Sazuna/UAT_keywords huggingface dataset:
Low Injection Rate of Cosmic-Ray Protons in the Turbulent Reacceleration Model of Radio Halos in Galaxy Clusters. A giant radio halo (RH) is a diffuse synchrotron emission observed on the scale of megaparsecs, typically found in the central region of merging galaxy clusters. Its large size and steep spectrum suggest that it originates from the reenergization of an aged population of cosmic-ray electrons (CREs), while the secondary leptons produced in the pp hadronic collision of cosmic-ray protons (CRPs) may contribute to the emission. In this study, we investigate the reacceleration model including both primary and secondary CREs, assuming that the primary cosmic rays (CRs) originate from internal galaxies. In our new method, we follow the cosmological evolution of each cluster and calculate the energy spectra and 1D spatial distributions of CRs. The primary CRE model with a ∼3 Gyr duration of reacceleration successfully reproduces the statistical properties of the RHs observed in the recent LOFAR survey, as well as the spectrum and profile of the Coma cluster. The gamma-ray and neutrino emissions produced by reaccelerated CRPs are consistent with the upper limits. However, if the CRP injection rate is high and the secondary CREs become significant, the model with the required ∼3 Gyr reacceleration overproduces the number of RHs. The limit on the CRP injection rate, L  p  ≲ 1041 erg s‑1, is significantly lower than that expected from the early starburst activity or jets from active galactic nuclei. This discrepancy requires a revision of either the model of CR supply from galaxies or the turbulent reacceleration model.

Keywords: Galaxy clusters
The Intrinsic Flattening of Galaxy Disks. Highly inclined (edge-on) disk galaxies offer the unique perspective to constrain their intrinsic flattening, c/a, where c and a are, respectively, the vertical and long radial axes of the disk measured at suitable stellar densities. The ratio c/a is a necessary quantity in the assessment of galaxy inclinations, three-dimensional structural reconstructions, and total masses, as well as a constraint to galaxy formation models. The 3.6 μm maps of 133 edge-on spiral galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G) and its early-type galaxy extension are used to revisit the assessment of c/a free from dust extinction and away from the influence of a stellar bulge. We present a simple definition of c/a and explore trends with other galactic physical parameters: total stellar mass, concentration index, total H I mass, mass of the central mass concentration, circular velocity, model-dependent scales, and Hubble type. Other than a dependence on early/late Hubble types and a related trend with light concentration, no other parameters were found to correlate with the intrinsic flattening of spiral galaxies. The latter is mostly constant with &lt;c/a&gt; = 0.124 ± 0.001 (stat) ± 0.033 (intrinsic/systematic) and greater for earlier types.

Keywords: Galaxy properties, Galaxy dynamics, Galaxy structure, Galaxy disks, Galaxy kinematics
Diffusion-HMC: Parameter Inference with Diffusion-model-driven Hamiltonian Monte Carlo. Diffusion generative models have excelled at diverse image generation and reconstruction tasks across fields. A less explored avenue is their application to discriminative tasks involving regression or classification problems. The cornerstone of modern cosmology is the ability to generate predictions for observed astrophysical fields from theory and constrain physical models from observations using these predictions. This work uses a single diffusion generative model to address these interlinked objectives—as a surrogate model or emulator for cold dark matter density fields conditional on input cosmological parameters, and as a parameter inference model that solves the inverse problem of constraining the cosmological parameters of an input field. The model is able to emulate fields with summary statistics consistent with those of the simulated target distribution. We then leverage the approximate likelihood of the diffusion generative model to derive tight constraints on cosmology by using the Hamiltonian Monte Carlo method to sample the posterior on cosmological parameters for a given test image. Finally, we demonstrate that this parameter inference approach is more robust to small perturbations of noise to the field than baseline parameter inference networks.

