Sazuna/UAT_keywords huggingface dataset:
Enhanced X-Ray Emission from the Most Radio-powerful Quasar in the Universe's First Billion Years. We present deep (265 ks) Chandra X-ray observations of PSO J352.4034-15.3373, a quasar at z = 5.831 that, with a radio-to-optical flux ratio of R &gt; 1000, is one of the radio-loudest quasars in the early universe and is the only quasar with observed extended radio jets of kiloparsec scale at z ≳ 6. Modeling the X-ray spectrum of the quasar with a power law, we find a best fit of ${\rm{\Gamma }}={1.99}_{-0.28}^{+0.29}$ , leading to an X-ray luminosity of ${L}_{2\mbox{--}10}={1.26}_{-0.33}^{+0.45}\times {10}^{45}\ \mathrm{erg}\ {{\rm{s}}}^{-1}$ and an X-ray to UV brightness ratio of αOX = -1.45 ± -0.11. We identify a diffuse structure 50 kpc (∼8″) to the NW of the quasar along the jet axis that corresponds to a 3σ enhancement in the angular density of emission and can be ruled out as a background fluctuation with a probability of P = 0.9985. While with few detected photons the spectral fit of the structure is uncertain, we find that it has a luminosity of L2-10 ∼ 1044 erg s-1. These observations therefore potentially represent the most distant quasar jet yet seen in X-rays. We find no evidence for excess X-ray emission where the previously reported radio jets are seen (which have an overall linear extent of 0"28), and a bright X-ray point source located along the jet axis to the SE is revealed by optical and NIR imaging to not be associated with the quasar.

Keywords: X-ray astronomy, Jets, Quasars, Radio loud quasars, X-ray quasars
Electron Vorticity at Dipolarization Fronts. Using magnetospheric multiscale high-resolution measurements, we present the first comprehensive investigation of electron vorticity developing at earthward-propagating dipolarization fronts (DFs). Superposed epoch analysis reveals that electron vorticity increases at and behind the DFs, with its average magnitude slightly larger than lower hybrid frequency, indicating that vorticity is related to Hall dynamics at the DFs. Vorticity at the DFs exhibits clear anisotropy, ω⊥ &gt; ω∥, where ω⊥, ω∥ are the components perpendicular and parallel to local magnetic field, respectively. Parametric dependence analysis shows that electron vorticity is well anticorrelated with electron density. We find that in a statistical sense, vorticity-induced magnetic field perturbations are not significant, although in a few cases vorticity can generate intense magnetic field perturbations. This study can improve our current understanding of the DF dynamics.

Keywords: Space plasmas, Solar magnetic reconnection, Plasma physics
Simultaneous NICER and NuSTAR Observations of the Ultracompact X-Ray Binary 4U 1543-624. We present the first joint NuSTAR and NICER observations of the ultracompact X-ray binary (UCXB) 4U 1543-624 obtained in 2020 April. The source was at a luminosity of L0.5-50 keV = 4.9(D/7 kpc)2 × 1036 erg s-1 and showed evidence of reflected emission in the form of an O VIII line, Fe K line, and Compton hump within the spectrum. We used a full reflection model, known as XILLVERCO, that is tailored for the atypical abundances found in UCXBs, to account for the reflected emission. We tested the emission radii of the O and Fe line components and conclude that they originate from a common disk radius in the innermost region of the accretion disk (Rin ≤ 1.07 RISCO). Assuming that the compact accretor is a neutron star (NS) and the position of the inner disk is the Alfvén radius, we placed an upper limit on the magnetic field strength to be B ≤ 0.7(D/7 kpc) × 108 G at the poles. Given the lack of pulsations detected and position of Rin, it was likely that a boundary layer region had formed between the NS surface and inner edge of the accretion disk with an extent of 1.2 km. This implies a maximum radius of the neutron star accretor of RNS ≤ 12.1 km when assuming a canonical NS mass of 1.4 M⊙.

