Sazuna/UAT_keywords huggingface dataset:
Gas and Dust Dynamics in Starlight-heated Protoplanetary Disks. Theoretical models of the ionization state in protoplanetary disks suggest the existence of large areas with low ionization and weak coupling between the gas and magnetic fields. In this regime hydrodynamical instabilities may become important. In this work we investigate the gas and dust structure and dynamics for a typical T Tauri system under the influence of the vertical shear instability (VSI). We use global 3D radiation hydrodynamics simulations covering all 360° of azimuth with embedded particles of 0.1 and 1 mm size, evolved for 400 orbits. Stellar irradiation heating is included with opacities for 0.1-10 μm sized dust. Saturated VSI turbulence produces a stress-to-pressure ratio of $\alpha \simeq {10}^{-4}$ . The value of α is lowest within 30 au of the star, where thermal relaxation is slower relative to the orbital period and approaches the rate below which VSI is cut off. The rise in α from 20 to 30 au causes a dip in the surface density near 35 au, leading to Rossby wave instability and the generation of a stationary, long-lived vortex spanning about 4 au in radius and 40 au in azimuth. Our results confirm previous findings that millimeter-sized grains are strongly vertically mixed by the VSI. The scale height aspect ratio for 1 mm grains is determined to be 0.037, much higher than the value H/r = 0.007 obtained from millimeter-wave observations of the HL Tau system. The measured aspect ratio is better fit by nonideal MHD models. In our VSI turbulence model, the millimeter grains drift radially inwards and many are trapped and concentrated inside the vortex. The turbulence induces a velocity dispersion of ∼12 m s-1 for the millimeter grains, indicating that grain-grain collisions could lead to fragmentation.

Keywords: Hydrodynamical simulations, Gas-to-dust ratio, Protoplanetary disks, Radiative transfer
A Wind-driven Model: Application to Peculiar Transients AT2018cow and iPTF14hls. We propose a wind-driven model for peculiar transients, and apply the model to AT2018cow and iPTF14hls. In the wind-driven model, we assume that a continuous outflow like a stellar wind is injected from a central system. While these transients have different observational properties, this model can explain their photometric properties which are not reproduced by a supernova-like instantaneous explosion. Furthermore, the model predicts characteristic spectral features and evolution, which are well in line with those of AT2018cow and iPTF14hls. Despite the different observational properties, the wind model shows that they have some common features; the large mass-loss rates (up to $\sim 20{M}_{\odot }\,{\mathrm{yr}}^{-1}$ for AT2018cow and $\sim 75{M}_{\odot }\,{\mathrm{yr}}^{-1}$ for iPTF14hls), and the characteristic radii of $\sim {10}^{13}\,\mathrm{cm}$ for the launch of the wind. It would indicate that both may be related to events involving a red supergiant (RSG), in which the RSG envelope is rapidly ejected by an event at a stellar core scale. On the other hand, the main differences are the kinetic energies, the total ejected mass, and the timescales. We then suggest that iPTF14hls may represent a dynamical common-envelope evolution induced by a massive binary system ( $\sim 120{M}_{\odot }+100{M}_{\odot }$ ). AT2018cow may be either a tidal disruption event of a low-mass RSG by a black hole (BH), or a BH-forming failed supernova.

Keywords: Stellar winds, Transient sources, Red supergiant stars
Hard X-Ray Emission from an Activated Flux Rope and Subsequent Evolution of an Eruptive Long-duration Solar Flare. In this paper, we present a comprehensive study of the evolutionary phases of a major M6.6 long duration event with special emphasize on its pre-flare phase. The event occurred in NOAA 12371 on 2015 June 22. A remarkable aspect of the event was an active pre-flare phase lasting for about an hour during which a hot EUV coronal channel was in the build-up stage and displayed cospatial hard X-ray (HXR) emission up to energies of 25 keV. This is the first evidence of the HXR coronal channel. The coronal magnetic field configuration based on nonlinear-force-free-field modeling clearly exhibited a magnetic flux rope (MFR) oriented along the polarity inversion line (PIL) and cospatial with the coronal channel. We observed significant changes in the AR's photospheric magnetic field during an extended period of ≈42 hr in the form of rotation of sunspots, moving magnetic features, and flux cancellation along the PIL. Prior to the flare onset, the MFR underwent a slow rise phase (≈14 km s-1) for ≈12 minutes, which we attribute to the faster build-up and activation of the MFR by tether-cutting reconnection occurring at multiple locations along the MFR itself. The sudden transition in the kinematic evolution of the MFR from the phase of slow to fast rise (≈109 km s-1 with acceleration ≈110 m s-2) precisely divides the pre-flare and impulsive phase of the flare, which points toward the feedback process between the early dynamics of the eruption and the strength of the flare magnetic reconnection.