Keywords: Cosmology, Cosmological parameters, Neural networks, Astrostatistics, Dark matter, Astronomical simulations
New Insight of Time-transformed Symplectic Integrator. I. Hybrid Methods for Hierarchical Triples. Accurate N-body simulations of multiple systems such as binaries and triples are essential for understanding the formation and evolution of interacting binaries and binary mergers, including gravitational wave sources, blue stragglers, and X-ray binaries. The logarithmic time-transformed explicit symplectic integrator (LogH), also known as algorithmic regularization, is a state-of-the-art method for this purpose. However, we show that this method is accurate for isolated Kepler orbits because of its ability to trace Keplerian trajectories, but much less accurate for hierarchical triple systems. The method can lead to an unphysical secular evolution of inner eccentricity in Kozal–Lidov triples, despite a small energy error. We demonstrate that hybrid methods, which apply LogH to the inner binary and alternative methods to the outer bodies, are significantly more effective, though not symplectic. Additionally, we introduce a more efficient hybrid method, BlogH, which eliminates the need for time synchronization and is time symmetric. The method is implemented in the few-body code SDAR. We explore suitable criteria for switching between the LogH and BlogH methods for general triple systems. These hybrid methods have the potential to enhance the integration performance of hierarchical triples.

Keywords: Multiple stars, N-body problem, N-body simulations, Few-body systems, Algorithms
An Improved Halo Coronal Mass Ejection Geoeffectiveness Prediction Model Using Multiple Coronal Mass Ejection Features Based on the DC-PCA-KNN Method. Coronal mass ejections (CME) are regarded as the main drivers of geomagnetic storms (GSs). In the prediction of geoeffectiveness, various CME features have been introduced without adequately considering the geoeffectiveness of CMEs and strong correlations among the features. In this study, a feature dimension reduction method combining distance correlation (DC) and principal component analysis (PCA) was employed for the K-nearest neighbors (KNN) model to predict the geoeffectiveness of halo CME by using the multiple CME features. First, based on CME features and the Disturbance Storm Time index, there are 169 CME-related GS (CME-GS) pairs that were defined as positive samples during the entire phases of solar cycles 23 and 24. Next, DC was used to screen the eight original CME features. It was found that the three CME features, such as acceleration, kinetic energy, and measurement position angle, were weakly correlated with CME-GS pairs according to the performance of KNN prediction models and then were discarded. In order to further reduce the dimension of the input features for the KNN prediction model, PCA was subsequently applied. And the above remaining five principal components were reduced to one. Finally, the DC-PCA-KNN prediction model, achieving a mean true positive rate of 0.6519 and an accuracy of 0.6494, performed well in the prediction of halo CME geoeffectiveness and was superior to the DC or PCA model alone.

Keywords: Principal component analysis, Solar coronal mass ejections, Solar-terrestrial interactions, Magnetic storms, Dimensionality reduction
Intrinsic and Environmental Effects on the Distribution of Star Formation in TNG100 Galaxies. We present radial profiles of luminosity-weighted age (ageL) and ΔΣSFR for various populations of high- and low-mass central and satellite galaxies in the TNG100 cosmological simulation. Using these profiles, we investigate the impact of intrinsic and environmental factors on the radial distribution of star formation. For both central galaxies and satellites, we investigate the effects of black hole mass, cumulative active galactic nucleus (AGN) feedback energy, morphology, halo mass, and local galaxy overdensity on the profiles. In addition, we investigate the dependence of radial profiles of the satellite galaxies as a function of the redshifts at which they joined their hosts, as well as the net change in star-forming gas mass since the satellites joined their host. We find that high-mass (M* &gt; 1010.5M⊙) central and satellite galaxies show evidence of inside-out quenching driven by AGN feedback. Effects from environmental processes only become apparent in averaged profiles at extreme halo masses and local overdensities. We find that the dominant quenching process for low-mass galaxies (M* &lt; 1010M⊙) is environmental, generally occurring at low halo mass and high local galaxy overdensity for low-mass central galaxies and at high host halo masses for low-mass satellite galaxies. Overall, we find that environmental processes generally drive quenching from the outside-in.

