Sazuna/UAT_keywords huggingface dataset:
Direct Collapse Pre-supermassive Black Hole Objects as Lyα Emitters. The Direct Collapse scenario to form the supermassive black hole (SMBH) seeds offers the most promising way to explain the origin of quasars at z &gt; 7. Assuming atomic primordial gas, can Lyα photons escape from the central regions of the collapse and serve as a diagnostic for the detection of these pre-SMBH objects? Models of spherical collapse have found these photons to be trapped and destroyed. We use Lyα radiation transfer within the inflow-outflow geometry, based on earlier zoom-in cosmological modeling involving radiation transfer and magnetic forces. Adopting geometry that includes ongoing disk and spherical accretion, and formation of a biconical outflow funnel, we obtain the formation of a dense radiatively driven expanding shell. The Lyα transfer is performed using a Monte Carlo algorithm, accounting for the destruction of Lyα photons and the emergence of two-photon emission. We find that a substantial fraction of Lyα photons can escape through the funnel and calculate the line profiles, their line peak velocity shift, asymmetry, and cuspiness, by varying basic model parameters. The escaping Lyα emission is anisotropic and sensitive to the overall inflow-outflow geometry. The escaping fraction of Lyα radiation exceeds 95% from a z = 10 pre-SMBH object in principle detectable by the JWST NIRSpec in the multiobject spectroscopy mode, during ∼104 s for a 10σ signal-to-noise ratio. Moreover, comparisons with line shapes from high-z galaxies and quasars allow us to separate them from pre-SMBH objects based on the line shape: the pre-SMBH lines show a profound asymmetry and extended red tail.

Keywords: Supermassive black holes, Galaxy formation, Hydrodynamics, Quasars, Gravitational collapse, Radiative processes
Energy Spectrum and Mass Composition of Ultra-high-energy Cosmic Rays Originating from Relativistic Jets of Nearby Radio Galaxies. Relativistic jets of radio galaxies (RGs) are possible sources of ultra-high-energy cosmic rays (UHECRs). Recent studies combining relativistic hydrodynamic simulations with Monte Carlo particle transport have demonstrated that UHECRs can be accelerated to energies beyond 1020 eV through shocks, turbulence, and relativistic shear in jet-induced flows of Fanaroff–Riley type RGs. The resulting time-asymptotic UHECR spectrum is well modeled by a double power law with an "extended" exponential cutoff, primarily shaped by relativistic shear acceleration. In this study, we adopt this novel source spectrum and simulate the propagation of UHECRs from nearby RGs using the CRPropa code. We focus on Virgo A (Vir A), Centaurus A (Cen A), Fornax A (For A), and Cygnus A (Cyg A), expected to be the most prominent UHECR sources among RGs. We then analyze the energy spectrum and mass composition of UHECRs arriving at Earth. We find that, due to the extended high-energy tail in the source spectrum, UHECRs from Vir A, which has a higher Lorentz factor, exhibit a higher flux at the highest energies and a lighter mass composition at Earth compared to those from Cen A and For A with lower Lorentz factors. Despite Cyg A having an even higher Lorentz factor, the large distance limits its contribution. With a small number of nearby prominent RGs, our findings suggest that if RGs are the major sources of UHECRs, the energy spectrum and mass composition of observed UHECRs would exhibit hemispheric differences between the Northern and Southern skies at the highest energies.

Keywords: Relativistic jets, Fanaroff-Riley radio galaxies, Cosmic rays
Zones of Tayler Instability in Stars. The Tayler instability (TI) of toroidal magnetic fields is a candidate mechanism for driving turbulence, angular momentum (AM) transport, and dynamo action in stellar radiative zones. Recently V. A. Skoutnev &amp; A. M. Beloborodov (2024) revisited the linear stability analysis of a toroidal magnetic field in a rotating and stably stratified fluid. In this paper, we extend the analysis to include both thermal and compositional stratification, allowing for general application to stars. We formulate an analytical instability criterion for use as a "toggle switch" in stellar evolution codes. It determines when and where in a star the TI develops with a canonical growth rate as assumed in existing prescriptions for AM transport based on Tayler–Spruit dynamo. We implement such a toggle switch in the MESA stellar evolution code and map out the stability of each mode of the TI on a grid of stellar evolution models. In evolved lower-mass stars, the TI becomes suppressed in the compositionally stratified layer around the hydrogen-burning shell. In higher-mass stars, the TI can be active throughout their radiative zones but at different wavenumbers than previously expected.

