Astrophysics of Galaxies
Superdiffusion at the Galactic Centre
Pau Amaro Seoane, Kostas Tzanavaris, Reinhard Genzel et al. (+14 more)
Tracking S-
star cluster orbits around Sgr A* calibrates orbital transport models for space-borne gravitational wave detectors. Standard kinetic theories model this cluster via local Fokker-Planck equations, which predict that general relativistic precession halts angular momentum
diffusion at the Schwarzschild barrier. Because inverse-square gravitational encounters generate a Holtsmark torque distribution with infinite variance, resonant relaxation operates as a space-fractional process governed by non-local Lévy flights. We simulate this superdiffusive continuous-time random walk using a Markov chain initialized with empirical S-
star orbits, including the recently observd S301. Integro-differential fractional operators allow trajectories to cross regions of quenched local
diffusion without density buildup at the barrier. Non-
equilibrium regimes yield immediate linear flux growth, while secular
tidal heating at periastron inflates
stellar radii to shift disruption boundaries. Regularized backward integration of the fractional transport equation traces current phase space configurations back to initial deposition states, matching the energy requirements of the
Fermi bubbles. Relativistic precession does not suppress mass-ratio inspiral rates, which provides a model for event
topologies in target
galactic nuclei.
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All authors Pau Amaro Seoane, Kostas Tzanavaris, Reinhard Genzel, Frank Eisenhauer, Thomas Ott, Stefan Gillessen, Guillaume Bourdarot, Diogo C. Ribeiro, Matteo Sadun Bordoni, Simran Joharle, Felix Mang, Andreas Burkert, Jorge Cuadra, Diego Calderón, Hagai B. Perets, Tsvi Piran, Re'em Sari
Astrophysics of Galaxies
Semi-analytic Inference of Satellite Densities in the Cold Dark Matter Model Part I. Comparison to Ultra-faint Dwarf Kinematics
Kailash Raman, Dylan Folsom, Manoj Kaplinghat et al. (+2 more)
Ultra-faint
dwarf galaxies are critical testing grounds for probing the limits of
galaxy formation in the cold dark matter (CDM) paradigm. Employing a semi-analytic cosmological satellite generator that captures the expected CDM
halo population, we estimate Milky Way
dwarf density profiles through two methods: a kinematic approach using
stellar velocity dispersions and a separate method based on
dwarf stellar masses. The kinematic approach yields a larger diversity in central dark matter densities than expected from the CDM population, as inferred from the
stellar-to-
halo mass relation, with compact ultra-faints appearing overdense and larger systems appearing underdense. For the ultra-faint
dwarfs with at least 10
stars with spectroscopic measurements, this discrepancy persists at the ~2.4$\sigma$ level across all considered systematic variations on the semi-analytic modeling. Our framework introduces a novel, robust procedure for testing the consistency of the observed population of Milky Way satellites with cosmological expectations. As future surveys discover new
dwarf satellites and refine
stellar velocity measurements, updating this analysis will provide an increasingly stringent test of the CDM paradigm.
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All authors Kailash Raman, Dylan Folsom, Manoj Kaplinghat, Mariangela Lisanti, Benjamin R. Safdi
Cosmology and Nongalactic Astrophysics
Andrew Liu, Anirudh Prabhu, Akaxia Cruz et al. (+1 more)
Dark matter that self interacts through long-range forces exhibits coherent, collective effects that are absent in short-range interactions. In the case where dark matter interacts through a hidden-
photon mediator, its dynamics closely resemble those of Standard Model
plasmas. In such models, various astrophysical environments, including cluster collisions and subhalos orbiting their host
halo, are susceptible to
plasma instabilities: processes that modify the dark matter velocity distribution and lead to exponential growth of dark electromagnetic fields. In this paper, we present the first study of the non-linear
evolution of electrostatic instabilities in dark matter subhalos orbiting within the Milky Way potential using a suite of particle-in-
cell simulations. We find that the growth and saturation of these instabilities produce substantial turbulent heating and mass loss, with an efficiency that depends sensitively on subhalo mass and orbital eccentricity. For highly eccentric orbits,
plasma heating can reduce the initial mass of a $10^7$ ($10^9$) $\text{M}_\odot$ subhalo by as much as $\sim 97\%$ ($\sim 84\%$) soon after first pericenter.
Plasma-induced heating and stripping may therefore leave observable signatures in the Milky Way subhalo population, including a suppression of the low-mass subhalo mass function.
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All authors Andrew Liu, Anirudh Prabhu, Akaxia Cruz, Mariangela Lisanti
Instrumentation and Methods for Astrophysics
Assessing the Impact of Instrumental Requirements on the Scientific Performance of the Einstein Telescope
Ulyana Dupletsa, Francesco Iacovelli, Mikhail Korobko et al. (+23 more)
We investigate the relationship between instrumental requirements and the scientific performance of the Einstein
Telescope (ET), a third-generation (3G) gravitational-wave (GW) observatory. Different technical design choices result in distinct noise budgets, ultimately shaping the detector's scientific capabilities. To systematically assess and compare their impact, we define a comprehensive set of performance metrics spanning compact binary coalescence (CBC) detection and parameter estimation, as well as other sources, including
stochastic GW backgrounds, isolated spinning
neutron stars, and core-collapse
supernovae (CCSNe). We build a comparative reference framework that links degradations in specific noise contributions and frequency bands to losses in scientific capabilities. We consider a representative selection of technical parameters, such as coating and suspension temperatures, the filter cavity length in the low-frequency instrument, and the beam size in the high-frequency instrument. We evaluate how sensitivity variations across specific frequency bands affect different scientific objectives. We quantify how the sensitivity below 30 Hz impacts the detectability of massive and/or high-
redshift sources and the reconstruction of long-duration CBC signals, affecting early warning and sky localization for binary
neutron stars (BNSs). Sensitivity in the 30-450 Hz range governs most CBC parameter-estimation metrics, while high-frequency sensitivity above ~450 Hz predominantly impacts BNS post-merger studies and CCSN detectability, with modest effects on detection rates. Even with the most significant degradations considered, the ET science case remains robust overall. Our results provide a comprehensive
benchmark linking scientific objectives to instrumental requirements, particularly important as the final design and infrastructure of 3G observatories are being defined.
