Cosmology and Nongalactic Astrophysics · Cross-listed from gr-qc
Inflation driven by repulsive-like primordial black holes
Konstantinos Dialektopoulos, Theodoros Papanikolaou and Vasilios Zarikas
We review a new natural inflationary mechanism operated by repulsive-like
primordial black holes (PBHs). In particular, working within the “Swiss - Cheese" cosmological framework, we find that a Universe filled with PBHs, whose spacetime metric presents a repulsive-like behaviour, is characterised by an early quasi-de-Sitter
cosmic expansion phase. Notably, for light PBHs with $m < 5 \times 10^8 \mathrm{g}$, evaporating before Big Bang Nucleosynthesis (BBN), one is met with an exponential inflationary phase with graceful exit and reheating proceeding through PBH evaporation. Furthermore, one finds as well that PBHs with $m \sim 10^{12}\mathrm{g}$ and abundances $0.107 < \Omega^\mathrm{eq}_\mathrm{PBH} < 0.5$ near matter-radiation equality can act as an early dark energy component, easing in this way naturally the Hubble tension.
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Earth and Planetary Astrophysics · Cross-listed from physics.chem-ph
Novel Chemical Pathways for the Formation of Nucleobase Precursors via Benzene {\pi}-Bond Addition to HCN
Jeehyun Yang, Danica J. Adams, Renyu Hu et al. (+1 more)
We propose a simple and efficient pathway for the formation of precursors to core nucleobases in DNA and RNA using a suite of computational chemistry methods. Benzene, which is thermochemically stable in N2- or CO2-dominated atmospheres, could have formed via upper-atmospheric photochemistry or surface lightning and accumulated on the early Earth or Mars. However, nitrogen insertion into the benzene ring to form pyrimidine and purine is widely considered to be challenging. We propose that nitrogen incorporation occurred through HCN 1,4-cycloaddition to benzene's {\pi}-system, followed by a C2H2 fragmentation mechanism, as confirmed by
quantum chemistry calculations. This pathway, potentially facilitated by photochemistry at the ocean surface or episodic impact events on local reservoirs, can lead to pyrimidine formation, which can further react with NH3 and HCN to produce purine. Extending this pathway to early Mars, our photochemical model simulates heterocyclic compound formation under cold, dry surface conditions that favor high benzene and HCN concentrations but lack
liquid water. We thus propose that organics formed during dry phases may have later dissolved into surface waters during wet phases and become concentrated as ocean sediments. This result supports Mars Sample Return efforts focused on ancient aqueous environments likely to retain prebiotic signatures.
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All authors Jeehyun Yang, Danica J. Adams, Renyu Hu, Yuk L. Yung
Astrophysics of Galaxies
Unique photometric variability in SDSS J134628.62+173659.5: clues for moving dust clouds as physical origin of changing-look AGN
Zhang XueGuang
The scenario of variations in accreting process around central black hole has been widely accepted as the preferred physical origin of changing-look active
galactic nuclei (CLAGN), rather than obscuration effects by moving
dust clouds. In this manuscript, after analyzing long-term photometric variability in Type-1.8 AGN SDSS J1346+1736 with apparent broad H$\alpha$ but very weak broad H$\beta$, robust clues for obscurations can be confirmed with confidence level higher than 10$\sigma$. Then, based on obscurations related to moving
dust clouds, from dark state with E(B-V)$\sim$1.26 to bright state with E(B-V)$\sim$0.55, apparent both broad H$\alpha$ and broad H$\beta$ can be clearly expected. Meanwhile, the expected line luminosity from reddening corrected continuum luminosity is consistent with the reddening corrected line luminosity, to support the obscuration effects. Furthermore, through symmetric features in the light curves, probability is only 3.2% in SDSS J1346+1736 to support the scenario of variations of
accretion rates traced by CAR process. Therefore, besides the more and more preferred scenario of variations in accreting process, the scenario of moving
dust clouds could be more reasonable in some CLAGN with apparent variations in optical colors.
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Solar and Stellar Astrophysics
Evolving Low- and Intermediate-Mass Binaries: Departures from Classical Theory
Lionel Siess
This review explores the physical mechanisms driving the
evolution of low- and intermediate-mass binary
star systems, with particular emphasis on emerging mechanisms that challenge classical paradigms. We begin by describing the principal formation channels and orbital properties of binary systems. A critical reassessment of the Roche lobe formalism is presented, focusing on systems with eccentric orbits and asynchronous rotation, where deviations from traditional approximations become significant. We then review current theoretical models of mass and angular momentum exchange via Roche-lobe overflow, incorporating results from recent hydrodynamical simulations of wind
accretion. The review also reports advances in
tidal dissipation theory. Finally, we explore mechanisms capable of sustaining or exciting orbital eccentricity, including perturbations induced by mass transfer and interactions with circumbinary disks. These discussions aim to outline underexplored facets of binary
evolution, offering new perspectives for theoretical and observational studies.
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Solar and Stellar Astrophysics
Parker Solar Probe Observations of Compound Reconnection Exhaust Boundaries and Mirror-Mode Structures in the Near-Sun Heliospheric Current Sheet
Weijie Sun, Tai Phan, Jia Huang et al. (+12 more)
Magnetic reconnection is a fundamental physical process that can drive rapid conversion of
magnetic energy into
plasma bulk flows, thermal heating, and particle acceleration in space and astrophysical
plasmas. Classical reconnection theory predicts that the Alfvenic reconnection exhausts are bounded by pairs of slow-mode shocks. However, identifying and characterizing these shocks through in situ spacecraft observations remains a challenge. Here we report Parker
Solar Probe (PSP) observations of a reconnection exhaust embedded in the heliospheric current sheet (HCS) at a heliocentric distance of 12.2 R_O. The reconnection exhaust is bounded on both boundaries by compound
magnetic structures rather than a pair of pure slow shocks. Each boundary consists of a rapidly evolving, steep inner slow shock, whose Mach numbers and shock-normal angles change significantly within several minutes, and an outer, gradual compound structure which comprises a slow shock and a rotational discontinuity. These slow shocks are quasi-perpendicular and are accompanied by enhanced
proton perpendicular heating. Deep within the reconnection exhaust, high perpendicular temperature together with large
plasma beta trigger mirror instability and generate mirror-mode structures. These observations provide new insights into the structure of reconnection exhaust boundaries and their role in energy conversion in the near-Sun
plasma.
