a theoretical acceleration framework informed by
plasma kinetic simulations, enabling a more self-consistent connection between coronal conditions, nonthermal
proton populations, and
neutrino production. In this picture, the
neutrino luminosity depends primarily on the coronal X-ray luminosity and magnetization, and only weakly on black hole mass. We find that the cosmologically integrated emission from these systems can account for the sub-PeV diffuse extragalactic
neutrino flux observed by IceCube. We further argue that, although diffusive confinement is relatively well understood, the
magnetic field
topology near black holes naturally allows for
cosmic ray-driven
outflows near the X-ray corona. Such
outflows may accompany additional efficient
neutrino production at the PeV-level and influence the dynamics of the innermost
galactic environment.
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Astrophysics of Galaxies
When galaxies burst: enhanced shot-noise for line-intensity mapping in the JWST era
Ely D. Kovetz, Hovav Lazare, Sarah Libanore et al. (+2 more)
Recent JWST observations indicate that
star formation at $z\!\sim\!4-6$ is more
stochastic than previously assumed, with rms log-SFR scatter $\sim\!0.6$ dex at $M_h\!\sim\!10^{11}M_{\odot}$, growing toward smaller
halos and time-correlated on $\sim\!25$ Myr. This is significantly higher than the typical $\sim\!0.3$ dex phenomenological lognormal scatter assumed in standard line-intensity mapping (LIM) forecasts. We propagate the JWST-era burstiness through to the LIM shot-noise power spectrum and show that the result is a simple multiplicative correction: the deterministic shot noise multiplied by a line-dependent boost factor $B_\lambda$ derived in closed form by convolving the SFR correlation function with the
stellar-population-synthesis kernel of each line. At $z\!\sim\!6$, we find $B_{{\rm H}\alpha}\!\simeq\!7$ and $B\!\sim\!2.5$-$3.5$ for longer-window tracers ([CII], CO, UV) - factors of $\sim\!2$-$5$ above the standard prescription, and growing further toward higher
redshift. The enhancement transforms the LIM landscape: it improves auto-spectrum detectability and suppresses lower-
redshift interloper contamination, but degrades cosmological applications such as BAO that rely on a clean clustering measurement. Crucially, it also opens a new use of LIM as a diagnostic of high-
redshift star-formation physics beyond the regime of individually resolved
galaxies:
redshift tomography of a single line constrains the amplitude and mass dependence of the burstiness, while cross-line shot-noise correlations probe its time coherence.
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All authors Ely D. Kovetz, Hovav Lazare, Sarah Libanore, Julian B. Muñoz, Eleonora Vanzan
Astrophysics of Galaxies
Massive Galaxies Form Early and Gray: Stellar Assembly and Dust Attenuation at $\mathbf{z>3.5}$ from CAPERS
Katherine Chworowsky, Steven L. Finkelstein, Anthony J. Taylor et al. (+27 more)
The
stellar mass assembly of massive
galaxies in the first few billion years of
cosmic history remains a central challenge in
galaxy formation.
Galaxies with $M_\star \gtrsim 10^{10}M_\odot$ observed at $z \gtrsim 4$ must grow rapidly under conditions of intense gas
accretion, feedback, and
dust production. Observationally, their
star-formation histories (SFHs) have been poorly constrained due to degeneracies inherent to broadband photometry. The advent of JWST enables direct spectroscopic access to detailed continuum shapes and rest-frame optical diagnostics at high
redshift, providing a critical opportunity to reconstruct formation timescales of massive early
galaxies. Here, we investigate massive
galaxies using joint spectro-photometric SED fitting of JWST/NIRSpec prism spectroscopy from the CANDELS-Area Prism Epoch of Reionization Survey (CAPERS). Our sample comprises 148
galaxies selected photometrically with log $(M_\star/M_\odot) > 9.5$ at $z > 3.5$. We find that the most massive
galaxies (log $(M_\star/M_\odot) > 10.5$) preferentially exhibit shallow, gray
dust attenuation curves, consistent with higher
dust optical depths and large grain sizes. We also find significant diversity in the time at which
galaxies form 25% of their
stellar mass. While formation timescales converge toward later
cosmic times,
galaxies with lower sSFR ($\lesssim -9$) at the observation epoch formed significantly earlier than systems with higher sSFRs. Across the full mass range, inferred assembly times are systematically earlier than model predictions, suggesting more rapid early growth than currently captured theoretically. These results underscore the importance of spectroscopic constraints and flexible SFH and
dust models for reconstructing high-
redshift massive
galaxy formation histories.
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All authors Katherine Chworowsky, Steven L. Finkelstein, Anthony J. Taylor, Alexa M. Morales, Mark Dickinson, L. Y. Aaron Yung, Pablo Arrabal Haro, Bren E. Backhaus, Davide Bevacqua, Óscar Chávez Ortiz, Adam C. Carnall, Callum T. Donnan, Mauro Giavalisco, Michaela Hirschmann, Kartheik G. Iyer, Anton M. Koekemoer, Rebecca L. Larson, Ray A. Lucas, Jed McKinney, Derek J. McLeod, Casey Papovich, Pablo G. Pérez-González, Lu Shen, Rachel S. Somerville, Laura Sommovigo, Thomas M. Stanton, Xin Wang, Stephen M. Wilkins, Jorge A. Zavala, the CAPERS Collaboration
High Energy Astrophysical Phenomena
The Demographics of Sagittarius A* X-ray Flares over 25 Years with Chandra
Zach Sumners, Nicole M. Ford, Daryl Haggard et al. (+10 more)
We present the Chandra 25-year Sagittarius A* (Sgr A*) X-ray
flare catalog: a systematic analysis of 6.8 Ms of Sgr A* monitoring spanning the Chandra X-ray Observatory's mission lifetime. This is the most complete Chandra Sgr A* X-ray
flare catalog to date, consisting of 100
flares with 2$-$10 keV unabsorbed luminosities ranging from $\sim$ 4$-$575 $\times 10^{33}$ erg s$^{-1}$. 18
flares are reported for the first time, including the second brightest Sgr A*
flare observed by Chandra. The expanded
dataset supports previous indications of a correlation between X-ray
flare hardness and luminosity. Spectral modeling corroborates this finding, showing a change in the X-ray spectral index, from $\Gamma \sim 3$ to 2 with increasing
flare brightness. Previously-established correlations between
flare duration, fluence, and maximum count rate are strengthened via the greater sample size. These results likely reflect variations in the underlying particle distribution that produce weak and strong
flares, and the new catalog serves as a rich archive for ongoing observational and numerical investigations into the physical mechanisms responsible for producing Sgr A*'s X-ray
flares.