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All authors Ulyana Dupletsa, Francesco Iacovelli, Mikhail Korobko, Valeria Sequino, Alessandro Agapito, Manuel Arca Sedda, Biswajit Banerjee, Nicolò Cibrario, Andrea Cozzumbo, Francesco Crescimbeni, Alessio Ludovico De Santis, Gabriele Franciolini, Yufeng Li, Michele Mancarella, Benedetta Mestichelli, Niccolò Muttoni, Lavinia Paiella, Ippocratis D. Saltas, Filippo Santoliquido, Pawan Tiwari, Cristiano Ugolini, Marica Branchesi, Archisman Ghosh, Jan Harms, Michele Maggiore, Fiodor Sorrentino
Cosmology and Nongalactic Astrophysics
Non-Minimally Coupled Chain Inflation at High Scales
Miguel Barroso Varela, Orfeu Bertolami, Katherine Freese et al. (+1 more)
Chain inflation offers an alternative to standard slow-roll dynamics, with accelerated expansion proceeding through a sequence of rapid
quantum tunneling events between metastable
vacua. At the high energy scales relevant for the early Universe, scalar fields are generically expected to couple non-minimally to
gravity via operators like $\xi R\phi^2$, allowed by
symmetry and required as counterterms for interacting theories in curved spacetime. We study the dynamical and observational consequences of this coupling for chain inflation. We find the modifications to the model for arbitrary $\xi$ and focus on interesting phenomenology for $\xi ={\cal O}( 10)$. We show that, in the Einstein frame, the non-minimal coupling induces a field-dependent amplification of the Euclidean bounce action, thus modifying the tunneling rate across the chain. We develop an analytic framework connecting this modified tunneling dynamics to the scalar spectral index, its running, the
primordial curvature power spectrum, and the
stochastic gravitational wave background from bubble collisions. As one consequence, the non-minimal coupling breaks the rigid relation between the scalar tilt and inflationary scale that drives the minimally coupled pure tilted cosine model to very low energies ($V_*^{1/4}\lesssim 3\,\rm{GeV}$, where $V_*$ is the value of the inflationary potential when the CMB-relevant modes exit the horizon), allowing for viable high-scale chain inflation with $V_*^{1/4}\sim 10^{11}\,\rm{GeV}$. Furthermore, non-minimally coupled chain inflation at high scales produces a peaked
stochastic gravitational wave signal in the dHz-kHz bands, accessible to upcoming interferometers such as the Einstein
Telescope and
Cosmic Explorer. Finally, the model predicts a distinct running of the spectral index that will be testable by the Simons Observatory, making it a
prime target for multi-messenger cosmology.
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All authors Miguel Barroso Varela, Orfeu Bertolami, Katherine Freese, Evangelos Sfakianakis
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Quadratic Axion Couplings in String Theory
Naman Agarwal, Andrew R. Frey, Ratul Mahanta et al. (+1 more)
Axions and
axion-like particles are a compelling candidate for physics beyond the standard model. While many
axion searches are focused on the linear coupling to
photons $\theta F \tilde{F}$, the possibility of a quadratic coupling to the electromagnetic kinetic term, $\theta^2 F^2$, leads to novel phenomenology and new opportunities for testing
axion-like particles. In this work we propose mechanisms for generating this coupling in string theory, which can be broadly classified as classical, perturbative, and non-perturbative. In
benchmark examples, we find that both perturbative and non-perturbative
quantum contributions such as instantons lead to couplings that are suppressed, $g \ll 1$ in units of $1/f^2$ where $f$ is
axion decay constant, though easily larger than analogous coupling of the QCD
axion that is generated through loops of charged pions. These analyses suggest that quadratic
axion couplings to gauge fields are ubiquitous in string theory, and should be taken seriously as a probe of the string theory axiverse, both of string theory candidates for dynamical
axions, such as dark matter or dark energy, and for spectroscopy of the string theory axiverse.
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All authors Naman Agarwal, Andrew R. Frey, Ratul Mahanta, Evan McDonough
Earth and Planetary Astrophysics
An Inclined, Eccentric Planet and an Inner Debris Disk Could Reproduce AU Mic Structure
Arcelia Hermosillo Ruiz, Ruth Murray-Clay, Meredith A. MacGregor et al. (+1 more)
The debris disk orbiting the M
star AU Microscopii has a series of large-scale clumps that move away from the
star at high velocities above the mid-plane on the southeast side. Two more bright features lie on the northwest side of the disk, localized below the mid-plane and moving toward the
star. These clumps are only observed in scattered light indicating that they affect small 0.2$\mu$m-sized grains. We present a mechanism for emitting periodic
dust clumps by appealing to
stellar forces and an inclined, eccentric
planet interacting with an exterior debris disk. In our best-matching simulations, the
planet exerts an impulse on the disk every orbital period, generating periodic enhancements in
dust above the mid-plane. We assume that the
stellar wind only acts on grains once they reach a height above the mid-
planet that exceeds a threshold value (a free parameter in our model), at which point they are accelerated outward. The behavior of periodic particle ejections and trajectories depends significantly on the
planet's mass, eccentricity, and inclination; separation between the
planet and disk; and the ratio of
stellar wind force to the
star's gravitational force ($\beta$). We find a promising qualitative match to observations with simulations that include an as-yet-undiscovered and observationally allowed
planet with mass $2 M_J$, semi-major axis between 3-4 au, eccentricity of 0.37, and inclination of 30$^\circ$, a ring of particles between 5-6 au, and a
stellar wind height threshold of $z_h = hr$, where $h \approx 0.02$. We visualize our simulation with surface brightness maps to compare with existing observations of AU Mic. We find that a value of $\beta \approx 1.8$ accelerates the clumps radially outward at velocities that are comparable to the clumps seen in the AU Mic disk and produces features similar to those observed.