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All authors Weijie Sun, Tai Phan, Jia Huang, Yi-Hsin Liu, James A. Slavin, Orlando Romeo, Mingzhe Liu, Vassilis Angelopoulos, Ali Rahmati, Davin Larson, Nehpreet Walia, Stuart Bale, Marc Pulupa, Jiutong Zhao, Roberto Livi
High Energy Astrophysical Phenomena
Label Propagation for Identifying Gamma-Ray Burst Progenitors from Prompt Emission
Skye Strain, Nicoló Cibrario, Michela Negro et al. (+1 more)
Gamma-ray bursts (GRBs) are the most energetic bursts of light in our universe, and rapid progenitor association of these events can lead to targeted and optimized follow-up observations, ultimately providing better insights about the physics involved. In this note, we investigate a semi-supervised machine learning
algorithm, that utilizes label propagation, as a classification method. Using a
dataset of 2512 GRBs we evaluate the method's ability to assign probabilistic class memberships based on a subset of events with known progenitors. Further analysis is ongoing to improve the method and future progress will be made to refine the classification
algorithm and the
dataset.
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All authors Skye Strain, Nicoló Cibrario, Michela Negro, Eric Burns
Instrumentation and Methods for Astrophysics
Charge diffusion and modulation transfer function in a Nancy Grace Roman Space Telescope detector
Emily Macbeth, Katherine Laliotis, Christopher M. Hirata et al. (+1 more)
The Nancy Grace Roman Space
Telescope (Roman) is an observatory motivated by the search to understand dark energy,
exoplanets, and general astrophysics. Roman will bring unprecedented amounts of precision to weak gravitational
lensing measurements, which necessitates an improved understanding of instrumental signatures in
star and
galaxy images. One feature is the modulation transfer function (MTF), which includes contributions from charge
diffusion in Roman's infrared detector arrays. As part of the detector characterization effort, a detector from the flight lots (but ultimately not selected for flight) was illuminated with a
laser speckle pattern. We present an analysis of the
laser speckle data, including MTF measurements in several wavelengths. We fit several models for the charge
diffusion profile, including: (i) a Gaussian profile; (ii) a
hyperbolic secant (sech) profile; and (iii) a general drift-
diffusion model that includes the Gaussian and sech as limiting cases. We find that the sech model produces an acceptable fit with no need for the additional parameter and is strongly preferred over the Gaussian. The standard deviation per axis of the sech profile is $0.3279^{+0.0043}_{-0.0042}$(stat)$\pm0.0093$(sys) pixels, with the systematic error dominated by non-linearities. We find no detectable wavelength dependence over the range from 850–2000 nm. The model informs survey strategy for weak
lensing measurements and has been included in simulations used to develop the data processing pipelines for the Roman mission.
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All authors Emily Macbeth, Katherine Laliotis, Christopher M. Hirata, Christopher Merchant
Cosmology and Nongalactic Astrophysics
Sensitivity of binary pulsar timing to spin-0 and spin-1 ultralight dark matter
Federico Huxhagen and Diana López Nacir
If dark matter consists of ultralight
bosons, on
galactic scales it can be effectively described as a coherent classical field experiencing oscillations. Such a field could perturb the dynamics of celestial bodies via a direct coupling to ordinary matter, introducing signatures detectable through high-precision
pulsar timing analysis. In this work, we extend a two-step
Bayesian inference framework, originally developed for linearly coupled scalar ultralight dark matter (ULDM), to probe a quadratic scalar coupling and
spin-1 vector dark matter. By explicitly marginalising over nuisance orbital parameters, our approach provides robust sensitivity limits that avoid the artificial overestimation often associated with direct fitting techniques. For quadratic scalar ULDM, we establish new constraints on the coupling $\beta$ for masses between $2 \times 10^{-22}$ eV and $2 \times 10^{-21}$ eV inaccessible to other experiments, while identifying mass regimes where the sensitivity is dominated by the orbital phase $\Psi'$ or the projected semi-major axis $x$. For vector ULDM, we characterize resonant signatures present even in circular orbits and obtain bounds on the coupling $g$ within the $10^{-23}$ eV to $10^{-18}$ eV range, yielding results within the same orders of magnitude as current laboratory and space-based experiments.
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Cosmology and Nongalactic Astrophysics
Cosmic-web Environmental Impacts on the Halo Substructure Boosts to Dark Matter Annihilation Signals
Feven Markos Hunde, Wojciech A. Hellwing and Maciej Bilicki
The annihilation of dark matter (DM) particles is expected to produce Standard Model particles, providing a potential indirect signature of DM. The clumpy substructure of DM
haloes amplifies the expected annihilation signal, an effect commonly quantified by the subhalo boost factor. Standard semi-analytic models usually treat this boost as a universal function of host-
halo mass, neglecting systematic variations induced by the large-scale environment. In this work, we extend this framework by incorporating the influence of the
cosmic web on subhalo populations. Using simulation-calibrated, environment-dependent ratios for host-
halo concentrations, the subhalo mass function, and internal-structure proxies of subhalos based on the $V_{\max}$–$R_{\max}$ relation, we compute environment-conditioned boost predictions for
haloes residing in filaments, walls, and voids. Our main result is the boost factor at fixed host-
halo mass, expressed relative to the
cosmic-mean prediction, $B(M,\mathrm{env})/B_{\mathrm{CM}}(M)$. We find a clear environmental modulation: in the fiducial distance-dependent model, filament
haloes show a mass-dependent transition from a $\sim 15\%$ suppression at the low-mass end to a modest enhancement of $\sim 12\%$ for massive hosts, wall
haloes remain intermediate, while void
haloes stay suppressed by roughly $30$–$33\%$ across the explored host-mass range. These results should be interpreted as deterministic model predictions obtained by propagating environment-dependent ingredient ratios through two standard semi-analytic boost frameworks. We provide an environment-aware prescription for subhalo boosts, together with modular environmental corrections that may also be useful in indirect-detection forecasts, strong-
lensing mass modeling, and related
halo-population applications.
