Sazuna/UAT_keywords huggingface dataset:
Massive Black Holes Regulated by Luminous Blue Variable Mass Loss and Magnetic Fields. We investigate the effects of mass loss during the main-sequence (MS) and post-MS phases of massive star evolution on black hole (BH) birth masses. We compute solar metallicity Geneva stellar evolution models of an 85 ${M}_{\odot }$ star with mass-loss rate ( $\dot{M}$ ) prescriptions for MS and post-MS phases and analyze under which conditions such models could lead to very massive BHs. Based on the observational constraints for $\dot{M}$ of luminous stars, we discuss two possible scenarios that could produce massive BHs at high metallicity. First, if a massive BH progenitor evolves from the observed population of massive MS stars known as WNh stars, we show that its average post-MS mass-loss rate has to be less than $1\times {10}^{-5}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ . However, this is lower than the typical observed mass-loss rates of luminous blue variables (LBV). Second, a massive BH progenitor could evolve from a yet undetected population of 80-85 ${M}_{\odot }$ stars with strong surface magnetic fields, which could quench mass loss during the evolution. In this case, the average mass-loss rate during the post-MS LBV phase has to be less than 5 × 10-5 ${M}_{\odot }\,{\mathrm{yr}}^{-1}$ to produce 70 ${M}_{\odot }$ BHs. We suggest that LBVs that explode as SNe have large envelopes and small cores that could be prone to explosion, possibly evolving from binary interaction (either mergers or mass gainers that do not fully mix). Conversely, LBVs that directly collapse to BHs could have evolved from massive single stars or binary-star mergers that fully mix, possessing large cores that would favor BH formation.

Keywords: Evolved stars, Massive stars, Stellar evolutionary models, Luminous blue variable stars, Hypergiant stars
Hydrodynamic Simulations of Pre-supernova Outbursts in Red Supergiants: Asphericity and Mass Loss. The activity of a massive star approaching core-collapse can strongly affect the appearance of the star and its subsequent supernova. Late-phase convective nuclear burning generates waves that propagate toward the stellar surface, heating the envelope and potentially triggering mass loss. In this work, we improve on previous one-dimensional models by performing two-dimensional simulations of the pre-supernova mass ejection phase due to deposition of wave energy. Beginning with stellar evolutionary models of a 15 M☉ red supergiant star during core O-burning, we treat the rate and duration of energy deposition as model parameters and examine the mass-loss dependence and the pre-explosion morphology accordingly. Unlike one-dimensional models, density inversions due to wave heating are smoothed by Rayleigh-Taylor instabilities, and the primary effect of wave heating is to radially expand the star's hydrogen envelope. For low heating rates with long durations, the expansion is nearly homologous, whereas high but short-lived heating can generate a shock that drives envelope expansion and results in a qualitatively different density profile at the time of core-collapse. Asymmetries are fairly small, and large amounts of mass loss are unlikely unless the wave heating exceeds expectations. We discuss implications for pre-supernova stellar variability and supernovae light curves.

Keywords: Hydrodynamical simulations, Stellar atmospheres, Stellar evolution
Magnetic Reconnection and Hot Spot Formation in Black Hole Accretion Disks. Hot spots, or plasmoids, which form due to magnetic reconnection in current sheets, are conjectured to power frequent X-ray and near-infrared flares from Sgr A*, the black hole in the center of our Galaxy. It is unclear how, where, and when current sheets form in black hole accretion disks. We perform axisymmetric general-relativistic resistive magnetohydrodynamics simulations to model reconnection and plasmoid formation in a range of accretion flows. Current sheets and plasmoids are ubiquitous features that form regardless of the initial magnetic field in the disk, the magnetization in the quasisteady-state phase of accretion, and the spin of the black hole. Within 10 Schwarzschild radii from the event horizon, we observe plasmoids forming, after which they can merge, grow to macroscopic scales of the order of a few Schwarzschild radii, and are ultimately advected along the jet's sheath or into the disk. Large plasmoids are energized to relativistic temperatures via reconnection and contribute to the jet's limb brightening. We find that only hot spots forming in magnetically arrested disks can potentially explain the energetics of Sgr A* flares. The flare period is determined by the reconnection rate, which we find to be between $0.01c$ and $0.03c$ in all cases, consistent with studies of reconnection in isolated Harris-type current sheets. We quantify magnetic dissipation and nonideal electric fields, which can efficiently inject nonthermal particles. We show that explicit resistivity allows for converged numerical solutions, such that the electromagnetic energy evolution and dissipation become independent of the grid scale for the extreme resolutions considered here.