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All authors Arcelia Hermosillo Ruiz, Ruth Murray-Clay, Meredith A. MacGregor, Renata Frelikh
Cosmology and Nongalactic Astrophysics
Searching for signatures of inflationary massive fields in DESI Imaging data and Stage-V galaxy surveys
Walter Riquelme, Santiago Avila, Lucas Pinol et al. (+2 more)
We investigate the cosmological imprints of massive fields during inflation through
primordial non-Gaussianity (PNG). When these fields are sufficiently light, they produce a signal in
galaxy clustering, $\propto f_{\rm NL,\Delta}k^{\Delta-2}$ with $\Delta\in(0,3/2]$, corresponding to a beyond-local PNG contribution to the scale-dependent bias. We use the angular correlation function to constrain $f_{\rm NL,\Delta}$ and $\Delta$ using imaging data used for the targeting of the Dark Energy Spectroscopic Instrument (DESI). For the most aggressive systematics treatment, there is no evidence for local PNG, hence no constraint on $\Delta$. However, when considering a less aggressive treatment, a hint is found with $f_{\rm NL}^{\rm loc}=27^{+10}_{-9}$, consistent with previous analyses. For beyond-local PNG, that signal gives a preference for $f_{\rm NL, \Delta}=5.12^{+6.13}_{-3.62}\times10^{3}$ and $\Delta=0.91^{+0.25}_{-0.19}$. This preference is not robust under decontamination choices, likely driven by residual systematics, and we present it as a showcase for future constraints. Additionally, we forecast the sensitivity of upcoming Stage-V surveys, the Wide-field Spectroscopic
Telescope (WST), the MUltiplexed Survey
Telescope (MUST), and the Spectroscopic Stage 5 Experiment (Spec-S5), to constrain $\Delta$ using Lyman-break
galaxies. Around the local limit, $\Delta^{\rm fid}=0$, we find that they can reach uncertainties of $\sigma(\Delta)\simeq0.17-0.50$, depending on the survey, for a fiducial $f_{\rm NL,\Delta}^{\rm fid}=4$. The constraining power on $\Delta$ increases as we increase $f_{\rm NL,\Delta}^{\rm fid}$ and decreases for larger fiducial $\Delta$. Finally, we derive a relation between the detectability of $\Delta$ and the local PNG constraints, $\sigma(f_{\rm NL}^{\rm loc})$. This provides a tool to estimate the survey sensitivity required to resolve massive-field signatures.
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All authors Walter Riquelme, Santiago Avila, Lucas Pinol, Hui Kong, Anna Porredon
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Outcomes of Grand Unified Symmetry Breaking
Harish Hemming, Tanmay Vachaspati and Anja Wachowitz
We numerically study the outcome of
symmetry breaking motivated by Grand Unified models. Our results show the formation of biased domain walls for a range of parameters together with
magnetic monopoles. The interactions of walls and monopoles leads to novel processes such as the absorption of monopoles on walls, production of monopoles when domain walls annihilate, collapse of walls with
magnetic charge that can, with
gravity taken into account, produce magnetically charged black holes, and production of a
stochastic gravitational wave background from biased domain walls. Our findings open new avenues for probing the grand unification epoch by cosmological observables.
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Cosmology and Nongalactic Astrophysics
Shear-kSZ: A New Estimator for the Matter-Electron Power Spectrum from kSZ Tomography and Weak Lensing
Boryana Hadzhiyska
We propose a new
estimator of the electron–matter power spectrum, $P_{me}(k)$, which correlates the kinematic Sunyaev–Zel'dovich (kSZ) temperature with the product of the line-of-sight velocity field and the weak-
lensing convergence. Like the stacked kSZ
estimator, it factorizes into a calibratable velocity kernel times $P_{me}(k)$, but it probes the full matter distribution rather than the gas around a biased tracer. It therefore measures the baryonic suppression of the matter power spectrum, $S(k)$, one of the dominant astrophysical systematics for Stage-IV
cosmic shear. We derive an analytic expression for the
estimator, validate it against simulations at the per-cent level, and show that its parity structure cancels
cosmic microwave background (CMB) foregrounds. We forecast the detectability with a realistic pipeline: velocities reconstructed from the simulated tracers, with and without photometric-
redshift errors; the kSZ signal of all the ionized gas along the line of sight; a CMB map with Simons Observatory (SO) noise; and LSST source samples free of intrinsic
alignments. A DESI-like spectroscopic sample at $0.5<z<1$ over the $20\%$ of the sky that DESI, LSST and SO share gives a $4$–$7\sigma$ detection. Photometric
redshifts cost only $5$–$10\%$ of the significance, so LSST can supply its own velocity tracers over its full overlap with SO: with tracers at $0.1<z<1.3$ and five source samples we find $10\sigma$ in an end-to-end simulation, and $13\sigma$ with Advanced SO (16$\sigma$ if extending to $z < 1.5$). This corresponds to a few-per-cent measurement of $S(k)$ at $k\simeq1$–$4\,h\,{\rm Mpc}^{-1}$, the scales that matter most for
cosmic shear.
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Cosmology and Nongalactic Astrophysics
The art of simulating the early Universe. Part III: Scalar-Gauge-Fluid Dynamics
Daniel G. Figueroa, Kenneth Marschall, Antonino S. Midiri et al. (+1 more)
We discuss
lattice methods for the simulation of fluid dynamics in the early Universe. This review represents a third entry in the monographic series on
lattice cosmology techniques~\cite{Figueroa:2020rrl,Baeza-Ballesteros:2025tme}, which previously covered canonical and non-canonical field theory dynamics. Here, we first review the continuum theory of fluid dynamics in flat spacetime, and then in an FLRW background. We consider conservation and non-conservation forms of the equations of motion for fluids in isolation or coupled to scalar and/or gauge fields, and either fully relativistic or subrelativistic regimes of fluid bulk motion. After reviewing basic
lattice concepts, we introduce detailed discretization schemes for fluid dynamics in expanding backgrounds for: $i)$ isolated perfect fluids, $ii)$ isolated imperfect (viscous) fluids, $iii)$ fluids coupled to gauge fields, and $iv)$ fluids coupled to scalar fields. Our
evolution algorithms accommodate self-consistent expansion sourced by all scalar, gauge, and fluid sectors, preserving gauge invariance to machine precision in some cases. We also review
lattice methods to set up the initial conditions for fluids, and the implementation of gravitational wave dynamics sourced by all scalar, gauge, and fluid degrees of freedom. This document represents the theoretical basis for the scalar-gauge-fluid module that will be publicly released as part of ${\mathcal C}{\tt osmo}{\mathcal L}{\tt attice}~{\tt v3.0}$ after publication of this monograph, check http://www.cosmolattice.com for updates.