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All authors Zach Sumners, Nicole M. Ford, Daryl Haggard, Joseph M. Michail, Joey Neilsen, Michael A. Nowak, Mayura Balakrishnan, Sophia Sánchez-Maes, Sebastiano D. von Fellenberg, S. P. Willner, Sera Markoff, Howard A. Smith, Joseph L. Hora
Earth and Planetary Astrophysics
Gravitational-wave Tomography of the Moon: Constraining Lunar Structure with Calibrated Gravitational Waves
Han Yan and Jan Harms
The recent success of gravitational-wave (GW) astronomy together with renewed plans for lunar geophysical instrumentation has revived interest in using the Moon as a resonant detector for mid-frequency (mHz-Hz) GWs. In realistic observational scenarios, the GW strain amplitude is expected to be constrained independently by networks of GW detectors, which motivates an inverse, tomographic question: to what extent can measurements of the Moon's seismic response to known GWs be used to infer its internal structure? In this work, we develop a first-principles, perturbative framework that maps spherically symmetric perturbations of the elastic and density structure to measurable changes in observables, especially GW-driven modal amplitudes of the Moon. The formalism combines (i) a normal-mode representation of the elastic response, (ii) first-order perturbation theory for
eigenvalues and eigenfunctions, and (iii) a linearized observation model that links frequency and amplitude observables to model parameters (bulk and shear
moduli, density, and interface locations) and their perturbations. We show that the estimation errors of the Moon's elastic parameters can be reduced by about an order of magnitude with observations of calibrated GWs.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Baryoid Dark Matter from $\mathbb{Z}_N$ Domain Walls: The $(N-1):1$ origin of the dark matter-baryon coincidence
Yang Bai and Ting-Kuo Chen
We propose an explanation for the dark matter-
baryon coincidence based on collapsing $\mathbb{Z}_N$ domain walls, which form a novel compact baryonic state: the baryoid. A baryoid has an asteroid-scale mass and up-to-
nuclear-scale energy density, and can serve as a dark matter candidate. Starting from equal
baryon numbers in the domains formed in the early universe, the collapse of the domain walls after the QCD phase transition leads to a
baryon-number ratio of $(N-1):1$ between the false- and true-
vacuum domains. Since
baryons are slightly lighter in the false-
vacuum domains than in the true-
vacuum domain, the resulting dark matter-to-
baryon energy-density ratio is naturally close to, but slightly smaller than, $(N-1):1$, or $6:1$ for $N=7$. We calculate the domain-wall dynamics and the efficiency of
baryon-number trapping, derive the resulting baryoid properties, and discuss a broad set of phenomenological probes.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Exploring neutrino loss with diffuse astrophysical neutrino fluxes
Ivan Esteban, Alberto M. Gago, M. C. Gonzalez-Garcia et al. (+1 more)
We study the sensitivity of the diffuse high-energy
neutrino flux observed in IceCube to new-physics effects resulting in an exponential flux attenuation along the trajectory, such as invisible
neutrino decay or new interactions with the background encountered during propagation. We argue that, even though the sources and production
redshifts of these astrophysical
neutrinos are unknown, conservative energy-conservation arguments allow to severely constrain
neutrino loss in most scenarios beyond the strongest existing bounds. By performing a fit to the High-Energy Starting Events from IceCube, we quantify the bounds and study their variation with the energy dependence of the attenuation, the assumed
redshift distribution of the
neutrino sources, and whether the attenuation affects
neutrinos exclusively or no. We also show that including an energy-dependent attenuation at the level allowed in the fit may impact the determination of the spectral index of the diffuse flux.
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All authors Ivan Esteban, Alberto M. Gago, M. C. Gonzalez-Garcia, Gabriel D. Zapata
High Energy Astrophysical Phenomena
Spin Demographics of Active Supermassive Black Holes: Updated Estimates from X-ray reflection and Future opportunities
Julia M. Sisk-Reynes, Christopher S. Reynolds, James H. Matthews et al. (+5 more)
Understanding the growth of supermassive black holes (SMBHs) requires observational constraints on how their angular momentum (or
spin) varies with mass, since the relative importance of coherent
accretion, chaotic
accretion, and mergers will be reflected in SMBH
spin populations. Here we present an updated compilation of reflection-based SMBH
spin measurements from the literature and assemble a set of ancillary quantities of interest for each SMBH (including
redshift, Eddington ratio, and X-ray luminosity). No obvious apparent correlation between the Eddington-scaled
accretion rate and the black hole
spin is seen, noting that formal statistical tests are beyond the scope of this review. We discuss the limitations of using this heterogeneous mass–
spin sample to test predictions of SMBH growth from semi-analytic models and cosmological simulations, emphasizing the need for a more uniform sample. We then highlight the encouraging prospects enabled by the next-generation NewAthena X-ray flagship observatory. Finally, we summarize how hierarchical
Bayesian population inference applied to observed SMBH mass–
spin populations will constitute a powerful framework for confirming tentative mass–
spin trends in future samples.
