Sazuna/UAT_keywords huggingface dataset:
J1406+0102: A Dust-obscured Galaxy Hiding a Super-Eddington Accretion System with Bright Radio Emission. Recent high-z quasar observations strongly indicate that super-Eddington accretion is a crucial phase to describe the presence of supermassive black holes (SMBHs) with MBH ≳ 109 M⊙ at z ≳ 7. Motivated by theoretical predictions that the super-Eddington phase efficiently produces outflows and bright jets in radio bands, we identify a super-Eddington radio-loud dust-obscured galaxy (DOG) J1406+0102 at z = 0.2367. This source is discovered by cross-matching the infrared-bright DOGs of A. Noboriguchi et al. with the Very Large Array/Far-Infrared and Submillimetre Telescope 1.4 GHz radio survey data and the Sloan Digital Sky Survey optical spectral catalog. J1406+0102 shows broad components in the Balmer lines, and by assuming that those lines are from the broad-line region, they give black hole (BH) mass estimations of  log(MBH/M⊙)=7.30±0.25 . Combined with an active galactic nucleus (AGN) luminosity of  log(Lbol,[OIII]/ergs−1)=45.91±0.38  estimated from the intrinsic [O III] luminosity, this implies a super-Eddington accretion rate of λEdd ≃ 3. We show that (1) J1406+0102 shows strong AGN feedback, with the [O III] outflow velocity exceeding the escape velocity of the host galaxy halo and a kinetic efficiency of ≍8%, sufficient to quench the host galaxy; (2) its expected growth trajectory places it on an overmassive BH track; and (3) if representative of radio-loud DOGs, such sources can contribute significantly to the high-energy (≳100 TeV) cosmic neutrino background.

Keywords: Supermassive black holes, Quasars, Neutrino astronomy, Radio loud quasars, Active galactic nuclei
The Thermal Index of Neutron-star Matter in the Virial Approximation. Motivated by gravitational-wave observations of binary neutron-star mergers, we study the thermal index of low-density, high-temperature dense matter. We use the virial expansion to account for nuclear interaction effects. We focus on the region of validity of the expansion, which reaches 10‑3 fm‑3 at T = 5 MeV up to almost saturation density at T = 50 MeV. In pure neutron matter, we find an analytical expression for the thermal index, and show that it is nearly density and temperature independent, within a fraction of a percent of the noninteracting, nonrelativistic value of Γth ≈ 5/3. When we incorporate protons, electrons, and photons, we find that the density and temperature dependence of the thermal index changes significantly. We predict a smooth transition between an electron-dominated regime with Γth ≈ 4/3 at low densities to a neutron-dominated region with Γth ≈ 5/3 at high densities. This behavior is by and large independent of the proton fraction and is not affected by nuclear interactions in the region where the virial expansion converges. We model this smooth transition analytically and provide a simple but accurate parameterization of the inflection point between these regimes. When compared to tabulated realistic models of the thermal index, we find an overall agreement at high temperatures that weakens for colder matter. The discrepancies can be attributed to the missing contributions of nuclear clusters. The virial approximation provides a clear and physically intuitive framework for understanding the thermal properties of dense matter, offering a computationally efficient solution that makes it particularly well suited for the regimes relevant to neutron-star binary remnants.

Keywords: Neutron stars, Nuclear astrophysics, Astrophysical processes, Nuclear physics
Flickers, Bursts, and Dips: Detecting Rapid Variability with the g<SUP>(2)</SUP> Autocorrelation Function. Rapid optical transient events can be hard to detect because of the limited number of photons they produce. I discuss a method of inferring the presence of fast, chaotic variability in photometry using the normalized autocorrelation function, what is called g(2) in quantum optics. The variability's signature is a bump in the function at short lags. No periodicity is needed for the method to work. Versions of this method are attested in stellar variability studies, but its uses in some other subfields apparently have not been realized. I calculate expected signal-to-noise ratios with shot noise and scintillation. This method could be used to find unknown phenomena, particularly submillisecond optical variability. I present simple models of three example use cases: a flickering artificial "lantern" near a host Sun, optical microbursts from the Crab pulsar, and frequent irregular transits of a star by cometary bodies.

