Sazuna/UAT_keywords huggingface dataset:
Using the Starlight Polarization Efficiency Integral to Constrain Shapes and Porosities of Interstellar Grains. We have developed a new method for using the observed starlight polarization and polarized submillimeter emission to constrain the shapes and porosities of interstellar grains. We first present the modified picket-fence approximation and verify that it is sufficiently accurate for modeling starlight polarization. We then introduce the observed starlight polarization integral Πobs as a measure of the overall strength of the observed polarization of starlight, and the starlight polarization efficiency integral Φ to characterize the effectiveness of different grain types for producing polarization of starlight. The ratio Πobs/Φ determines the mass-weighted alignment ⟨falign⟩ of the grains. Approximating the aligned grains in the ISM as spheroids, we use Πobs/Φ to show that the observed starlight polarization constrains the grains to have a minimum degree of asphericity. For porosity ${ \mathcal P }=0$ , the minimum axial ratio is ~1.4 for oblate spheroids, or ~1.8 for prolate spheroids. If the grains are porous, more extreme axial ratios are required. The same grains that produce the starlight polarization are able to provide the observed polarized emission at submillimeter wavelengths but with further limits on shape and porosity. Porosities ${ \mathcal P }\gtrsim 0.75$ are ruled out. If interstellar grains can be approximated by "astrodust" spheroids, we predict the ratio of 10 μm polarization to starlight polarization pV: p(10 μm)/pV = 0.219 ± 0.029. For Cyg OB2-12, we predict p(10 μm) = (2.1 ± 0.3)%, which should be observable.

Keywords: Silicate grains, Interstellar dust extinction, Far infrared astronomy, Starlight polarization, Dust continuum emission
Constraints on the Assembly History of the Milky Way's Smooth, Diffuse Stellar Halo from the Metallicity-dependent, Radially Dominated Velocity Anisotropy Profiles Probed with K Giants and BHB Stars Using LAMOST, SDSS/SEGUE, and Gaia. We analyze the anisotropy profile of the Milky Way's smooth, diffuse stellar halo using the Sloan Digital Sky Survey (SDSS) SEGUE blue horizontal branch stars and the SDSS/SEGUE and LAMOST K giants. These intrinsically luminous stars allow us to probe the halo to approximately 100 kpc from the Galactic center. Line-of-sight velocities, distances, metallicities, and proper motions are available for all stars via SDSS/SEGUE, LAMOST, and Gaia, and we use these data to construct a full 7D set consisting of positions, space motions, and metallicity. We remove substructure from our samples using integrals of motion based on the method of Xue et al. We find radially dominated kinematic profiles with nearly constant anisotropy within 20 kpc, beyond which the anisotropy profile gently declines but remains radially dominated to the farthest extents of our sample. Independent of star type or substructure removal, the anisotropy depends on metallicity, such that the orbits of the stars become less radial with decreasing metallicity. For -1.7 &lt; [Fe/H] &lt; -1, the smooth, diffuse halo anisotropy profile begins to decline at Galactocentric distances ~20 kpc, from $\beta \sim 0.9$ to 0.7 for K giants and from $\beta \sim 0.8$ to 0.1 for blue horizontal branch stars. For [Fe/H] &lt; -1.7, the smooth, diffuse halo anisotropy remains constant along all distances with $0.2\lt \beta \lt 0.7$ depending on the metallicity range probed, but independent of star type. These samples are ideal for estimating the total Galactic mass as they represent the virialized stellar halo system.

Keywords: Milky Way stellar halo
Probing Intra-Halo Light with Galaxy Stacking in CIBER Images. We study the stellar halos of 0.2 ≲ z ≲ 0.5 galaxies with stellar masses spanning M* ~ 1010.5 to 1012M⊙ (approximately L* galaxies at this redshift) using imaging data from the Cosmic Infrared Background Experiment (CIBER). A previous CIBER fluctuation analysis suggested that intra-halo light (IHL) contributes a significant portion of the near-infrared extragalactic background light (EBL), the integrated emission from all sources throughout cosmic history. In this work, we carry out a stacking analysis with a sample of ~30,000 Sloan Digital Sky Survey (SDSS) photometric galaxies from CIBER images in two near-infrared bands (1.1 and 1.8 μm) to directly probe the IHL associated with these galaxies. We stack galaxies in five sub-samples split by brightness and detect an extended galaxy profile beyond the instrument point-spread function (PSF) derived by stacking stars. We jointly fit a model for the inherent galaxy light profile plus large-scale one- and two-halo clustering to measure the extended galaxy IHL. We detect nonlinear one-halo clustering in the 1.8 μm band at a level consistent with numerical simulations. By extrapolating the fraction of extended galaxy light we measure to all galaxy mass scales, we find ~30%/15% of the total galaxy light budget from galaxies is at radius r &gt; 10/20 kpc, respectively. These results are new at near-infrared wavelengths at the L* mass scale and suggest that the IHL emission and one-halo clustering could have appreciable contributions to the amplitude of large-scale EBL background fluctuations.