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All authors Julia M. Sisk-Reynes, Christopher S. Reynolds, James H. Matthews, Dominic J. Walton, Joanna M. Piotrowska, James F. Steiner, Javier A. Garcia, Angelo Ricarte
Cosmology and Nongalactic Astrophysics
Improved recipes for peculiar velocity power spectra using Evolution Mapping
Matteo Esposito, Ariel G. Sánchez, Julien Bel et al. (+1 more)
We present new fitting functions for the velocity divergence auto- and cross-power spectra, $P_{\theta\theta}(k)$ and $P_{\delta\theta}(k)$, calibrated on
gravity-only $N$-body simulations. By applying the
Evolution Mapping framework, we revise existing prescriptions to introduce a physically motivated parametrisation in terms of the clustering amplitude $\sigma_{12}$, the RMS density fluctuation smoothed at $12\,\text{Mpc}$. This approach improves robustness and extends the range of applicability beyond that of previous models. Our fits are calibrated using a suite of multi-resolution simulations, with numerical convergence carefully quantified and sampling artefacts mitigated through a conservative patching strategy. This yields converged measurements up to $k\simeq0.56\,\mathrm{Mpc}^{-1}$ and percent-level accuracy for both $P_{\theta\theta}(k)$ and $P_{\delta\theta}(k)$ over a wide range of $\sigma_{12}$. Validation against independent simulations spanning a broad range of cosmological models confirms an accuracy of $1$-$2$ per cent on scales where the measurements are robust, systematically outperforming existing prescriptions. We further assess the impact of deviations from the exact
evolution mapping relation induced by differing growth histories. For most cosmologies of practical interest, we find that neglecting these effects introduces only subdominant errors. We show that expressing fitting functions in $h$-dependent units leads to spurious, unphysical dependencies on the Hubble parameter, even for models with identical linear clustering. This provides strong empirical support for parametrising non-linear
evolution in terms of $\sigma_{12}$ rather than $\sigma_{8}$. Our fitting functions provide a robust description of velocity power spectra, with direct applications to
redshift-space distortion modelling in
galaxy redshift surveys.
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All authors Matteo Esposito, Ariel G. Sánchez, Julien Bel, Andrés N. Ruiz
Astrophysics of Galaxies
The Hunt for Red Dual AGNs I: Spatially-Resolved Mid-IR Dual AGNs in the DeCam Legacy Survey
Ryan W. Pfeifle, Kimberly A. Weaver, Barry Rothberg et al. (+13 more)
Theoretical studies predict that dual AGNs are a critical stage of
galaxy merger-driven supermassive black hole growth. Systematic searches for dual AGNs typically target late-stage mergers ($\leq10$ kpc
nuclear separations) and select AGNs based on optical diagnostics. Yet, simulations predict that obscuration can occur early in the merger sequence, and that a significant fraction of dual AGNs can be found beyond $10$ kpc. Here, we report on a new sample of 157 spatially resolved mid-IR dual AGNs candidates selected based upon their mid-IR $W1-W2$ colors from the Wide-Field Infrared Survey Explorer and optically classified as
galaxy merger candidates using imaging from the Dark Energy Camera Legacy Survey. Spectroscopic results are presented for approximately 2/3 of the sample. 76 candidates have been confirmed to reside in
galaxy mergers; among these, 13 have been confirmed as bona fide mid-IR dual AGNs, while 63 represent strong dual AGN candidates that require further examination. 46 candidates have been rejected as non-merger contaminants (foreground-background AGNs, separations inconsistent with interacting
galaxies, etc.). 35 candidates still await spectroscopic coverage. The confirmed and high confidence dual AGN candidates exhibit separations of 14.5-129 kpc; $>50$% reside at separations $>50$ kpc. Confirmed and high confidence candidates also exhibit a diversity of
nuclear optical BPT classes. Seyfert-Seyferts and Seyfert-HIIs dominate the overall BPT pairs sample. 31% of confirmed mid-IR dual AGNs reside in multi-mergers involving three or more
galaxies. The diversity in AGN properties and environments identified in this work highlights the importance of multiwavelength selection strategies and analyses in the quest to holistically understand dual AGNs as a population.
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All authors Ryan W. Pfeifle, Kimberly A. Weaver, Barry Rothberg, Miranda McCarthy, Emma Schwartzman, Nathan J. Secrest, Peter G. Boorman, Daniel Stern, Joanna Piotrowska, Kevin McCarthy, Emily Moravec, Jenna M. Cann, Kimberly Engle, Kyla Mullaney, Ryan Tanner, Kelly Whalen
Cosmology and Nongalactic Astrophysics
Spherical collapse and cluster number counts in DHOST theories that pass the constraints from gravitational waves
Sakdithut Jitpienka, Khamphee Karwan and David F. Mota
We investigate the spherical collapse model and the abundance of
galaxy clusters in a class of degenerate higher-order scalar–tensor (DHOST) theories in which gravitational waves do not decay into scalar perturbations and which are consistent with current constraints from gravitational-wave observations. We find that deviations from Einstein
gravity can become significant at late times when the background universe is close to the scaling regime during the matter-dominated epoch. These deviations suppress the growth of linear matter perturbations on small scales while increasing the extrapolated linear density contrast at collapse, obtained from the spherical collapse model. Using the analytic mass function, we compute the corresponding cluster number counts. The minimum mass threshold in the mass integration for each
redshift bin is determined by matching the predicted number counts in the $\Lambda$CDM model with those inferred from the eROSITA survey. We find that the cluster abundance reaches its maximum at low
redshift bin, and that the number of clusters in the highest
redshift bin is suppressed as the deviation from Einstein
gravity becomes larger. The parameters of the theory are chosen such that the deviation from Einstein
gravity at present is consistent with the local astrophysical bounds from binary
pulsar observations. We find that even under such strict constraints, the upper bound on the deviation leads to lower predicted number counts compared with the Poisson error of the eROSITA survey results. However, this may be a consequence of the uncertainties in computing the number counts for the DHOST theories using the spherical collapse model and the analytical mass function. In general, it may be concluded that the suppression of the cluster number counts is a consequence of the enhancement of the extrapolated linear density contrast.