Keywords: Optical bursts, Variable radiation sources, Technosignatures, Astronomical techniques, Time series analysis
High-velocity Molecular Clouds in M83. High-velocity clouds (HVCs), which are gas clouds moving at high velocity relative to the galactic disk, may play a critical role in galaxy evolution, potentially supplying gas to the disk and triggering star formation. In this study, we focus on the nearby face-on barred spiral galaxy M83, where high-spatial-resolution, high-sensitivity CO(1–0) data are available. We identified molecular clouds and searched for clouds with velocities deviating by more than 50 km s‑1 from the disk velocity field as HVCs. A total of 10 HVCs were detected—9 redshifted and 1 blueshifted—clearly highlighting an asymmetry in their velocity distribution. These HVCs have radii of 30–80 pc, masses on the order of 105 M⊙, and velocity dispersions of 3–20 km s‑1, displaying a tendency toward higher velocity dispersion compared to disk molecular clouds in M83. Most of the HVCs do not overlap with the candidates of supernova remnants, and the energy needed to drive HVCs at such high velocities exceeds single supernova energy. Together with the asymmetry in their velocity distribution, we thus conclude that most of the HVCs found in this study are inflow from outside the M83's disk.

Keywords: High-velocity clouds, Molecular clouds, Interstellar medium
Quantifying the Velocity Anisotropy Profile of Galaxy Clusters Using the Uchuu Cosmological Simulation. Galaxy clusters are powerful laboratories for studying both cosmic structure formation and galaxy evolution. We present a comprehensive analysis of the velocity anisotropy profile, β(r), in galaxy clusters using the Uchuu-UniverseMachine mock galaxy catalog, which combines the large-volume Uchuu N-body simulation with the UniverseMachine galaxy formation model. Focusing on clusters with  logM200≥13.9[h‑1M⊙]  up to redshift z = 1.5, we investigate the behavior of β(r) as a function of clustercentric radius, mass, and redshift. We find that β(r) exhibits a universal shape: it rises from isotropic values near the cluster core, peaks at ∼1.7R200, declines around 3.4R200 due to orbital mixing, and increases again in the outskirts, due to the dominance of first-infalling galaxies. Our results show that more massive clusters have higher radial anisotropy and larger peak β values. Moreover, β(r) evolves with redshift, with high-redshift clusters displaying more radially dominated orbits and enhanced infall motions. We further derive redshift-dependent power-law scaling relations between M200 and key physical radii—hydrostatic (Rhs), infall ( Rinf ), and turnaround (Rta). These findings offer a robust theoretical framework for interpreting the dynamical properties of observed galaxy clusters and provide key insights into the evolution of their dynamical state over cosmic time.

Keywords: Galaxy clusters, N-body simulations, Galaxies, Dynamical evolution
Magnetized Accretion onto Neutron Stars: From Photon-trapped to Neutrino-cooled Flows. When a neutron star (NS) intercepts gas from a nondegenerate star, e.g., in a tidal disruption event, a common-envelope phase, or the collapsing core of a massive star, photons become trapped in the hot flow around the NS. This gas forms a radiatively inefficient accretion flow (RIAF) until the density and temperature close to the NS surface grow large enough for binding energy to be converted to neutrinos. Here, we present three-dimensional, general-relativistic, magnetohydrodynamic simulations of accretion onto a nonrotating, unmagnetized NS. These connect, for the first time, an extended accretion disk with a self-consistent hydrostatic atmosphere around the star. The impact of different seed magnetic fields and accretion rates is studied by approximating the radiation-pressure-dominated flow as an ideal gas with an adiabatic index of 4/3, coupled to a variable neutrino emissivity. At low accretion rates, the hydrostatic atmosphere shows slow rotation and weak magnetization, transitioning to an outer RIAF structure. A toroidal magnetic field mediates the inward flow of energy and angular momentum through the atmosphere, which reaches a steady state when neutrino emission balances the accretion power. We develop a one-dimensional analytical model connecting these results with more general initial conditions and describing the main features of the flow. Our results have implications for the spin and mass evolution of hypercritically accreting NSs.