Keywords: Stellar interiors, Magnetohydrodynamics, Stellar physics, Stellar rotation, Astrophysical fluid dynamics
JWST UNCOVERs the Optical Size–Stellar Mass Relation at 4 &lt; z &lt; 8: Rapid Growth in the Sizes of Low-mass Galaxies in the First Billion Years of the Universe. We study the rest-frame optical and ultraviolet (UV) morphology of galaxies in the first billion years of the Universe. Using James Webb Space Telescope data from the UNCOVER and MegaScience surveys targeting the lensing cluster A2744, we present multiband morphological measurements for a sample of 995 galaxies selected using 20-band NIRCam photometry and 35 using NIRSpec Prism spectroscopy over the redshift range of 4 &lt; z &lt; 8. The wavelength-dependent morphology is measured using pysersic by simultaneously modeling the images in six NIRCam wide filters covering the rest-frame UV to optical. The joint modeling technique increases the precision of measured radii by 50%. Galaxies in our sample show a wide range of Sérsic indices, with no systematic difference between optical and UV morphology. We model the size–mass relation in a Bayesian manner using a continuity model to directly fit the redshift evolution while accounting for observational uncertainties. We find the average size of galaxies at  logM*/M⊙=8.5  grows rapidly, from 400 pc at z = 8 to 830 pc at z = 4. This is faster evolution than expected from power-law scalings of the Hubble parameter or scale factor that describe well previous results at z &lt; 2. This suggests that different and/or much stronger processes affect low-mass systems during the epoch of reionization. The measured logarithmic slope (0.25) and scatter (0.23 dex) are nonevolving. We discuss the remarkable consistency of the slope and scatter over cosmic time in the context of the galaxy–halo connection.

Keywords: Galaxy formation, High-redshift galaxies, Scaling relations, Galaxy radii
Galactic Magnetic Fields. II. Applying the Model to Nearby Galaxies. Many spiral galaxies host magnetic fields with energy densities comparable to those of the turbulent and thermal motions of their interstellar gas. However, quantitative comparison between magnetic field properties inferred from observation and those obtained from theoretical modeling has been lacking. In L. Chamandy et al. (Paper I), we developed a simple, axisymmetric galactic dynamo model that uses various observational data as input. Here, we apply our model to calculate radial profiles of azimuthally and vertically averaged magnetic field strength and pitch angle, gas velocity dispersion and scale height, turbulent correlation time and length, and the sizes of supernova remnants for the galaxies M31, M33, M51, and NGC 6946, using input data collected from the literature. Scaling factors are introduced to account for a lack of precision in both theory and observation. Despite the simplicity of our model, its outputs agree fairly well with galaxy properties inferred from observation. Additionally, we find that most of the parameter values are similar between galaxies. We extend the model to predict the magnetic field pitch angles arising from a combination of mean-field dynamo action and the winding up of the random small-scale field owing to the large-scale radial shear. We find their magnitudes to be much smaller than those of the pitch angles measured in polarized radio and far-infrared emission. This suggests that effects not included in our model, such as effects associated with spiral arms, are needed to explain the pitch angle values.

Keywords: Galaxy magnetic fields, Scaling relations, Supernova remnants, Interstellar medium, Radio continuum emission, Spiral pitch angle, Scale height
The Influence of the Nuclear Shadowing Effect on Astrophysical Neutrino Flux. The production of neutrinos from ultrahigh-energy cosmic rays (UHECRs) is modulated by nuclear shadowing effects that are often overlooked in theoretical models. Nuclear shadowing, the suppression of pion production in photonuclear interactions within heavy nuclei, plays a critical role in determining neutrino yields. Current predictions frequently assume that UHECRs are proton-dominated and neglect the nuclear medium's influence on pion cross sections, leading to overestimates of neutrino fluxes. Here, we incorporate nuclear shadowing effects into simulations of proton–photon (pγ) and proton–proton (pp) interactions in astrophysical source environments. We also account for nuclear photodisintegration in pγ processes, which further modifies secondary particle production. We integrate these effects into pure composition scenarios (p, He, N, and Fe) to calculate the resultant neutrino background flux. Our results demonstrate that nuclear shadowing can reduce neutrino fluxes from heavy nuclei by a factor of 2–3 compared to proton-only scenarios.