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Cosmology and Nongalactic Astrophysics
The Amplitude-Growth Degeneracy and Implied $A_s$ Diagnostic for Background-Inert Modified Gravity
Ameya Kolhatkar and P. K. Sahoo
We prove that any background-inert perturbative coupling $ \lambda $ in coincident $ f(Q) $
gravity exhibits a degeneracy with the clustering amplitude $ \sigma_{80} $, when using compressed CMB distance priors. This degeneracy is, in fact, a direct materialization of a deeper $ A_s-D_0(\lambda) $ degeneracy between the
primordial amplitude $ A_s $ and the present day growth factor $ D_0(\lambda) $. We outline a consistency check scheme, whose logic extends to any model in which the coupling is background inert, by computing $ A_s $ per posterior sample, needed to reproduce the $ \sigma_{80} $ preferred by the sampler. We perform our analysis with two
dataset pipelines, based on the coupled/decoupled $ f\sigma_8(z) $ data. To ensure theoretical diversity, we include $ \Lambda $CDM and the Hybrid model in the $ f(Q) $ framework. Our results illustrate that adding the $ \lambda_0\sqrt{QQ_0} $ correction to the models inflates $ \sigma_{80} $ by $ 5\%-8\% $ as compared to its vanilla variant, while the
Bayesian evidence disfavors every alternative considered - $\Delta\log\mathcal{Z} = -0.5$ to $-2.6$ against $\Lambda$CDM on the same pipeline. Propagating this inflated $ \sigma_{80} $ through a per-sample computation of the implied
primordial amplitude accounting for both the transfer function and the modified growth factor yields $\ln(10^{10}A_s)$ in $1.5\sigma-2.6\sigma$ tension with Planck 2018. Imposing the $ \ln(10^{10}A_s) $ constraint from Planck 2018 as an additional prior removes this inflation, pulling $ \sigma_{80} $ to the Planck value and $ \lambda_0 $ to values consistent with $ 0 $, with the implied amplitude recovering to within $ 0.2\sigma $ of Planck in every case. We find no model-
dataset combination preferred over $ \Lambda $CDM.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Analytical Fluxes from Generic Schwarzschild Geodesics
Majed Khalaf, Chris Kavanagh and Ofri Telem
We present an analytic method for computing gravitational-wave fluxes from bound Schwarzschild geodesics with arbitrary eccentricity. Our approach systematically expands the
Fourier coefficients of the emitted radiation in a Chebyshev basis, allowing them to be reduced to sums of Keplerian-like
Fourier coefficients previously derived in the
Quantum Spectral Method. Because the construction does not rely on a small-eccentricity expansion, it applies to a broad range of bound eccentric orbits. As an illustration, we implement the method using a $15$PN-expanded input and find that it reproduces the total flux for the case $(p,e)=(12.5,0.5)$ to relative accuracy $10^{-5}$, while for the stronger-field case $(p,e)=(10,0.8)$ it yields weighted mode-by-mode errors below $10^{-6}$ for the selected dominant modes analyzed. These results provide an analytic route to frequency-domain flux calculations relevant to extreme-mass-ratio inspirals.
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Astrophysics of Galaxies
The Galaxy Luminosity Functions in ASTRID: Predictions for LSST
Fatemeh Hafezianzadeh, Tianqing Zhang, Paul Rogozenski et al. (+6 more)
We present validated and forward-modelled
galaxy luminosity functions and photometric predictions for the Vera C. Rubin Observatory Legacy Survey of Space and Time using the ASTRID cosmological hydrodynamical simulation.
Galaxy magnitudes are computed by combining
stellar population synthesis modeling with a physically motivated
dust attenuation prescription in which the optical depth scales with metal surface density. The
dust model is calibrated at z = 0 using SDSS luminosity functions and tested at intermediate
redshifts (z = 0.5, 1.0, and 1.5) in rest-frame B, V , R, and I bands. We find that the attenuated luminosity functions reproduce observed
galaxy statistics across multiple wavelengths and
redshifts. Using this calibrated framework, we construct LSST-ready mock photometric catalogs over 0 <= z <= 2 in steps of Delta z = 0.1, containing ~378 million
galaxies. We provide predicted apparent-magnitude luminosity functions in the LSST ugrizy bands, derive best-fit Schechter parameters as a compact analytic representation, and compute differential and cumulative
galaxy number counts as a function of survey depth from Year 1 to Year 10.
