Sazuna/UAT_keywords huggingface dataset:
Parameterizing the Outflow from a Central Black Hole in Dwarf Spheroidal Galaxies: A 3D Hydrodynamic Simulation. Large galaxies harbor massive central black holes and their feedback exerts a substantial impact on their evolution. Recently, observations have suggested that dwarf galaxies might host black holes in their centers, but with lower masses (intermediate-mass black holes-IMBHs). The impact of IMBHs on the evolution of dwarf spheroidal galaxies (dSphs), however, has so far not been properly analyzed. In this work, we investigate the effects of an outflow from an IMBH on gas dynamics in dSphs by means of noncosmological, three-dimensional hydrodynamic simulations, letting the galactic gas distribution evolve over 3 Gyr under the influence of the IMBH's outflow and supernova feedback. All simulations have a numerical resolution of 20.0 pc cell-1. Two scenarios are considered to infer differences in the propagation of the outflow, one with a homogeneous interstellar medium (ISM) and another one with inhomogeneities caused by supernova feedback. A minimal initial speed and a minimal initial density are required for the outflow to propagate, with the values depending on the conditions of the medium. In an unperturbed medium, the outflow propagates freely in both directions with the same velocity (lower than the initial one), removing a small fraction of gas from the galaxy (the exact fraction depends on the initial physical conditions of the outflow). However, in an inhomogeneous ISM, the impact of the outflow is substantially reduced, and its contribution to the removal of gas from the galaxy is almost negligible.

Keywords: Local Group, Hydrodynamical simulations, Dwarf galaxies
The Influence of the Secular Perturbation of an Intermediate-mass Companion. II. Ejection of Hypervelocity Stars from the Galactic Center. There is a population of stars with velocities in excess of 500 km s-1 relative to the Galactic center. Many, perhaps most, of these hypervelocity stars (HVSs) are B stars similar to the disk and S stars in a nuclear cluster around a supermassive black hole (SMBH) near Sgr A⋆. In Paper I of this series, we showed that the eccentricity of the stars emerged from a hypothetical disk around the SMBH that can be rapidly excited by the secular perturbation of its intermediate-mass companion (IMC), and we suggested IRS 13E as a potential candidate for the IMC. Here we show that this process leads to an influx of stars on parabolic orbits to the proximity of Sgr A⋆ on a secular timescale of a few megayears. This timescale is much shorter than the diffusion timescale into the lost cone through either the classical or the resonant relaxation. Precession of the highly eccentric stars' longitude of periastron, relative to that of the IMC, brings them to its proximity within a few megayears. The IMC's gravitational perturbation scatters a fraction of the stars from nearly parabolic to hyperbolic orbits with respect to the SMBH. Their follow-up close encounters with the SMBH induce them to escape with hypervelocity. This scenario is a variant of the hypothesis proposed by Hills based on the anticipated breakup of some progenitor binary stars in the proximity of the SMBH, and its main objective is to account for the limited life span of the known HVSs. We generalize our previous numerical simulations of this process with a much wider range of orbital configurations. We demonstrate the robustness and evaluate the efficiency of this channel of HVS formation. From these numerical simulations, we infer observable kinematic properties for the HVSs.

Keywords: Intermediate-mass black holes, Galactic center, Orbits, Hypervelocity stars, OB stars, Dynamical evolution
High-resolution Laboratory Measurements of K-shell X-Ray Line Polarization and Excitation Cross Sections in Helium-like S XV Ions. We report measurements of electron-impact excitation cross sections for the strong K-shell n = 2 → 1 transitions in S XV, using the LLNL EBIT-I electron beam ion trap, two crystal spectrometers, and the EBIT Calorimeter Spectrometer. The cross sections are determined by direct normalization to the well-known cross sections of radiative electron capture, measured simultaneously. Using contemporaneous polarization measurements with the two crystal spectrometers, whose dispersion planes are oriented parallel and perpendicular to the electron beam direction, the polarization of the direct excitation line emission is determined, and in turn the isotropic total cross sections are extracted. We further experimentally investigate various line-formation mechanisms, finding that radiative cascades and collisional inner-shell ionization dominate the degree of linear polarization and total line-emission cross sections of the forbidden line, z.

