Sazuna/UAT_keywords huggingface dataset:
The Impact of Realistic Foreground and Instrument Models on 21 cm Epoch of Reionization Experiments. Predictions for the ability of 21 cm interferometric experiments to discriminate Epoch of Reionization (EoR) signal models are typically limited by the simplicity of data models, whereby foreground signals and characteristics of the instrument are often simplified or neglected. To move toward more realistic scenarios, we explore the effects of applying more realistic foreground and instrument models to the 21 cm signal, as well as the ability to estimate astrophysical parameters with these additional complexities. We use a highly optimized version of 21cm FAST, integrated into 21cm MC, to generate lightcones of the brightness temperature fluctuation for Bayesian parameter estimation. We include a statistical point-source foreground model and an instrument model based on the Murchison Widefield Array scaled in observation time to have an effective sensitivity similar to the future Square Kilometre Array. We also extend the current likelihood prescription to account for the presence of beam convolution and foregrounds, the two-dimensional power spectrum (PS), and the correlation of PS modes. We use frequency bands between 150 and 180 MHz to constrain the ionizing efficiency (ζ), the minimum virial temperature of halos ( ${T}_{\mathrm{vir}}$ ), the soft X-ray emissivity per unit star formation rate (SFR) (LX/SFR), and the X-ray energy threshold (E0). We find that the inclusion of realistic foregrounds and instrumental components biases the parameter constraints, due to unaccounted for cross-power between the EoR signal, foregrounds, and thermal noise. This causes estimates of ζ to be biased by up to 5σ, but the estimates of Tvir, LX/SFR and E0 remain unaffected and are all within 1σ.

Keywords: Cosmology, Reionization, Astronomical instrumentation, Large-scale structure of the universe
An Examination of Galactic Polarization with Application to the Planck TB Correlation. Angular power spectra computed from Planck HFI 353 GHz intensity and polarization maps produce a TB correlation that can be approximated by a power law. Whether the observed TB correlation is an induced systematic feature or a physical property of Galactic dust emission is of interest both for cosmological and Galactic studies. We investigate the large angular scale E- and B-mode morphology of microwave polarized thermal dust emission, and relate it to physical quantities of polarization angle and polarization fraction. We use empirical models of polarized dust to show that dust polarization angle is a key factor in producing the TB correlation. A small sample of both simulated and observed polarization angle maps are combined with 353 GHz intensity and dust polarization fraction to produce a suite of maps from which we compute TB and EB. Model realizations that produce a positive TB correlation are common and can result from large-scale (&gt;5°) structure in the polarization angle. The TB correlation appears robust to introduction of individual intensity, polarization angle, and polarization fraction model components that are independent of the 353 GHz observations. We conclude that the observed TB correlation is likely the result of large-scale Galactic dust polarization properties.

Keywords: Galaxy structure, Observational cosmology, Dust continuum emission
A Mysterious Ring in Dark Space?. We report the discovery of a low-surface-brightness (27.42 mag arcsec-2 in g band) nebula, which has a ring-like shape in the Beijing-Arizona Sky Survey (BASS). Positive detections have been found in multiband data from far-ultraviolet to far-infrared, except the z band from BASS and W1, W2 from the Wide-field Infrared Survey Explorer. The reddening of the nebula E(B - V) ∼ 0.02 mag is estimated from Infrared Astronomical Satellite (IRAS) 100 μm intensity and H I column density. With the help of the 3D reddening map from Pan-STARRS 1, the Two Micron All Sky Survey, and Gaia, the distance to the nebula of about 500 pc from Earth is derived. Such a low-surface-brightness nebula whose energy can be interpreted by the diffuse Galactic light could account for the optical counterpart of the infrared cirrus, which was detected by IRAS more than 30 yr ago. The ring-like structure might be the ultimate phase of an evolved planetary nebula, while the central white dwarf star has been ejected from the nebula for an unclear reason. On the other hand, the ring structure being a superposition of two close filaments might be another reasonable explanation. Considering the lack of spectroscopic data and uncertainty in the distance measurement, these interpretations need to be checked by future observations.