Keywords: Neutrino astronomy, Cosmic ray astronomy
A Glimpse of Satellite Galaxies in the Milky Way with the 2.5 m Wide Field Survey Telescope (WFST): Boötes III and Draco. We carry out deep imaging of the Milky Way satellite galaxies, Boötes III and Draco, with the Wide Field Survey Telescope (WFST) as one pilot observing program to demonstrate the capability of WFST. Combining catalogs with PS1 DR2 and Gaia DR3, we derive proper motions for candidate member stars in these two satellite galaxies over a 12 yr time baseline, yielding uncertainties of ∼1.8 mas yr‑1 at 21 mag and ∼3.0 mas yr‑1 at 22 mag in the r band. The proper motions derived from bright and faint stars are consistent, indicating no significant variation in proper motion across stellar luminosity as these galaxies undergo tidal interactions with the Milky Way (MW). Meanwhile, we suggest that Boötes III represents the bound remnant of the progenitor galaxy that gave rise to the Styx stream, as evidenced by its elongated density profile and overdensity in both spatial and kinematic space. This is the first paper to use WFST to measure the proper motions of faint stars in MW satellite galaxies. More detailed analyses will be presented in forthcoming papers from the wide field survey program.

Keywords: Dwarf galaxies, Galaxies, Galactic and extragalactic astronomy
The Vela Pulsar and Its Pulsar Wind Nebula Vela-X Using 13 Yr of Fermi-LAT Observations. We present results of more than 13 yr of Fermi─Large Area Telescope (LAT) data analysis for the Vela pulsar from 60 MeV to 100 GeV and its pulsar wind nebula (PWN), Vela X, for E &gt; 1 GeV in the off-pulse phases. We find that the Vela X PWN can be best characterized using two extended components: a large radial Gaussian accompanied by an offset, compact radial disk, both with a similar spectral index, Γ ∼ 2.3. The common spectral properties support a common PWN origin, but a supernova remnant component is plausible for the compact radial disk. With an updated Vela X model, the phase-resolved spectral properties of the Vela pulsar are explored through a phase-resolved analysis. The phase-resolved spectral properties of the pulsar, such as the spectral energy distribution (SED) peak energy Ep, the width of the SED at its peak dp, and the asymptotic (low-energy) spectral index Γ0, are presented. The best-fit spectral models for each LAT pulse peak (Peak 1 and Peak 2) are extrapolated to UV energies and compared to archival, phase-resolved spectra at UV, X-ray, soft γ-ray, and TeV energies. We also discuss the physical implications of our modeling and the data comparisons.

Keywords: Neutron stars, Pulsar wind nebulae, Pulsars
Detection of Four Intermediate-mass Stars with Cool Companions in Low Mass Ratio Eclipsing Binaries. According to the core fragmentation and dynamical capture theories of binary formation, binaries tend to form with nearly equal masses. The detection of intermediate-mass binaries with low mass ratios challenges these theories, as such binaries may form via disk fragmentation and are very important to investigate binary formation and evolution. However, there are few confirmed samples to robustly test theories of the formation and evolution of binaries due to observational challenges. The development of high-precision space telescopes brings opportunities to study such samples. Based on TESS data, we present the first study on four intermediate-mass eclipsing binaries with the Wilson–Devinney method, which are: TIC 283881816, TIC 343757299, TIC 72444347, and TIC 353077789. All are totally detached eclipsing binaries with q &lt; 0.4. TIC 283881816, TIC 343757299, and TIC 72444347 are A-type binaries with mass ratios of q = 0.34, 0.28, 0.39, respectively. TIC 353077789 is a B-type binary with an extremely low mass ratio of q = 0.18. These low mass ratio systems imply that they are highly likely to be formed via disk fragmentation and will undergo a common envelope evolution. Particularly, TIC 72444347 with a period of 4 .d 4 still shows an eccentric orbit, while TIC 343757299 with a longer period (5 .d 8) does not, which poses a challenge to the Kraft break. By plotting these components in the H-R diagram, it hints that all systems are main-sequence (MS) primaries with pre-MS companions. They are valuable targets for testing theories of binary formation and evolution.