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Astrophysics of Galaxies
Blueberry and Green Pea galaxies live in low density environments
Maitrayee Gupta, Jiří Svoboda, Konstantinos Kouroumpatzakis et al. (+3 more)
Little is currently known about the large-scale environments of Green Pea (GP) and Blueberry (BB)
galaxies, which are low-mass, compact systems with extreme specific
star-formation rates (sSFR). Their environments are inherently linked to their formation mechanism, and they may serve as crucial local analogues for high-
redshift, reionizing
galaxies. This paper aims to investigate the clustering properties of GPs and BBs, leveraging large-scale survey data to quantify their spatial distribution relative to the broader
galaxy population. We here investigate a sample of these
galaxies, consisting of 339 GPs $\rm (0.1 < z \le 0.33)$ and 56 BBs $\rm (0 < z \le 0.1)$, whose clustering properties we analyse relative to an extensive control sample derived from the SDSS MPA-JHU DR8 catalogue, binned by
stellar mass and sSFR. We use the number of neighbours within a 5 Mpc radius as a proxy for environmental density, i.e. clustering, and employ a pair-matching and bootstrapping methodology to ensure statistical robustness. We observe that
galaxy clustering depends strongly on
star-formation activity, with passive
galaxies being more clustered than their high
star-formation rate counterparts, with GPs and BBs lying at the extreme end of this relation, exhibiting the lowest neighbour counts among all subsamples. The nearest neighbours of BBs also tend to have lower masses than other classes of
dwarf galaxies. GPs and BBs predominantly reside in isolated, low-density environments, suggesting that their intense starbursts are unlikely to be triggered by common environmental processes such as mergers or starburst cycles. Their low
metallicities and weak clustering instead support scenarios in which recent starbursts are driven by internal processes or pristine gas
accretion, reinforcing their role as nearby analogues of young, low-mass
galaxies in the early Universe.
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All authors Maitrayee Gupta, Jiří Svoboda, Konstantinos Kouroumpatzakis, Nicolas Peschken, Peter G. Boorman, Abhijeet Borkar
Solar and Stellar Astrophysics
Brightenings AnD Polarity Inversion Tracking (BADPIT) method for studying solar active region evolution before major solar flares
Augustin André-Hoffmann, Marianna B. Korsós, Alexander Nindos et al. (+3 more)
This study investigates the relationship between extreme ultraviolet (EUV) transient brightenings (TBs) and the onset of GOES X-class
solar flares in active regions (ARs). We introduce the Brightenings AnD Polarity Inversion Tracking (BADPIT) method that detects TBs across multiple SDO/AIA channels. To identify TBs, we impose two independent thresholds: a 3-(sigma) intensity-based criterion and a power-law divergence approach. We apply the BADPIT method to
datasets of a flaring and a non-flaring AR for 24 hours as a pathfinder to a comprehensive statistical study for a complete performance verification: the
flare-productive AR 11429 and the quiescent AR 13186, both sharing a similar Hale sunspot classification. Preliminary results are encouraging: significantly more TBs are detected in the flaring AR, with up to five times more 3-(sigma) thresholded TBs, while power-law thresholded events were frequent only in the flaring AR and mostly absent in the non-flaring AR. We find that both the power-law threshold method and the 3-(sigma) method can be useful diagnostic tools for distinguishing between imminent flaring or not, several hours before the onset of major
solar flares.
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All authors Augustin André-Hoffmann, Marianna B. Korsós, Alexander Nindos, Spiros Patsourakos, Manolis K. Georgoulis, Robertus Erdélyi
Astrophysics of Galaxies
Exploring the gaseous halos of z>3 radio galaxies with UVES and JWST/NIRSpec
Jelena Ritter, Wuji Wang, Dominika Wylezalek et al. (+3 more)
High-
redshift radio galaxies (HzRGs) are among the most massive
galaxies in the Universe and sites of extreme active
galactic nuclei (AGN) feedback processes, powering energetic
radio jets. They are typically embedded in
giant Ly$\alpha$
halos that are known to extend over $100\,\text{kpc}$ into the circumgalactic medium (CGM). In this paper, we target the Ly$\alpha$
halos around four high-
redshift radio galaxies in a
redshift range of 3.1 < z < 4.5 using high-resolution spectroscopy from the Ultraviolet Echelle Spectograph (UVES) at the VLT, focusing on absorption features in the Ly$\alpha$ emission that trace neutral hydrogen (HI) systems. We compare the UVES data to Multi Unit Spectroscopic Explorer (MUSE) observations of the same targets and find that the higher spectral resolution of UVES ($\Delta v \approx 12\,\text{km} \text{s}^{-1}$) allows for a more complete identification of absorbers and reveals the splitting of deep absorbers into multiple components. We identify between 6 and 14 absorbers for each target in our sample with column densities of $N_{\text{HI}} = 10^{12}-10^{17}\,\text{cm}^{-2}$. About 70 % of the absorbers can be spatially resolved along the
radio jet axis, showing minimal variation in column densities over extents of more than 30 kpc. Our results indicate that a fraction of the absorbers may be physically associated with the host systems. Complementary JWST/NIRSpec observations of two of the targets, 4C+03.24 and TNJ0205, reveal potential
outflows in the ionized interstellar medium (ISM). We discuss a kinematic link between the [OIII]-emitting gas and the cool
halo gas as traced by Ly$\alpha$, suggesting a common
outflow origin.