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All authors Daniel G. Figueroa, Kenneth Marschall, Antonino S. Midiri, Alberto Roper Pol
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-th
Quantum Field Theory Of Cosmological Perturbations Induced By Ultralight Dark Matter
Tomislav Prokopec and Marco Vecchioni
The growth of
primordial perturbations during the matter-dominated era is primarily driven by dark matter. Ultralight scalar fields (ULDM) are a promising candidate for this role, conventionally modeled as operating in a classical, high-occupation regime. In this work, we develop a first-principles field-theoretic framework to investigate the impact of ULDM on linear cosmological perturbations during matter domination, explicitly retaining its
quantum nature. Deriving a closed equation for the graviton field dynamics, we compute and regularize its source terms for a generic Gaussian initial state of the ULDM field within the adiabatic (WKB) approximation, employing the middle-point working assumption for non-local terms. After gauge-fixing we find that, contrary to previous claims, the classical condensate of ULDM has no influence on gravitational wave propagation. However, the time-dependent graviton effective mass induced by
quantum pressure of the squeezed state can drive parametric resonance in specific
primordial gravitational wave modes. We demonstrate this growth is negligible for non-relativistic ULDM at matter-radiation equality under the assumption of a power-law squeezing spectrum for masses in the range $m \sim 10^{-21}{-}10^{-24}$ eV.
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Astrophysics of Galaxies
J-ATLAS: Javalambre Andromeda and Triangulum Legacy Astrophysical Survey
Borja Anguiano and Andres del Pino
The outskirts of nearby
galaxies preserve long-lived signatures of hierarchical assembly and provide a fossil record of
galaxy formation. J-ATLAS, the Javalambre Andromeda and Triangulum Legacy Astrophysical Survey, is a proposed wide-field optical photospectroscopic survey of the M31–M33 system with JST/T250 and JPCam. Using the dense J-PAS filter system, it will deliver homogeneous low-resolution optical SEDs for resolved
stars, compact
stellar systems, emission-line sources, and background objects across the nearest massive spiral-
galaxy environment visible from the northern sky. The survey will map disks,
halos, streams, satellites, and the intergalactic region, constraining
stellar populations, photometric
metallicities, carbon-rich evolved
stars,
star clusters, planetary nebulae, and low-surface-brightness substructure. We also present the ongoing pilot survey, centred on the
Giant Southern Stream and Andromeda~I, whose 92 complete pointings are being analysed to validate crowded-field photometry, calibration, source classification, and photometric
metallicity diagnostics before extending the methodology to the full J-ATLAS footprint survey.
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Instrumentation and Methods for Astrophysics
High-speed, low-noise, multi-megapixel CCDs for next generation X-ray observatories
Haley R. Stueber, Tanmoy Chattopadhyay, Peter Orel et al. (+17 more)
Next generation X-ray observatories require fast, low-noise, low-power, multi-megapixel imaging spectrometers. To meet these demands, the X-ray Astronomy and Observational Cosmology (XOC) Group at Stanford, in partnership with the MIT Kavli Institute and MIT Lincoln Laboratory (MIT-LL), is developing multi-channel X-ray charge-coupled devices (CCDs) and fast readout architectures. We report the energy resolution and noise performance achieved with a full-scale (1440x1440-pixel), 16-channel, front-illuminated MIT-LL CCD detector developed for the Advanced X-ray Imaging Satellite (AXIS) concept, the CCID-100, read out using two Multi-Channel Readout Chip (MCRC) V1 application-specific integrated
circuit (ASIC) chips in the new Stanford CCID-100 test setup. We describe an automated method for bias optimization on each CCD channel, and integrated debugging features of the front-end ASIC and readout system. The demonstrated performance confirms that these systems can meet the speed and noise requirements of future strategic X-ray missions.
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All authors Haley R. Stueber, Tanmoy Chattopadhyay, Peter Orel, Steven W. Allen, Marshall W. Bautz, Michael Cooper, Kevan Donlon, Catherine E. Grant, Sven Herrmann, Jill Juneau, Beverly J. LaMarr, Christopher Leitz, Eric D. Miller, R. Glenn Morris, Declan O'Neill, Abigail Y. Pan, Tonya L. Peshel, Artem Poliszczuk, Gregory Y. Prigozhin, Keith Warner
High Energy Astrophysical Phenomena
Braking indices as probes of r-mode spin-down in young pulsars
Shahram Abbassi, Armin Memarian, Evelyn Sophia Guest et al. (+1 more)
We present a timing-based framework for interpreting braking-index measurements in young
pulsars using a four-channel
spin-down model that includes particle-wind,
magnetic-dipole, mass-quadrupole, and current-quadrupole torques. The observed braking index is a torque-weighted average of the channel exponents, enabling equation-of-state-independent constraints on the torque fraction of a possible r-mode-like current-quadrupole component from timing data alone. For positive, slowly varying secular torques, the allowed range is (1\le n_obs\le 7), with (f_{7,\min}=\max[0,(n_obs-5)/2]) and (f_{7,\max}^phys=\min{1,\max[0,(n_obs-1)/6]}). These bounds rely on non-negative, slowly evolving torque coefficients; if these assumptions fail, a large braking index need not uniquely indicate a current-quadrupole torque. Applied to young
pulsars with measured braking indices, the analysis shows that most sources do not require gravitational-wave
spin-down and are consistent with wind-plus-dipole braking. Sources with (3<n_obs<5) require an additional higher-order contribution, but timing alone cannot identify it uniquely as an r-mode torque. PSR~J0537$-$6910 is the most suggestive case: its large inter-glitch braking index approaches the (n\simeq7) limit and is consistent, within the restricted secular model, with a strong current-quadrupole-like contribution. However,
vortex-creep and superfluid-recovery effects may produce similar inter-glitch behaviour without gravitational-wave emission. We also derive
stellar-model-dependent r-mode amplitude bounds, braking-index-corrected ages, and continuous-wave ranking metrics for current and future detectors, including the reduced sensitivity expected for glitch-limited semi-coherent searches.