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All authors Fatemeh Hafezianzadeh, Tianqing Zhang, Paul Rogozenski, Patrick Lachance, Yihao Zhou, Tiziana Di Matteo, Rupert A. C. Croft, Simeon Bird, Rachel Mandelbaum
Astrophysics of Galaxies
From DES to KiDS: Domain adaptation for cross-survey detection of low-surface-brightness galaxies
Hareesh Thuruthipilly, Krzysztof Lisiecki, Junais et al. (+19 more)
Low-surface-brightness
galaxies (LSBGs) are vital for understanding
galaxy formation, but their diffuse nature makes them challenging to detect. Upcoming large-scale surveys are expected to uncover large numbers of LSBGs, requiring robust automated methods to identify them across heterogeneous
datasets. As a precursor to the Legacy Survey of Space and Time (LSST) and Euclid, we explore domain adaptation techniques for cross-survey LSBG identification. Using models trained on the Dark Energy Survey (DES), we search for LSBGs in the Kilo-Degree Survey Data Release 5 (KiDS DR5). We used an ensemble consisting of one convolutional neural network (CNN) and two
transformer models trained on DES cutouts and applied to KiDS DR5 imaging data. Structural parameters were estimated with galfitm, and photometric
redshifts and
stellar population properties were estimated through spectral energy distribution fitting with CIGALE. We identify 20,180 LSBGs and 434 ultra-diffuse
galaxies (UDGs) in KiDS DR5. Their structural parameters are similar to known LSBGs from DES and the Hyper Suprime-Cam SSP Survey (HSC-SSP). The KiDS-LSBGs follow a continuous size-luminosity relation connecting classical
dwarf galaxies and UDGs, and their colours are bimodal ($\sim73\%$ blue, $\sim27\%$ red). Cross-matching with spectroscopic and cluster catalogues provides
redshifts for 4,913 systems, enabling a systematic characterisation of the
star-forming main sequence of LSBGs. Strong environmental trends are evident, with cluster LSBGs and UDGs exhibiting redder colours and reduced
star formation compared to non-cluster systems. We demonstrate that domain adaptation enables robust cross-survey LSBG identification with deep learning models, providing a scalable pathway for constructing homogeneous LSBG catalogues for the LSST and Euclid era.
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All authors Hareesh Thuruthipilly, Krzysztof Lisiecki, Junais, Katarzyna Małek, Agnieszka Pollo, William J. Pearson, Antonio Vanzanella, Saptarshi Pal, Miguel Figueira, Pratik Dabhade, Anna Durkalec, Aidan P. Cotter, Unnikrishnan Sureshkumar, Nandini Hazra, Patryk Matera, Subhrata Dey, Michal Vrábel, Anirban Dutta, Henry Willems, Nicola Principi Cavaterra, Natalia Dobrowolska, Wojciech Knop
Solar and Stellar Astrophysics
Mahiguhappriya Prakash, Susmita Das, Harinder P. Singh et al. (+1 more)
We present a new, calibrated $G$-band relationship between pulsation period $P$,
Fourier parameter $\phi_{31}$, and
metallicity [Fe/H] for
galactic RR Lyrae
stars from the
Gaia survey. A set of 72 fundamental mode RR Lyrae
stars were identified for deriving the relation in the $G$-band, after visual examination of their light curves. Unlike recent large-scale calibrations, our relation prioritizes calibration purity by anchoring exclusively to a homogeneously analyzed sample of high-resolution spectroscopic
metallicities from the literature. Our best fit relation is $\text{[Fe/H]} = (-6.93 \pm 0.58) - (6.04 \pm 0.37)P + (1.65 \pm 0.11)\phi_{31}$. We compare the [Fe/H] predicted by our relation for the
stars in our calibration sample with that obtained from previously established relations in the $G$-band using different approaches. Our calibrated $G$-band $P$-$\phi_{31}$-[Fe/H] relationship demonstrates high reliability when validated against spectroscopic data, achieving a negligible bias of $0.00$ dex and an empirical RMS scatter of 0.26 dex. Furthermore, by applying an Orthogonal Distance Regression (ODR) routine that fully propagates parameter covariance, we establish a mathematically strict empirical baseline whose theoretical uncertainties perfectly align with this observed dispersion. We find that the inclusion of the $R_{21}$
Fourier parameter offers no significant improvement in
metallicity estimation. Comparisons with literature confirm that our linear relation aligns closely with other
Gaia DR3-based studies, while offering improved precision over older DR2-based relations.
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All authors Mahiguhappriya Prakash, Susmita Das, Harinder P. Singh, Nitesh Kumar
High Energy Astrophysical Phenomena
Tidal disruption of a low-mass star in an active galactic nucleus as the origin of the PS16dtm outburst
Marzena Śniegowska, Bożena Czerny, Michal Zajaček et al. (+7 more)
The event PS16dtm, which occured in the center of the Narrow Line Seyfert 1 (NLS1)
galaxy SDSS J015804.75-005221.8 (z = 0.080440), is one of the few candidates for a
tidal disruption event in an already-acretting active
galactic nucleus (AGN). We aim to shed light on the character of the
tidal disruption event in this source since it exhibits unusual peculiarities, such as the double-peak optical/UV light curve and a low blackbody temperature with a lack of X-ray emission. We perform spectral analysis of the source before and during the event. We model the time
evolution of the luminosity profile using a numerical code that describes the viscous
evolution of the flow. From the combined spectral and timing studies, we interpret the event as the disruption of a $\sim 0.3 M_{\odot}$ main-sequence
star, or gradual partial disruption of the low-mass
giant star. The
star is likely on a circular orbit, embedded in the
accretion disc. The discussion of the
evolution of the
star rather suggests that the orbit is counter-rotating. We observe the system at a sufficiently large viewing angle that the actual disruption process is not directly observed. The disrupted
star and inner disc are shielded from the observer by a gaseous envelope. Further observations of the system returning to the previous NLS1 state, particularly in the X-ray band, are needed to confirm the proposed scenario and to put constraints on the return to a regular NLS1 state.