Keywords: Solar flares, Solar magnetic reconnection, Solar active region filaments, Solar x-ray emission, Solar active regions
Isomers in Interstellar Environments. I. The Case of Z- and E-cyanomethanimine. In this work, we present the results of our investigation into the chemistry of Z- and E-cyanomethanimine (HNCHCN), both of which are possible precursors to the nucleobase adenine. Ab initio quantum chemical calculations for a number of reactions with atomic hydrogen were carried out. We find that the reaction H + Z/E-HNCHCN leading both to H-addition as well as H2-abstraction proceed via similar short-range barriers with bimolecular rate coefficients on the order of ∼10-17 cm3 s-1. These results were then incorporated into astrochemical models and used in simulations of the giant molecular cloud G+0.693. The calculated abundances obtained from these models were compared with previous observational data and found to be in good agreement, with a predicted [Z/E] ratio of ∼3—somewhat smaller than the previously derived value of 6.1 ± 2.4. We find that the [Z/E] ratio in our simulations is due mostly to ion-molecule destruction rates driven by the different permanent dipoles of the two conformers. Based on these results, we propose a general rule-of-thumb for estimating the abundances of isomers in interstellar environments, which we call the "relative dipole principle."

Keywords: Interstellar molecules, Galactic center, Astrochemistry, Giant molecular clouds, Pre-biotic astrochemistry
Constraining the Source of the High-velocity Ejecta in Type Ia SN 2019ein. We present multiwavelength photometric and spectroscopic observations of SN 2019ein, a high-velocity Type Ia supernova (SN Ia) discovered in the nearby galaxy NGC 5353 with a two-day nondetection limit. SN 2019ein exhibited some of the highest measured expansion velocities of any SN Ia, with a Si II absorption minimum blueshifted by 24,000 km s-1 at 14 days before peak brightness. More unusually, we observed the emission components of the P Cygni profiles to be blueshifted upward of 10,000 km s-1 before B-band maximum light. This blueshift, among the highest in a sample of 28 other SNe Ia, is greatest at our earliest spectroscopic epoch and subsequently decreases toward maximum light. We discuss possible progenitor systems and explosion mechanisms that could explain these extreme absorption and emission velocities. Radio observations beginning 14 days before B-band maximum light yield nondetections at the position of SN 2019ein, which rules out symbiotic progenitor systems, most models of fast optically thick accretion winds, and optically thin shells of mass $\lesssim {10}^{-6}$ ${M}_{\odot }$ at radii $\lt 100\,\mathrm{au}$ . Comparing our spectra to models and observations of other high-velocity SNe Ia, we find that SN 2019ein is well fit by a delayed-detonation explosion. We propose that the high emission velocities may be the result of abundance enhancements due to ejecta mixing in an asymmetric explosion, or optical depth effects in the photosphere of the ejecta at early times. These findings may provide evidence for common explosion mechanisms and ejecta geometries among high-velocity SNe Ia.

Keywords: Type Ia supernovae, Supernovae
A Large Population of Obscured AGN in Disguise as Low-luminosity AGN in Chandra Deep Field South. Population synthesis models of actively accreting supermassive black holes (or active galactic nuclei (AGN)) predict a large fraction that must grow behind dense, obscuring screens of gas and dust. Deep X-ray surveys are thought to have provided the most complete and unbiased samples of AGN, but there is strong observational evidence that a portion of the population of obscured AGN is being missed. In this paper, we use a sample of AGN derived from the deepest X-ray survey to date, the Chandra 7 Ms GOODS-South Survey, to investigate the nature of low-flux X-ray sources. We make full use of the extensive multiwavelength coverage of the GOODS-South field and cross-match our objects with wavelengths from the radio to the IR. We find that the low X-ray flux AGN in our sample have X-ray luminosities that indicate low-luminosity AGN classification, while their radio, IR, and optical counterparts indicate moderate to powerful AGN classification. We find that the predicted column densities are, on average, an order of magnitude higher than the calculated column densities via X-ray detections for X-ray-faint sources. We interpret our results as evidence of obscured AGN disguised as low-luminosity AGN via their X-ray luminosities. When we compare the estimation of the obscured AGN space density with and without these objects, we find a difference of 40% in the lowest X-ray luminosity regime probed by our sample.