Keywords: Ring nebulae, Neutral hydrogen clouds, Interstellar dust extinction, Diffuse nebulae, Planetary nebulae, Dark interstellar clouds, Interstellar medium, Reflection nebulae, Runaway stars
The Orbital Histories of Magellanic Satellites Using Gaia DR2 Proper Motions. With the release of Gaia DR2, it is now possible to measure the proper motions (PMs) of the lowest-mass, ultrafaint satellite galaxies in the Milky Way's (MW) halo for the first time. Many of these faint satellites are posited to have been accreted as satellites of the Magellanic Clouds (MCs). Using their six-dimensional phase-space information, we calculate the orbital histories of 13 ultrafaint satellites and five classical dwarf spheroidals in a combined MW+LMC+SMC potential to determine which galaxies are dynamically associated with the MCs. These 18 galaxies are separated into four classes: (I) long-term Magellanic satellites that have been bound to the MCs for at least the last two consecutive orbits around the MCs (Carina 2, Carina 3, Horologium 1, Hydrus 1); (II) Magellanic satellites that were recently captured by the MCs &lt; 1 Gyr ago (Reticulum 2, Phoenix 2); (III) MW satellites that have interacted with the MCs (Sculptor 1, Tucana 3, Segue 1); and (IV) MW satellites (Aquarius 2, Canes Venatici 2, Crater 2, Draco 1, Draco 2, Hydra 2, Carina, Fornax, Ursa Minor). Results are reported for a range of MW and LMC masses. Contrary to previous work, we find no dynamical association between Carina, Fornax, and the MCs. Finally, we determine that the addition of the SMC's gravitational potential affects the longevity of satellites as members of the Magellanic system (long-term versus recently captured), but it does not change the total number of Magellanic satellites.

Keywords: Local Group, Galaxy dynamics, Dwarf galaxies, Magellanic Clouds, Milky Way Galaxy
Joint Radial Velocity and Direct Imaging Planet Yield Calculations. I. Self-consistent Planet Populations. Planet yield calculations may be used to inform the target selection strategy and science operations of space observatories. Forthcoming and proposed NASA missions, such as the Wide-Field Infrared Survey Telescope, the Habitable Exoplanet Imaging Mission, and the Large UV/Optical/IR Surveyor, are expected to be equipped with sensitive coronagraphs and/or starshades. We are developing a suite of numerical simulations to quantify the extent to which ground-based radial velocity (RV) surveys could boost the detection efficiency of direct imaging missions. In this paper, we discuss the first step in the process of estimating planet yields: generating synthetic planetary systems consistent with observed occurrence rates from multiple detection methods. In an attempt to self-consistently populate stars with orbiting planets, it is found that naive extrapolation of occurrence rates (mass, semimajor axis) results in an unrealistically large number density of Neptune-mass planets beyond the ice line (a ≳ 5 au), causing dynamic interactions that would destabilize orbits. We impose a stability criterion for multiplanet systems based on mutual Hill radii separation. Considering the influence of compact configurations containing Jovian-mass and Neptune-mass planets results in a marked suppression in the number of terrestrial planets that can exist at large radii. This result has a pronounced impact on planet yield calculations particularly in regions accessible to high-contrast imaging and microlensing. The dynamically compact configurations and occurrence rates that we develop may be incorporated as input into joint RV and direct imaging yield calculations to place meaningful limits on the number of detectable planets with future missions.

Keywords: Radial velocity, Exoplanet detection methods, Direct imaging, Astronomical simulations
Electric Current Neutralization in Solar Active Regions and Its Relation to Eruptive Activity. It is well established that magnetic free energy associated with electric currents powers solar flares and coronal mass ejections (CMEs) from solar active regions (ARs). However, the conditions that determine whether an AR will produce an eruption are not well understood. Previous work suggests that the degree to which the driving electric currents, or the sum of all currents within a single magnetic polarity, are neutralized may serve as a good proxy for assessing the ability of ARs to produce eruptions. Here, we investigate the relationship between current neutralization and flare/CME production using a sample of 15 flare-active and 15 flare-quiet ARs. All flare-quiet and four flare-active ARs are also CME-quiet. We additionally test the relation of current neutralization to the degree of shear along polarity inversion lines (PILs) in an AR. We find that flare-productive ARs are more likely to exhibit non-neutralized currents, specifically those that also produce a CME. We find that flare/CME-active ARs also exhibit higher degrees of PIL shear than flare/CME-quiet ARs. We additionally observe that currents become more neutralized during magnetic flux emergence in flare-quiet ARs. Our investigation suggests that current neutralization in ARs is indicative of their eruptive potential.

