Sazuna/UAT_keywords huggingface dataset:
The Interface between the Outer Heliosphere and the Inner Local ISM: Morphology of the Local Interstellar Cloud, Its Hydrogen Hole, Strömgren Shells, and <SUP>60</SUP>Fe Accretion. We describe the interface between the outer heliosphere and the local interstellar medium (LISM) surrounding the Sun. The components of the inner LISM are the four partially ionized clouds (the Local Interstellar Cloud (LIC), G cloud, Blue cloud, and Aql cloud) that are in contact with the outer heliosphere, and ionized gas produced by EUV radiation primarily from ɛ CMa. We construct the three-dimensional shape of the LIC based on interstellar line absorption along 62 sightlines and show that in the directions of ɛ CMa, β CMa, and Sirius B the neutral hydrogen column density from the center of the LIC is a minimum. We call this region the “hydrogen hole.” In this direction, the presence of Blue cloud absorption and the absence of LIC absorption can be simply explained by the Blue cloud lying just outside the heliosphere. We propose that the outer edge of the Blue cloud is a Strömgren shell driven toward the heliosphere by high pressures in the H II region. We find that the vectors of neutral and ionized helium flowing through the heliosphere are inconsistent with the LIC flow vector, and that the nearby intercloud gas is consistent with ionization by ɛ CMa and other stellar sources without requiring additional sources of ionization or million-degree plasma. In the upwind direction, the heliosphere is passing through an environment of several LISM clouds, which may explain the recent influx of interstellar grains containing 60Fe from supernova ejecta measured in Antarctic snow. Based on observations made with the NASA/ESA Hubble Space Telescope obtained from the Data Archive at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS AR-09525.01A. These observations are associated with programs #12475, 12596.

Keywords: Interstellar dust, Photoionization, Astrosphere interstellar medium interactions, Heliosphere, Strömgren spheres, Interstellar clouds, Interstellar medium
The Radius-Luminosity Relationship Depends on Optical Spectra in Active Galactic Nuclei. The radius-luminosity ({R}{{H}β }{--}{L}5100) relationship of active galactic nuclei (AGNs) established by the reverberation mapping (RM) observations has been widely used as a single-epoch black hole mass estimator in the research of large AGN samples. However, the recent RM campaigns discovered that the AGNs with high-accretion rates show shorter time lags by factors of a few comparing with the predictions from the {R}{{H}β }{--}{L}5100 relationship. The explanation of the shortened time lags has not been finalized yet. We collect eight different single-epoch spectral properties to investigate how the shortening of the time lags correlates with those properties and to determine the origin of the shortened lags. We find that the flux ratio between Fe II and Hβ emission lines shows the most prominent correlation, thus confirming that accretion rate is the main driver for the shortened lags. In addition, we establish a new scaling relation including the relative strength of Fe II emission. This new scaling relation can provide less biased estimates of the black hole mass and accretion rate from the single-epoch spectra of AGNs.

Keywords: Supermassive black holes, Quasars, Reverberation mapping, Active galaxies, Active galactic nuclei
On Doppler Shift and Its Center-to-limb Variation in Active Regions in the Transition Region. A comprehensive understanding of the structure of Doppler motions in the transition region including the center-to-limb variation and its relationship with the magnetic field structure is vital for the understanding of mass and energy transfer in the solar atmosphere. In this paper, we have performed such a study in an active region using the Si IV 1394 Å emission line recorded by the Interface Region Imaging Spectrograph and the line-of-sight photospheric magnetic field obtained by the Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory. The active region has two opposite polarity strong field regions separated by a weak field corridor, which widened as the active region evolved. On average, the strong field regions (corridor) show(s) redshifts of 5-10 (3-9) km s-1 (depending on the date of observation). There is, however, a narrow lane in the middle of the corridor with near-zero Doppler shifts at all disk positions, suggesting that any flows there are very slow. The Doppler velocity distributions in the corridor seem to have two components—a low velocity component centered near 0 km s-1 and a high-velocity component centered near 10 km s-1. The high-velocity component is similar to the velocity distributions in the strong field regions, which have just one component. Both exhibit a small center-to-limb variation and seem to come from the same population of flows. To explain these results, we suggest that the emission from the lower transition region comes primarily from warm type II spicules, and we introduce the idea of a “chromospheric wall”—associated with classical cold spicules—to account for a diminished center-to-limb variation.