Keywords: Galaxy environments, Star formation, Galaxy evolution, Galaxy quenching, Astronomical simulations
Magnetic Flux Transport in Advection-dominated Accretion Flow toward the Formation of a Magnetically Arrested Disk. Magnetically arrested disks (MADs) have attracted much attention in recent years. The formation of MADs is usually attributed to the accumulation of a sufficient amount of dynamically significant poloidal magnetic flux. In this work, the magnetic flux transport within an advection-dominated accretion flow (ADAF) and the formation of an MAD are investigated. The structure and dynamics of an inner MAD connected with an outer ADAF are derived by solving a set of differential equations with suitable boundary conditions. We find that an inner MAD is eventually formed at a region about several 10 RS outside the horizon. Due to the presence of a strong large-scale magnetic field, the radial velocity of the accretion flow is significantly decreased. The angular velocity of the MAD region is highly sub-Keplerian with Ω ∼ (0.4–0.5)ΩK, and the corresponding ratio of gas to magnetic pressure is about β ≲ 1. Also, we find that an MAD is unlikely to be formed through the inward flux advection process when the external magnetic field strength is weak enough with βout ≳ 100 around Rout ∼ 1000 Rs. Based on a rough estimate, we find that the jet power of a black hole, with mass MBH and spin a*, surrounded by an ADAF with an inner MAD region is about 2 orders of magnitude larger than that of a black hole surrounded by a normal ADAF. This may account for the powerful jets observed in some Fanaroff–Riley type I galaxies with a very low Eddington ratio.

Keywords: Accretion, Galaxy accretion disks, Magnetic fields, Astrophysical black holes
Hierarchical Searches for Subsolar-mass Binaries and the Third-generation Gravitational Wave Detector Era. Detecting gravitational waves (GWs) from coalescing compact binaries has become routine with ground-based detectors like Advanced LIGO and Advanced Virgo. However, beyond standard sources such as binary black holes and neutron stars and neutron star black holes, no exotic sources revealing new physics have been discovered. Detecting ultracompact objects, such as subsolar mass (SSM), offers a promising opportunity to explore diverse astrophysical populations. However, searching for these objects using standard matched-filtering techniques is computationally intensive due to the dense parameter space involved. This increasing computational demand not only challenges current search methodologies but also poses a significant obstacle for third-generation (3G) ground-based GW detectors. In the 3G detectors, signals are expected to be observed for tens of minutes and detection rates to reach one per minute. This requires efficient search strategies to manage the computational load of long-duration signal search. In this paper, we demonstrate how hierarchical search strategies can address the computational challenges associated with detecting long-duration signals in current detectors and the 3G era. Using SSM searches as an example, we show that optimizing data sampling rates and adjusting the number of templates in matched filtering at each stage of low-frequency searches can improve the signal-to-noise ratio by 6% and detection volume by 10%–20%. This sensitivity improvement is achieved with a 2.5-fold reduction in computational time compared to standard PyCBC searches. We also discuss how this approach could be adapted and refined for searches involving eccentric and precessing binaries with future detectors.

Keywords: Gravitational wave detectors, Gravitational waves, Primordial black holes
NGC 628 in SIGNALS: Explaining the Abundance-ionization Correlation in H II Regions. The variations of oxygen abundance and ionization parameter in H II regions are usually thought to be the dominant factors that produced variations seen in observed emission-line spectra. However, if and how these two quantities are physically related is hotly debated in the literature. Using emission line data of NGC 628 observed with SITELLE as part of the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey (SIGNALS), we use a suite of photoionization models to constrain the abundance and ionization parameters for over 1500 H II regions throughout its disk. We measure an anticorrelation between these two properties, consistent with expectations, although with considerable scatter. Secondary trends with dust extinction and star formation rate surface density potentially explain the large scatter observed. We raise concerns throughout regarding various modeling assumptions and their impact on the observed correlations presented in the literature.

Keywords: Interstellar medium, Photoionization, H II regions, Galaxy chemical evolution
Detecting Dark Objects with Plasma Microlensing by Their Gravitational Wakes. A moving mass makes a gravitational wake in the partially ionized interstellar medium, which acts as a lens for radio-frequency light. Consequently, plasma microlensing could complement gravitational microlensing in the search for invisible massive objects, such as stellar remnants or compact dark matter. This work explores the spatial structure of the plasma lens associated with a gravitational wake. Far away from the moving mass, the characteristic lensing signal is the steady demagnification or magnification of a radio source as the wake passes in front of it at the speed of sound. Sources can be plasma-lensed at a much greater angular distance than they could be gravitationally lensed to the same degree by the same object. However, only the wakes of objects greatly exceeding stellar mass are expected to dominate over the random turbulence in the interstellar medium.