Keywords: Large-scale structure of the universe, Diffuse radiation, Galaxy evolution, Cosmic background radiation, Near infrared astronomy
Comprehensive Chemistry of HeH<SUP>+</SUP> in the Early Universe. The recent detection of the helium hydride ion (HeH+) in the planetary nebula NGC 7027 has inspired studies revisiting the dominant processes for its formation and destruction. Because radiative association is the primary formation mechanism for the helium hydride ion at all redshifts, and many early universe chemistry models rely on accurate results for calculations of destruction rates, we explicitly computed rovibrationally distinguished partial cross sections and rate coefficients of helium hydride formation via radiative association, and modeled the abundance of HeH+ in the early universe using recently available rate coefficients for all relevant formation and destruction reactions. The rate coefficients for the radiative association formation reaction of HeH+ and radiative charge transfer in He+ + H collisions were obtained using two distinct methods. Our newly calculated rate coefficients along with other recently reported He chemistry reactions and updated cosmological parameters were incorporated into a new calculation of the abundance of HeH+ for redshifts between z = 10 and 4000. We find that the abundance of the helium hydride ion is at least three orders of magnitude larger than previous predictions for redshifts near z = 20. Rovibrationally distinguished radiative association rate coefficients are given as a function of temperature, and the significance of stimulated radiative association for redshifts z &gt; 400 is also shown. * Released on Month Date Year.

Keywords: Early universe, Interstellar abundances
Kinetic Alfvén Waves in Space Plasma Environment with κ-electrons. A resonant instability of kinetic Alfvén waves (KAWs) driven by ion beam is discussed through a theoretical model encompassing Maxwellian background ions and beam ions and non-Maxwellian κ-electrons. The ion beam velocity alone as a source is able to excite the KAWs up to a significant growth. The non-Maxwellian parameter κ impedes the growth of KAWs by restricting the wave unstable region. The effects of other plasma parameters such as propagation angle, temperature of the plasma species, and ion plasma beta on the excitation of KAWs are also examined. The present model can generate waves with frequencies in the range of ≈6.6-51.2 mHz, which are relevant to explaining the observed ultralow frequency waves at auroral ionospheric altitudes. Theoretical model predictions will also be applicable to other planetary environments where ion beams and non-Maxwellian κ-electrons are present.

Keywords: Space plasmas, Solar wind, Alfven waves
Evidence for Ultra-diffuse Galaxy Formation through Tidal Heating of Normal Dwarfs. We have followed up two ultra-diffuse galaxies (UDGs), detected adjacent to stellar streams, with Hubble Space Telescope (HST) imaging and H I mapping with the Jansky Very Large Array in order to investigate the possibility that they might have a tidal origin. With the HST F814W and F555W images we measure the globular cluster (GC) counts for NGC 2708-Dw1 and NGC 5631-Dw1 as ${2}_{-1}^{+1}$ and ${5}_{-2}^{+1}$ , respectively. NGC 2708-Dw1 is undetected in H I down to a 3σ limit of log (MH I/M⊙) = 7.3, and there is no apparent H I associated with the nearby stellar stream. There is a 2σ H I feature coincident with NGC 5631-Dw1. However, this emission is blended with a large gaseous tail emanating from NGC 5631 and is not necessarily associated with the UDG. The presence of any GCs and the lack of clear H I connections between the UDGs and their parent galaxies strongly disfavor a tidal dwarf galaxy origin, but cannot entirely rule it out. The GC counts are consistent with those of normal dwarf galaxies, and the most probable formation mechanism is one where these UDGs were born as normal dwarfs and were later tidally stripped and heated. We also identify an overluminous (MV = -11.1) GC candidate in NGC 2708-Dw1, which may be a nuclear star cluster transitioning to an ultra-compact dwarf as the surrounding dwarf galaxy gets stripped of stars.