Keywords: Accretion, Low-mass x-ray binary stars
Orbital Evolution of Binary Black Holes in Active Galactic Nucleus Disks: A Disk Channel for Binary Black Hole Mergers?. We perform a series of high-resolution 2D hydrodynamical simulations of equal-mass binary black holes (BBHs) embedded in active galactic nucleus (AGN) accretion disks to study whether these binaries can be driven to merger by the surrounding gas. We find that the gravitational softening adopted for the BBH has a profound impact on this result. When the softening is less than 10% of the binary separation, we show that, in agreement with recent simulations of isolated equal-mass binaries, prograde BBHs expand in time rather than contract. Eventually, however, the binary separation becomes large enough that the tidal force of the central AGN disrupts them. Only when the softening is relatively large do we find that prograde BBHs harden. We determine through detailed analysis of the binary torque, that this dichotomy is due to a loss of spiral structure in the circum-single disks orbiting each black hole when the softening is a significant fraction of the binary separation. Properly resolving these spirals—both with high resolution and small softening—results in a significant source of binary angular momentum. Only for retrograde BBHs do we find consistent hardening, regardless of softening, as these BBHs lack the important spiral structure in their circum-single disks. This suggests that the gas-driven inspiral of retrograde binaries can produce a population of compact BBHs in the gravitational-wave-emitting regime in AGN disks, which may contribute a large fraction to the observed BBH mergers.

Keywords: Black hole physics, Hydrodynamical simulations, Black holes, Gravitational wave sources, Active galactic nuclei
Size Limit of Superparamagnetic Inclusions in Dust Grains and Difficulty of Magnetic Grain Alignment in Protoplanetary Disks. Alignment of nonspherical grains with magnetic fields is an important problem, as it lays the foundation of probing magnetic fields with polarized dust thermal emissions. In this paper, we investigate the feasibility of magnetic alignment in protoplanetary disks (PPDs). We use an alignment condition that Larmor precession should be fast compared with the damping timescale. We first show that the Larmor precession timescale is some 3 orders of magnitude longer than the damping time for millimeter-sized grains under conditions typical of PPDs, making the magnetic alignment unlikely. The precession time can be shortened by superparamagnetic inclusions (SPIs), but the reduction factor strongly depends on the size of the SPI clusters, which we find is limited by the so-called "Néel's relaxation process." In particular, the size limit of SPIs is set by the so-called "anisotropic energy constant" of the SPI material, which describes the energy barrier needed to change the direction of the magnetic moment of an SPI. For the most common iron-bearing materials, we find maximum SPI sizes corresponding to a reduction factor of the Larmor precession timescale of order 103. We also find that reaching this maximum reduction factor requires fine-tuning on the SPI sizes. Lastly, we illustrate the effects of the SPI size limits on magnetic alignment of dust grains with a simple disk model, and we conclude that it is unlikely for relatively large grains of order 100 μm or more to be aligned with magnetic fields, even with SPIs.

Keywords: Interplanetary dust, Magnetic fields, Protoplanetary disks
Effects of Thermal Emission on Chandrasekhar's Semi-infinite Diffuse Reflection Problem. The analytical results of Chandrasekhar's semi-infinite diffuse reflection problem is crucial in the context of the stellar or planetary atmosphere. However, the atmospheric emission effect was not taken into account in this model, and the solutions are applicable only for a diffusely scattering atmosphere in the absence of emission. We extend the model of the semi-infinite diffuse reflection problem by including the effects of thermal emission B(T), and present how this affects Chandrasekhar's analytical end results. Hence, we aim to generalize Chandrasekhar's model to provide a complete picture of this problem. We use Invariance Principle Method to find the radiative transfer equation accurate for diffuse reflection in the presence of B(T). Then we derive the modified scattering function S(μ, φ; μ0, φ0) for different kinds of phase functions. We find that the scattering function S(μ, φ; μ0, φ0) as well as the diffusely reflected specific intensity I(0, μ; μ0) for different phase functions are modified due to the emission B(T) from layer τ = 0. In both cases, B(T) is added to the results of the only scattering case derived by Chandrasekhar, with some multiplicative factors. Thus the diffusely reflected spectra will be enriched and carry the temperature information of the τ = 0 layer. As the effects are additive in nature, hence our model reduces to the sub-case of Chandrasekhar's scattering model in the case of B(T) = 0. We conclude that our generalized model provides more accurate results due to the inclusion of the thermal emission effect in Chandrasekhar's semi-infinite atmosphere problem.