Keywords: Solar corona, Solar coronal mass ejections, Solar flares, Solar magnetic fields
Difference of Intermittency between Electric Field and Magnetic Field Fluctuations from Ion Scale Down to Sub-electron Scale in the Magnetosheath Turbulence. We use the measurements from the Magnetospheric MultiScale spacecraft to study the intermittency of the magnetic field (B-field) and electric field (E-field) fluctuations from ion scales (around 1 Hz in the spacecraft frame) to sub-electron scales (about 1000Hz) in the magnetosheath. For the first time, this study shows remarkable differences of intermittent properties between these two fields: (1) The multiorder structure functions of E-field trace fluctuations are more flattened as compared to those of B-field trace fluctuations. (2) The flatness of E-field fluctuations increases monotonically with decreasing scales and eventually exceeds 100 at 1000 Hz, whereas the flatness of B-field fluctuations does not rise so high (less than 100) and tends to fall off at frequencies larger than 1000 Hz. (3) It is revealed that ζ(p) monotonically and quasi-linearly increases with increasing p for B-field fluctuations even at sub-electron scales. However, ζ(p) for E-field is concave, turning over at around p = 2 from increasing to decreasing trends. We quantitatively analyze and find that, with decreasing scales (defined as τ), the variance of $\mathrm{ln}\sigma $ (defined as λ2), where σ is the local standard deviation, increases much more slowly than the most probable $\mathrm{ln}\sigma $ (defined as μ) decreases (I.e., $\left|\tfrac{d{\lambda }^{2}}{d\mathrm{ln}\tau }\right|\ll \left|\tfrac{d\mu }{d\mathrm{ln}\tau }\right|$ ) for the B-field case, while the changing rate of the two quantities are of the same order $(-\tfrac{d{\lambda }^{2}}{d\mathrm{ln}\tau }\approx \tfrac{1}{3}\tfrac{d\mu }{d\mathrm{ln}\tau })$ for the E-field case. These results indicate the distinct intermittency nature between magnetic and electric fields and impose a constraint on theoretical turbulence models.

Keywords: Interplanetary turbulence, Planetary bow shocks
Scattering-induced Intensity Reduction: Large Mass Content with Small Grains in the Inner Region of the TW Hya disk. Dust continuum observation is one of the best methods to constrain the properties of protoplanetary disks. Recent theoretical studies have suggested that dust scattering at the millimeter wavelength potentially reduces the observed intensity, which results in an underestimate in the dust mass. We investigate whether dust scattering indeed reduces the observed continuum intensity by comparing the ALMA archival data of the TW Hya disk at Bands 3, 4, 6, 7, and 9 to models obtained by radiative transfer simulations. We find that the model with scattering by 300 μm-sized grains well reproduces the observed spectral energy distribution of the central part of the TW Hya disk while the model without scattering is also consistent within the errors of the absolute fluxes. To explain the intensity at Band 3, the dust surface density needs to be ∼10 g cm-2 at 10 au in the model with scattering, which is 26 times more massive than previously predicted. The model without scattering needs a 2.3 times higher dust mass than the model with scattering because it needs a lower temperature. At Band 7, scattering reduces the intensity by ∼35%, which makes the disk look optically thin even though it is optically thick. Our study suggests the TW Hya disk is still capable of forming cores of giant planets at locations analogous to where the current solar system planets exist.

Keywords: Dust continuum emission, Protoplanetary disks, Planet formation
Astrophysical S(E) for the <SUP>9</SUP>Be(p, d)<SUP>8</SUP>Be and <SUP>9</SUP>Be(p, α)<SUP>6</SUP>Li Reactions by Direct Measurement. The p-9Be reactions play a key role in accurate prediction of the primordial abundance of beryllium, and its abundance can be used to exquisitely probe the nucleosynthesis and mixing mechanism of stars. In the present work, astrophysical S(E) factors of the 9Be(p, d)8Be and 9Be(p, α)6Li reactions have been obtained from the thick-target yield Yield(EI) for proton energies from 18 to 100 keV. A full R-matrix analysis was performed to fit both the 9Be(p, α)6Li and 9Be(p, d)8Be reactions simultaneously. The resulting astrophysical S(E) factors agree well with direct measurements, leading to S(0) = 17.3 ± 2.1 and 13.9 ± 1.8 MeV·b for the 9Be(p, α)6Li and 9Be(p, d)8Be reactions, respectively. However, the obtained screening potential (Us = 512 ± 77 eV) is lower than results of previous work (900 ± 50 and 806 eV), and all of them are larger than the adiabatic limit of 264 eV. The reaction rates were also calculated in the temperature range (0.01-1) ⨯ 109 K, which improves on the precision of the standard database NACRE and NACRE II.