Keywords: Globular star clusters, Galaxy formation, Galaxy interactions, Dwarf galaxies, H I line emission, Tidal tails, Low surface brightness galaxies
Anomalous Hα Emission Line Profile Detected at the Center of DDO 53. We present the detection of a very broad (FWHM = 670 ± 17 km s-1), low-intensity Hα emission line component near the center of DDO 53, a star-forming dwarf irregular galaxy located in the M81 group. The broad component is found at the base of a bright and narrow (FWHM = 38 ± 2 km s-1) component. Using WIYN/Sparsepak optical spectroscopy of the region in addition to multiwavelength archival data, we evaluate the plausibility of several candidate sources, and find that stellar winds from embedded young stars are the most likely origin. However, this result is surprising for such a faint H II region.

Keywords: Dwarf irregular galaxies, Stellar feedback, Stellar wind bubbles, Interstellar medium, Wolf-Rayet stars
A Statistical Study of Propagating MHD Kink Waves in the Quiescent Corona. The Coronal Multi-channel Polarimeter (CoMP) has opened up exciting opportunities to probe transverse MHD waves in the Sun's corona. The archive of CoMP data is utilized to generate a catalog of quiescent coronal loops that can be used for studying propagating kink waves. The catalog contains 120 loops observed between 2012 and 2014. This catalog is further used to undertake a statistical study of propagating kink waves in the quiet regions of the solar corona, investigating phase speeds, loop lengths, footpoint power ratio (a measure of wave power entering the corona through each footpoint of a loop) and equilibrium parameter (which provides a measure of the change in wave amplitude) values. The statistical study enables us to establish the presence of a relationship between the rate of damping and the length of the coronal loop, with longer coronal loops displaying weaker wave damping. We suggest the reason for this behavior is related to a decreasing average density contrast between the loop and ambient plasma as loop length increases. The catalog presented here will provide the community with the foundation for the further study of propagating kink waves in the quiet solar corona.

Keywords: Magnetohydrodynamics, Solar coronal loops, Quiet sun, Solar coronal heating, Quiet solar corona, Solar activity
Nature of Electrostatic Fluctuations in the Terrestrial Magnetosheath. The high cadence plasma, electric, and magnetic field measurements by the Magnetospheric MultiScale spacecraft allow us to explore the near-Earth space plasma with an unprecedented time and spatial resolution, resolving electron-scale structures that naturally emerge from plasma complex dynamics. The formation of small-scale turbulent features is often associated to structured, non-Maxwellian particle velocity distribution functions that are not at thermodynamic equilibrium. Using measurements in the terrestrial magnetosheath, this study focuses on regions presenting bumps in the power spectral density of the parallel electric field at subproton scales. Correspondingly, it is found that the ion velocity distribution functions exhibit beam-like features at nearly the local ion thermal speed. Ion-cyclotron waves in the ion-scale range are frequently observed at the same locations. These observations, supported by numerical simulations, are consistent with the generation of ion-bulk waves that propagate at the ion thermal speed. This represents a new branch of efficient energy transfer at small scales, which may be relevant to weakly collisional astrophysical plasmas.

Keywords: Interplanetary turbulence, Space plasmas, Alfven waves, Plasma physics
Migrating Planets into Ultra-short-period Orbits during Episodic Accretion Events. Ultra-short-period (USP) planets reside inside the expected truncation radius for typical T Tauri disks. As a result, their current orbital locations require an explanation beyond standard disk migration or in situ formation. Modern theories of planet-disk interactions indicate that once a planet migrates close to the disk's inner truncation radius, Type I torques vanish or switch direction, depending on the stellar and disk conditions, so that the planet is expected to stop its orbital decay and become trapped. In this work, we show that that magnetically driven sub-Keplerian gas flow in the inner disk can naturally counteract these effects and produce systems with USP planets at their observed orbital radii. The sub-Keplerian gas flow provides a headwind to small planets, and the resulting torque can overcome the effects of outward Type I migration near the corotation radius. For suitable disk and planet parameters, the torques due to the sub-Keplerian gas flow lead to inward migration on a rapid timescale. Over the time span of an FU Ori outburst, which moves the disk truncation radius inward, the rapid headwind migration can place planets in USP orbits. The combination of headwind migration and FU Ori outbursts thus provides a plausible mechanism to move small planets from a = 0.05-0.1 au down to a = 0.01-0.02 au. This effect is amplified for low-mass planets, consistent with existing observations.