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All authors Shahram Abbassi, Armin Memarian, Evelyn Sophia Guest, S.R. Valluri
High Energy Astrophysical Phenomena
Universality of dual mass-scaled fundamental modes in two-fluid neutron stars with mirror dark matter
Hajime Sotani and Ankit Kumar
Universal relations provide a particularly useful way to extract physical information from
neutron star observables in the presence of various uncertainties by reducing the dependence on uncertain model parameters and microphysical inputs. In this study, we examine the oscillation frequencies of mirror dark matter admixed
neutron stars using a two-fluid description, where the outer and inner fluids give rise to two distinct fundamental frequencies. We confirm that the universal relation between the mass-scaled fundamental frequency of the outer-fluid-led mode and the
stellar compactness, established previously for self-interacting dark matter admixed
neutron stars, also holds in the mirror dark matter scenario. However, this universal relation becomes less robust when metric perturbations are included, compared with the corresponding results in the Cowling approximation. We further find that the inner-fluid-led fundamental frequency can also be expressed as a compactness-dependent relation that is largely independent of the normal matter equation of state, provided that the dark matter mass fraction is fixed. These results suggest that the simultaneous detection of the two fundamental frequencies could provide a way to constrain the dark matter mass fraction, even when the equation of state of normal matter remains uncertain. Finally, we find that the Cowling approximation estimates the fundamental frequency associated with the outer fluid with an accuracy comparable to that found for standard
neutron stars without dark matter, while it performs even better for the frequency associated with the inner fluid.
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Astrophysics of Galaxies
Constraining the shape of dark matter haloes using only starlight II. Tests of the technique with objects of known gravitational potential
Jorge Sanchez Almeida, Angel R. Plastino, Sergio Guerra Arencibia et al. (+2 more)
Under the collisionless cold dark matter (CDM) paradigm,
galaxies with
stellar masses below 10**(5-6) Msun are expected to preserve
primordial cuspy dark matter (DM) profiles. Because baryonic feedback should be too weak to transform cusps into cores at these masses, such
galaxies provide especially sensitive tests of DM physics. If cores are observed in these systems, they could indicate departures from CDM. To address this problem, Sanchez Almeida et al. (2025) introduced the Eddington Inversion Method tool (EIM-tool), a photometry-based diagnostic that avoids the need for long-term spectroscopic observations and is suitable for the analysis of the forthcoming large photometric surveys of
galaxies. The method relies on the fact that
embedding a
stellar distribution with a central core inside a cuspy NFW
halo can require a negative phase-space distribution function f, which is physically impossible. By fitting observed
stellar surface densities using f as a free parameter, EIM-tool tests whether an assumed gravitational potential is physically consistent with an observed
stellar distribution. This paper validates EIM-tool using globular clusters,
dwarf spheroidal
galaxies (dSphs), and numerical simulations with independently known potentials. Applied to 21 globular clusters, the method rejected NFW cusps in 71% of cases while consistently favoring cored Schuster-Plummer models, accurately recovering expected core radii. Applied to dSphs, EIM-tool reproduced conclusions from classical dynamical studies: Sculptor and Fornax favored cored
halos, whereas Draco remained compatible with a cusp. Tests on EDGE and FIRE simulations further showed that the tool reliably rejects cuspy NFW profiles when the true DM distribution is core-like. Overall, these results establish EIM-tool as a robust and efficient photometric method for distinguishing cored and cuspy DM
halos.
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All authors Jorge Sanchez Almeida, Angel R. Plastino, Sergio Guerra Arencibia, Nitya Kallivayalil, Jack T. Warfield
Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
On a cosmological Oppenheimer-Snyder model: matching McVittie and FLRW spacetimes
Brien C. Nolan
We consider the necessary and sufficient conditions for the smooth matching of an expanding McVittie spacetime and a spatially flat Friedmann-Lemaître-Robertson-Walker (FLRW) spacetime across a general hypersurface - that is, a hypersurface of arbitrary causal character, where the character possibly changes from point to point. We identify a number of special cases, and determine some no-go results. In the general case, we show that the full set of matching conditions is equivalent to a 3-dimensional non-linear system of first order ODEs, subject to a single initial value constraint. Taking the perspective that the McVittie region is specified, we prove a semi-global existence result for this system and interpret these solutions in terms of the physical set-up. Solutions exist and are unique globally to the future. In this direction, the required FLRW spacetime exists and is unique and the matching hypersurface exists almost everywhere and is unique. To the past, the matching hypersurface extends to meet the past singularity of the McVittie region. We determine the causal character of the matching hypersurface in these limits, and consider the implications for the existence (or otherwise) of an isotropic source of the McVittie cosmological black hole spacetime. We find that generically, the matching hypersurface has spacelike as well as timelike portions, and so the isotropic region cannot be considered to be an interior for the McVittie exterior. This is in distinction to the Oppenheimer-Snyder model, in which an isotropic
dust sphere matches across an everywhere-timelike boundary to the Schwarzschild exterior. On the basis of the sometimes-spacelike nature of the hypersurface, we conclude that an isotropic source of the McVittie spacetime does not exist in a global sense.
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Instrumentation and Methods for Astrophysics
Dish Assembly Precision for HIRAX
Jennifer Studer, Devin Crichton, Alexandre Refregier et al. (+16 more)
The Hydrogen Intensity and Real-time Analysis eXperiment (HIRAX) is a
radio interferometer array that is being deployed at the South African
Radio Astronomy Observatory (SARAO) Square Kilometer Array (SKA) site in South Africa. Mapping the southern sky, its aim is to observe neutral hydrogen (HI) through intensity mapping (IM) across the
redshift range of 0.78-2.55. The observation of HI makes it possible to tomographically probe large cosmological volumes, enabling constraints on, for example, the dark energy equation of state. Systematics are a significant concern in deriving cosmological constraints from HI IM due to the presence of strong foreground signals. Instrumental effects such as dish surface deviations and feed placement errors need to be carefully controlled and monitored to preserve the sensitivity of HIRAX's redundant array configuration. These instrumental systematics cause bright foreground power to leak into the faint cosmological signal. The 6 m
parabolic dishes are made from fiberglass with an embedded aluminum mesh that acts as the reflector. The feed is held in place at the
prime focus (f/D = 0.21) by four fiberglass legs. This paper presents the dish surface and feed placement precision of the first 28 dishes, derived from photogrammetry metrology measurements taken during the dish fabrication, as well as from measurements in the field. While surface deviations are predominantly well within requirements, feed placement satisfies all accuracy criteria but fails precision limits; however, precision is expected to improve with a larger sample size. These results establish a baseline for modeling primary beam effects, ultimately enabling the characterization and mitigation of systematic errors in the HI IM signal with the full HIRAX array.