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All authors Jelena Ritter, Wuji Wang, Dominika Wylezalek, Carlos De Breuck, Joël Vernet, Fabrizio Arrigoni Battaia
Cosmology and Nongalactic Astrophysics
Secondary Dependence of Baryonic Effects on the Density Profile of Dark Matter Halos
Yikun Wang, Idit Zehavi, Sergio Contreras et al. (+3 more)
Baryonic physics is anticipated to be a major source of systematic uncertainty in current and future large-scale cosmological surveys. We investigate how baryonic effects on
halo density profiles vary with secondary
halo properties at fixed
halo mass, using the large-volume MillenniumTNG hydrodynamical simulation and its dark matter-only counterpart. We focus on the impact of
halo concentration and large-scale environment on the ratio of density profiles of matched
halos in the hydrodynamical and dark matter-only simulations. At
redshift $z = 0.0$, we find a strong dependence on
halo concentration, especially at lower
halo mass ($12.5 < \log(M_h/h^{-1}M_{\odot}) < 13.0$), where more concentrated
halos exhibit weaker inner enhancement and stronger intermediate-radius suppression at fixed
halo mass, with variations reaching $\sim 15\%$ at small scales and decreasing toward larger scales. This trend weakens and reverses at higher
halo mass. In contrast, the secondary dependence on large-scale environment is weaker ($\sim 2\%$) and largely scale-independent, with
halos in denser regions exhibiting slightly weaker intermediate suppression. By separating internal profile redistribution from total mass suppression, we show that concentration impacts both components, whereas the environmental dependence is primarily associated with an overall mass shift. These secondary dependencies persist at $ z = 0.5$ and correlate with variations in internal baryonic properties. We examine additional
halo properties, including
halo spin and velocity dispersion, and find significant secondary dependence. Overall, our results highlight the important role of secondary
halo properties in modulating baryonic effects on
halo density profiles, with potential implications for future modeling efforts.
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All authors Yikun Wang, Idit Zehavi, Sergio Contreras, Giovanni Aricò, Sownak Bose, Lars Hernquist
Cosmology and Nongalactic Astrophysics
Kinematic Lensing Ratio: Reviving Weak Lensing Cosmography as a Geometric Dark Energy Probe
Qinxun Li
We introduce the kinematic
lensing ratio (KiLeR), a
geometric dark-energy probe from weak
lensing. Combining shear ratios with intrinsic
galaxy shapes inferred from kinematics, KiLeR naturally mitigates most first-order
lensing systematics, including
redshift errors, intrinsic
alignments, and baryonic effects. The forecast on Roman shows a 192% improvement in the state-of-the-art dark energy constraints from adding KiLeR, providing independent tests of the evolving dark energy hint in the DESI DR2 BAO+CMB+SN analysis. We quantify the science requirements on systematic and statistical error control and discuss the pathways towards KiLeR observation.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Pedro Dedin Neto, AmirFarzan Esmaeili, Guilherme A. Nogueira et al. (+2 more)
A millicharged
neutrino propagating through
magnetic fields experiences a small Lorentz-force deflection, which induces a
geometric time delay. In the ultra-relativistic regime relevant for
supernova neutrinos, this delay scales as $q_\nu^2 E_\nu^{-2}$, where $q_\nu$ and $E_\nu$ denote the
neutrino millicharge and energy, respectively, and thus shares the same leading energy dependence as the standard time-of-flight delay induced by
neutrino mass. Motivated by this similarity, we propose a framework to reinterpret
supernova time-of-flight limits on
neutrino mass as constraints on
neutrino millicharge. We express both effects in terms of a common $E_\nu^{-2}$ dispersion coefficient and compute the millicharge-induced contribution using a line-of-sight-dependent
magnetic delay kernel, extending the original SN1987A uniform-field estimate. Applying this translation to existing SN1987A limits and to projected sensitivities for future
Galactic core-collapse
supernova observations, we obtain bounds ranging from the $\sim 10^{-17}\, e$ level for SN1987A to the low-$10^{-19}\, e$ regime for next-generation
Galactic bursts, with optimistic combinations of detector sensitivity and
Galactic sightline approaching $\sim 10^{-20}\, e$. We compare these results with other bounds in the literature and discuss how nonzero
neutrino mass affects the interpretation.
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All authors Pedro Dedin Neto, AmirFarzan Esmaeili, Guilherme A. Nogueira, Pedro Cunha de Holanda, Ernesto Kemp
Astrophysics of Galaxies
Nature and nurture: the dynamical ages of in situ and accreted globular clusters in the Milky Way
Eugenio Carretta
The bifurcated age-
metallicity relation of globular clusters (GCs) in the Milky Way (MW) shows that GCs are either originated in situ or accreted into the
Galaxy from former satellites of the MW. The effects of the
Galactic tidal field can leave signatures on the dynamical
evolution and structural properties of GCs. We present a homogeneous census of dynamical ages for a sample of 93 GCs in the MW, coupled with the knowledge of their common progenitors from the chemo-dynamical parameters from the
Gaia mission, unavailable some years ago. We found that the majority of accreted GCs (61%) is dynamically young. This percentage drops to 38% for in situ GCs. Excluding the enigmatic low-energy (LE) GCs, with ambiguous origin, the fraction of dynamically young ex situ GCs raises to 70%. A two tail Kolmogorov-Smirnov test shows that the distribution of dynamical ages of LE GCs cannot be distinguished from the distribution of in situ bulge and disc GCs. Yet, the LE GCs are firmly located on the satellite branch of the age-
metallicity relation. An explanation may be that the progenitor of LE GCs plunged very early into the MW, so that the gravitational field of the MW had time enough to act on the associated GCs. The dynamical ages offer a statistically robust evidence corroborating the scenario of an early
accretion proposed by several recent studies on the origin of LE GCs.
