Sazuna/UAT_keywords huggingface dataset:
The Population III Origin of GW190521. We explore the possibility that the recently detected black hole binary (BHB) merger event GW190521 originates from the first generation of massive, metal-free, so-called Population III (Pop III) stars. Based on improved binary statistics derived from N-body simulations of Pop III star clusters, we calculate the merger rate densities of Pop III BHBs similar to GW190521, in two evolution channels: classical binary stellar evolution and dynamical hardening in high-redshift nuclear star clusters. Both channels can explain the observed rate density. However, the latter is favored by better agreement with observation and less restrictions on uncertain parameters. Our analysis also indicates that given the distinct features of the two channels, future observation of BHB mergers similar to GW190521 with third-generation gravitational wave detectors will greatly improve our knowledge of the evolution of Pop III BHBs, especially for their dynamics during cosmic structure formation.

Keywords: Gravitational wave astronomy, Early universe, Population III stars
The Clustering of Submillimeter Galaxies Detected with ALMA. Previous studies measuring the clustering of submillimeter galaxies (SMGs) have based their measurements on single-dish-detected sources, finding evidence for strong clustering. However, ALMA has revealed that, due to the coarse angular resolution of these instruments, single-dish sources can be composed of multiple sources. This implies that the clustering inferred from single-dish surveys may be overestimated. Here, we measure the clustering of SMGs based on the ALESS survey, an ALMA follow-up of sources previously identified in the LABOCA ECDFS Submillimeter Survey (LESS). We present a method to measure the clustering of ALMA sources that have been previously identified using single-dish telescopes, based on forward modeling both the single-dish and the ALMA observations. We constrain upper limits for the median mass of halos hosting SMGs at 1 &lt; z &lt; 3, finding ${M}_{\mathrm{halo}}\leqslant 2.4\times {10}^{12}\,{M}_{\odot }$ for SMGs with flux densities ${S}_{870}\geqslant 4.0\,$ mJy, which is at least ${3.8}_{-2.6}^{+3.8}$ times lower than the mass inferred based on the clustering of the LESS sources alone. This suggests that the strength of SMG clustering based on single-dish observations was overestimated, and therefore SMGs might be hosted by dark matter halos less massive than has previously been estimated. By extrapolating our models down to flux densities of ${S}_{870}\geqslant 1.2\,\,$ mJy, we find that such SMGs inhabit halos with median mass ${M}_{\mathrm{halo}}\leqslant 3.2\times {10}^{11}\,{M}_{\odot }$ . We conclude that only the brightest ( ${S}_{870}\gtrsim 5-6\,\,$ mJy) SMGs would trace massive structures at z ∼ 2 and only SMGs with ${S}_{870}\gtrsim 6\,\,$ mJy may be connected to massive local elliptical galaxies, quasars at intermediate redshifts, and high-redshift star-forming galaxies, whereas fainter SMGs are unlikely linked to these populations.

Keywords: Starburst galaxies, Astronomy data modeling, Large-scale structure of the universe, Clustering, Galaxy evolution, Submillimeter astronomy, High-redshift galaxies
Study of the 27 Day Variations in GCR Fluxes during 2007-2008 Based on PAMELA and ARINA Observations. Using measurements from the PAMELA and ARINA spectrometers on board the Resurs-DK1 satellite, we have examined the 27 day intensity variations in galactic cosmic ray (GCR) proton fluxes in 2007-2008. The PAMELA and ARINA data allow for the first time a study of time profiles and the rigidity dependence of the 27 day variations observed directly in space in a wide rigidity range from ∼300 MV to several gigavolts. We find that the rigidity dependence of the amplitude of the 27 day GCR variations cannot be described by the same power law at both low and high energies. A flat interval occurs at rigidity $R=\langle 0.6\mbox{--}1.0\rangle $ GV with a power-law index γ = -0.13 ± 0.44 for PAMELA, whereas for R ≥ 1 GV, the power-law dependence is evident with index γ = -0.51 ± 0.11. We describe the rigidity dependence of the 27 day GCR variations for PAMELA and ARINA data in the framework of the modulation potential concept using the force-field approximation for GCR transport. For a physical interpretation, we have considered the relationship between the 27 day GCR variations and solar wind plasma and other heliospheric parameters. Moreover, we have discussed possible implications of MHD modeling of the solar wind plasma together with a stochastic GCR transport model concerning the effects of corotating interaction regions.