Keywords: Solar photosphere, The Sun, Sunspots, Solar spicules, Solar active regions, Solar magnetic fields, Solar transition region, Solar activity
Nucleosynthesis Constraints on the Energy Growth Timescale of a Core-collapse Supernova Explosion. Details of the explosion mechanism of core-collapse supernovae (CCSNe) are not yet fully understood. There are an increasing number of numerical examples by ab initio core-collapse simulations leading to an explosion. Most, if not all, of the ab initio core-collapse simulations represent a “slow” explosion in which the observed explosion energy (∼1051 erg) is reached in a timescale of ≳1 s. It is, however, unclear whether such a slow explosion is consistent with observations. In this work, by performing nuclear reaction network calculations for a range of the explosion timescale t grow, from the rapid to slow models, we aim at providing nucleosynthetic diagnostics on the explosion timescale. We employ one-dimensional hydrodynamic and nucleosynthesis simulations above the proto-neutron star core, by parameterizing the nature of the explosion mechanism by t grow. The results are then compared to various observational constraints: the masses of 56Ni derived for typical CCSNe, the masses of 57Ni and 44Ti observed for SN 1987A, and the abundance patterns observed in extremely metal-poor stars. We find that these observational constraints are consistent with the “rapid” explosion (t grow ≲ 250 ms), and especially the best match is found for a nearly instantaneous explosion (t grow ≲ 50 ms). Our finding places a strong constraint on the explosion mechanism; the slow mechanism (t grow ≳ 1000 ms) would not satisfy these constraints, and the ab initio simulations will need to realize a rapid explosion.

Keywords: Explosive nucleosynthesis, Supernova dynamics, Nucleosynthesis, Core-collapse supernovae, Supernovae
Mining for Dark Matter Substructure: Inferring Subhalo Population Properties from Strong Lenses with Machine Learning. The subtle and unique imprint of dark matter substructure on extended arcs in strong-lensing systems contains a wealth of information about the properties and distribution of dark matter on small scales and, consequently, about the underlying particle physics. However, teasing out this effect poses a significant challenge since the likelihood function for realistic simulations of population-level parameters is intractable. We apply recently developed simulation-based inference techniques to the problem of substructure inference in galaxy-galaxy strong lenses. By leveraging additional information extracted from the simulator, neural networks are efficiently trained to estimate likelihood ratios associated with population-level parameters characterizing substructure. Through proof-of-principle application to simulated data, we show that these methods can provide an efficient and principled way to simultaneously analyze an ensemble of strong lenses and can be used to mine the large sample of lensing images deliverable by near-future surveys for signatures of dark matter substructure. We find that, within our simplified modeling framework, analyzing a sample of around 100 lenses can already pin down the overall abundance of substructure within lensing galaxies to a precision of { \mathcal O }(10)% with greater sensitivity expected from a larger lens sample. (https://github.com/smsharma/StrongLensing-Inference)

Keywords: Cosmology, Nonparametric inference, Astrostatistics techniques, Convolutional neural networks, Strong gravitational lensing, Gravitational lensing, Dark matter
High Angular Resolution ALMA Images of Dust and Molecules in the SN 1987A Ejecta. We present high angular resolution (∼80 mas) ALMA continuum images of the SN 1987A system, together with CO J = 2 \to 1, J = 6 \to 5, and SiO J = 5 \to 4 to J = 7 \to 6 images, which clearly resolve the ejecta (dust continuum and molecules) and ring (synchrotron continuum) components. Dust in the ejecta is asymmetric and clumpy, and overall the dust fills the spatial void seen in Hα images, filling that region with material from heavier elements. The dust clumps generally fill the space where CO J = 6 \to 5 is fainter, tentatively indicating that these dust clumps and CO are locationally and chemically linked. In these regions, carbonaceous dust grains might have formed after dissociation of CO. The dust grains would have cooled by radiation, and subsequent collisions of grains with gas would also cool the gas, suppressing the CO J = 6 \to 5 intensity. The data show a dust peak spatially coincident with the molecular hole seen in previous ALMA CO J = 2 \to 1 and SiO J = 5 \to 4 images. That dust peak, combined with CO and SiO line spectra, suggests that the dust and gas could be at higher temperatures than the surrounding material, though higher density cannot be totally excluded. One of the possibilities is that a compact source provides additional heat at that location. Fits to the far-infrared-millimeter spectral energy distribution give ejecta dust temperatures of 18-23 K. We revise the ejecta dust mass to M dust = 0.2-0.4 {M}☉  for carbon or silicate grains, or a maximum of &lt;0.7 {M}☉  for a mixture of grain species, using the predicted nucleosynthesis yields as an upper limit.