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High Energy Astrophysical Phenomena · Cross-listed from gr-qc
Parameter-estimation bias induced by transient orbital resonances in extreme-mass-ratio inspirals
Edoardo Levati and Alejandro Cárdenas-Avendaño
Given the multifrequency nature of relativistic orbits, transient orbital resonances are expected to be ubiquitous during an extreme-mass-ratio inspiral (EMRI). At a resonance, the orbital dynamics is modified in a nontrivial way, imprinting an overall dephasing in the emitted gravitational waves and potentially impacting both the detection and parameter estimation of these sources. In this work, using a Fisher-
matrix approach, we investigate the bias induced by transient orbital resonances in EMRI parameter estimation. We focus on the most dynamically significant low-order resonances, 3 : 2 and 2 : 1, as well as on the high-order, subdominant resonances 3 : 1 and 4 : 3. We find that, for most of the orbits considered, neglecting the effect of a resonance crossing leads to significant losses in signal-to-noise ratio and induces bias in parameter recovery. Furthermore, both the sign and the amplitude of the resonance-induced modifications to the integrals of motion play a crucial role and must be modeled accurately. Our results provide further evidence that failing to model transient orbital resonances accurately can hinder EMRI detection and parameter estimation, thereby limiting their scientific potential.
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Astrophysics of Galaxies
Towards A Universal Analytical Model of Population III Star Formation: A Bridge Between Cosmological Scales and Protostars
James Gurian, Boyuan Liu, Donghui Jeong et al. (+4 more)
We construct an analytical model of Population III
star formation that connects the cosmological radiation background to sub-AU protostellar disk fragmentation, a dynamic range inaccessible to any single simulation. Our approach is based on combining separate models of the disparate relevant scales: from the cosmological environment to the host-
halo scale, from the
halo scale to the scale of the
star-forming cloud, and from the cloud scale to the fragmenting, accreting protostellar disk. Individually and collectively, the models agree well with the predictions of state of the art simulations, while remaining computationally inexpensive and physically transparent. As an example of the applicability of the model, we study the effects of varying the Lyman-Werner flux on the Pop. III
star formation efficiency. We show that depending on the
halo properties and the strength of the dissociating radiation field, the
halo-scale Pop. III
star formation efficiency varies by more than two orders of magnitude from $\varepsilon_{\rm SFE,H} \approx 10^{-3}$ to $\varepsilon_{\rm SFE, H} \approx 0.5$. The abrupt transitions between hydrogen-deuteride cooling (in low virial temperature mini-
halos subjected to low radiation backgrounds), molecular hydrogen cooling (at intermediate temperatures and radiation intensities), and atomic cooling (in higher temperature
halos exposed to strong radiation fields) produces sharp features in the
halo-scale
star formation efficiency as a function of the
halo properties. Meanwhile, at the scale of individual
star-forming clouds, the
star formation efficiency is $\varepsilon_{\rm SFE,c} \gtrsim 0.2$. That is, pristine gas in a
halo is converted into unstable clouds at a wide range of efficiencies, and these unstable clouds are efficiently converted into Pop. III
stars.
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All authors James Gurian, Boyuan Liu, Donghui Jeong, Takashi Hosokawa, Shingo Hirano, Volker Bromm, Naoki Yoshida
Cosmology and Nongalactic Astrophysics · Cross-listed from hep-ph
Asteroid-mass Primordial Black Holes as Dark Matter from Supersymmetry
Andrea Boccia and Marco Chianese
We study the formation of asteroid-mass
Primordial Black Holes (PBHs) as a dark matter candidate in supersymmetric extensions of the Standard Model. We show that the presence of heavy particles predicted in the Minimal Supersymmetric Standard Model (MSSM) can lead to a transient softening of the equation of state of the Universe during their non-relativistic transition, enhancing PBH formation. We compute the effective equation of state for different realizations of the MSSM mass spectrum, parametrized by three characteristic mass scales. Assuming a broad and approximately scale-invariant
primordial curvature power spectrum, we evaluate the resulting PBH mass functions and compare them with current observational constraints. We find that, for supersymmetric masses above $\sim 10^5\,\mathrm{GeV}$, the PBH mass function is significantly enhanced in the asteroid-mass window, allowing PBHs to account for the total dark matter abundance without violating existing bounds. In contrast, within the Standard Model the same configurations lead to PBH mass functions that are observationally excluded. For lighter supersymmetric mass spectra, PBH production is shifted toward masses above $\sim 10^{22}\,\mathrm{g}$, which are strongly constrained by microlensing searches, thereby reducing their allowed contribution to the dark matter density.
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High Energy Astrophysical Phenomena · Cross-listed from hep-ph
Revisiting Turner Window Axions: The Untapped Potential of NaI Dark Matter Detectors
W. C. Haxton, Xing Liu, Anupam Ray et al. (+1 more)
The "Turner window" corresponds to
axions with masses $\gtrsim$ 1 eV that have sufficiently strong couplings to matter to evade limits from the cooling of SN1987A. This window, through which the trajectories for the KSVZ and DFSZ QCD
axions run, has been thought to be largely closed because of (1) the floor established by SN1987A cooling, (2) the absence of SN1987A-associated
photons in the Kamioka II detector, and (3) the limit on
neutrons produced by
solar axions in the Sudbury
Neutrino Observatory. We show that a more complete treatment of the
axion opacity in SN1987A, significantly weakens (2). Consequently, for
axion or
axion-like particles with hadronic couplings, $g_{ann}$ and $g_{app}$, significant regions within the Turner window now become viable. We describe a new opportunity to constrain such hadronically coupled
axions via their resonant absorption in NaI detectors. The source is the Milky Way's carbon-burning
stars – the progenitors of ONeMg white
dwarfs as well as electron-capture and core-collapse
supernovae – which synthesize significant quantities of $^{23}$Na, keeping it at temperatures $\sim 10^9$K for periods up to tens of thousands of years. $^{23}$Na acts as a thermal pump to convert
stellar energy into
axions, which arrive at the Earth as a thermally broadened line at 440 keV. These
axions can be detected via resonant absorption in NaI, with the needed detector arrays already in place, developed by DAMA/LIBRA and other collaborations to search for the elastic scattering of light WIMPs. In
axion detection, NaI serves as both the target, producing $\gamma$'s following resonant absorption, and the detector for those $\gamma$'s. With current array masses and backgrounds, we find that the coupling range $|g_{app}| \sim 10^{-6.5}$–$10^{-2}$ can be covered after two years of data, including QCD
axions with $m_a \gtrsim 10$ eV.