Keywords: Galactic cosmic rays, Solar wind, Corotating streams, Heliosphere
High-energy Neutrinos and Gamma Rays from Nonrelativistic Shock-powered Transients. Shock interaction has been argued to play a role in powering a range of optical transients, including supernovae, classical novae, stellar mergers, tidal disruption events, and fast blue optical transients. These same shocks can accelerate relativistic ions, generating high-energy neutrino and gamma-ray emission via hadronic pion production. The recent discovery of time-correlated optical and gamma-ray emission in classical novae has revealed the important role of radiative shocks in powering these events, enabling an unprecedented view of the properties of ion acceleration, including its efficiency and energy spectrum, under similar physical conditions to shocks in extragalactic transients. Here we introduce a model for connecting the radiated optical fluence of nonrelativistic transients to their maximal neutrino and gamma-ray fluence. We apply this technique to a wide range of extragalactic transient classes in order to place limits on their contributions to the cosmological high-energy gamma-ray and neutrino backgrounds. Based on a simple model for diffusive shock acceleration at radiative shocks, calibrated to novae, we demonstrate that several of the most luminous transients can accelerate protons up to 1016 eV, sufficient to contribute to the IceCube astrophysical background. Furthermore, several of the considered sources—particularly hydrogen-poor supernovae—may serve as "gamma-ray-hidden" neutrino sources owing to the high gamma-ray opacity of their ejecta, evading constraints imposed by the nonblazar Fermi Large Area Telescope background. However, adopting an ion acceleration efficiency of ∼0.3%-1% motivated by nova observations, we find that currently known classes of nonrelativistic, potentially shock-powered transients contribute at most a few percent of the total IceCube background.

Keywords: Neutrino astronomy, Supernovae, Gamma-rays, Novae
DY Pegasi: An SX Phoenicis Star in a Binary System with an Evolved Companion. In this work, the photometric data from the American Association of Variable Star Observers are collected and analyzed on the SX Phoenicis star DY Pegasi (DY Peg). From the frequency analysis, we get three independent frequencies: f0 = 13.71249 c d-1, f1 = 17.7000 c d-1, and f2 = 18.138 c d-1, in which f0 and f1 are the radial fundamental and first overtone mode, respectively, while f2 is detected for the first time and should belong to a nonradial mode. The O - C diagram of the times of maximum light shows that DY Peg has a period change rate (1/P0)(dP0/dt) = -(5.87 ± 0.03) × 10-8 yr-1 for its fundamental pulsation mode, and should belong to a binary system that has an orbital period Porb = 15425.0 ± 205.7 days. Based on the spectroscopic information, single star evolutionary models are constructed to fit the observed frequencies. However, some important parameters of the fitted models are not consistent with that from observations. Combing the information from observation and theoretical calculation, we conclude that DY Peg should be an SX Phoenicis star in a binary system and accreting mass from a dust disk, which was the residue of its evolved companion (most probably a hot white dwarf at the present stage) produced in the asymptotic giant branch phase. Further observations are needed to confirm this inference, and it might be potentially a universal formation mechanism and evolutionary history for SX Phoenicis stars.