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All authors Jennifer Studer, Devin Crichton, Alexandre Refregier, Keshav Bechoo, H. Cynthia Chiang, Chandrachud B. V. Dash, Sindhu Gaddam, Aditya Krishna Karigiri Madhusudhan, Martin Kunz, Kavilan Moodley, Warren Naidoo, Tasmiya Papiah, Isibabale Qhoboshiyane, Liantsoa F. Randrianjanahary, Benjamin R. B. Saliwanchik, Ajith Sampath, Corrie Ungerer, Thierry Viant, Anthony Walters
Solar and Stellar Astrophysics
Constraints from parallaxes and average period spacings in the asteroseismic study of 8 DAVs
Agnès Kim and Keaton J. Bell
With space missions such as Kepler, TESS, and
Gaia, we have a wealth of data on pulsating white
dwarfs that can be leveraged in white
dwarf asteroseismology. We address the question of the proportion of white
dwarfs with thin hydrogen layers versus those with thick hydrogen layers. We also provide a mass-radius relation for carbon-oxygen core, hydrogen atmosphere white
dwarfs. Such a relationship can be used in conjunction with magnitudes and distance measurements to constrain the mass and effective temperature of the white
dwarfs. We select eight hydrogen atmosphere, pulsating white
dwarfs (DAVs), for their rich pulsation spectra. From such pulsation spectra, we can derive an asymptotic period spacing, which in turn allows us to determine the thickness of the hydrogen and helium envelope of the models, without having to perform period by period fitting. We find that the majority of the white
dwarfs have thicker hydrogen layers and determine an upper limit of Mr = 1 - 10 to the -2.2 for the location of the base of the helium layer, in accordance with
stellar evolution models. We confirm a finding from earlier studies that used a mass-radius relation and
Gaia data to determine the effective temperatures of white
dwarfs. The
Gaia data systematically points to white
dwarfs of lower effective temperature than indicated by the spectroscopy. Our results also support the hypothesis that white
dwarfs with thicker hydrogen layers are more common than those with thinner layers.
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Instrumentation and Methods for Astrophysics
Characterization and on-sky testing of photonic, AWG-based astronomical spectrographs
Jeronimo Calderon-Gomez, Frantz Martinache, Nick Cvetojevic et al. (+14 more)
Astrophotonics is a field that intends to meet the needs of next-generation instruments at a small footprint, low cost, and high stability, compared to bulk-optics-based alternatives. Much development effort is driven by the stringent requirements of direct detection and characterization of
exoplanets. Our team works in characterizing Arrayed-Waveguide Grating (AWG) chips for photonics-based, high-resolution, near infrared spectro-interferometry. AWG spectrographs allow to test the feasibility of photonic spectro-interferometers for
exoplanet characterization, another step towards fully photonic instruments for astronomy. We present the current status of our AWG characterization and a preliminary on-sky qualification campaign at the PAPYRUS AO system. We present the CoLiBRIS-AWG spectrograph prototype built for on-sky testing, and preliminary results using our high-resolution (H band, R~18000) AWG for observations of Arcturus (alpha Boötes) and Betelgeuse (alpha Orionis). This work contributes to assessing the capabilities of photonic spectroscopy for the development of future compact instruments.
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All authors Jeronimo Calderon-Gomez, Frantz Martinache, Nick Cvetojevic, Marc-Antoine Martinod, Vincent Foriel, Nemanja Jovanovic, Pradip Gatkine, Gregory Sercel, Alexis Carlotti, Marc Ferlet, Matteo Pasinetti, Angelie Alagao, Arnaud Striffling, Guillermo Martin, David Mary, Roxanne Ligi, Sylvie Robbe-Dubois
Cosmology and Nongalactic Astrophysics
An efficient one-loop EFTofLSS framework for Vainshtein-screened Horndeski gravity
Stan Verhoeve, Dani de Boe, Gen Ye et al. (+1 more)
We present an extension of PyBird for one-loop large-scale structure analyses of modified
gravity models. We implement support for quasi-static, Vainshtein-screened luminal Horndeski models (in EFTofDE and covariant formalisms) and nDGP, and replace the Green's function approach with a direct ODE method for computing the exact time-dependent functions entering the perturbation kernels. The new implementation improves computational efficiency while maintaining numerical consistency with the standard approach, and we validate the resulting one-loop matter power spectrum against $N$-body simulations for the $\alpha_i\propto\Omega_{\rm DE}$ parametrization. We apply this framework to constrain the $\alpha_i \propto a^3$ and $\alpha_i \propto \Omega_{\rm DE}$ parametrizations using Planck CMB, BOSS full-shape, and DESI DR2 BAO data, finding that full-shape information significantly tightens the constraints. We further showcase the pipeline for the cubic Galileon and nDGP models, demonstrating its applicability beyond the phenomenological amplitude parametrizations to covariant modified-
gravity theories. Finally, we assess the impact of the Einstein–de Sitter approximation and find that exact time dependence can be retained at modest computational cost, which may become relevant for future large-scale structure surveys.
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All authors Stan Verhoeve, Dani de Boe, Gen Ye, Alessandra Silvestri
Cosmology and Nongalactic Astrophysics
J-PAS & FLAMINGO: Cosmic voids and void galaxies in the gravitational landscape of photometric surveys
J.A. Mansour, B. McCarthy, L. J. Liivamägi et al. (+34 more)
Photometric surveys offer a powerful way to map the large-scale structure of the Universe, but their
redshift errors complicate the identification of
cosmic voids, challenging studies of their environmental effect on
galaxy properties. We present an approach to robustly identify dynamically relevant voids and void
galaxies in
galaxy mocks of the Javalambre Physics of the Accelerating Universe Astrophysical Survey (J-PAS), testing whether known trends in void
galaxy properties survive photometric
redshift errors. Using FLAMINGO mocks at z = 0.3 and mi < 20, we compare a FLAMINGO-based ideal (FBI) mock to a FLAMINGO-based JP mock with J-PAS-like
redshift errors. We mitigate
redshift errors using a quasi-gravitational potential field in the two
galaxy mocks. We apply a watershed
algorithm to the thresholded quasi-potential field to identify dynamically dominant voids, and define massive void
galaxies alongside a comparison sample in high-density regions. Photometric errors lead to a slightly lower void abundance and a marginal shift toward larger, less spherical voids, but overall size and ellipticity distributions agree well between mocks. Their main impact is contamination of void interiors in the JP density profiles by
galaxies scattered from high-density regions. We recover a reasonable number of FBI sample voids in the JP sample, with excellent size and shape agreement, occupying ~63% of the thresholded quasi-potential volume. In both mocks, void
galaxies show lower
stellar masses, bluer colours, and enhanced
star formation relative to equal-mass
galaxies in high-density regions. These results suggest a quasi-potential can mitigate
redshift errors at the level expected for J-PAS, enabling identification of reliable, dynamically dominant voids that are less sensitive to small-scale noise. The massive void
galaxy population shows the expected trends relative to high-density environments.