Keywords: Black holes, Analytical mathematics, Interstellar medium, Interstellar scintillation, Astrophysical fluid dynamics, Dark matter
Frozen-field Modeling of Coronal Condensations with MPI-AMRVAC. II. Optimization and Application in 3D Models. The frozen-field hydrodynamic (ffHD) model is a simplification of the full magnetohydrodynamical equations under the assumption of a rigid magnetic field, which significantly reduces computational complexity and enhances efficiency. In this work, we combine the ffHD prescription with hyperbolic thermal conduction (TC) and the Transition Region Adaptive Conduction (TRAC) method to achieve further optimization. A series of 2D tests are done to evaluate the performance of the hyperbolic TC and the TRAC method. The results indicate that hyperbolic TC, while showing limiter-affected numerical dissipation, delivers outcomes comparable to classic parabolic TC. The TRAC method effectively compensates for the underestimation of enthalpy flux in low-resolution simulations, as evaluated on tests that demonstrate prominence formation. We present an application of the ffHD model that forms a 3D prominence embedded in a magnetic flux rope, which develops into a stable slab-like filament. The simulation reveals a prominence with an elongated spine and a width consistent with observations, highlighting the potential of the ffHD model in capturing the dynamics of solar prominences. Forward modeling of the simulation data produces synthetic images at various wavelengths, providing insights into the appearance of prominences and filaments in different observational contexts. The ffHD model, with its computational efficiency and the demonstrated capability to simulate complex solar phenomena, offers a valuable tool for solar physicists, and is implemented in the open-source MPI-AMRVAC framework.

Keywords: Solar atmosphere, Solar physics, Solar prominences, Magnetohydrodynamical simulations
Magnetic Field Geometry and Anisotropic Scattering Effects on Solar Radio Burst Observations. The fine structures of solar radio bursts reveal complex dynamics in the corona, yet the observed characteristics of these subsecond bursts are additionally complicated by radio wave scattering in the turbulent solar corona. We examine the impact of anisotropic turbulence in radio wave propagation simulations with nonradial magnetic field structures in shaping the morphology, time characteristics, and source positions of fine structures. The apparent sources are found to move along the direction of the magnetic field lines and not along the density gradient, whereas the major axis of the scattered source is perpendicular to the local magnetic field (the scattering anisotropy axis). Using a dipolar magnetic field structure of an active region, we reproduce observed radio fine-structure source motion parallel to the solar limb associated with a coronal loop and provide a natural explanation for puzzling observations of solar radio burst position motions with the Low Frequency Array. Furthermore, the anisotropy aligned with a dipolar magnetic field causes the apparent-source images to bifurcate into two distinct components, with characteristic sizes smaller than in unmagnetized media. The temporal broadening induced by scattering reduces the observed frequency drift rate of fine structures, depending on the contribution of scattering to the time profile. The findings underscore the role of magnetic field geometry and anisotropic scattering for the interpretation of solar radio bursts and highlight that anisotropic scattering produces more than a single source.