Keywords: Interstellar dust, Interstellar molecules, Supernovae
Ruling Out the Supersoft High-density Symmetry Energy from the Discovery of PSR J0740+6620 with Mass {2.14}_{-0.09}^{+0.10}{M}_{\odot }. Using the very recently reported mass {2.14}-0.09+0.10{M}⊙  of PSR J0740+6620 together with the data of finite nuclei and the constraints on the equation of state of symmetric nuclear matter at suprasaturation densities from flow data in heavy-ion collisions, we show that the symmetry energy E sym(n) cannot be supersoft so that it becomes negative at suprasaturation densities in neutron stars (NSs) and thus may make the NS have a pure neutron matter core. This is in contrast to the fact that using the mass 2.01 ± 0.04M ⊙ of PSR J0348+0432 as the NS maximum mass cannot rule out the supersoft high-density E sym(n). Furthermore, we find the stiffer high-density E sym(n) based on the existence of 2.14M ⊙ NSs leads to a strong constraint of {{{Λ }}}1.4≥slant {348}-51+88 for the dimensionless tidal deformability of the canonical 1.4M ⊙ NS.

Keywords: Neutron stars, Nuclear astrophysics, Nuclear physics
Electron Scattering by Low-frequency Whistler Waves at Earth’s Bow Shock. Electrons are accelerated to nonthermal energies at shocks in space and astrophysical environments. While shock drift acceleration (SDA) has been considered a key process of electron acceleration at Earth’s bow shock, it has also been recognized that SDA needs to be combined with an additional stochastic process to explain the observed power-law energy spectra. Here, we show mildly energetic (∼0.5 keV) electrons are locally scattered (and accelerated while being confined) by magnetosonic-whistler waves within the shock transition layer, especially when the shock angle is large ({θ }Bn}≳ 70^\circ ). When measured by the Magnetospheric Multiscale mission at a high cadence, ∼0.5 keV electron flux increased exponentially in the shock transition layer. However, the flux profile was not entirely smooth and the fluctuation showed temporal/spectral association with large-amplitude (δ B/B∼ 0.3), low-frequency (≲ 0.1{{{Ω }}}ce} where {{{Ω }}}ce} is the cyclotron frequency), obliquely propagating ({θ }kB}∼ 30^\circ {--}60^\circ , where {θ }kB} is the angle between the wave vector and background magnetic field) whistler waves, indicating that the particles were interacting with the waves. Particle simulations demonstrate that, although linear cyclotron resonances with ∼0.5 keV electrons are unlikely due to the obliquity and low frequencies of the waves, the electrons are still scattered beyond 90° pitch angle by (1) resonant mirroring (transit-time damping), (2) non-resonant mirroring, and (3) subharmonic cyclotron resonances. Such coupled nonlinear scattering processes are likely to provide the stochasticity needed to explain the power-law formation.

Keywords: Shocks, Interplanetary particle acceleration, Space plasmas
Weibel-mediated Shocks Propagating into Inhomogeneous Electron-Positron Plasmas. The external forward shock emitting the gamma-ray burst (GRB) afterglow is collisionless, and it is mediated by the Weibel instability which generates the magnetic field. The GRB afterglow shows that the magnetic field in the large downstream region is much stronger than the shock-compressed preshock field. However, particle-in-cell (PIC) simulations of relativistic shocks propagating into homogeneous media show that the Weibel generated field decays near the shock front. Some GRB observations and theoretical studies suggest that the preshock medium is inhomogeneous. We perform the PIC simulation of a relativistic shock propagating into inhomogeneous plasma. It is found that the post-shock magnetic field decays slowly compared with the homogeneous case. Sound waves and entropy waves are also generated by the shock-wave interaction, and temperature anisotropy is produced by the sound wave in the downstream region. The free energy of the temperature anisotropy is large enough to explain the observed field strength. Our results show that the upstream density fluctuation has a significant effect in the downstream region of collisionless shocks even if the wavelength of the upstream inhomogeneity is much larger than the kinetic scale.