Keywords: Exoplanet migration, Protoplanetary disks, FU Orionis stars
An ALMA Gas-dynamical Mass Measurement of the Supermassive Black Hole in the Local Compact Galaxy UGC 2698. We present 0"14 resolution Atacama Large Millimeter/submillimeter Array (ALMA) CO(2-1) observations of the circumnuclear gas disk in UGC 2698, a local compact galaxy. The disk exhibits regular rotation with projected velocities rising to 450 km s-1 near the galaxy center. We fit gas-dynamical models to the ALMA data cube, assuming the CO emission originates from a dynamically cold, thin disk, and measured the mass of the supermassive black hole (BH) in UGC 2698 to be MBH = (2.46 ± 0.07 [1σ statistical] ${}_{-0.78}^{+0.70}$ [systematic]) × 109 M⊙. UGC 2698 is part of a sample of nearby early-type galaxies that are plausible z ~ 2 red nugget relics. Previous stellar-dynamical modeling for three galaxies in the sample found BH masses consistent with the BH mass-stellar velocity dispersion (MBH - σ⋆) relation but over-massive relative to the BH mass-bulge luminosity (MBH - Lbul) correlation, suggesting that BHs may gain the majority of their mass before their host galaxies. However, UGC 2698 is consistent with both MBH - σ⋆ and MBH - Lbul. As UGC 2698 has the largest stellar mass and effective radius in the local compact galaxy sample, it may have undergone more recent mergers that brought it in line with the BH scaling relations. Alternatively, given that the three previously measured compact galaxies are outliers from MBH - Lbul, while UGC 2698 is not, there may be significant scatter at the poorly sampled high-mass end of the relation. Additional gas-dynamical MBH measurements for the compact galaxy sample will improve our understanding of BH-galaxy co-evolution.

Keywords: Supermassive black holes, Molecular gas, Astronomy data modeling, Millimeter astronomy, Galaxy kinematics, Submillimeter astronomy, Early-type galaxies
On Radiative Dissipation in Stellar Turbulent Flows. The purpose of this paper is to study the exchange of momentum between photons and material particles in a stellar turbulent flow located far away from the outer boundary of the star. The flow is assumed to possess a wide interval of characteristic scales, such that the largest turbulent eddies are optically thick while the smallest ones are optically thin. An asymptotic analysis of the radiation hydrodynamics transport equations is performed in the limit of small velocities. All of the angular information carried by the radiative intensity is kept, and an exact expression for its perturbed state is derived. From it, an expression for the radiative force exerted by photons on matter is deduced. This force reverts to the standard radiative viscous stress in the optically thick regime and takes the form of a return-to-the-mean term in the opposite regime. The transition between the two is controlled by a local average of the velocity field taken on a domain of the size of a photon mean free path. Besides, the radiative force is found to always dissipate kinetic energy. But, as opposed to a purely viscous situation, the corresponding dissipation has an upper bound that is reached in the optically thin regime. All of these results are valid not only in the gray case but also for frequency-dependent opacities, including when true and scattering components are present. To validate these results, Monte Carlo simulations are performed on a simplified configuration.

Keywords: Stellar physics, Radiative transfer, Hydrodynamics
Calibrating the Davis-Chandrasekhar-Fermi Method with Numerical Simulations: Uncertainties in Estimating the Magnetic Field Strength from Statistics of Field Orientations. The Davis-Chandrasekhar-Fermi (DCF) method is widely used to indirectly estimate the magnetic field strength from the plane-of-sky field orientation. In this work, we present a set of 3D MHD simulations and synthetic polarization images using radiative transfer of clustered massive star-forming regions. We apply the DCF method to the synthetic polarization maps to investigate its reliability in high-density molecular clumps and dense cores where self-gravity is significant. We investigate the validity of the assumptions of the DCF method step by step and compare the model and estimated field strength to derive the correction factors for the estimated uniform and total (rms) magnetic field strength at clump and core scales. The correction factors in different situations are cataloged. We find the DCF method works well in strong-field cases. However, the magnetic field strength in weak-field cases could be significantly overestimated by the DCF method when the turbulent magnetic energy is smaller than the turbulent kinetic energy. We investigate the accuracy of the angular dispersion function (ADF; a modified DCF method) method on the effects that may affect the measured angular dispersion and find that the ADF method correctly accounts for the ordered field structure, the beam smoothing, and the interferometric filtering, but may not be applicable to account for the signal integration along the line of sight in most cases. Our results suggest that the DCF methods should be avoided to be applied below ~0.1 pc scales if the effect of line-of-sight signal integration is not properly addressed.