Keywords: AGN host galaxies, Optical observation, Surveys, Extragalactic radio sources, Active galaxies, X-ray active galactic nuclei, Active galactic nuclei, Infrared sources
Atmospheric Erosion by Giant Impacts onto Terrestrial Planets. We examine the mechanisms by which the atmosphere can be eroded by giant impacts onto Earth-like planets with thin atmospheres, using 3D smoothed particle hydrodynamics simulations with sufficient resolution to directly model the fate of low-mass atmospheres. We present a simple scaling law to estimate the fraction lost for any impact angle and speed in this regime. In the canonical Moon-forming impact, only around 10% of the atmosphere would have been lost from the immediate effects of the collision. There is a gradual transition from removing almost none to almost all of the atmosphere for a grazing impact as it becomes more head-on or increases in speed, including complex, nonmonotonic behavior at low impact angles. In contrast, for head-on impacts, a slightly greater speed can suddenly remove much more atmosphere. Our results broadly agree with the application of 1D models of local atmosphere loss to the ground speeds measured directly from our simulations. However, previous analytical models of shock-wave propagation from an idealized point-mass impact significantly underestimate the ground speeds and hence the total erosion. The strong dependence on impact angle and the interplay of multiple nonlinear and asymmetrical loss mechanisms highlight the need for 3D simulations in order to make realistic predictions.

Keywords: Impact phenomena, Hydrodynamical simulations, Planetary atmospheres, Earth atmosphere
Toward an Understanding of the Massive Red Spiral Galaxy Formation. To understand the formation and quenching processes of local massive red spiral galaxies with M* &gt; 1010.5 M⊙, we perform a statistical analysis of their spectroscopic and structural properties and compare them with elliptical and blue spiral galaxies of similar mass. The sample was selected from the stellar mass catalog of galaxies in SDSS DR7, according to their locations on the u - r color-stellar mass diagram. We find that red spirals harbor compact cores with high stellar mass surface densities measured by Σ1 and are bulge dominated. Particularly, the red spirals, especially their bulges, follow the Σ1-M* ridgeline for quenched galaxies. Furthermore, the red spirals show similarly large central Dn(4000), high [Mg/Fe], and dark matter halo mass to ellipticals. These results suggest that the bulges of red spirals formed within a short timescale before redshift ∼1-2 and were quenched via a fast mode, similar to ellipticals. Careful examinations of the optical morphologies reveal that ∼70% of red spirals show strong bars, rings/shells, and even merging features, which suggests that interactions or mergers might have played an important role in the formation of red spirals. In contrast, most of the massive blue spirals have completely different spectral and structural properties from red spirals. However, the blue spirals with high Σ1 ( ${{\rm{\Sigma }}}_{1}\gt {10}^{9.5}\,{M}_{\odot }\,{\mathrm{kpc}}^{-2}$ ) show similar structural and morphological properties, as well as similar halo mass and H I mass to red spirals. We discuss rejuvenation from red to blue as a possible explanation for these high-Σ1 blue spirals.

Keywords: Galaxy formation, Spiral galaxies, Galaxy bulges, Galaxy structure, Star formation, Galaxy evolution
High-z Universe Probed via Lensing by QSOs (HULQ). I. Number Estimates of QSO-QSO and QSO-Galaxy Lenses. It is unclear how galaxies and their central supermassive black holes coevolve across cosmic time, especially for the nonlocal universe (z ≳ 0.5). The High-z Universe probed via Lensing by QSOs project proposes to utilize quasi-stellar object (QSO) host galaxies acting as gravitational lenses (QSO lenses) to investigate this topic. This paper focuses on the feasibility of this project, that is, whether sufficiently large numbers of QSO lenses are expected to be found in various concurrent and future imaging surveys. We find that ∼440 QSO lenses will reside in the Hyper Suprime-Cam Wide survey (HSC/Wide), which is expected to be the most prolific concurrent survey, with this number being boosted by one to two orders of magnitude (to ∼10,000) with upcoming surveys such as that conducted with the Large Synoptic Survey Telescope (LSST). We discuss several methods of how to study the redshift evolution of the ${M}_{\mathrm{BH}}\mbox{--}{\sigma }_{* }$ relation, which is a standout illustration of the coevolution. In addition, we demonstrate how the intimacy of lensed images to the bright deflector QSO for most systems will affect the detectability of QSO lenses. We estimate that only ∼82 and 900 will be detectable for HSC/Wide and LSST, respectively; the decrease is significant yet still yields an acceptable sample for the main objective. This decrease will be less of a problem for space-based imaging surveys, for their small point-spread function FWHMs will allow detections of lensed images lying relatively close to the deflector QSO, and thus unveil the less massive yet more numerous QSO hosts.