Keywords: SX Phoenicis variable stars, Pulsating variable stars
Magnetic Helicity Flux across Solar Active Region Photospheres. I. Hemispheric Sign Preference in Solar Cycle 24. A hemispheric preference in the dominant sign of magnetic helicity has been observed in numerous features in the solar atmosphere, i.e., left-handed/right-handed helicity in the northern/southern hemisphere. The relative importance of different physical processes that may contribute to the observed hemispheric sign preference (HSP) of magnetic helicity is still under debate. Here, we estimate magnetic helicity flux (dH/dt) across the photospheric surface for 4802 samples of 1105 unique active regions (ARs) that appeared over an 8 yr period from 2010 to 2017 during solar cycle 24, using photospheric vector magnetic field observations by the Helioseismic and Magnetic Imager (HMI) on board the Solar Dynamics Observatory (SDO). The estimates of dH/dt show that 63% and 65% of the investigated AR samples in the northern and southern hemispheres, respectively, follow the HSP. We also find a trend that the HSP of dH/dt increases from ∼50%-60% up to ∼70%-80% as ARs (1) appear at the earlier inclining phase of the solar cycle or higher latitudes and (2) have larger values of $| {dH}/{dt}| $ , the total unsigned magnetic flux, and the average plasma-flow speed. These observational findings support the enhancement of the HSP mainly by the Coriolis force acting on a buoyantly rising and expanding flux tube through the turbulent convection zone. In addition, the differential rotation on the solar surface as well as the tachocline α-effect of a flux-transport dynamo may reinforce the HSP for ARs at higher latitudes.

Keywords: Solar active region magnetic fields, Solar active region velocity fields, Solar photosphere, Astronomy data analysis, Solar magnetic fields, Solar activity
Magnetic Energy Balance in the Quiet Sun on Supergranular Spatial and Temporal Scales. Small-scale magnetic fields are ubiquitous in the quiet solar photosphere and may store and transfer huge amounts of energy to the upper atmospheric layers. For this reason, it is fundamental to constrain the energetics of the quiet Sun. By taking advantage of a 24 hr long magnetogram time series acquired by the Hinode mission without interruption, we computed, for the first time, the average rate of change of magnetic energy density on supergranular spatial and temporal scales. We found that the regions where this quantity is positive correspond with the longest magnetic field decorrelation times, with the latter being consistent with the timescales of magnetic energy density variation. This suggests that, on average, the energy provided by photospheric electric and magnetic fields and current density is effective in sustaining the magnetic fields in the network.

Keywords: Supergranulation, Solar photosphere, Quiet sun, Space weather, Solar magnetic fields
The Impact of Outflows Driven by Active Galactic Nuclei on Metals in and around Galaxies. Metals in the hot gaseous halos of galaxies encode the history of star formation as well as the feedback processes that eject metals from the galaxies. X-ray observations suggest that massive galaxies have extended distributions of metals in their gas halos. We present predictions for the metal properties of massive galaxies and their gaseous halos from recent high-resolution zoom-in simulations that include mechanical and radiation-driven feedback from active galactic nuclei (AGN). In these simulations, AGN launch high-velocity outflows, mimicking observed broad absorption line winds. By comparing two sets of simulations with and without AGN feedback, we show that our prescription for AGN feedback is capable of driving winds and enriching halo gas "inside-out" by spreading centrally enriched metals to the outskirts of galaxies, into the halo and beyond. The metal (iron) profiles of halos simulated with AGN feedback have a flatter slope than those without AGN feedback, consistent with recent X-ray observations. The predicted gas iron abundance of group scale galaxies simulated with AGN feedback is ZFe = 0.23 ZFe,⊙ at 0.5r500, which is 2.5 times higher than that in simulations without AGN feedback. In these simulations, AGN winds are also important for the metal enrichment of the intergalactic medium, as the vast majority of metals ejected from the galaxy by AGN-driven winds end up beyond the halo virial radius.

Keywords: Galactic winds, Galaxy chemical evolution, Chemical enrichment, Active galactic nuclei, Galaxy evolution
Multiphase Circumnuclear Gas in a Low-β Disk: Turbulence and Magnetic Field Reversals. We studied the magnetic field structures and dynamics of magnetized multiphase gas on parsec scales around supermassive black holes by using global 3D magnetohydrodynamics (MHD) simulations. We considered the effect of radiative cooling and X-ray heating due to active galactic nuclei (AGNs). The gas disk consists of a multiphase gas with (1) cold (≤103 K) and thin, and (2) warm (∼104 K) and thick components with a wide range of number densities. The turbulent magnetic energy at maximum is comparable to the thermal and turbulent kinetic energies in the turbulent motion. We confirmed that the turbulent velocity of the warm gas in the ambient cold gas is caused by magnetoconvective instability. The turbulent magnetic field due to magnetorotational instability (MRI) is developed in the disk, but the mean toroidal magnetic field dominates and supports in a quasi-steady state, where the plasma-β, the ratio between gas pressure and magnetic pressure, is low (β &lt; 1). As often seen in adiabatic MHD simulations of rotating disks, the direction of the mean toroidal field periodically reverses with time even in multiphase gas structures. The direction reversal is caused by magnetic flux vertically escaping from the disk and by the combination of the MRI and the Parker instability.