Keywords: Shocks, Gamma-ray bursts, Magnetic fields, Plasma astrophysics
Parsec-scale Dusty Winds in Active Galactic Nuclei: Evidence for Radiation Pressure Driving. Infrared interferometry of the local active galactic nucleus (AGN) has revealed a warm (∼300-400 K) polar dust structure that cannot be trivially explained by the putative dust torus of the unified model. This led to the development of the disk+wind scenario which comprises a hot (∼1000 K) compact equatorial dust disk and a polar dust wind. This wind is assumed to be driven by radiation pressure and, therefore, we would expect that long-term variation in radiation pressure would influence the dust distribution. In this paper we attempt to quantify if and how the dust distribution changes with radiation pressure. We analyze so far unpublished Very Large Telescope Interferometer (VLTI)/MID-infrared Interferometer (MIDI) data on 8 AGN and use previous results on 25 more to create a sample of 33 AGN. This sample comprises all AGN successfully observed with VLTI/MIDI. For each AGN, we calculate the Eddington ratio, using the intrinsic 2-10 keV X-ray luminosity and black hole mass, and compare this to the resolved dust emission fraction as seen by MIDI. We tentatively conclude that there is more dust in the wind at higher Eddington ratios, at least in type 2 AGN where such an effect is expected to be more easily visible. Based on European Southern Observatory (ESO) observing programs 71.B-0062, 078.B-0303, 083.B-0288, 083.B-0452, 084.B-0366, 086.B-0019, 086.B-0242, 087.B-0018, 087.B0401, 091.B-0025, 091.B-0647, 092.B-0718, 092.B-0738, 093.B-0287, 093.B-0647, 094.B-0918, 095.B-0376,0101.B-0411 and 290.B-5113 as well as the Spitzer programs 86, 526, 3269, 3605, 30572, and 50588.

Keywords: Long baseline interferometry, Active galactic nuclei, Dust continuum emission, Interferometry
Obliquity Evolution of Circumstellar Planets in Sun-like Stellar Binaries. Changes in planetary obliquity, or axial tilt, influence the climates on Earth-like planets. In the solar system, the Earth’s obliquity is stabilized by interactions with our moon, and the resulting small amplitude variations (∼2.°4) are beneficial for advanced life. Most Sun-like stars have at least one stellar companion, and the habitability of circumstellar exoplanets is shaped by their stellar companion. We show that a stellar companion can dramatically change whether Earth-like obliquity stability is possible through planetary orbital precession relative to the binary orbit or resonant pumping of the obliquity through spin-orbit interactions. We present a new formalism for the planetary spin precession that accounts for orbital misalignments between the planet and binary. Using numerical modeling in α Centauri AB, we show the following: there is a stark contrast between the planetary obliquity variations depending on the host star, planetary neighbors limit the possible spin states for Earth-like obliquity stability, and the presence of a moon can destabilize the obliquity, defying our Earth-based expectations. An Earth-like rotator orbiting the primary star would experience small obliquity variations for 87%, 74%, or 54% of solar-type binaries, depending on the mass of the primary (0.8, 1.0, or 1.2 M ⊙, respectively). Thus, Earth-like planets likely experience much larger obliquity variations, with more extreme climates, unless they are in specific states, such as orbiting nearly planar with the binary and rotating retrograde (backward) like Venus.

Keywords: Exoplanet dynamics, Natural satellites (Extrasolar), Binary stars, Exoplanets, Habitable planets
High-velocity Feature as the Indicator of the Stellar Population of Type Ia Supernovae. Although Type Ia supernovae (SNe Ia) are very useful in many astrophysical fields, their exact nature is still unclear, e.g., the progenitor and explosion models. The high-velocity features (HVFs) in optical spectra of SNe Ia could provide some meaningful information to constrain the nature of SNe Ia. Here, I show strong evidence that the SNe Ia with a strong Ca II infrared triple (Ca II IR3) HVF around maximum brightness are associated with a relatively younger population than those with a weak Ca II IR3 HVF, e.g., the SNe Ia with a strong Ca II IR3 HVF tend to occur in a late-type galaxy or in an early-type galaxy with significant star formation. In addition, using pixel statistics, I find that the SNe Ia with a strong maximum-light Ca II IR3 HVF show a higher degree of association with the star formation index, e.g., Hα or near-UV emission, than those with a weak Ca II IR3 HVF. Moreover, I find that the strength of the Ca II IR3 HVF is linearly dependent on the difference of the absorption-weighted velocities between the Ca II IR3 and Si II 635.5 nm absorption lines, which then is a good index for diagnosing whether there is a high-velocity component in the Ca II IR3 absorption feature in the spectra of SNe Ia. I finally discuss the origin of the HVFs and the constraints from our discoveries on the progenitor model of SNe Ia.