Keywords: Reaction rates, Nucleosynthesis, Nuclear reaction cross sections
Real-time, Value-driven Data Augmentation in the Era of LSST. The deluge of data from time-domain surveys is rendering traditional human-guided data collection and inference techniques impractical. We propose a novel approach for conducting data collection for science inference in the era of massive large-scale surveys that uses value-based metrics to autonomously strategize and coordinate follow-up in real time. We demonstrate the underlying principles in the Recommender Engine For Intelligent Transient Tracking (REFITT) that ingests live alerts from surveys and value-added inputs from data brokers to predict the future behavior of transients and design optimal data augmentation strategies given a set of scientific objectives. The prototype presented in this paper is tested to work given simulated Rubin Observatory Legacy Survey of Space and Time (LSST) core-collapse supernova (CC SN) light curves from the Photometric LSST Astronomical Time-series Classification Challenge data set. CC SNe were selected for the initial development phase as they are known to be difficult to classify, with the expectation that any learning techniques for them should be at least as effective for other transients. We demonstrate the behavior of REFITT on a random LSST night given ∼32,000 live CC SNe of interest. The system makes good predictions for the photometric behavior of the events and uses them to plan follow-up using a simple data-driven metric. We argue that machine-directed follow-up maximizes the scientific potential of surveys and follow-up resources by reducing downtime and bias in data collection.

Keywords: Surveys, Core-collapse supernovae, Supernovae, Astronomy data acquisition
The Fraction of Gamma-Ray Bursts with an Observed Photospheric Emission Episode. There is no complete description of the emission physics during the prompt phase in gamma-ray bursts. Spectral analyses, however, indicate that many spectra are narrower than what is expected for nonthermal emission models. Here, we reanalyze the sample of 37 bursts in Yu et al. by fitting the narrowest time-resolved spectrum in each burst. We perform a model comparison between photospheric and synchrotron emission models based on Bayesian evidence. We compare the shapes of the narrowest expected spectra: emission from the photosphere in a non-dissipative flow and slow cooled synchrotron emission from a narrow electron distribution. We find that the photospheric spectral shape is preferred by 54% ± 8% of the spectra (20/37), while 38% ± 8% of the spectra (14/37) prefer the synchrotron spectral shape; three spectra are inconclusive. We hence conclude that GRB spectra are indeed very narrow and that more than half of the bursts have a photospheric emission episode. We also find that a third of all analyzed spectra, not only prefer, but are also compatible with a non-dissipative photosphere, confirming previous similar findings. Furthermore, we notice that the spectra that prefer the photospheric model all have low-energy power-law indices α ≳ -0.5. This means that α is a good estimator for which model is preferred by the data. Finally, we argue that the spectra that statistically prefer the synchrotron model could equally as well be caused by subphotospheric dissipation. If that is the case, photospheric emission during the early, prompt phase would be even more dominant.

Keywords: Gamma-ray sources, Burst astrophysics, Gamma-ray bursts
Neutron Star Radius-to-mass Ratio from Partial Accretion Disk Occultation as Measured through Fe Kα Line Profiles. We present a new method to measure the radius-to-mass ratio (R/M) of weakly magnetic, disk-accreting neutron stars by exploiting the occultation of parts of the inner disk by the star itself. This occultation imprints characteristic features on the X-ray line profile that are unique and are expected to be present in low-mass X-ray binary systems seen under inclinations higher than ∼65°. We analyze a Nuclear Spectroscopic Telescope Array observation of a good candidate system, 4U 1636-53, and find that X-ray spectra from current instrumentation are unlikely to single out the occultation features owing to insufficient signal-to-noise. Based on an extensive set of simulations we show that large-area X-ray detectors of the future generation could measure R/M to ∼ $2\div3$ % precision over a range of inclinations. Such is the precision in radius determination required to derive tight constraints on the equation of state of ultradense matter and it represents the goal that other methods also aim to achieve in the future.