Keywords: Galaxy circumnuclear disk, Magnetohydrodynamics, Active galactic nuclei, Galaxy nuclei
Finding Signs of Life on Transiting Earthlike Planets: High-resolution Transmission Spectra of Earth through Time around FGKM Host Stars. The search for life in the universe mainly uses modern Earth as a template. However, we know that Earth's atmospheric composition changed significantly through its geological evolution. Recent discoveries show that transiting, potentially Earthlike, exoplanets orbit a wide range of host stars, which strongly influence their atmospheric composition and remotely detectable spectra. Thus, a database for transiting terrestrial exoplanets around different host stars at different geological times is a crucial missing ingredient to support observational searches for signs of life in exoplanet atmospheres. Here, we present the first high-resolution transmission spectra database for Earthlike planets, orbiting a wide range of host stars, throughout four representative stages of Earth's history. These correspond to a prebiotic high-CO2 world—about 3.9 billion years ago in Earth's history—and three epochs through the increase in oxygen from 0.2% to modern atmospheric levels of 21%. We demonstrate that the spectral biosignature pairs O2+CH4 and O3+CH4 in the atmosphere of a transiting Earthlike planet would show a remote observer that a biosphere exists for oxygen concentrations of about 1% of modern Earth's—corresponding to about 1-2 billion years ago in Earth's history—for all host stars. The full model and high-resolution transmission spectra database, covering 0.4-20 μm, for transiting exoplanets—from young prebiotic worlds to modern Earth analogs orbiting a wide range of host stars—is available online. It is a tool to plan and optimize our observation strategy, train retrieval methods, and interpret upcoming observations with ground- and space-based telescopes.

Keywords: Exoplanet atmospheric composition , Exoplanet atmospheric variability, Transmission spectroscopy, Exoplanet astronomy, Biosignatures, Exoplanet atmospheres
Binding Energies of Interstellar Molecules on Crystalline and Amorphous Models of Water Ice by Ab Initio Calculations. In the denser and colder (≤20 K) regions of the interstellar medium (ISM), near-infrared observations have revealed the presence of submicron-sized dust grains covered by several layers of H2O-dominated ices and "dirtied" by the presence of other volatile species. Whether a molecule is in the gas or solid-phase depends on its binding energy (BE) on ice surfaces. Thus, BEs are crucial parameters for the astrochemical models that aim to reproduce the observed evolution of the ISM chemistry. In general, BEs can be inferred either from experimental techniques or by theoretical computations. In this work, we present a reliable computational methodology to evaluate the BEs of a large set (21) of astrochemical relevant species. We considered different periodic surface models of both crystalline and amorphous nature to mimic the interstellar water ice mantles. Both models ensure that hydrogen bond cooperativity is fully taken into account at variance with the small ice cluster models. Density functional theory adopting both B3LYP-D3 and M06-2X functionals was used to predict the species/ice structure and their BEs. As expected from the complexity of the ice surfaces, we found that each molecule can experience multiple BE values, which depend on its structure and position at the ice surface. A comparison of our computed data with literature data shows agreement in some cases and (large) differences in others. We discuss some astrophysical implications that show the importance of calculating BEs using more realistic interstellar ice surfaces to have reliable values for inclusion in the astrochemical models.