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All authors W. C. Haxton, Xing Liu, Anupam Ray, Evan Rule
Solar and Stellar Astrophysics
Determination of the Solar System contribution to the soft X-ray sky
K. Dennerl, G. Ponti, X. Zheng et al. (+4 more)
Solar wind charged particles interact with diffuse gas within the heliosphere, producing soft X-rays. This
solar wind charge exchange (SWCX) process produces foreground emission that complicates interpretation of X-ray observations. In this work, we analyze X-ray observations of the western
Galactic hemisphere by the Extended Roentgen Survey with an Imaging
Telescope Array (eROSITA) instrument on the Spectrum-Roentgen-Gamma (SRG) spacecraft. These data avoid contamination by Earth's geocorona and are derived from four surveys of the full sky, including during the minimum of the Sun's activity cycle. We determine the SWCX contribution and subtract it from the survey, providing a less contaminated view of the diffuse soft X-ray sky. We also demonstrate that X-rays can be used to map the flow of interstellar matter through the
Solar System.
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All authors K. Dennerl, G. Ponti, X. Zheng, M. J. Freyberg, S. Friedrich, Th. Müller, M. C. H. Yeung
Astrophysics of Galaxies
A quantum theory of the alignment and polarization of very small dust grains
Boy Lankhaar
Context. Anomalous microwave emission (AME) is a component of interstellar medium emission peaking at 10-60 GHz. Its polarization is both a CMB foreground and a probe of the
alignment physics of very small
dust grains. Aims. We quantify when the purely rotational electric-dipole emission from very small interstellar grains (spinning
dust/AME) can become measurably polarized, and we quantify related UV/optical/IR polarization diagnostics. Methods. We develop a
quantum-mechanical symmetric-top model for an axisymmetric very small grain and express polarized emission and absorption coefficients in terms of irreducible density-
matrix moments.
Alignment is driven by anisotropic illumination; we solve a simplified two-
manifold pumping model and compute (polarized) emission and absorption signatures for different dipole configurations and grain-size distributions. Results. Anisotropic illumination can generate polarized spinning-
dust emission; in optimal geometries, polarization fractions near the emission peak reach the percent level, while more modest anisotropies reduce the polarization fraction. The same physics predicts polarized UV/optical/IR absorption that can be appreciable in strongly illuminated environments, whereas IR vibrational emission is predicted to be negligibly polarized. Conclusions. Spinning-
dust polarization depends on radiation anisotropy, dipole geometry, and the competition between
alignment pumping and depolarization by rotational emission. Joint constraints from AME polarization and UV/optical/IR absorption polarimetry provide a direct test of
alignment by anisotropic radiation fields and help bound polarized microwave foregrounds.
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High Energy Astrophysical Phenomena
Distortion of a relativistic jet echoing a magnetic flux eruption
Krzysztof Nalewajko, Mateusz Kapusta, Bart Ripperda et al. (+1 more)
Magnetized
accretion onto spinning black holes can accumulate a large
magnetic flux across the event horizon and launch a pair of relativistic jets via the Blandford-Znajek mechanism. In the magnetically saturated (arrested) state, excess
magnetic flux is ejected from the black hole in episodic
magnetic flux eruptions, which result in a significant yet temporary reduction of jet power. We analyze results of a high-resolution 3D general-relativistic magneto-hydro-dynamic numerical simulation of geometrically thick magnetically saturated
accretion onto a high-
spin Kerr black hole for a single cycle of
magnetic flux eruption and accumulation. We show that following an eruption, a weakened jet develops a strong helical distortion with distinct structure of
magnetic fields - the poloidal field along the jet core is unaffected by the eruption; while toroidal field lines, ejected from the black hole during the eruption and later re-advected onto it, form poloidal `bypasses' along the inner jet sheath. Such a distortion may appear in sources fed by geometrically thick
accretion flows as an asymmetric superluminal
knot, strongly interacting with the jet sheath along an oblique working surface. The jet section re-powered by
magnetic flux re-accumulated on the black hole is tilted by a few degrees, implying significant variations in radiation boost towards observers of BL Lac blazars. The intrinsic structure of the jet spine is consistent with axisymmetric semi-analytical models.
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All authors Krzysztof Nalewajko, Mateusz Kapusta, Bart Ripperda, Alexander A. Philippov
High Energy Astrophysical Phenomena
Properties of black hole mergers in disks of active galactic nuclei
Hiromichi Tagawa, Zoltán Haiman and Bence Kocsis
Ground-based gravitational wave (GW) observatories have detected approximately 200 binary black hole (BH) mergers. The astrophysical origin of these events are debated, with evidence suggesting that at least a subset originated from dynamic environments characterized by frequent close encounters.
Accretion disks in active
galactic nuclei (AGNs) are of particular interest, as certain observed features could be more readily produced within such environments. In this paper, we investigate the expected properties of mergers in these environments, and their dependence on various parameters, using one-dimensional $N$-body simulations combined with a comprehensive semi-analytical model. In our fiducial model, the distributions of masses and mass ratios ($q$) are similar to those observed. However, they depend strongly on the lifetime and density of the AGN disk and on the number and
accretion efficiency of BHs, with higher masses predicted as these quantities increase. The most massive mergers, such as GW231123, can be produced either by efficient gas
accretion or by hierarchical mergers among $\geq 3$ generations of BHs. The observed negative correlation between $q$ and the average effective
spin ($\chi_{\rm eff}$), along with the positive correlation between $\chi_{\rm eff}$ and the chirp mass ($M_{\rm chirp}$), can be explained by a combination of efficient gas
accretion, which promotes
spin alignment, and hierarchical mergers, which produce high-$|\chi_{\rm eff}|$ and low-$q$ binaries. Hierarchical mergers can also explain the negative correlation between $q$ and the dispersion of $\chi_{\rm eff}$, as well as the positive correlation between $|\chi_{\rm eff}|$ and $M_{\rm chirp}$. We present a comprehensive study on how the expected distribution of each of these quantities depends on model parameters and assumptions, which will aid the interpretation of observed GW population properties.