Keywords: Close binary stars, Multiple stars, Eclipsing binary stars
Time-integrated Polarization of Structured Jets in Gamma-Ray Burst Prompt Emission. The structure of gamma-ray burst (GRB) jets remains one of the most significant open questions in high-energy astrophysics. Observations of events like GRB 170817A, associated with gravitational waves, and the exceptionally bright GRB 221009A suggest that jets may be structured rather than uniform. Polarization studies offer a powerful tool to probe jet structures, complementing traditional spectral analyses. This study examines the polarization degree (PD) of two types of structured jets under different magnetic field configurations (MFCs). The first type features a core with constant energy per unit solid angle, transitioning to a power-law decay at the edges. The second type exhibits a continuous decay of both energy per unit solid angle and Lorentz factor, controlled by a decay index. Additionally, motivated by jet-ambient medium interactions, we introduce a structured magnetic field model: the jet core region is dominated by an ordered magnetic field, while the ratio of ordered to random field strengths in the jet outer region follows a power-law decay. The results show that structured jets with ordered magnetic fields exhibit higher PD than uniform jets, especially when viewed off-axis, while random magnetic fields have minimal impact on structured jet PD. The PD difference between on-axis and off-axis observations decreases for jets with a shallow decay index, contrasting with uniform jets. If observed, PD shows little variation with fluence ratio, which strongly indicates a structured jet. Furthermore, within the structured magnetic field framework, random fields generally suppress polarization, but the random MFC can enhance off-axis polarization to some extent.

Keywords: Gamma-ray bursts, Magnetic fields
Radio Prospects of Extrasolar Aurorae Polaris as a Probe of Planetary Magnetism. Magnetized exoplanets are expected to emit auroral cyclotron radiation in the radio regime due to the interactions between their magnetospheres, the interplanetary magnetic field, and the stellar wind. Prospective extrasolar auroral emission detections will constrain the magnetic properties of exoplanets, allowing the assessment of the planets' habitability and their protection against atmospheric escape by photoevaporation, enhancing our understanding of exoplanet formation and demographics. We construct a numerical model to update the estimates of radio emission characteristics of confirmed exoplanets while quantifying the uncertainties of our predictions for each system by implementing a Monte Carlo error propagation method. We identify 16 candidates that have expected emission characteristics that render them potentially detectable from current ground-based telescopes. Among these, the hot Jupiter tau Boötis b is the most favorable target, with an expected flux density of  51‑22+36  mJy. Notably, 11 candidates are super-Earths and sub-Neptunes, for which magnetism is key to understanding the associated demographics. Together with the other predictive works in the literature regarding the characteristics and the geometry of magnetospheric emissions, our predictions are expected to guide observational campaigns in pursuit of discovering magnetism on exoplanets.

Keywords: Star-planet interactions, Magnetic fields, Exoplanets
Estimating Bolometric Luminosities of Type 1 Quasars with Self-organizing Maps. We present a new method to calculate bolometric luminosities for unobscured, type 1 quasars with multiband photometric data. Bolometric luminosity is a fundamental property for understanding quasars, and it is commonly estimated from monochromatic luminosities using bolometric corrections that often neglect quasar spectral energy distribution (SED) diversity. We take advantage of the fact that most quasars now have multiband observations from UV to mid-IR and construct SEDs for a well-defined sample of Sloan Digital Sky Survey (SDSS) quasars at 0.5 ≤ z ≤ 2. Based on this fiducial sample, we explore quasar SEDs, their diversity, and their relations with bolometric luminosities. We then use unsupervised neural network self-organizing maps (SOM) to describe the SED diversity and compute the bolometric luminosities with a fully trained SOM model. This method reduces systematical uncertainties compared to the traditional method. In addition, we update the multilinear regression relations between bolometric luminosity and monochromatic luminosities at rest frame 1450 Å, 3000 Å, and 5100 Å. Our method is applicable to large quasar samples with a wide range of luminosity and redshift. We have applied it to the SDSS Data Release 16 quasars. We have also made our code publicly available.