Keywords: Interstellar dust, Interstellar molecules, Solid matter physics, Dense interstellar clouds, Computational methods, Surface ices, Interstellar medium, Interstellar dust processes
Kinetic Simulation of Nonrelativistic Perpendicular Shocks of Young Supernova Remnants. IV. Electron Heating. High-Mach-number collisionless shocks are found in planetary systems and supernova remnants (SNRs). Electrons are heated at these shocks to temperatures well above the Rankine-Hugoniot prediction. However, the processes responsible for causing the electron heating are still not well understood. We use a set of large-scale particle-in-cell simulations of nonrelativistic shocks in the high-Mach-number regime to clarify the electron heating processes. The physical behavior of these shocks is defined by ion reflection at the shock ramp. Further interactions between the reflected ions and the upstream plasma excites electrostatic Buneman and two-stream ion-ion Weibel instabilities. Electrons are heated via shock surfing acceleration, the shock potential, magnetic reconnection, stochastic Fermi scattering, and shock compression. The main contributor is the shock potential. The magnetic field lines become tangled due to the Weibel instability, which allows for parallel electron heating by the shock potential. The constrained model of electron heating predicts an ion-to-electron temperature ratio within observed values at SNR shocks and in Saturn's bow shock.

Keywords: Supernova remnants, Shocks, Plasma astrophysics, Interstellar medium
A Distance Determination to the Small Magellanic Cloud with an Accuracy of Better than Two Percent Based on Late-type Eclipsing Binary Stars. We present a new study of late-type eclipsing binary stars in the Small Magellanic Cloud (SMC) undertaken with the aim of improving the distance determination to this important galaxy. A sample of 10 new detached, double-lined eclipsing binaries identified from the OGLE variable star catalogs and consisting of F- and G-type giant components has been analyzed. The absolute physical parameters of the individual components have been measured with a typical accuracy of better than 3%. All but one of the systems consist of young and intermediate population stars with masses in the range of 1.4 to 3.8 M☉. This new sample has been combined with five SMC eclipsing binaries previously published by our team. Distances to the binary systems were calculated using a surface brightness—color calibration. The targets form an elongated structure, highly inclined to the plane of the sky. The distance difference between the nearest and most-distant system amounts to 10 kpc with the line-of-sight depth reaching 7 kpc. We find tentative evidence of the existence of a spherical stellar substructure (core) in the SMC coinciding with its stellar center, containing about 40% of the young and intermediate age stars in the galaxy. The radial extension of this substructure is ∼1.5 kpc. We derive a distance to the SMC center of DSMC = 62.44 ± 0.47 (stat.) ± 0.81 (syst.) kpc corresponding to a distance modulus (m - M)SMC = 18.977 ± 0.016 ± 0.028 mag, representing an accuracy of better than 2%.

Keywords: Galaxy distances, Galaxy structure, Small Magellanic Cloud, Late-type giant stars, Eclipsing binary stars, Stellar distance
Optical and Near-infrared Observations of the Nearby SN Ia 2017cbv. Supernova (SN) 2017cbv in NGC 5643 is one of a handful of Type Ia supernovae (SNe Ia) reported to have excess blue emission at early times. This paper presents extensive BVRIYJHKs-band light curves of SN 2017cbv, covering the phase from -16 to +125 days relative to B-band maximum light. The SN 2017cbv reached a B-band maximum of 11.710 ± 0.006 mag, with a postmaximum magnitude decline of ∆m15(B) = 0.990 ± 0.013 mag. The SN suffered no host reddening based on Phillips intrinsic color, the Lira-Phillips relation, and the CMAGIC diagram. By employing the CMAGIC distance modulus μ = 30.58 ± 0.05 mag and assuming H0 = 72 km s-1 Mpc-1, we found that 0.73 M☉ 56Ni was synthesized during the explosion of SN 2017cbv, which is consistent with estimates using reddening- and distance-free methods via the phases of the secondary maximum of the near-IR- (NIR-) band light curves. We also present 14 NIR spectra from -18 to +49 days relative to the B-band maximum light, providing constraints on the amount of swept-up hydrogen from the companion star in the context of the single degenerate progenitor scenario. No Paβ emission feature was detected from our postmaximum NIR spectra, placing a hydrogen mass upper limit of 0.1 M☉. The overall optical/NIR photometric and NIR spectral evolution of SN 2017cbv is similar to that of a normal SN Ia, even though its early evolution is marked by a flux excess not seen in most other well-observed normal SNe Ia. We also compare the exquisite light curves of SN 2017cbv with some Mch delayed detonation models and sub-Mch double detonation models.

Keywords: Type Ia supernovae