Keywords: Neutron stars, Stellar accretion disks, General relativity, X-ray sources, Low-mass x-ray binary stars
Particle-in-cell Simulations of the Parallel Proton Firehose Instability Influenced by the Electron Temperature Anisotropy in Solar Wind Conditions. In situ observations of the solar wind show a limited level of particle temperature anisotropy with respect to the interplanetary magnetic field direction. Kinetic electromagnetic instabilities are efficient to prevent the excessive growth of the anisotropy of particle velocity distribution functions. Among them, the firehose instabilities are often considered to prevent the increase of the parallel temperature and hence to shape the velocity distribution functions of electrons and protons in the solar wind. We present a nonlinear modeling of the parallel firehose instability, retaining a kinetic description for both the electrons and protons. One-dimensional (1D) fully kinetic particle-in-cell simulations using the energy conserving semi-implicit method (ECsim) are performed to clarify the role of the electron temperature anisotropy in the development of the parallel proton firehose instability. We found that in the presence of an electron temperature anisotropy, such that the temperature parallel to the background magnetic field is higher than the temperature in the perpendicular direction, the onset of the parallel proton firehose instability occurs earlier and its growth rate is faster. The enhanced wave fluctuations contribute to the particle scattering reducing the temperature anisotropy to a stable, nearly isotropic state. The simulation results compare well with linear theory. A test case of 1D simulations at oblique angles with respect to the magnetic field is also considered, as a first step to study the cumulative effect of protons and electrons on the full spectrum of instabilities.

Keywords: Space plasmas, Solar wind, Plasma astrophysics
Flux Tubes Forming Instability Near the Base of the Rotating Convection Zone: A Possible Explanation for the Low Latitudes of Sunspots. The rise of flux tubes with intense magnetic fields from the base of the convection zone to the solar surface has been substantiated as a probable mechanism for sunspot formation. The origin of flux tubes of a sufficient strength (∼105 G) is, however, uncertain. This paper considers the instability of a large-scale toroidal magnetic field caused by the magnetic suppression of convective heat transport as a candidate for the flux-tube formation mechanism. The consideration employs the analytical dependence of eddy diffusion on the magnetic field supplied by mean-field magnetohydrodynamics. The instability tends to produce regions of increased field strength with spatial scales of the order of 100 Mm at the base of the convection zone. Characteristic growth times of the instability are short compared to the 11 yr cycle. The threshold field strength for the onset of the instability increases from several hundred Gauss in the vicinity of the equator to some kilo-Gauss at middle latitudes. Growth rates of unstable disturbances decrease with latitude. These latitudinal trends can be the reason for the observed confinement of sunspot activity to a near-equatorial belt.

Keywords: Solar magnetic fields
The Broad-lined Ic Supernova ZTF18aaqjovh (SN 2018bvw): An Optically Discovered Engine-driven Supernova Candidate with Luminous Radio Emission. We present ZTF18aaqjovh (SN 2018bvw), a high-velocity ("broad-lined") stripped-envelope (Type Ic) supernova (Ic-BL SN) discovered in the Zwicky Transient Facility one-day cadence survey. ZTF18aaqjovh shares a number of features in common with engine-driven explosions: the photospheric velocity and the shape of the optical light curve are very similar to those of the Type Ic-BL SN 1998bw, which was associated with a low-luminosity gamma-ray burst (LLGRB) and had relativistic ejecta. However, the radio luminosity of ZTF18aaqjovh is almost two orders of magnitude fainter than that of SN 1998bw at the same velocity phase, and the shock velocity is at most mildly relativistic (V = 0.06-0.4c). A search of high-energy catalogs reveals no compelling gamma-ray burst (GRB) counterpart to ZTF18aaqjovh, and the limit on the prompt GRB luminosity of ${L}_{\gamma ,\mathrm{iso}}\approx 1.6\times {10}^{48}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ excludes a classical GRB but not an LLGRB. Altogether, ZTF18aaqjovh represents another transition event between engine-driven SNe associated with GRBs and "ordinary" Ic-BL SNe.

Keywords: Type Ic supernovae, Sky surveys, Hypernovae, Core-collapse supernovae, High energy astrophysics, Transient sources, Time domain astronomy, Supernovae, Radio transient sources