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All authors J.A. Mansour, B. McCarthy, L. J. Liivamägi, A. Tamm, R. van de Weygaert, J. Laur, E. Tempel, M. Einasto, P. Heinämäki, J. Schaye, M. Schaller, R. Abramo, A. Hernán-Caballero, V. Marra, J. Alcaniz, N. Benitez, S. Bonoli, S. Carneiro, J. Cenarro, D. Cristóbal-Hornillos, S. Daflon, R. Dupke, A. Ederoclite, Rosa M. González Delgado, C. Hernández-Monteagudo, J. Liu, C. López-Sanjuan, A. Marín-Franch, C. M. de Oliveira, M. Moles, F. Roig, L. Sodré Jr, K. Taylor, J. Varela, H. Vázquez Ramió, J. Vilchez, J. Zaragoza-Cardiel
Solar and Stellar Astrophysics
Evolutionary variations of superficial iron and calcium abundance in main sequence A stars
Yu.A. Fadeyev and R.M. Bayazitov
Main sequence
stellar evolution models were computed together with solution of the equations of atomic
diffusion for 16 elements from hydrogen to nickel. The grid of evolutionary tracks comprises the models with
stellar masses ranged from 1.4 to $2.5M_\odot$ computed for initial helium and metal abundances $Y=0.28$ and $Z=0.02$, respectively. The calculations were done for the mass loss rates $10^{-15}M_\odot/\textrm{yr}\le\dot M\le 10^{-12}M_\odot/\textrm{yr}$ as well as for $\dot M=0$. The high superficial abundance of iron in Am
stars is shown to be due to the radiative acceleration acting on the atoms of iron. The significantly smaller absorption coefficient of calcium is responsible for its gravitational settling and accumulation above its opacity maximum at $T\sim 10^6\:\textrm{K}$. Recover of the superficial calcium abundance is due to plunge of the outer convection zone bottom to layers with its excessive abundance. A significant role in the evolutionary variations of superficial abundances of chemical elements belongs to the intermediate convection zone arising for the first $\lesssim 300$ Myr due to accumulation of the atoms of iron and nickel in the layers with temperature $T\sim 2\times 10^5\:\textrm{K}$. In
stars with mass $M\le 1.9M_\odot$ both the outer and intermediate convection zones merge due to evolutionary descend of the bottom of the outer convection zone so that overabundant iron and nickel are transported to the outer layers by convection. The merging of the convective zones is responsible for considerable variations of superficial abundances of calcium and iron with duration ranging from a quarter to a half of the main–sequence lifetime depending on the
stellar mass. Therefore, Am
stars as well as slowly rotating nonmagnetic A main–sequence
stars have the common origin, whereas appearance of their chemical anomalies depend of the
stellar mass and age.
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Cosmology and Nongalactic Astrophysics
Impact of numerical stability in Bayesian noise wave calibration on global 21-cm experiments
Saswata Dasgupta, Adarsh Kumar Dash, Dominic Anstey et al. (+3 more)
Detecting the global 21-cm signal from the
Cosmic Dawn and Epoch of Reionization requires calibration accuracy far below the level of astrophysical foregrounds. REACH models its receiver using the noise wave formalism, with five frequency-dependent low-noise amplifier parameters fitted jointly to multiple calibration sources. We identify a numerical instability in this
Bayesian calibration pipeline: the condition number of the posterior covariance
matrix reaches $\kappa(\mathbf{V}^*) \sim 10^{9}$–$10^{11}$, making solutions non-reproducible across computing environments. Singular value decomposition shows that the instability is driven by near-collinearity between the design-
matrix columns associated with the excess noise source temperature, $X_\mathrm{NS}$, and the load temperature, $X_\mathrm{L}$. Using a Chebyshev basis, we develop a two-step mitigation. First, fixing $T_\mathrm{NS}$ to a scalar removes the degeneracy and reduces $\kappa(\mathbf{V}^*)$ to $\sim 60$. Second, to retain frequency dependence, we recover $T_\mathrm{NS}(\nu)$ directly from the hot-load calibration measurement. On mock data, this method preserves the stability of the reduced model while achieving comparable calibration accuracy. Masking narrow channels around cable standing-wave degeneracies further removes local artefacts in the design
matrix. These steps provide a stable, reproducible, and data-driven calibration procedure. Because the $X_\mathrm{NS}$–$X_\mathrm{L}$ degeneracy is inherent to the noise wave formalism, the method is relevant to other global 21-cm experiments.
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All authors Saswata Dasgupta, Adarsh Kumar Dash, Dominic Anstey, Harry T. J. Bevins, Christian Kirkham, Eloy de Lera Acedo
High Energy Astrophysical Phenomena
Outflow Behavior from the Transonic Advective Disks: A Hydrodynamical Simulation Study
Sanjit Debnath, Indranil Chattopadhyay, Raj Kishor Joshi et al. (+3 more)
We investigate the properties of
outflows from the transonic advective
accretion disk using hydrodynamical numerical simulations. We consider two different disk temperatures with an order-of-magnitude difference. For the hotter disk, we adopt initial conditions for velocity, specific angular momentum, and temperature from analytical solutions. In the colder disk case, the velocity and angular momentum profiles are kept identical, while an order of magnitude reduction in the temperature. The simulations are performed in the presence of viscosity and radiative cooling, considering bremsstrahlung and synchrotron processes. In both disk models, the
outflow rate increases with viscosity. We also examine the poloidal velocity structures for both cases. We analyze the influence of viscosity on the mass flux-weighted energy and momentum fluxes of the
outflows. Our results show that both energy and momentum fluxes increase with higher viscosity and may play a significant role in
accretion feedback mechanisms.