Keywords: X-ray astronomy, Theoretical models, Plasma physics, Atomic physics, Laboratory astrophysics, Experimental techniques, Atomic data benchmarking
Multiepoch Optical Images of IRC+10216 Tell about the Central Star and the Adjacent Environment. Six images of IRC+10216 taken by the Hubble Space Telescope at three epochs in 2001, 2011, and 2016 are compared in the rest frame of the central carbon star. An accurate astrometry has been achieved with the help of Gaia Data Release 2. The positions of the carbon star in the individual epochs are determined using its known proper motion, defining the rest frame of the star. In 2016, a local brightness peak with compact and red nature is detected at the stellar position. A comparison of the color maps between 2016 and 2011 epochs reveals that the reddest spot moved along with the star, suggesting a possibility of it being the dusty material surrounding the carbon star. The relatively red, ambient region is distributed in an Ω shape and corresponds well to the dusty disk previously suggested based on near-infrared polarization observations. In a larger scale, differential proper motion of multiple ring-like patterns in the rest frame of the star is used to derive the average expansion velocity of transverse wind components, resulting in ~12.5 km s-1(d/123 pc), where d is the distance to IRC+10216. Three-dimensional geometry is implied from its comparison with the line-of-sight wind velocity determined from half widths of submillimeter emission line profiles of abundant molecules. Uneven temporal variations in brightness for different searchlight beams and anisotropic distribution of the extended halo are revisited in the context of the stellar light illumination through a porous envelope with postulated longer-term variations for a period of ≲10 yr.

Keywords: Circumstellar matter, Asymptotic giant branch stars, Stellar winds
Subaru High-z Exploration of Low-luminosity Quasars (SHELLQs). XIII. Large-scale Feedback and Star Formation in a Low-luminosity Quasar at z = 7.07 on the Local Black Hole to Host Mass Relation. We present Atacama Large Millimeter/submillimeter Array [C II] 158 μm line and underlying far-infrared (FIR) continuum emission observations (0"70 × 0"56 resolution) toward HSC J124353.93+010038.5 (J1243+0100) at z = 7.07, the only low-luminosity (M1450 &gt; -25 mag) quasar currently known at z &gt; 7. The FIR continuum is bright (1.52 mJy) and resolved with a total luminosity of LFIR = 3.5 × 1012 L⊙. The spatially extended component is responsible for ~40% of the emission. The area-integrated [C II] spectrum shows a broad wing (FWHM = 997 km s-1, L[C II] = 1.2 × 109 L⊙), as well as a bright core (FWHM = 235 km s-1, L[C II] = 1.9 × 109 L⊙). This wing is the first detection of a galactic-scale quasar-driven outflow (atomic outflow rate &gt;447 M⊙ yr-1) at z &gt; 7. The estimated large mass-loading factor of the total outflow (e.g., ≳9 relative to the [C II]-based star formation rate) suggests that this outflow will soon quench the star formation of the host. The core gas dynamics are governed by rotation, with a rotation curve suggestive of a compact bulge (~3.3 × 1010 M⊙), although it is not yet spatially resolved. Finally, we found that J1243+0100 has a black hole mass-to-dynamical mass (and -to-bulge mass) ratio of ~0.4% (~1%), consistent with the local value within the uncertainties. Our results therefore suggest that the black hole-host coevolution relation is already in place at z ~ 7 for this object.

Keywords: AGN host galaxies, Quasars, Active galaxies, Galaxy evolution, Interstellar medium, Submillimeter astronomy, High-redshift galaxies
The Search for Binary Supermassive Black Holes among Quasars with Offset Broad Lines Using the Very Long Baseline Array. In several previous studies, quasars exhibiting broad emission lines with ≳1000 km s-1 velocity offsets with respect to the host galaxy rest frame have been discovered. One leading hypothesis for the origin of these velocity-offset broad lines is the dynamics of a binary supermassive black hole (SMBH). We present high-resolution radio imaging of 34 quasars showing these velocity-offset broad lines with the Very Long Baseline Array (VLBA), aiming to find evidence for the putative binary SMBHs (such as dual radio cores), and testing the competing physical models. We detect exactly half of the target sample from our VLBA imaging, after implementing a 5σ detection limit. While we do not resolve double radio sources in any of the targets, we obtain limits on the instantaneous projected separations of a radio-emitting binary for all of the detected sources under the assumption that a binary still exists within our VLBA angular resolution limits. We also assess the likelihood that a radio-emitting companion SMBH exists outside of our angular resolution limits, but its radio luminosity is too weak to produce a detectable signal in the VLBA data. Additionally, we compare the precise sky positions afforded by these data to optical positions from both the SDSS and Gaia DR2 source catalogs. We find projected radio/optical separations on the order of ~10 pc for three quasars. Finally, we explore how future multi-wavelength campaigns with optical, radio, and X-ray observatories can help discriminate further between the competing physical models.