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Astrophysics of Galaxies
The GlimmIr: Spectroscopic Variability in a z~7 LRD Indicates Rapid Changes in Both the Narrow and Broad Line Regions
Erini Lambrides, Taylor A. Hutchison, Rebecca L. Larson et al. (+39 more)
The enigmatic population of “Little Red Dots” (LRDs) sit at the center of some of the largest debates in extragalactic astronomy today. The source(s) of ionizing emission and the physical scale over which it governs is still largely unknown. We show for the first time spectroscopic variability in a z ~ 7 LRD. Comparing a recently obtained 10.2 hr JWST/NIRSpec F290LP/G395M spectrum via the C3PO survey to an 8.4 hr F290LP/G395M spectrum taken 99 days earlier (~13 rest-days) via the THRILS survey, we find a ~30% $ difference in the continuum and broad-line flux, and a 42% difference between [OIII]5008 flux in the two epochs. Through rigorous testing, we confirm that such differences are not the result of differing MSA slit placements on source nor merely flux calibration offsets. These results are further corroborated by both a similar continuum and [OIII]5008 flux differences found in NIRSpec prism/clear observations of the source at an epoch taken approximately a year earlier than the THRILS observations via RUBIES and an additional observation fortuitously taken during the THRILS epoch (within a rest-day) via the CAPERS survey. Assuming LRDs are a type of accreting black hole system, this implies direct sight-lines must exist from the
accretion disk to the surrounding nebular gas on scales beyond the broad-line region, and thus any high-density gas interpretations must allow for covering fractions < 100%. Furthermore, these results show the [OIII] line emission is likely not
galaxy process-dominated, with a significant population of the narrow-line emitting gas closest to the broad-line region being directly ionized by the LRD. Finally, these results highlight the need for new approaches in inferring black hole properties of these systems, accounting for the lack of significant ionization via
star formation, and/or exploring more exotic host-
galaxy conditions at these early epochs.
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All authors Erini Lambrides, Taylor A. Hutchison, Rebecca L. Larson, Pablo Arrabal Haro, Casey Papovich, Weida Hu, Nikko J. Cleri, Steven L. Finkelstein, Jonathan R. Trump, Pablo G. Perez-Gonzalez, Bingjie Wang, Dale D. Kocevski, John Chisholm, Amy Secunda, Sarah E. I. Bosman, Hollis Akins, Mitchell Karmen, Mark Dickinson, Volker Bromm, Bren E. Backhaus, Marco Chiaberge, Olivia R. Cooper, Yukta Ajay, Guillermo Barro, Danielle A. Berg, Jenna Cann, M. C. Cooper, Norman A. Grogin, Michaela Hirschmann, Marc Huertas-Company, Jeyhan S. Kartaltepe, Anton M. Koekemoer, Ray A. Lucas, Arianna S. Long, Roberto Gilli, Colin Norman, Andrew F. Ptak, Chris T. Richardson, Jane R. Rigby, Brittany N. Vanderhoof, L. Y. Aaron Yung, Jorge A. Zavala
Earth and Planetary Astrophysics
Measuring Apsidal Clustering
Amir Siraj, Christopher F. Chyba and Scott Tremaine
The decade-long debate over the existence of apsidal clustering in the outer
solar system is poised for reignition given the plethora of distant trans-Neptunian object (TNO) discoveries expected from the forthcoming Vera C. Rubin Observatory's Legacy Survey of Space and Time (LSST). Here, we present a new conditional-likelihood method to measure apsidal clustering that is insensitive to uneven survey footprints. We calculate the long-term orbital stability of distant TNOs, which allows us to expand the known sample of relevant objects from 21 to 25. We apply our new method to this up-to-date sample, showing that the significance of the apsidal clustering in the outer
solar system has fallen from $2.7\sigma$ to $1.9\sigma$, and that the direction of clustering is not well constrained. This new method is suitable for application to the growing sample of known TNOs, and the results will reveal whether the evidence for a hypothetical
Planet X from apsidal clustering is real or spurious.
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High Energy Astrophysical Phenomena
Learning Neural Operator Surrogates for the Black Hole Accretion Code
Matthias Nägele, Cedric Bös, Chester Tan et al. (+3 more)
General-relativistic magnetohydrodynamic (GR-MHD) simulations are essential for studying black hole
accretion, relativistic jets, and
magnetic reconnection, yet their computational cost severely limits systematic parameter exploration. We investigate neural operator surrogates for two astrophysically relevant simulation scenarios produced by the Black Hole
Accretion Code (BHAC). First, a Physics Informed
Fourier Neural Operator (PINO) is trained on the special-relativistic resistive MHD (SRRMHD)
evolution of the Orszag-Tang
vortex over a range of resistivities spanning the Sweet-Parker and fast reconnection regimes. By
embedding the governing equations as an additional loss term evaluated at finer temporal resolution than the available data supervision, the model learns dynamics at time steps where no simulation data is provided, enabling recovery of plasmoid formation that a data-only baseline trained on the same sparse snapshots fails to reproduce. To our knowledge, the present work is the first application of a physics informed neural operator to special relativistic resistive MHD, and the first to investigate the capability of such models to resolve plasmoid formation in SRRMHD. In a second line of investigation, an OFormer-style
Transformer Neural Operator is trained on the
evolution of spine-sheath relativistic jets created with BHAC, in special-relativistic MHD (SRMHD). The model is directly applied on the adaptive mesh, highlighting the need for linear
attention due to long sequences. The neural surrogate model is capable of capturing most of the major details, especially in early predictions. To our knowledge, this constitutes the first application of a neural operator directly on a high resolution adaptive mesh refinement grid in the context of MHD simulations.