Keywords: Atmospheric effects, Radiative transfer
Spectro-temporal Studies of Rapid Transition of the Quasi-periodic Oscillations in the Black Hole Source H1743-322. An appearance or disappearance of quasi-periodic oscillations (QPOs) associated with the variation of X-ray flux can be used to decipher the accretion-ejection mechanism of black hole X-ray sources. We searched for and studied such rapid transitions in H1743-322 using archival data from the Rossi X-ray Timing Explorer and found eight such events, where a QPO vanishes suddenly along with the variation of X-ray flux. The appearance/disappearance of QPOs was associated with four events exhibiting type-B QPOs at ∼4.5 Hz: one was a type-A QPO at ν ∼ 3.5 Hz, and the other three were connected to type-C QPOs at ∼9.5 Hz. Spectral studies of the data revealed that the inner disk radius remained at the same location around 2-9 rg, depending on the model used, but power-law indices were varying, indicating that either a corona or a jet is responsible for the events. The probable ejection radii of coronas were estimated to be around 4.2-15.4 rg based on the plasma ejection model. Our X-ray and quasi-simultaneous radio correlation studies suggest that the type-B QPOs are probably related to the precession of a weak jet, though a small and weak corona is present at its base, and the type-C QPOs are associated with the base of a relatively strong jet, which is acting like a corona.

Keywords: Low-mass x-ray binary stars
Star Formation Efficiency and Dispersal of Giant Molecular Clouds with UV Radiation Feedback: Dependence on Gravitational Boundedness and Magnetic Fields. Molecular clouds are supported by turbulence and magnetic fields, but quantifying their influence on cloud life cycle and star formation efficiency (SFE) remains an open question. We perform radiation magnetohydrodynamic simulations of star-forming giant molecular clouds (GMCs) with UV radiation feedback, in which the propagation of UV radiation via ray tracing is coupled to hydrogen photochemistry. We consider 10 GMC models that vary in either initial virial parameter (1 ≤ αvir,0 ≤ 5) or dimensionless mass-to-magnetic flux ratio (0.5 ≤ μΦ,0 ≤ 8 and ∞ ); the initial mass 105 M⊙ and radius 20 pc are fixed. Each model is run with five different initial turbulence realizations. In most models, the duration of star formation and the timescale for molecular gas removal (primarily by photoevaporation) are 4-8 Myr. Both the final SFE (ɛ*) and time-averaged SFE per freefall time (ɛff) are reduced by strong turbulence and magnetic fields. The median ɛ* ranges between 2.1% and 9.5%. The median ɛff ranges between 1.0% and 8.0%, and anticorrelates with αvir,0, in qualitative agreement with previous analytic theory and simulations. However, the time-dependent αvir(t) and ɛff,obs(t) based on instantaneous gas properties and cluster luminosity are positively correlated due to rapid evolution, making observational validation of star formation theory difficult. Our median ɛff,obs(t) ≈ 2% is similar to observed values. We show that the traditional virial parameter estimates the true gravitational boundedness within a factor of 2 on average, but neglect of magnetic support and velocity anisotropy can sometimes produce large departures from traditional virial parameter estimates. Magnetically subcritical GMCs are unlikely to represent sites of massive star formation given their unrealistic columnar outflows, prolonged lifetime, and low escape fraction of radiation.