Keywords: Neutron stars, Accretion, Magnetohydrodynamical simulations
Mass Ratio Dependence of Strong Guide Field Reconnection Based on a Gyrokinetic Electron and Fully Kinetic Ion Particle Simulation. Magnetic reconnection under a strong guide field  BG/By0≫1 , as in solar wind and laboratory plasmas, is investigated using the gyrokinetic electron and fully kinetic ion (GeFi) particle simulation model, where  By0  is the antiparallel component of the magnetic field and  BG  is the guide field. Cases with two-dimensional force-free current sheets are presented in conditions with a large guide field and low plasma beta, similar to the reconnection events associated with solar flares. To gain insights into how the ion-to-electron mass ratio ( mi/me ) and normalized guide field ( BG/By0 ) affect the rate and structures of reconnection, we present a series of simulations by varying  mi/me  from 100 to 1836 and  BG/By0  from 5 to 15. First, linear eigenmode analysis is performed for the collisionless tearing mode. We find that the eigenmode structure and growth rate of the tearing mode obtained from the GeFi simulation are in excellent agreement with the eigenmode theory for strong  BG . Subsequently, we employ GeFi simulations to explore the reconnection rate and current sheet structure across a wide range of  mi/me  and  BG/By0 . Intriguingly, it is found that the reconnection rate is insensitive to  mi/me . The growth rate of the tearing mode, however, has a strong dependence on  mi/me . The reconnection rate exhibits a clear increase with decreasing  BG/By0  and also strongly depends on  BG/By0 . Furthermore, the length of the electron diffusion region increases with  mi/me . These findings advance understanding of the reconnection dynamics in solar flares and other astrophysical phenomena.

Keywords: Space plasmas, Solar magnetic reconnection
Origin of the IRAS Vela Shell: New Insights from 3D Dust Mapping. The IRAS Vela Shell (IVS) is a structure of enhanced far-IR (FIR) emission located toward the Gum Nebula, a prominent region of Hα emission in the local Milky Way shaped by various galactic stellar feedback over the past several million years. We constrain the 3D spatial geometry of the IVS using a parsec-resolution 3D dust map and contextualize it within the broader Gum Nebula. Our analysis reveals a dense, bowl-like IVS structure below the Galactic plane, with a more diffuse component above. We obtain a total shell mass of  5.1‑2.4+2.4×104M⊙  and, incorporating previous studies on shell expansion, a momentum of  6.0‑3.4+4.7×105M⊙kms‑1 . We find a spatial correlation between the morphology of the dust-traced IVS and the Gum Nebula's Hα emission when projected onto the sky. We quantify contributions of feedback from stellar winds, an expanding H II region, and supernovae to the IVS formation, finding that stellar winds are subdominant. Our momentum analysis shows that both an H II region and supernova feedback could drive the shell's expansion. Using astrometric constraints from Gaia and Hipparcos, we trace back nearby feedback sources and find that the massive stars γ2 Velorum and ζ Puppis are currently within the IVS, producing enough ionizing luminosity to form an H II region of comparable size. Alternatively, if the IVS' momentum is primarily driven by supernovae, one to two events would be required. We also identify several young massive clusters that could have hosted supernovae within the past 3 Myr.

Keywords: Stellar feedback, Young star clusters, Young stellar objects, Interstellar medium, H II regions, Superbubbles
Galaxy Zoo CEERS: Bar Fractions Up to z ∼ 4.0. We study the evolution of the bar fraction in disk galaxies between 0.5 &lt; z &lt; 4.0 using multiband colored images from JWST Cosmic Evolution Early Release Science Survey (CEERS). These images were classified by citizen scientists in a new phase of the Galaxy Zoo (GZ) project called GZ CEERS. Citizen scientists were asked whether a strong or weak bar was visible in the host galaxy. After considering multiple corrections for observational biases, we find that the bar fraction decreases with redshift in our volume-limited sample (n = 398); from  25‑4+6 % at 0.5 &lt; z &lt; 1.0 to  3‑1+6 % at 3.0 &lt; z &lt; 4.0. However, we argue it is appropriate to interpret these fractions as lower limits. Disentangling real changes in the bar fraction from detection biases remains challenging. Nevertheless, we find a significant number of bars up to z = 2.5. This implies that disks are dynamically cool or baryon dominated, enabling them to host bars. This also suggests that bar-driven secular evolution likely plays an important role at higher redshifts. When we distinguish between strong and weak bars, we find that the weak bar fraction decreases with increasing redshift. In contrast, the strong bar fraction is constant between 0.5 &lt; z &lt; 2.5. This implies that the strong bars found in this work are robust long-lived structures, unless the rate of bar destruction is similar to the rate of bar formation. Finally, our results are consistent with disk instabilities being the dominant mode of bar formation at lower redshifts, while bar formation through interactions and mergers is more common at higher redshifts.