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All authors Marzena Śniegowska, Bożena Czerny, Michal Zajaček, Valentina Rosa, Vladimír Karas, Taj Jankovič, Tanja Petrushevska, Dragana Ilić, Benny Trakhtenbrot, Petr Kurfürst
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Thin Accretion Disks around Rotating Charged Black Holes in an Effective Higher-Curvature Spacetime
Mohammad Hassani, Kourosh Nozari and Sara Saghafi
We investigate the structure and emission properties of a thin
accretion disk around a rotating charged black hole described by an effective higher-
curvature-inspired spacetime, constructed as a phenomenological deformation of the Kerr Newman geometry. In this framework, the deformation is introduced through a modification of the metric function $\Delta$ by an effective Gauss-Bonnet-like parameter $\alpha$, such that the spacetime reduces to the standard Kerr Newman solution in the limit $\alpha \to 0$. Adopting a kinematical approach, we use test-particle motion to derive the specific energy, specific angular momentum, and angular velocity of circular orbits, and analyze the effects of the parameters $\alpha$ and charge $Q$ on the innermost stable circular orbit (ISCO), radiative efficiency, radiation flux, temperature, and differential luminosity of the disk. We find that increasing $\alpha$ shifts the ISCO inward and enhances the disk's radiation flux and temperature, while the presence of charge suppresses these quantities due to electrostatic effects. Our results demonstrate that effective higher
curvature deformations of rotating black hole spacetimes can lead to observable deviations from the Kerr case, highlighting
accretion disks as sensitive probes of strong-
gravity effects without relying on a specific underlying gravitational theory.
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Earth and Planetary Astrophysics
Global evolution of electric fields during planet encircling dust storms on Mars
Ina Taxis, Leonardos Gkouvelis, Richard A. Urata et al. (+2 more)
Planet-encircling
dust storms fundamentally reshape Martian weather and the near-surface electrostatic environment. We investigate the generation and
evolution of electric fields during global
dust storms using bimodal
dust size distributions from the NASA Ames Mars Global
Climate Model, coupled with a triboelectric charging and electrostatic diagnostic scheme that links collisional charging to the local dynamical state of the atmosphere. Focusing on the
dust-lifting and buildup phase and its subsequent
evolution, we quantify the electric-field energy density and discharge characteristics, including onset thresholds, event frequency, and spatial clustering. The simulations reveal broad storm-active belts of enhanced electrification, with the most frequent threshold exceedances occurring in southern low-to-mid latitudes and secondary activity in northern low-to-mid latitudes. Modeled near-surface electric fields reach $10^{2}$–$10^{3}\ \mathrm{V\,m^{-1}}$ comparable to values inferred for smaller-scale
dust phenomena. The results indicate that electric-field generation is controlled by the interplay between
dust loading,
turbulence-driven collisional activity, and conductivity-dependent charge relaxation, with diurnal conductivity variations strongly suppressing daytime electric-field buildup and most events remaining in the weak glow or Townsend discharge regime. While the model captures the large-scale distribution of electrically favorable conditions, the predicted spatial extent of activity likely represents an upper bound, as small-scale turbulent structures are not fully resolved. These results provide a quantitative framework to identify regions where electrostatic discharges are most likely during GDSs and to inform instrument design, power-system protection, and operations planning for future robotic and human missions.
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All authors Ina Taxis, Leonardos Gkouvelis, Richard A. Urata, Melinda A. Kahre, Amanda S. Brecht
Instrumentation and Methods for Astrophysics
Inpainting to search for premerger massive black hole binaries in realistic LISA datasets
Gareth Cabourn Davies and Ian Harry
A key science target of the Large Interferometer Space
Antenna (LISA) is to carry out multi-messenger observations of massive black hole binaries, observing the merger simultaneously in gravitational waves and with electromagnetic observatories. Identifying that a merger is happening and providing an updating estimate of the sky location in the hours, days and weeks before the merger is critical to enable electromagnetic observations of the merger event. In this work we demonstrate and compare two methods for premerger identification of massive black hole binaries; a zero-latency filter approach and, for the first time, an approach using an “inpainting” technique. We apply these methods to the LISA Data Challenge
dataset 2a–Sangria-HM–and demonstrate the successful recovery of the 14 signals in the
dataset that we expected to be identifiable at least half a day before merger. We show that the inpainting method can identify premerger signals even when gaps are present in the data, demonstrating the recovery of a signal even when 3 day-long data gaps are added to the 14 days preceding merger. Finally, we explore the challenge of overlapping signals, using a region of overlapping signals in the Sangria-HM
dataset, all of which merge within a 10-day window, and show how removing signals that have been confidently identified from the data allows us to identify quieter signals in the same period.
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Astrophysics of Galaxies
A New PSF Deconvolution Algorithm: Simultaneous Spatial Resolution Enhancement and Point Source Removal for Morphological Analysis of AGN Host Galaxies
Ren Kawase, Takatoshi Shibuya and Kazunori Matsuda
We propose a new point-spread function (PSF) deconvolution
algorithm for images of
galaxies hosting an active
galactic nucleus (AGN), designed to simultaneously enhance the spatial resolution of the host
galaxy and remove the bright central point source. In this
algorithm, an intrinsic image is reconstructed by decomposing an observed image into two components: an image $I_{\rm sm}$ of an extended component (i.e., a host
galaxy) and an image $I_{\rm sp}$ of a point-source component (i.e., an AGN). During image reconstruction, three constraints are imposed: (1) a smooth constraint on the image $I_{\rm sm}$ , which spatially smooths the host-
galaxy structures; (2) a sparse constraint on the image $I_{\rm sp}$ , which localizes the point source to a small number of pixels; and (3) a new constraint, the point-source balance constraint, based on the pixel-wise product $I_{\rm sm} \times I_{\rm sp}$ , which removes the point source from the host
galaxy without over- or under-subtraction. As a test, we apply this
algorithm to images of artificial and $z \sim 0-1$ real AGNs observed with Hyper Suprime-Cam on the Subaru
Telescope. We find that the spatial resolution of the host-
galaxy images is improved to a level comparable to that of images from the Hubble Space
Telescope and that the bright central point sources are removed. This
algorithm is expected to enable statistical morphological studies of distant AGN host
galaxies when applied to wide-field survey data from the Vera C. Rubin Observatory, the Euclid Space
Telescope, and the Roman Space
Telescope.