Keywords: Circumstellar matter, White dwarf stars, Type Ia supernovae
A Global Magnetohydrodynamic Simulation Study of Ultra-low-frequency Wave Activity in the Inner Magnetosphere: Corotating Interaction Region + Alfvénic Fluctuations. Using global magnetohydrodynamic (MHD) simulations, we investigate the role played by a complex solar structure composed of a corotating interaction region (CIR) followed by solar wind Alfvénic fluctuations on the magnetosphere’s nightside, equatorial electric field oscillations in the ultra-low-frequency range. A series of numerical experiments are performed employing synthetic solar wind inputs resembling those of a real CIR+Alfvénic fluctuation event that reached Earth’s magnetosphere on 2003 April 20. The following is found: (i) Radial electric field component fluctuations are excited via magnetopause boundary motions driven either by solar wind density variations characteristic of CIRs or by solar wind Alfvénic fluctuations with a given oscillation period. (ii) Azimuthal electric field component fluctuations nearer to Earth, that is, at radial distances R less than about 5R E ({R}{{E}}=1 Earth radius), are apparently not related to either of the two types of sinusoidal solar wind Alfvénic fluctuations used in this study featuring monochromatic frequencies of 0.833 mHz (20-minute period) and 1.666 mHz (10-minute period). Instead, these innermost azimuthal component fluctuations show enhanced activity when inner magnetosphere convection increases as a result of a southward turning of the interplanetary magnetic field component B  z . (iii) Lastly, outermost (R ≳ 7 R E) azimuthal electric field oscillations weakly respond to monochromatic solar wind Alfvénic fluctuations by showing power spectral density peaks at both driving frequencies, but only near the flanks of the magnetopause, thus suggesting that such oscillations are being excited also owing to magnetopause boundary motions driven by solar wind Alfvénic fluctuations.

Keywords: Solar-terrestrial interactions, Alfven waves, Magnetohydrodynamical simulations
Using [C II] 158 μm Emission from Isolated ISM Phases as a Star Formation Rate Indicator. The brightest observed emission line in many star-forming galaxies is the [{{C}} {{II}}] 158 μm line, making it detectable up to z ∼ 7. In order to better understand and quantify the [{{C}} {{II}}] emission as a tracer of star formation, the theoretical ratio between the [{{N}} {{II}}] 205 μm emission and the [{{C}} {{II}}] 158 μm emission has been employed to empirically determine the fraction of [{{C}} {{II}}] emission that originates from the ionized and neutral phases of the interstellar medium (ISM). Sub-kiloparsec measurements of the [{{C}} {{II}}] 158 μm and [{{N}} {{II}}] 205 μm lines in nearby galaxies have recently become available as part of the Key Insights in Nearby Galaxies: a Far Infrared Survey with Herschel (KINGFISH) and Beyond the Peak programs. With the information from these two far-infrared lines along with the multi-wavelength suite of KINGFISH data, a calibration of the [{{C}} {{II}}] emission line as a star formation rate (SFR) indicator and a better understanding of the [{{C}} {{II}}] deficit are pursued. [{{C}} {{II}}] emission is also compared to polycyclic aromatic hydrocarbon (PAH) emission in these regions to compare photoelectric heating from PAH molecules to cooling by [{{C}} {{II}}] in the neutral and ionized phases of the ISM. We find that the [{{C}} {{II}}] emission originating in the neutral phase of the ISM does not exhibit a deficit with respect to the infrared luminosity and is therefore preferred over the [{{C}} {{II}}] emission originating in the ionized phase of the ISM as an SFR indicator for the normal star-forming galaxies included in this sample.

Keywords: Star forming regions, Photodissociation regions, Far infrared astronomy, Galactic and extragalactic astronomy, Interstellar medium