Keywords: Galaxy bars, Disk galaxies, Galaxy classification systems, Galaxy evolution, High-redshift galaxies
Milliarcsecond X-Ray Positions and X-Ray Varstrometry for the Strongly Lensed Active Galactic Nucleus HE 0435-1223. Active galactic nuclei (AGN) are some of the most powerful objects in the Universe. For this reason, they can be observed up to high redshifts (z), giving valuable insights into the evolution of our Universe. However, high-z AGN are too distant to be spatially resolved with current or upcoming X-ray facilities. In this paper, we show how we can exploit gravitationally lensed AGN to significantly increase spatial resolution even at high z. We combine astrometric data from Gaia DR3 with imaging from the Chandra X-ray Observatory of the quadruply lensed quasar HE 0435-1223 to measure for the first time possible offsets between the optical and the X-ray emissions. We measure the X-ray source position for HE 0435-1223 within a 1σ quasi-elliptical region of 0.5 × 1.3 milliarcsecond (mas), about 150 pc2 at the redshift of the source (z = 1.689). We find evidence for the X-ray emission being offset by a projected 3 mas from the Gaia (optical) emission. The positional offset is most likely associated with a portion of the X-ray emission arising from an X-ray jet or outflow. We also discuss how this method can be used to indicate the presence of a binary/offset AGN system.

Keywords: X-ray astronomy, Active galactic nuclei, Gravitational lensing
Softness Ratio of SWIFT Gamma-Ray Bursts and Relevant Correlations. The properties of X-ray flashes (XRFs) and X-ray-rich gamma-ray bursts (XRRs) as compared with classical gamma-ray bursts (C-GRBs) have been widely discussed during the SWIFT era. It has been proposed that XRFs and XRRs are low-energy extensions of the gamma-ray burst (GRB) population, and therefore, they should follow similar correlations. To further examine this idea, we collect a sample of 303 GRBs detected by SWIFT over the past two decades, all of which have reliable redshifts and spectral parameters. The bursts are classified into XRFs, XRRs, and C-GRBs based on their softness ratio (SR), which is calculated by dividing the 25–50 keV fluence with the 50–100 keV fluence. A strong correlation is found among the isotropic energy Eiso, peak luminosity Lp, and rest-frame burst duration T90,rest, i.e.,  Eiso∝Lp0.88±0.02T90,rest0.58±0.02 . Additionally, two tight three-parameter correlations involving SR and the rest-frame peak energy Ep are also derived, i.e.,  Ep∝Eiso0.20±0.02SR‑2.27±0.15  and  Ep∝Lp0.17±0.02SR‑2.33±0.14 . It is interesting to note that XRFs, XRRs, and C-GRBs all follow the above correlations. The implications of these correlations and their potential application in cosmology are discussed.

Keywords: Gamma-ray bursts, High energy astrophysics, Astronomy data analysis, Non-thermal radiation sources, Markov chain Monte Carlo
Why is the Star Formation Rate Proportional to Dense Gas Mass?. One of the most profound empirical laws of star formation is the Gao─Solomon relation, a linear correlation between the star formation rate (SFR) and the dense molecular gas mass. It is puzzling how the complicated physics in star formation results in this surprisingly simple proportionality. Using archival Herschel and Atacama Large Millimeter/submillimeter Array observations, we derived the masses of the most massive cores ( Mcoremax ) and masses of the gravitationally bound gas ( Mgasbound ) in the parent molecular clouds for a sample of low-mass and high-mass star-forming regions. We discovered a significant correlation of  log(Mcoremax/M⊙)=0.506log(Mgasbound/M⊙)−0.32 . Our discovered  Mcoremax ─ Mgasbound  correlation can be approximately converted to the Gao─Solomon relation if there is (1) a constant 30% efficiency of converting  Mcoremax  to the mass of the most massive star ( mstarmax ), and (2) if the SFR and  mstarmax  are tightly related through  log(SFR/(M⊙yr−1))=2.04log(mstarmax/M⊙)−5.80 . Intriguingly, both requirements have been suggested by previous theoretical studies. Based on this result, we hypothesize that the Gao─Solomon relation is a consequence of combining the following three nontrivial relations (i) SFR versus  mstarmax , (ii)  mstarmax  versus  Mcoremax , and (iii)  Mcoremax  versus  Mgasbound . This finding may open a new possibility to understand the Gao─Solomon relation in an analytic sense.