Keywords: AGN host galaxies, Supermassive black holes, Quasars, Strong gravitational lensing, Active galaxies, Gravitational lensing, Galaxy evolution, Galaxies
Mid-infrared Diagnostics of the Circumnuclear Environments of the Youngest Radio Galaxies. We present a systematic analysis of the mid-infrared (MIR) properties of the youngest radio galaxies, based on low-resolution data provided by the Wide-field Infrared Survey Explorer and IRAS satellites. We restrict our analysis to sources with available X-ray data that constitute the earliest phase of radio galaxy evolution, I.e., those classified as gigahertz-peaked spectrum and/or compact symmetric objects. In our sample of 29 objects, we find that the host galaxies are predominantly red/yellow ellipticals, with some of them displaying distorted morphology. We find a variety of MIR colors and observe that the sources in which the MIR emission is dominated by the ISM component uniformly populate the region occupied by galaxies with a wide range of pronounced (≥0.5M⊙ yr-1) star formation activity. We compare the MIR color distribution in our sample to that in the general population of local active galactic nuclei (AGNs), in the population of evolved FR II radio galaxies, and also in the population of radio galaxies with recurrent jet activity. We conclude that the triggering of radio jets in AGNs does not differentiate between elliptical hosts with substantially different fractions of young stars; instead, there is a relationship between the jet duty cycle and the ongoing star formation. The distribution of the subsample of our sources with z &lt; 0.4 on the low-resolution MIR versus absorption-corrected X-ray luminosity plane is consistent with the distribution of a sample of local AGNs. Finally, we comment on the star formation rates of the two γ-ray-detected sources in our sample, 1146+596 and 1718-649.

Keywords: X-ray astronomy, Radio jets, Infrared astronomy, Radio galaxies, Active galactic nuclei, Galaxy evolution, Interstellar medium
Bayesian Inference of Dense Matter Equation of State within Relativistic Mean Field Models Using Astrophysical Measurements. We present a Bayesian analysis to constrain the equation of state of dense nucleonic matter by exploiting the available data from symmetric nuclear matter at saturation, observations of compact X-ray sources, and the gravitational wave event GW170817. For the first time, such an analysis is performed by using a class of models, the relativistic mean field models, that allow one to consistently construct an equation of state in a wide range of densities, isospin asymmetries, and temperatures. The selected class of models contains five nuclear physics empirical parameters at saturation for which we construct the joint posterior distributions. By exploring different types of priors, we find that the equations of state with the largest evidence are the ones featuring a strong reduction of the effective mass of the nucleons in dense matter, which can be interpreted as an indication of a phase transition to a chiral symmetry restored phase. Those equations of state, in turn, predict R1.4 ∼ 12 km. Finally, we present a preliminary investigation of the effect of including Λ hyperons, showing that they appear in stars more massive than about 1.6 M⊙ and lead to radii larger than about R1.4 ∼ 14 km. Within the model explored here, the formation of such particles provides poor agreement with the constraints from GW170817.

Keywords: Neutron stars, Nuclear astrophysics, Bayesian statistics, Neutron star cores
Band-limited Features in the Primordial Power Spectrum Do Not Resolve the Hubble Tension. For a standard ΛCDM universe with a power-law primordial power spectrum, the discrepancy between early- and late-universe measurements of the Hubble constant continued to grow and recently reached 5.3σ. During inflation, local features in the inflationary potential often lead to band-limited features in the primordial power spectrum, hence breaking the power-law assumption in the derivation of the Hubble tension. We investigate whether such inflationary "glitches" can ease the Hubble tension. The recently released Planck temperature and polarization data and the 2019 SH0ES+H0LiCOW joint constraint on the Hubble constant are combined to drive a blind Daubechies wavelet signal search in the primordial power spectrum, up to a resolution ${\rm{\Delta }}\mathrm{ln}\,k\sim 0.1$ . We find no significant detection of any features beyond power law. With 64 more degrees of freedom injected in the primordial power spectrum, the Hubble tension persists at a 4.9σ level.