Keywords: Supermassive black holes, Radio cores, Active galaxies, Active galactic nuclei, Radio active galactic nuclei
How to Identify Exoplanet Surfaces Using Atmospheric Trace Species in Hydrogen-dominated Atmospheres. Sub-Neptunes (Rp ~ 1.25-4 REarth) remain the most commonly detected exoplanets to date. However, it remains difficult for observations to tell whether these intermediate-sized exoplanets have surfaces and where their surfaces are located. Here we propose that the abundances of trace species in the visible atmospheres of these sub-Neptunes can be used as proxies for determining the existence of surfaces and approximate surface conditions. As an example, we used a state-of-the-art photochemical model to simulate the atmospheric evolution of K2-18b and investigate its final steady-state composition with surfaces located at different pressures levels (Psurf). We find that the surface location has a significant impact on the atmospheric abundances of trace species, making them deviate significantly from their thermochemical equilibrium and "no-surface" conditions. This result arises primarily because the pressure-temperature conditions at the surface determine whether photochemically produced species can be recycled back to their favored thermochemical equilibrium forms and transported back to the upper atmosphere. For an assumed H2-rich atmosphere for K2-18b, we identify seven chemical species that are most sensitive to the existence of surfaces: ammonia (NH3), methane (CH4), hydrogen cyanide (HCN), acetylene (C2H2), ethane (C2H6), carbon monoxide (CO), and carbon dioxide (CO2). The ratio between the observed and the no-surface abundances of these species can help distinguish the existence of a shallow surface (Psurf &lt; 10 bar), an intermediate surface (10 bar &lt; Psurf &lt; 100 bar), and a deep surface (Psurf &gt; 100 bar). This framework can be applied together with future observations to other sub-Neptunes of interest.

Keywords: Extrasolar rocky planets, Exoplanet atmospheric composition , Exoplanet surfaces, Extrasolar gaseous planets, Exoplanet atmospheres
Modeling a Coronal Mass Ejection from an Extended Filament Channel. I. Eruption and Early Evolution. We present observations and modeling of the magnetic field configuration, morphology, and dynamics of a large-scale, high-latitude filament eruption observed by the Solar Dynamics Observatory. We analyze the 2015 July 9-10 filament eruption and the evolution of the resulting coronal mass ejection (CME) through the solar corona. The slow streamer-blowout CME leaves behind an elongated post-eruption arcade above the extended polarity inversion line that is only poorly visible in extreme ultraviolet (EUV) disk observations and does not resemble a typical bright flare-loop system. Magnetohydrodynamic (MHD) simulation results from our data-inspired modeling of this eruption compare favorably with the EUV and white-light coronagraph observations. We estimate the reconnection flux from the simulation's flare-arcade growth and examine the magnetic-field orientation and evolution of the erupting prominence, highlighting the transition from an erupting sheared-arcade filament channel into a streamer-blowout flux-rope CME. Our results represent the first numerical modeling of a global-scale filament eruption where multiple ambiguous and complex observational signatures in EUV and white light can be fully understood and explained with the MHD simulation. In this context, our findings also suggest that the so-called stealth CME classification, as a driver of unexpected or "problem" geomagnetic storms, belongs more to a continuum of observable/nonobservable signatures than to separate or distinct eruption processes.