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All authors Sanjit Debnath, Indranil Chattopadhyay, Raj Kishor Joshi, Philippe Laurent, Priyesh Kumar Tripathi, M. Saleem Khan
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Revising Indirect Dark Matter Constraints with Updated Astrophysical $J$-Factor Priors
Giacomo D'Amico
Indirect searches for particle dark matter with gamma-ray experiments have produced a large number of constraints on the annihilation cross section (or decay lifetime) over a wide range of dark matter masses. These constraints depend critically on the assumed astrophysical $J$ factor and its uncertainty, which encodes the dark matter distribution in the target and represents the dominant source of systematic uncertainty. As improved observational data and dynamical modeling are expected to revise current $J$-factor determinations, many published limits risk becoming obsolete unless the full experimental analyses are repeated. In this work we present a general and statistically consistent framework for updating published dark matter limits when revised $J$-factor estimates become available, without requiring access to the full experimental likelihood. We derive an analytical expression that quantifies the impact of astrophysical uncertainties on dark matter limits, treating both Gaussian and log-normal priors on the $J$ factor. The formalism is validated through toy Monte Carlo simulations, including dedicated studies of its numerical stability under successive reinterpretations, and demonstrate their accuracy by reproducing published limits. Lastly, we further show that the formalism naturally extends to the combination of multiple targets through a simple numerical procedure, allowing limits to be combined and updated using only publicly available information. The proposed method is intended as a complementary reinterpretation tool for situations in which a complete experimental reanalysis is impractical, offering a practical means to preserve and extend the scientific relevance of published dark matter constraints across present and future experiments.
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Solar and Stellar Astrophysics
eROSITA all-sky survey - stars and optical loading
J. Robrade, K. Dennerl, M.J. Freyberg et al. (+1 more)
eROSITA (extended ROentgen Survey with an Imaging
Telescope Array) on board the Spectrum-Roentgen-Gamma (SRG) spacecraft has performed the eROSITA All-Sky Survey (eRASS) at X-ray energies. We study the brighter
stars to assess the impact of optical loading in the eROSITA all-sky survey, here specifically the eRASS:3. Further we use thermal
plasma models to investigate the general properties of
stellar eRASS sources and compare optical loading affected
stars to coronal sources. We compare data from
Gaia DR3, Tycho-2, 2MASS and the SIMBAD database with the eRASS count rates of brighter
stars. We analyze X-ray images, light curves and spectra for sources suspected to be affected by optical loading and determine their properties. eROSITA source properties are checked in comparison to genuine coronal sources with generated sets of APEC model spectra, where we determine rate conversion factors and hardness ratios for
stellar X-ray emitter. Regarding optical loading we find a clear correlation between optical brightness and observed minimum count rate in the range of about 2\,–\,5 mag (V/G band), which then saturates for very bright sources. While magnitude and color are the main determinants, exposure depth and specific scanning paths also matter. For intrinsic X-ray emitters, optical contamination is likewise observed. We characterize the fake X-ray sources, address pseudo variability and spectral properties. To interpret
stellar eRASS data, hardness ratios and count rate conversions for thermal
plasma models are provided. The eROSITA data is prone to optical loading, which was studied in greater detail. The optical loading flag for the DR2 is set, if sources are brighter than 5.0~mag (B, V, G) or 3.5~mag (J). It is somewhat dependent on exposure depth, but we expect only minor changes for future data releases.
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All authors J. Robrade, K. Dennerl, M.J. Freyberg, J.H.M.M. Schmitt
High Energy Astrophysical Phenomena
Paleodetectors for neutrino signals from diverse Galactic stellar collapses
Mahiro Yamasaki and Ken'ichiro Nakazato
The detectability of
neutrinos from past
Galactic core collapse
supernovae (SNe) is investigated in terms of
nuclear recoil tracks in ancient minerals, known as paleodetectors. To account for the diversity of core-collapse outcomes, variations in
neutron star (NS) masses as well as failed SNe leading to black hole (BH) formation are taken into account. The role of the
nuclear equation of state (EOS) is also considered, as it determines NS radii and maximum masses. The enhancement of sensitivity is quantified for models with larger
neutrino emission. This emission reflects the gravitational energy released during core collapse and is larger for more compact remnants in the NS-forming case and for EOS with larger maximum masses in the BH-forming case. Furthermore, motivated by the hypothesis that nearby SN activity may have contributed to the snowball Earth events, the sensitivity to SNe occuring in a burst-like manner is also investigated. The results indicate that burst-like SN activity involving several tens of events at a distance of 10 pc would be within the reach of paleodetectors.
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Instrumentation and Methods for Astrophysics
Optimizing the extraction of information from redshift probability distribution functions
Rodrigo Duarte and Valerio Marra
Photometric
redshifts are essential for large-scale structure analyses, yet extracting optimal point estimates and reliability measures from the probability distribution functions (PDZs) delivered by photo-$z$ pipelines remains an open challenge. We introduce turboPDZ, a machine-learning framework that optimizes both quantities directly from the PDZ. We apply the framework to PDZs from the three independent HSC-SSP PDR3 pipelines (DEmP, DNNz, Mizuki) across Wide and DUD layers. Each PDZ is compressed via PCA and combined with summary descriptors; a multilayer perceptron, optimized with Optuna under a composite objective, produces the optimized point estimate $z_{\rm ml}$. A second network, trained in log-space and calibrated, yields the uncertainty $\sigma_{\rm ml}$, from which the reliability score $r_{\rm ml}$ is derived via percentile ranking. $z_{\rm ml}$ outperforms the catalog $z_{\rm best}$ in $\sigma_{\rm NMAD}$ and $\eta_{0.15}$ across all six pipeline-layer combinations. $r_{\rm ml}$ filters
galaxies more efficiently than the catalog risk and confidence indicators, as measured by the area under the $\sigma_{\rm NMAD}$ and $\eta_{0.15}$ versus retained-fraction curves. For Mizuki, the template-fitting pipeline, the catalog indicators fail dramatically, with AUC values up to ten times larger than those of $r_{\rm ml}$, whereas $r_{\rm ml}$ correctly identifies unreliable objects across all
redshift regimes. Feature-importance analysis reveals complementary patterns: point estimation is dominated by PCA components and location statistics, while reliability estimation depends on PCA components and peak statistics. The pipeline is survey-independent, publicly available at https://github.com/valerio-marra/turboPDZ, and trained models plus optimized quantities are released as a value-added catalog.
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