Keywords: Cosmology, Cosmological models, Cosmological parameters, Observational cosmology, Hubble constant, Dark energy
Wave-polarization Analysis of the Alfvénic Slow Solar Wind at Kinetic Scales. This paper reports the first polarization measurement in the Alfvénic slow solar wind. The normalized magnetic helicity is used as a diagnostic parameter for studying the polarization status of the high-frequency magnetic fluctuations, along with an attempt to identify various wave modes in the solar wind turbulence. Clear evidence for the existence of ion cyclotron waves (ICWs) and kinetic Alfvén waves (KAWs) is also found in the Alfvénic low-speed plasma, robustly supporting the idea that the Alfvénic content of the solar wind fluctuations at fluid scales is the key parameter driving wave generation at kinetic scales. By separating the contributions to helicity from the two modes, it is possible to address the thermodynamical properties of ICWs and KAWs and provide the first direct estimate of their magnetic compressibility. In particular, while ICWs are mainly associated with higher levels of anisotropy and appear to be bounded by the threshold of proton-cyclotron kinetic instability, KAWs (which end up being more compressive than ICWs) are found at lower anisotropies and seem to be limited by the mirror mode instability threshold, extending as well to near the parallel fire hose unstable region. These result are relevant to theories of turbulence and dissipation in the solar wind.

Keywords: Space plasmas, Magnetohydrodynamics, Interplanetary turbulence, Solar wind, Alfven waves
Oscillating Strange Quark Matter Objects Excited in Stellar Systems. It is shown that strange quark matter (SQM) objects, stars, and planets, can very efficiently convert the mechanical energy into hadronic energy when they oscillate. This is because the mass density at the edge of SQM objects, ${\rho }_{0}=4.7\times {10}^{14}\,{\rm{g}}\,{\mathrm{cm}}^{-3}$ , is the critical density below which SQM is unstable with respect to decay into photons, hadrons, and leptons. We consider here radial oscillations of SQM objects that could be induced in stellar or planetary systems where tidal interactions are ubiquitous. Oscillations of $0.1 \% $ radius amplitude already result in $1\,\mathrm{keV}$ per unit baryon number excitation near the surface of SQM stars. The excitation energy is converted into electromagnetic energy in a short time of $1\,\mathrm{ms}$ , during a few oscillations. Higher amplitude oscillations result in faster energy release that could lead to fragmentation or dissolution of SQM stars. This would have significant consequences for hypothetical SQM star binaries and planetary systems of SQM planets with regard to gravitational wave emission.

Keywords: Relativistic stars, Tidal distortion, High energy astrophysics, Compact binary stars, Gravitational wave sources, Compact objects, Stellar oscillations
A Search for Gravitational Waves from Binary Mergers with a Single Observatory. We present a search for merging compact binary gravitational-wave sources that produce a signal appearing solely or primarily in a single detector. Past analyses have heavily relied on coincidence between multiple detectors to reduce nonastrophysical background. However, for ∼40% of the total time of the 2015-2017 LIGO-Virgo observing runs only a single detector was operating. We discuss the difficulties in assigning significance and calculating the probability of astrophysical origin for candidates observed primarily by a single detector and suggest a straightforward resolution using a noise model designed to provide a conservative assessment given the observed data. We also describe a procedure to assess candidates observed in a single detector when multiple detectors are observing. We apply these methods to search for binary black hole (BBH) and binary neutron star (BNS) mergers in the open LIGO data spanning 2015-2017. The most promising candidate from our search is 170817+03:02:46UTC (probability of astrophysical origin pastro ∼ 0.4): if astrophysical, this is consistent with a BBH merger with primary mass ${67}_{-15}^{+21}\,{M}_{\odot }$ , suggestive of a hierarchical merger origin. We also apply our method to the analysis of GW190425 and find ${p}_{\mathrm{astro}}\sim 0.5$ , though this value is highly dependent on assumptions about the noise and signal models.

Keywords: Neutron stars, Gravitational waves, Compact objects, Black holes