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Solar and Stellar Astrophysics
Detector for fast wave trains in the solar radio emission
V. A. Dmitriev, E. G. Kupriyanova and A. V. Mikhalchuk
Quasi-periodic fast propagating (QFP) wave trains observed in the
solar corona after some energetic events (
solar flares, coronal mass ejections, jets) open possibilities for diagnostics of spatial and temporal scales of the impulsive energy release processes, that are absent in the standard model of a
solar flare. Besides, the dynamics of the wave trains and their characteristic spatial and temporal signatures allow to localize the initial energy release volume magenta and to perform fine diagnostics of the transverse structures of
plasma inhomogeneities in the
solar corona. However, the small number of such events registered significantly limits their promising diagnostic potential. The aim of this paper is to perform an automatic search for fast wave trains in
radio data. We apply classifying neural network/machine learning methods. Dynamic
radio spectra obtained by HiRAS
radio spectrographs within the 20 MHz – 2.5 GHz frequency band during 2011 were used. We consider 50 global coronal EUV waves as marker events for more a targeted search in HiRAS data. Our automatic detector revealed 50 independent QFP-candidates events with the temporal signatures similar to that of the fast wave trains, with 13 candidates connected with the global waves.
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High Energy Astrophysical Phenomena
The Very Late Time Afterglow of GW170817 Favors a Wobbling Jet
Hao Wang, Ore Gottlieb, Aman Katira et al. (+4 more)
GW170817 remains the only binary
neutron star merger detected through multimessenger emission. Its afterglow has been monitored for nearly a decade, offering an unprecedented opportunity to probe the properties of the
outflow. The shallow decay of the very late-time afterglow challenges the prediction of a collimated structured jet. Motivated by recent general-relativistic magnetohydrodynamic simulations, we propose that the GW170817 afterglow is powered by a wobbling jet that drags a ring on the sky. This structure predicts a post-break decay rate shallower than that of a collimated jet, as observers will see a progressively longer emitting arc after the break. A misaligned ring-shaped jet can therefore self-consistently explain the multimessenger data without invoking any extra component. Through a
Bayesian analysis of the multimessenger data, we find a ring-shaped jet is favored over a collimated jet at a significance level of 4.8$\sigma$. Our results imply a wobbling angle of $\sim 27^\circ$. Such a large angle points to a significant disk tilt, potentially arising from disk-infalling gas interaction or asymmetric angular momentum ejection. Similar shallow decays have also been found in other GRB afterglows, raising the possibility that wobbling jets are common among GRBs.
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All authors Hao Wang, Ore Gottlieb, Aman Katira, Muskan Yadav, Lei Lei, Yi-Zhong Fan, Da-Ming Wei
High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Quantum Field Theory of Black Hole Perturbations with Backreaction VI. Apparent Horizons, Quasi-Local Mass and Effective Classical Metrics
Jonas Neuser and Thomas Thiemann
In a recent series of papers we developed a first-principle and gauge invariant approach to black hole perturbation theory valid to any order. We included back reaction effects to tackle the situation of evaporating black holes and obtained an explicit expression for the dynamics of the reduced phase space to second order. The physics of evaporating black holes is in particular encoded by apparent horizons, an observer dependent generalisation of the event horizon. We determine the shape of the apparent horizon to second order in the perturbations. The area of the apparent horizon is an interesting observable which is expected to decrease in the
quantum theory due to Hawking evaporation. We show how the full four dimensional metric can be reconstructed in terms of the reduced phase space variables. In the
quantum theory, taking expectation values of this metric, we obtain an effective classical metric, whose causal structure can then be visualised in a
quantum corrected Penrose diagram. We conclude with an outlook into the quantisation procedure in the reduced phase space formalism and the implications on the area of the apparent horizon.
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Cosmology and Nongalactic Astrophysics
Apocalypse When? Solar System Constraints on an Imminent Big Rip
Robert J. Scherrer and Oem Trivedi
Phantom dark energy models with an equation of state parameter $w < -1$ lead generically to a future big rip singularity, in which the dark energy density becomes infinite in a finite time. Current limits on dark energy constrain $w$ to be close to $-1$, and if $w$ is assumed constant, then a future big rip cannot occur in less than the order of a Hubble time in the future. However, many models allow $w$ to decrease rapidly with time. In that case, or if one assumes an additional phantom component with current energy density far below the dark energy density and $w << -1$, it is possible to achieve an imminent big rip, which we define to be a future singularity occuring in much less than the Hubble time. Such a possibility cannot be constrained by any cosmological measurements, as these are all based on light emitted billions of years in the past. Indeed, it is not possible, on the basis of cosmological observations, to rule out a future big rip tomorrow. However,
solar system dynamics are sensitive to the behavior of phantom dark energy on timescales of decades rather than billions of years. Using
solar system measurements, we are able to derive limits on the timescale for a future big rip independent of the dynamics of the phantom component. We obtain $t_{rip} - t_0 > 30$ years. While admittedly a poor limit, these results are likely to be improved by future more precise measurements of
solar system dynamics. Our results also show that evidence for an imminent big rip would show up first in
solar system data, rather than in any cosmological observation.
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High Energy Astrophysical Phenomena
Guitar Nebula: extreme accelerator in extreme environment
Igor Nikolaevich Nikonorov, Maxim Vladimirovich Barkov and Maxim Lyutikov
Guitar nebula is a
prime example of a class of bow-shock
pulsar wind nebulae (PWNe), powered by a wind of a supersonically moving
neutron star. Bow-shock PWNe can probe particle acceleration processes in relativistic
pulsar winds, as well as the structure of the interstellar medium (ISM). We demonstrate that the Guitar is an exceptional object in a number of ways. First, particles escaping the PWN and forming the X-ray “kinetic jet” need to be accelerated to the energies corresponding to the maximal electric potential of the
neutron star $\eta_\text{acc}\gtrsim 3/4$ : it is another example of the class of extreme accelerators. Second, exceptionally bright H$_\alpha$ emission requires that the central
pulsar PSR J2225+6535 passes through a dense, low ionization ISM region. Bright X-ray emission of the “kinetic jet” then also requires exceptionally high
magnetic field, $\sim 100~\mu$G. We hypothesize that Guitar passes through the one of long-predicted, narrow dense shells of an old
supernova remnant, currently in the “pressure-driven snowplow” regime.