Keywords: Star formation, Radiative transfer simulations, Magnetic fields, Magnetohydrodynamical simulations
Ultra-delayed Neutrino-driven Explosion of Rotating Massive-star Collapse. Long-term neutrino-radiation hydrodynamics simulations in full general relativity are performed for the collapse of rotating massive stars that are evolved from He-stars with initial masses of 20 and 32 M⊙. It is shown that if the collapsing stellar core has sufficient angular momentum, the rotationally supported proto-neutron star (PNS) survives for seconds accompanying the formation of a massive torus of mass larger than 1 M⊙. Subsequent mass accretion onto the central region produces a massive and compact central object, and eventually enhances the neutrino luminosity beyond 1053 erg s-1, resulting in a very delayed neutrino-driven explosion, in particular toward the polar direction. The kinetic energy of the explosion can be appreciably higher than 1052 erg for a massive progenitor star and compatible with that of energetic supernovae like broad-line type-Ic supernovae. By the subsequent accretion, the massive PNS collapses eventually into a rapidly spinning black hole, which could be a central engine for gamma-ray bursts if a massive torus surrounds it.

Keywords: Type Ic supernovae, Core-collapse supernovae
Evidence for Low Kick Velocities among High-mass X-Ray Binaries in the Small Magellanic Cloud from the Spatial Correlation Function. We present the two-point cross-correlation function between high-mass X-ray binaries (HMXBs) in the Small Magellanic Cloud (SMC) and their likely birthplaces (OB associations: OBAs). This function compares the spatial correlation between the observed HMXB and OBA populations against mock catalogs in which the members are distributed randomly across the sky. A significant correlation (~15σ) is found for the HMXB and OBA populations when compared with a randomized catalog in which the OBAs are distributed uniformly over the SMC. A less significant correlation (4σ) is found for a randomized catalog of OBAs built with a bootstrap method. However, no significant correlation is detected when the randomized catalogs assume the form of a Gaussian ellipsoid or a distribution that reflects the star formation history from 40 Myr ago. Based on their observed distributions and assuming a range of migration timescales, we infer that the average value of the kick velocity inherited by an HMXB during the formation of its compact object is 2-34 km s-1. This is considerably less than the value obtained for their counterparts in the Milky Way hinting that the galactic environment affecting stellar evolution plays a role in setting the average kick velocity of HMXBs.

Keywords: Neutron stars, X-ray binary stars, High mass x-ray binary stars, OB associations, Astrostatistics, Small Magellanic Cloud, Compact objects, Two-point correlation function
Deep Learning with Quantized Neural Networks for Gravitational-wave Forecasting of Eccentric Compact Binary Coalescence. We present the first application of deep learning forecasting for binary neutron stars, neutron star-black hole systems, and binary black hole mergers that span an eccentricity range e ≤ 0.9. We train neural networks that describe these astrophysical populations, and then test their performance by injecting simulated eccentric signals in advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) noise available at the Gravitational Wave Open Science Center to (1) quantify how fast neural networks identify these signals before the binary components merge; (2) quantify how accurately neural networks estimate the time to merger once gravitational waves are identified; and (3) estimate the time-dependent sky localization of these events from early detection to merger. Our findings show that deep learning can identify eccentric signals from a few seconds (for binary black holes) up to tens of seconds (for binary neutron stars) prior to merger. A quantized version of our neural networks achieves 4× reduction in model size, and up to 2.5× inference speedup. These novel algorithms may be used to facilitate time-sensitive multimessenger astrophysics observations of compact binaries in dense stellar environments.

Keywords: Neutron stars, Convolutional neural networks, Gravitational waves, LIGO, Eccentricity