Keywords: Solar radio emission, Solar corona
The Relation between AGN and Host-galaxy Properties in the JWST Era. I. Seyferts at Cosmic Noon are Obscured and Disturbed. The morphology of a galaxy reflects the mix of physical processes occurring within and around it, offering indirect clues to its formation and evolution. We apply both visual classification and computer vision to test the suspected connection between galaxy mergers and active galactic nucleus (AGN) activity, as evidenced by a close/merging galaxy pair, or tidal features surrounding an apparently singular system. We use JADES JWST/NIRCam imagery of a complete, multiwavelength AGN sample recently expanded with JWST/Mid-Infrared Instrument (MIRI) photometry. This 0.9–25 μm data set enables constraints on the host-galaxy morphologies of a broad range of AGN beyond z ∼ 1, including heavily obscured examples missing from previous studies. Our primary AGN sample consists of 243 lightly to highly obscured X-ray-selected AGN and 138 presumed Compton-thick, mid-infrared-bright/X-ray-faint AGN revealed by MIRI. Utilizing the shape asymmetry morphology indicator, AS, as the metric for disturbance, we find that 88% of the Seyferts sampled are strongly spatially disturbed (AS &gt; 0.2). The experimental design we employ reveals a ≳3σ obscuration–merger (NH–AS) correlation at 0.6 &lt; z &lt; 2.4, and also recovers a physical distinction between the X-ray- and mid-IR-detected AGN suggestive of their link to a common evolutionary scenario. Placing the observed pattern of disturbances in the context of the other average host-galaxy properties, we conclude that mergers are common among obscured AGN. This finding presents tension with the leading model on AGN fueling that requires Seyfert AGN with subquasar luminosities (Lbol &lt; 1045 erg s‑1) to evolve only through nonmerger mechanisms.

Keywords: AGN host galaxies
A Spectro-temporal View of Normal Branch Oscillations in Cygnus X-2 as Seen by NICER and NuSTAR. We report the spectro-temporal study of the neutron star low mass X-ray binary Cygnus X-2 using NICER and NuSTAR data while the source was in the normal branch (NB). We detect a normal branch oscillation (NBO) feature at ∼5.41 Hz that appears in the middle portion of the NB branch. We note that the NBO appeared only in the 0.5–3 keV energy range, with maximum strength in the 1–2 keV energy band, but was absent in the 3–10 keV energy band of NuSTAR and NICER data. The energy spectrum of the source exhibits an emission feature at ∼1 keV, previously identified as the Fe L transition in the outer region of the accretion disk. Upon considering both the Fe L and NBO features, we suggest that the originating location of the Fe L line and the NBOs may coincide and perhaps be due to the same underlying mechanism. Therefore, lags seen in the frequency-/energy-dependent lag spectra of Cygnus X-2 could be considered to be arising from a region of photoionized material far from the central source. We study the frequency and energy-dependent lag spectra of the source, which exhibited a few millisecond hard lag at the NBO frequency (12–15 ms) and a switch from hard to soft lags at 1 keV. The rms spectrum peaks at 1 keV, and the covariance spectrum clearly resembles a thermal spectrum. We discuss the spectro-temporal behavior of the NBO and attempt to constrain its location of origin.

Keywords: Low-mass x-ray binary stars
Microlensing Events in Five Years of Photometry from the Zwicky Transient Facility. Microlensing has a unique advantage for detecting dark objects in the Milky Way, such as free-floating planets, neutron stars, and stellar-mass black holes. Most microlensing surveys focus on the Galactic bulge, where higher stellar density leads to a higher event rate. However, microlensing events in the Galactic plane have closer lenses and longer timescales, which leads to a greater chance of measuring microlens parallax, providing an additional constraint on the mass of the lens. This work searches for microlensing events in Zwicky Transient Facility (ZTF) Data Release 17 from 2018 to 2023 in the Galactic plane region. We find 124 high-confidence microlensing events and 54 possible events, all available online (see footnote 11). Thus, with 2 yr of additional ZTF data in DR17, we have more than doubled the number of microlensing events (60) found in the previous 3 yr DR5 search. In the event selection, we use the efficient EventFinder algorithm to detect microlensing signals, which could be used for large data sets such as future ZTF data releases or data from the Rubin Observatory Legacy Survey of Space and Time. Using detection efficiencies of ZTF fields obtained from catalog-level simulations, we calculate the mean Einstein timescale to be &lt;t E&gt; = 51.7 ± 3.3 days, smaller than previous results of the Galactic plane but within 1.5σ. We also calculate optical depths and event rates, although some caution is needed due to the use of visual inspection when creating our final sample. Spectroscopy of three possible candidates confirms their microlensing nature.

Keywords: Gravitational microlensing, Milky Way disk