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Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Calorimetric approach to paleo-detection of dark matter
Samuel Hedges and Patrick Huber
We present the first paleo-detector dark matter sensitivity analysis based on a calorimetric readout, in which the number of stable
lattice vacancies produced by each
nuclear recoil is used as a per-event observable complementary to the track length. Using full-cascade SRIM simulations in olivine, we compute the expected sensitivity for a 100 gGyr exposure. We find that a vacancy-only readout reaches a sensitivity envelope very similar to that of state-of-the-art track-only analyses. The combination of the two observables provides an event-by-event proxy for |dE/dx| and hence for the recoiling
nuclear species. Since the
neutron-
nucleus cross section is approximately flat in
nuclear mass while the dark-matter–
nucleus cross section scales as $A^2$, this discrimination suppresses the dominant
neutron background by more than an order of magnitude at moderate dark matter masses. The combined-analysis sensitivity reaches
spin-independent dark-matter–nucleon cross sections of order $10^{-48}\,\mathrm{cm}^2$ at WIMP masses of a few tens of GeV, comparable to future direct detection experiments. A two-stage readout combining selective-plane illumination microscopy with scanning electron microscopy is identified as a path to making a 100 g-scale analysis plausible.
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Astrophysics of Galaxies
Tracing the sulfur depletion in starless and pre-stellar cores
L. Schöller, S. Spezzano, O. Sipilä et al. (+4 more)
Sulfur is one of the most abundant elements in the Universe, yet the sulfur budget inferred from the observed sulfur-bearing molecules in dense cores is significantly lower than expected. Starless and pre-
stellar cores represent the earliest stages of
star formation and provide a laboratory for studying the physical and chemical processes that cause sulfur depletion. We aim to constrain sulfur chemistry in dense cores by measuring abundances of sulfur-bearing molecules and how they reflect core
evolution and environmental effects. We observed nine cores in the Taurus Molecular Cloud, targeting 13 sulfur-bearing molecules, including CS, CCS, C$_3$S, OCS, SO, SO$_2$, H$_2$CS, and isotopologs. Molecular abundances and six abundance ratios were compared to three evolutionary tracers: H$_2$ column density, N$_2$D$^+$/N$_2$H$^+$, and the CO depletion factor. We also compared observations with 0D chemical models with different initial sulfur abundances. We find variations in abundances across cores. L1517B exhibits low abundances and a high depletion factor, whereas L1495B shows enhanced levels in oxygen-bearing species within the L1495 filament. Ratios tracing carbon- and oxygen-bearing species (CCS/$^{34}$SO and C$^{34}$S/$^{34}$SO) decrease with increasing H$_2$ column density and N$_2$D$^+$/N$_2$H$^+$ ratio. Other species and ratios show weak or no correlation with tracers. Models reproduce OCS, H$_2$CS, and HDCS reasonably well, but not all species simultaneously, especially between carbon- and oxygen-bearing molecules. The variations and lack of consistent correlations suggest that a single evolutionary parameter cannot describe sulfur chemistry and that the local environmental conditions strongly influence the observed abundances. Reproducing the full sample of sulfur-bearing molecules would require improved chemical networks and models that account for the core's physical structure.
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All authors L. Schöller, S. Spezzano, O. Sipilä, E. I. Makarenko, P.Caselli, H. A. Bunn, S. S. Jensen
Instrumentation and Methods for Astrophysics
DEFROST: Detecting Excess in Faraday Rotation thrOugh Sophisticated analysis Techniques
Valentina Vacca, Sebastian Hutschenreuter, Andrea Cabriolu et al. (+7 more)
Understanding origin and
evolution of cosmological
magnetic fields requires knowledge of
magnetic fields in different extragalactic environments. In this context, a powerful tool is the statistical analysis of the Faraday effect on the linear polarization of a sample of
radio sources. This effect carries information about the
magnetic fields in our
Galaxy, extragalactic environments between the sources and the observer, and within the emitting
radio source itself. An accurate disentangling of all these components is crucial to characterize
magnetic fields in the LSS of the Universe. The significant amount of data delivered by new
radio instruments enables the investigation of increasingly weak
magnetic fields. However, a trustworthy characterization is only possible with advanced analysis techniques. In this work, we present a new
algorithm capable of simultaneously disentangling the Faraday effect due to our
Galaxy from extragalactic contributions, by properly taking into account the observing noise. The
algorithm takes as an input a catalog of RM complemented by auxiliary information as, e.g., the
redshift. We tested the
algorithm with synthetic data to assess its performance and identify the range of
Galactic magnetic field power spectrum slopes that allows us to properly disentangle
Galactic and extragalactic terms. Furthermore, we tested the
algorithm with synthetic catalogs, based on m- and cm-data currently available, corresponding to different observing setups, noise, and cuts in the absolute value of the
Galactic latitude of the
radio sources. Considering noise values and density of polarized sources consistent with existing catalogs, we demonstrated that the most robust results are obtained with sources with absolute
Galactic latitude > 45deg, with inference of the extragalactic parameters at most within 5sigma, both for dispersion in Faraday rotation of ~1 and 10rad/m2.
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All authors Valentina Vacca, Sebastian Hutschenreuter, Andrea Cabriolu, Torsten A. Ensslin, Jakob Roth, Martin Reineke, Philipp Frank, Federica Govoni, Matteo Murgia, Gianni Fenu