Keywords: Radiative magnetohydrodynamics, Stellar feedback, Magnetic fields, Giant molecular clouds, Star formation, Interstellar medium, H II regions
Energy Deposition by Cosmic Rays in the Molecular Cloud Using GEANT4 Code and Voyager I Data. Molecular clouds (MCs) are exposed to Galactic and extragalactic cosmic rays (CR) that trigger several physical and physicochemical changes, including gas and grain heating and molecular destruction and formation. Here we present a theoretical model describing the energy delivered by CRs, composed of protons, alphas, and electrons taken from Voyager I measurements, into a typical MC with 5400 M⊙ (composed mainly of H with a density law of r-1.2) and size around 1 × 106 au. The calculation was performed employing the Monte Carlo toolkit GEANT4 to obtain the energy deposition per mass from several types of secondary particles (considering nuclear and hadron physics). The results indicate that incoming protons contribute to most of the energy delivered in the MC in all regions (maximum ∼230 MeV g-1 s-1 at outer regions of the cloud). Secondary electrons are the second most important component for energy deposition in almost all layers of the MC and can deliver an energy rate of ∼130 MeV g-1 s-1 in the outer region of the MC. Other cascade particles have their major energy delivery in the central and denser core of the MC. From a temperature model (considering CR data from Voyager I), we observed (i) a small bump in temperature at the distance of 3 × 103-2 × 104 au from the center, (ii) a rapid temperature decrease (roughly 7 K) between the outer layer and the second most outer layer, and (iii) that, at a distance of 5 × 104 au (Av &gt; 10), the gas temperature of the MC is below 15 K.

Keywords: Secondary cosmic rays, Cosmic ray showers, Molecular clouds
Fast and Accurate Emulation of the SDO/HMI Stokes Inversion with Uncertainty Quantification. The Helioseismic and Magnetic Imager (HMI) on board NASA's Solar Dynamics Observatory produces estimates of the photospheric magnetic field, which are a critical input to many space weather modeling and forecasting systems. The magnetogram products produced by HMI and its analysis pipeline are the result of a per-pixel optimization that estimates solar atmospheric parameters and minimizes disagreement between a synthesized and observed Stokes vector. In this paper, we introduce a deep-learning-based approach that can emulate the existing HMI pipeline results two orders of magnitude faster than the current pipeline algorithms. Our system is a U-Net trained on input Stokes vectors and their accompanying optimization-based Very Fast Inversion of the Stokes Vector (VFISV) inversions. We demonstrate that our system, once trained, can produce high-fidelity estimates of the magnetic field and kinematic and thermodynamic parameters while also producing meaningful confidence intervals. We additionally show that despite penalizing only per-pixel loss terms, our system is able to faithfully reproduce known systematic oscillations in full-disk statistics produced by the pipeline. This emulation system could serve as an initialization for the full Stokes inversion or as an ultrafast proxy inversion. This work is part of the NASA Heliophysics DRIVE Science Center (SOLSTICE) at the University of Michigan, under grant NASA 80NSSC20K0600E, and will be open sourced.

Keywords: Computational methods, Convolutional neural networks, Solar magnetic fields
Effects of External Flow on Resonant Absorption of Coronal Loop Kink Oscillations Driven by an External Fast Wave: Selective Excitation Problem. Resonant absorption is considered to be a crucial mechanism for the damping of the coronal loop oscillations and plasma heating. We study resonant absorption of the coronal loop kink oscillations excited by such external drivers as flares, assuming that there is an intermediate shear flow region surrounding the loop. We find that for long coronal loops resonant absorption can be highly enhanced or reduced depending sensitively on the magnitude and direction of the flow and the spatial extent of the flow region when the transitional layer is thin. For short coronal loops, high flow speed and a thick transitional layer are needed to have a substantial resonant absorption. We provide a potential picture to explain the results where the external Alfvén speed and phase speed of the wave are important parameters. These results imply that the transport of the external wave energy into the loop is significantly changed by the shear flow region, which may cause the selective excitation of the coronal loop oscillations.

Keywords: Solar coronal loops, Magnetohydrodynamics
Multitracer Cosmological Line Intensity Mapping Mock Light-cone Simulation. Submillimeter emission lines are important tracers of the cold gas and ionized environments of galaxies and the targets for future line intensity mapping surveys. Physics-based simulations that predict multiple emission lines arising from different phases of the interstellar medium are crucial for constraining the global physical conditions of galaxies with upcoming line intensity mapping observations. In this work, we present a general framework for creating multitracer mock submillimeter line intensity maps based on physically grounded galaxy formation and submillimeter line emission models. We simulate a mock light cone of 2 deg2 over a redshift range $0\leqslant z\leqslant 10$ comprising discrete galaxies and galaxy [C II], CO, and [C I] emission. We present simulated line intensity maps for two fiducial surveys with resolution and observational frequency windows representative of COMAP and EXCLAIM. We show that the star formation rate and line emission scaling relations predicted by our simulation significantly differ at low halo masses from widely used empirical relations, which are often calibrated to observations of luminous galaxies at lower redshifts. We show that these differences lead to significant changes in key summary statistics used in intensity mapping, such as the one-point intensity probability density function and the power spectrum. It will be critical to use more realistic and complex models to forecast the ability of future line intensity mapping surveys to measure observables such as the cosmic star formation rate density.