Keywords: Star formation, Initial mass function, Molecular clouds
Prestellar Cores in Turbulent Clouds: Numerical Modeling and Evolution to Collapse. A fundamental issue in star formation is understanding the precise mechanisms leading to the formation of prestellar cores and their subsequent gravitationally unstable evolution. To address this question, we carefully construct a suite of turbulent, self-gravitating numerical simulations, and analyze the development and collapse of individual prestellar cores. We show that the numerical requirements for resolving the sonic scale and internal structure of anticipated cores are essentially the same in self-gravitating clouds, calling for the number of cells per dimension to increase quadratically with the cloud's Mach number. In our simulations, we follow the evolution of individual cores by tracking the region around each gravitational potential minimum over time. Evolution in nascent cores is toward increasing density and decreasing turbulence, and there is a wide range of critical density for initiating collapse. At a given spatial scale, the turbulence level also varies widely and tends to be correlated with density. By directly measuring the radial forces acting within cores, we identify a distinct transition to a state of gravitational runaway. We use our new theory for turbulent equilibrium spheres to predict the onset of each core's collapse. Instability is expected when the critical radius becomes smaller than the tidal radius; we find good agreement with the simulations. Interestingly, the imbalance between gravity and opposing forces is only ∼20% during core collapse, meaning that this is a quasi-equilibrium rather than a freefall process. For most of their evolution, cores exhibit both subsonic contraction and transonic turbulence inherited from core-building flows; supersonic radial velocities accelerated by gravity only appear near the end of the collapse.

Keywords: Star formation, Molecular clouds, Interstellar medium
Prospect of Gamma-Ray Burst Neutrino Detection with Enhanced Neutrino Detectors. Gamma-ray bursts (GRBs) have long been proposed as a potential source of high-energy neutrinos. Although no confirmed association between GRBs and neutrinos has been established, meaningful constraints have been placed on GRB prompt emission models. The nondetection of neutrinos, reported by the IceCube Collaboration, from both single and stacked GRB events suggests that the radiation zone is likely located at a considerable distance from the central engine, where the photon number density is relatively low. Here, we estimate future GRB neutrino detection probabilities using detectors with a higher simulated sensitivity than IceCube and explore the constraints on models if GRB neutrinos remain undetected despite improved sensitivity. Our findings reveal that if the effective area of a future neutrino detector can be enhanced by a factor of 10 compared to IceCube IC 86-II, there is a high likelihood of detecting neutrinos from a GRB 221009A-like event, even in the context of the ICMART model, which exhibits the lowest efficiency in neutrino production. With such an advanced detector (enhanced by a factor of 10) and 5–10 yr of data accumulation, neutrinos from stacked GRBs should be identifiable, or several popular models for GRB prompt emission (e.g., the dissipative photosphere model and internal shock model) could be effectively ruled out.

Keywords: Neutrino telescopes, Gamma-ray bursts, Cosmological neutrinos
In-depth Analysis of the 2022 March 28 <SUP>3</SUP>He-rich Solar Energetic Particle Event. On 2022 March 28, a solar eruption from active region AR 12975 produced a solar energetic particle (SEP) event observed by BepiColombo (BC; 0.57 au), STEREO-A (STA; 0.97 au), GOES (1.0 au), ACE (L1), and Wind (L1). The event was associated with an M4.0 soft X-ray flare peaking at 11:29 UTC, a Type III radio burst (0.1–16 MHz) at 11:24 UTC, a metric Type II radio burst (25–250 MHz) at 11:23 UTC, and a coronal mass ejection with a speed of 700 km s‑1. BC and STA, magnetically aligned along the same Parker spiral and well connected to the flare site (footpoint separations of 19 .° 8 and 16 .° 5, respectively), detected a gradual SEP event with remarkable impulsive characteristics, including a high 3He/4He ratio (0.7 at 1 MeV), elevated Fe/O ratio (∼0.5 increasing with energy), a 3He spectrum harder than that of other ions, and particle dropouts at BC linked to intermittent magnetic connections. Near-Earth spacecraft (44 .° 8 from the flare site) observed abundance ratios closer to coronal values, and more uniform proton/heavy-ion spectra. Our findings suggest both the contribution of particles accelerated by a quasi-parallel shock and a direct contribution from flare suprathermals, accelerated during postflare ongoing reconnection, at well connected spacecraft.

Keywords: Solar energetic particles