Keywords: Solar magnetic reconnection, Solar extreme ultraviolet emission, Quiet sun, Quiescent solar prominence, Solar filament eruptions, Solar coronal mass ejections, Magnetohydrodynamical simulations
The Heating and Pulsations of V386 Serpentis after Its 2019 Dwarf Nova Outburst. Following the pulsation spectrum of a white dwarf through the heating and cooling involved in a dwarf nova outburst cycle provides a unique view of the changes to convective driving that take place on timescales of months versus millennia for nonaccreting white dwarfs. In 2019 January the dwarf nova V386 Ser (one of a small number containing an accreting, pulsating white dwarf) underwent a large-amplitude outburst. Hubble Space Telescope ultraviolet spectra were obtained 7 and 13 months after outburst along with optical ground-based photometry during this interval and high-speed photometry at 5.5 and 17 months after outburst. The resulting spectral and pulsational analysis shows a cooling of the white dwarf from 21,020 to 18,750 K (with a gravity $\mathrm{log}(g)=8.1$ ) between the two UV observations, along with the presence of strong pulsations evident in both UV and optical at a much shorter period after outburst than at quiescence. The pulsation periods consistently lengthened during the year following outburst, in agreement with pulsation theory. However, it remains to be seen if the behavior at longer times past outburst will mimic the unusual nonmonotonic cooling and long periods evident in the similar system GW Lib.

Keywords: Cataclysmic variable stars
A Grid of Core-collapse Supernova Remnant Models. I. The Effect of Wind-driven Mass Loss. Massive stars can shed material via steady, line-driven winds, eruptive outflows, or mass transfer onto a binary companion. In the case of single stars, the mass is deposited by the stellar wind into the nearby environment. After the massive star explodes, the stellar ejecta interact with this circumstellar material (CSM), oftentimes resulting in bright X-ray line emission from both the shock-heated CSM and ejecta. The amount of material lost by the progenitor, the mass of ejecta, and its energetics all impact the bulk spectral characteristics of this X-ray emission. Here we present a grid of core-collapse supernova remnant models derived from models for massive stars with zero-age main-sequence masses of ~10-30 M⊙ evolved from the pre-main-sequence stage with wind-driven mass loss. Evolution is handled by a multistage pipeline of software packages. First, we use mesa (Modules for Experiments in Stellar Astrophysics) to evolve the progenitors from pre-main-sequence to iron core collapse. We then use the Supernova Explosion Code (snec) to explode the mesa models, and we follow them for the first 100 days following core collapse. Finally, we couple the snec output, along with the CSM generated from mesa mass-loss rates, into the cosmic-ray hydrodynamics code to model the remnant phase to 7000 yr after core collapse. At the end of each stage, we compare our outputs with those found in the literature, and we examine any qualitative and quantitative differences in the bulk properties of the remnants and their spectra based on the initial progenitor mass, as well as mass-loss history.

Keywords: X-ray astronomy, Core-collapse supernovae, Astronomy software, Stellar mass loss, Supernova remnants, Computational methods, Astronomical simulations, Stellar evolution
Radio Counterpart Candidates to Unassociated 4FGL-DR2 Sources. For the duration of the Fermi Gamma-Ray Space Telescope's mission, approximately one-third of the point sources detected have been noted as "unassociated," meaning that they seem to have no known counterpart at any other wavelength/frequency. This mysterious part of the gamma-ray sky is perhaps one of the largest unknowns in current astronomical pursuits and as such has been probed extensively by various techniques at various frequencies. Radio frequencies have been perhaps one of the most fruitful, producing a large fraction of the identified and associated active galactic nuclei and pulsars noted in each update of the point-source catalogs. Here we present a catalog of 7432 radio counterpart candidates for unassociated gamma-ray fields in the Second Data Release of the Fourth Fermi Point Source Catalog (4FGL-DR2). A description of the catalog and source types is provided followed by a discussion that demonstrates how the results of this work will aid new associations and identifications. As part of this work, we also present a first catalog derived from "quicklook" images of the Very Large Array Sky Survey.