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All authors Matthias Nägele, Cedric Bös, Chester Tan, Christian M. Fromm, Ingo Scholtes, Karl Mannheim
Astrophysics of Galaxies
JOYS+ analyses of OCN$^-$, N$_2$O, NO, and complex cyanides in ices – Thermal processing results in modest enhancement of OCN$^-$ ice
P. Nazari, N. Brunken, Y. Chen et al. (+12 more)
Nitrogen-bearing molecules are more difficult to observe than oxygen-bearing ones, mainly due to the lower abundance of nitrogen in the interstellar medium. Therefore, the formation pathways of many of these species is still under debate. Studies prior to the launch of the JWST did not have the sensitivity to observe ices toward the youngest and most deeply embedded Class 0 objects. Here we will focus on OCN$^-$, CH$_3$CN, C$_2$H$_5$CN, NO, and N$_2$O in ices to better understand their formation. We use the data from the JOYS+ program to study 8 Class 0 and 11 Class I objects with JWST. We firmly detect OCN$^-$ in ices for all these objects, tentatively detect CH$_3$CN, C$_2$H$_5$CN, and N$_2$O toward three sources, and find upper limits on the NO abundance in ices. The OCN$^-$/CO$_2$ ratios are found to be larger by a factor of ~2-3 for the objects that have a visible CO$_2$ double peak (a sign of ice thermal processing) pointing to the moderate effect of temperature on OCN$^-$ production. Relation of H$_2$O, CO$_2$, and OCN$^-$ with $A_{\rm V}$ indicates that OCN$^-$ may tentatively form at a later stage than H$_2$O and CO$_2$. We find that the ratios of CH$_3$CN, C$_2$H$_5$CN, and N$_2$O with respect to OCN$^-$ are relatively constant within one order of magnitude across our objects, likely suggesting that they have similar ice environments. The upper limit abundances of NO are ~1 order of magnitude lower than what was previously predicted in ices of a mature protoplanetary disk. This indicates that the detected gas-phase NO in that disk may be a product of another molecule (e.g. N$_2$O) in the ices. We conclude that OCN$^-$ can get enhanced at higher temperatures by only a factor of ~2-3 and thus OCN$^-$ detection alone does not imply ice heating. Large-sample studies of OCN$^-$ toward pre-
stellar cores will be useful to further confirm the formation timeline of this molecule.
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All authors P. Nazari, N. Brunken, Y. Chen, K. Slavicinska, E. F. van Dishoeck, W. R. M. Rocha, A. C. A. Boogert, M. G. Navarro, V. J. M. Le Gouellec, L. Francis, Ł. Tychoniec, A. Caratti o Garatti, C. Gieser, T. P. Greene, P. J. Kavanagh
Astrophysics of Galaxies
From short-lived to long-lived clouds: impact of star formation models on giant molecular cloud evolution in simulations of an NGC 300-like galaxy
Daniel Han, Taysun Kimm, Cheonsu Kang et al. (+3 more)
Multi-wavelength observations of molecular and ionized gas indicate that GMCs are short-lived, generally dispersing within one or two dynamical timescales. To investigate the physical origin of these short lifetimes and the role of
star formation prescriptions, we conduct radiation-hydrodynamic simulations of an NGC 300-like disk
galaxy with RAMSES-RT. We compare two distinct
star formation models, one based on a local gravo-thermo-turbulent (GTT) condition and the other employing sink particles, to examine how
star formation and feedback collectively regulate GMC
evolution. The sink-particle-based model yields bursty yet self-regulated global
star formation rates of $0.1$-$0.5$ $M_{\odot}\,yr^{-1}$ and produces GMC lifetimes of $\sim20$-$30$ Myr, with
star formation efficiencies (SFEs) per free-fall time of a few percent, consistent with observations. In contrast, the GTT model generates a population of long-lived clouds with lifetimes $\gtrsim200$ Myr, owing to the extremely low SFEs per free-fall time $(\lesssim3\times10^{-3})$, which renders
stellar feedback ineffective. With both models, cloud-cloud mergers extend the lifetimes of GMCs and increase their integrated SFEs by lengthening the
star-forming duty cycle, while having only a minor impact on instantaneous efficiencies. On
galactic scales, both models broadly reproduce the observed KS relation within its scatter, yielding gas depletion times of a few Gyr. In comparison, an extreme feedback model with the
supernova energy boosted by a factor of five, combined with the GTT
star formation model, excessively suppresses
star formation and produces much longer depletion times ($6$-$20$ Gyr) for this isolated system. These results demonstrate that GMC lifecycles are strongly governed by the adopted
star formation model, highlighting the need for improved prescriptions that realistically capture clump-scale
star formation.
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All authors Daniel Han, Taysun Kimm, Cheonsu Kang, Jaehyun Lee, Harley Katz, Joki Rosdahl
Cosmology and Nongalactic Astrophysics
Fast radio burst dispersion is an unbiased tracer of matter on large scales
Shion Andrew, Haochen Wang, Kiyoshi Masui et al. (+6 more)
The dispersion of fast
radio bursts (FRBs) measures the column density of free electrons, tracing the diffuse ionized gas that contains more than $90\%$ of all
baryons. On linear scales the FRB dispersion field is an approximately unbiased tracer of the matter distribution, an idea long assumed in the FRB large-scale structure literature and recently formalized by Zhou and Zhang [arXiv:2510.11022]. This follows from
baryon-mass conservation, which forces the total
baryon field to have unit linear bias, with dispersion inheriting this bias up to small corrections from the
stellar and neutral-gas components. We show these corrections can be bounded at the percent level using existing
galaxy and 21 cm surveys, and confirm with the FLAMINGO hydrodynamical simulations that the electron bias varies at the percent level across a wide range of feedback prescriptions. The dispersion-
galaxy cross-power spectrum at linear scales directly constrains $B_8 \equiv \sigma_8(\Omega_b/0.05)^{1/2}$, a baryonic analog of $S_8$, independently of feedback physics. Because most of the per-object variance in dispersion is cosmological signal rather than noise, $\sim\!10^5$ localized FRBs can match the statistical power of $\sim\!10^8$ weak-
lensing galaxy shape measurements. FRB dispersion thus joins weak
lensing and
redshift-space distortions as a new unbiased tracer of matter on large scales.
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All authors Shion Andrew, Haochen Wang, Kiyoshi Masui, Josh Borrow, Calvin Leung, Ryan Raikman, Matthieu Schaller, Joop Schaye, James M. Sullivan