Keywords: Diffuse radiation, Large-scale structure of the universe, Intergalactic medium
From Formation to Disruption: Observing the Multiphase Evolution of a Solar Flare Current Sheet. A current sheet, where magnetic energy is liberated through reconnection and converted to other forms, is thought to play the central role in solar flares, the most intense explosions in the heliosphere. However, the evolution of a current sheet and its subsequent role in flare-related phenomena such as particle acceleration is poorly understood. Here we report observations obtained with NASA's Solar Dynamics Observatory that reveal a multiphase evolution of a current sheet in the early stages of a solar flare, from its formation to quasi-stable evolution and disruption. Our observations have implications for the understanding of the onset and evolution of reconnection in the early stages of eruptive solar flares.

Keywords: Solar corona, Solar flares, Solar magnetic reconnection
The Diverse Morphologies and Structures of Dwarf Galaxies Hosting Optically Selected Active Massive Black Holes. We present a study of 41 dwarf galaxies hosting active massive black holes (BHs) using Hubble Space Telescope observations. The host galaxies have stellar masses in the range of M⋆ ∼ 108.5-109.5 M⊙ and were selected to host active galactic nuclei (AGNs) based on narrow emission line ratios derived from Sloan Digital Sky Survey spectroscopy. We find a wide range of morphologies in our sample including both regular and irregular dwarf galaxies. We fit the HST images of the regular galaxies using GALFIT and find that the majority are disk-dominated with small pseudobulges, although we do find a handful of bulge-like/elliptical dwarf galaxies. We also find an unresolved source of light in all of the regular galaxies, which may indicate the presence of a nuclear star cluster and/or the detection of AGN continuum. Three of the galaxies in our sample appear to be Magellanic-type dwarf irregulars and two galaxies exhibit clear signatures of interactions/mergers. This work demonstrates the diverse nature of dwarf galaxies hosting optically selected AGNs. It also has implications for constraining the origin of the first BH seeds using the local BH occupation fraction at low masses—we must account for the various types of dwarf galaxies that may host BHs.

Keywords: AGN host galaxies, Intermediate-mass black holes, Dwarf galaxies, Active galaxies, HST photometry, Active galactic nuclei
Testing F(R) Gravity with the Simulated Data of Gravitational Waves from the Einstein Telescope. In this paper we analyze the implications of gravitational waves (GWs) as standard sirens on the modified gravity models by using the third-generation GW detector, i.e., the Einstein Telescope. Two viable models in f(R) theories within the Palatini formalism are considered in our analysis ( ${f}_{1}({ \mathcal R })={ \mathcal R }-\tfrac{\beta }{{{ \mathcal R }}^{n}}$ and ${f}_{2}({ \mathcal R })={ \mathcal R }+\alpha \mathrm{ln}{ \mathcal R }-\beta $ ), with the combination of simulated GW data and the latest electromagnetic (EM) observational data (including the recently released Pantheon type Ia supernovae sample, the cosmic chronometer data, and baryon acoustic oscillation distance measurements). Our analysis reveals that the standard siren GWs, which provide an independent and complementary alternative to current experiments, could effectively eliminate the degeneracies among parameters in the two modified gravity models. In addition, we thoroughly investigate the nature of geometrical dark energy in the modified gravity theories with the assistance of Om(z) and statefinder diagnostic analysis. The present analysis makes it clear-cut that the simplest cosmological constant model is still the most preferred by the current data. However, the combination of future naturally improved GW data and the most recent EM observations will reveal the consistency or acknowledge the tension between the ΛCDM model and modified gravity theories.

Keywords: Gravitational waves, Cosmological parameters