Keywords: Radio source catalogs, High energy astrophysics, Surveys, Active galaxies, Radio continuum emission, Gamma-ray astronomy, Spectral index, Radio astronomy
A Detailed Kinematic Study of 3C 84 and Its Connection to γ-Rays. 3C 84 (NGC 1275) is the bright radio core of the Perseus cluster. Even in the absence of strong relativistic effects, the source has been detected at γ-rays up to TeV energies. Despite its intensive study, the physical processes responsible for the high-energy emission in the source remain unanswered. We present a detailed kinematics study of the source and its connection to γ-ray emission. The subparsec-scale radio structure is dominated by slow-moving features in both the eastern and western lanes of the jet. The jet appears to have accelerated to its maximum speed within less than 125,000 gravitational radii. The fastest reliably detected speed in the jet was ~0.9c. This leads to a minimum viewing angle to the source of ≳42° and a maximum Doppler factor of ≲1.5. Our analysis suggests the presence of multiple high-energy sites in the source. If γ-rays are associated with kinematic changes in the jet, they are being produced in both eastern and western lanes in the jet. Three γ-ray flares are contemporaneous with epochs where the slowly moving emission region splits into two subregions. We estimate the significance of these events being associated to be ~2σ-3σ. We tested our results against theoretical predictions for magnetic-reconnection-induced mini-jets and turbulence and find them compatible.

Keywords: High energy astrophysics, Gamma-ray astronomy, Very long baseline interferometry, Wavelet analysis
Cosmic Reionization May Still Have Started Early and Ended Late: Confronting Early Onset with Cosmic Microwave Background Anisotropy and 21 cm Global Signals. The global history of reionization was shaped by the relative amounts of starlight released by three halo mass groups: the first two groups are atomic-cooling halos (ACHs) with virial temperatures Tvir &gt; 104 K, either (1) massive enough to form stars even after reionization (high-mass ACHs, ≳ 109 M⊙) or (2) less massive (low-mass ACHs), subject to star formation suppression when overtaken by reionization, and the third group comprises (3) H2-cooling mini-halos (MHs) with Tvir &lt; 104 K, whose star formation is predominantly suppressed by the H2-dissociating Lyman-Werner background. Our previous work showed that including MHs caused two-stage reionization-early rise to x ≲ 0.1, driven by MHs, followed by a rapid rise, late, to x ~ 1, driven by ACHs-with a signature in cosmic microwave background (CMB) polarization anisotropy predicted to be detectable by the Planck satellite. Motivated by this prediction, we model global reionization semi-analytically for comparison with Planck CMB data and the Experiment to Detect the Global Epoch of Reionization (EDGES) global 21 cm absorption feature, for models with: (1) ACHs, no feedback; (2) ACHs, self-regulated; and (3) ACHs and MHs, self-regulated. Model (3) agrees well with Planck E-mode polarization data, even with a substantial tail of high-redshift ionization, beyond the limit proposed by the Planck Collaboration. No model reproduces the EDGES feature. For model (3), $\left|\delta {T}_{b}\right|\lesssim 60\,\mathrm{mK}$ across the EDGES trough, an order of magnitude too shallow, and absorption starts at higher z but is spectrally featureless. Early onset reionization by Population III stars in MHs is compatible with current constraints, but only if the EDGES interpretation is discounted, or else other processes we did not include account for it.

Keywords: Reionization, Cosmic microwave background radiation, Population III stars, H I line emission
Deprojecting Sérsic Profiles for Arbitrary Triaxial Shapes: Robust Measures of Intrinsic and Projected Galaxy Sizes. We present the analytical framework for converting projected light distributions with a Sérsic profile into three-dimensional light distributions for stellar systems of arbitrary triaxial shape. The main practical result is the definition of a simple yet robust measure of intrinsic galaxy size: the median radius rmed, defined as the radius of a sphere that contains 50% of the total luminosity or mass, that is, the median distance of a star to the galaxy center. We examine how rmed depends on projected size measurements as a function of Sérsic index and intrinsic axis ratios, and demonstrate its relative independence of these parameters. As an application we show that the projected semimajor axis length of the ellipse enclosing 50% of the light is an unbiased proxy for rmed, with small galaxy-to-galaxy scatter of ~10% (1σ), under the condition that the variation in triaxiality within the population is small. For galaxy populations with an unknown or a large range in triaxiality an unbiased proxy for rmed is 1.3 × Re, where Re is the circularized half-light radius, with galaxy-to-galaxy scatter of 20%-30% (1σ). We also describe how inclinations can be estimated for individual galaxies based on the measured projected shape and prior knowledge of the intrinsic shape distribution of the corresponding galaxy population. We make the numerical implementation of our calculations available.

Keywords: Galaxy mass distribution, Galaxy structure, Galaxies, Scaling relations