Keywords: Surveys, Neural networks, Spectral energy distribution, Quasars
N-body Simulations of Galaxy Bars Generated by Satellite Collisions: Effects of the Impact Geometry. Bars, a common and important structure in disk galaxies, can be induced by galaxy interactions. Although there have been some studies on bar formation in flybys or collisions, the vast parameter space still leaves many scenarios that require further investigation. Here, we focus on the role of collisions caused by small galaxies (denoted as intruders), referred to as satellite collisions, in bar formation for MW/M31-like galaxies (denoted as target galaxies). Multiple sets of simulations with varying intruder initial velocities, inclination angles, collision positions, and intruder masses were run to study the dependence of this mechanism on these parameters. Our simulations show that bar formation favors moderate collision velocity, large inclination angle, off-center collision position, and large intruder mass. However, the bar's pattern speed and length are insensitive to these parameters, as the intruder's mass is relatively small compared to that of the target galaxy itself. Moreover, based on our tests, the intruder mass should be more than ∼3 × 109 M⊙ in order for this bar formation mechanism to operate effectively in MW/M31-like galaxies. Our work suggests the possibility that satellite collisions may have contributed, to some extent, to the bar formation in the Milky Way or M31.

Keywords: N-body simulations, Barred spiral galaxies, Galaxy evolution, Galaxy collisions
Gaussian Process Modeling Coronal X-Ray Variability of Active Galactic Nuclei. The corona is an integral component of active galactic nuclei (AGNs) that can produce the X-ray emission. However, many of its physical properties and the mechanisms powering this emission remain a mystery. In this work, we study the coronal X-ray variabilities of 13 AGNs by the Gaussian process. Overall, 2–10 keV light curves of 13 AGNs can be successfully described by the damped random walk model. The extracted coronal X-ray timescales range from 3 to 50 days. In the plot of variability timescale versus black hole mass, the coronal X-ray timescales of four sources occupy almost the same region as the optical timescales of the accretion disk, with the latter matching the predicted thermal instability timescale of the disk. In contrast, the X-ray timescales of the remaining sources exhibit a systematic offset toward lower values. We propose that the coronal X-ray variability may be driven by internal processes within the corona itself (such as thermal conduction). On the other hand, it may also be triggered by local thermal instabilities occurring in different regions (close to the central black hole) of the accretion disk, which propagate to the corona via disk–corona coupling.

Keywords: Light curves, X-ray active galactic nuclei, Active galactic nuclei, Time series analysis
The Physical Mechanism of Radio-quiet Turn-on Changing-look Active Galactic Nuclei. It is suggested that the variation of the mass accretion rate in the accretion disk may be responsible for the occurrence of most changing-look active galactic nuclei (CL AGNs). However, the viscous timescale of a thin disk is far longer than the observed timescale of CL AGNs. Though this problem can be resolved by introducing the large-scale magnetic field, the mechanism for radio-quiet CL AGNs with a weak/absent large-scale magnetic field remains a mystery. In this work, we assume that the thin accretion disk is collapsed from the inner advection-dominated accretion flow (ADAF) instead of being formed from the outer thin disk through advection. This idea is tested by comparing the cooling timescale (tcool) of an ADAF with the observed timescale (ttran) of turn-on CL AGNs. We compile a sample of 102 turn-on CL AGNs from the archived data and calculate the cooling timescale of an ADAF with the critical mass accretion rate based on some conventional assumptions. It is found that tcool is much shorter than ttran in most of the CL AGNs, which validates our assumption, though tcool is not consistent with ttran (tcool &lt; ttran). However, this is reasonable since most of the CL AGNs were observed only two times, indicating that the observed timescale ttran is the maximum value because the changing-look behavior can indeed happen before the second observation.

Keywords: Accretion, Black hole physics, Active galactic nuclei, Magnetic fields