Keywords: Accretion, Black hole physics, Magnetohydrodynamics, Plasma astrophysics, General relativity
On the Velocity Drift between Ions in the Solar Atmosphere. The solar atmosphere is composed of many species, which are populated at different ionization and excitation levels. The upper chromosphere, transition region, and corona are nearly collisionless. Consequently, slippage between, for instance, ions and neutral particles, or interactions between separate species, may play important roles. We have developed a 3D MFMS numerical code (Ebysus) to investigate such effects. Ebysus is capable of treating species (e.g., hydrogen, helium, etc.) and fluids (neutrals, excited and ionized elements) separately, including nonequilibrium ionization, momentum exchange, radiation, thermal conduction, and other complex processes in the solar atmosphere. Treating different species as different fluids leads to drifts between different ions and an electric field that couples these motions. The coupling for two ionized fluids can lead to an anti-phase rotational motion between them. Different ionized species and momentum exchange can dissipate this velocity drift, i.e., convert wave kinetic energy into thermal energy. High-frequency Alfvén waves driven by, e.g., reconnection thought to occur in the solar atmosphere, can drive such multi-ion velocity drifts.

Keywords: Magnetohydrodynamics, Solar chromospheric heating, Solar coronal heating, Alfven waves, Solar corona, Solar chromosphere, Magnetohydrodynamical simulations
Multimessenger Gravitational-wave Searches with Pulsar Timing Arrays: Application to 3C 66B Using the NANOGrav 11-year Data Set. When galaxies merge, the supermassive black holes in their centers may form binaries and emit low-frequency gravitational radiation in the process. In this paper, we consider the galaxy 3C 66B, which was used as the target of the first multimessenger search for gravitational waves. Due to the observed periodicities present in the photometric and astrometric data of the source, it has been theorized to contain a supermassive black hole binary. Its apparent 1.05-year orbital period would place the gravitational-wave emission directly in the pulsar timing band. Since the first pulsar timing array study of 3C 66B, revised models of the source have been published, and timing array sensitivities and techniques have improved dramatically. With these advances, we further constrain the chirp mass of the potential supermassive black hole binary in 3C 66B to less than (1.65 ± 0.02) × 109 M⊙ using data from the NANOGrav 11-year data set. This upper limit provides a factor of 1.6 improvement over previous limits and a factor of 4.3 over the first search done. Nevertheless, the most recent orbital model for the source is still consistent with our limit from pulsar timing array data. In addition, we are able to quantify the improvement made by the inclusion of source properties gleaned from electromagnetic data over "blind" pulsar timing array searches. With these methods, it is apparent that it is not necessary to obtain exact a priori knowledge of the period of a binary to gain meaningful astrophysical inferences.

Keywords: Active galactic nuclei, Astronomy data analysis, Gravitational waves, Pulsars
A Diffuse Metal-poor Component of the Sagittarius Stream Revealed by the H3 Survey. The tidal disruption of the Sagittarius dwarf galaxy has generated a spectacular stream of stars wrapping around the entire Galaxy. We use data from Gaia and the H3 Stellar Spectroscopic Survey to identify $823$ high-quality Sagittarius members based on their angular momenta. The H3 Survey is largely unbiased in metallicity, and so our sample of Sagittarius members is similarly unbiased. Stream stars span a wide range in [Fe/H] from -0.2 to ≈-3.0, with a mean overall metallicity of $\langle [\mathrm{Fe}/{\rm{H}}]\rangle =-0.99$ . We identify a strong metallicity dependence to the kinematics of the stream members. At [Fe/H] &gt; -0.8 nearly all members belong to the well-known cold ( ${\sigma }_{v}\lt 20\,\mathrm{km}\,{{\rm{s}}}^{-1}$ ) leading and trailing arms. At intermediate metallicities (-1.9 &lt; [Fe/H] &lt; -0.8) a significant population (24%) emerges of stars that are kinematically offset from the cold arms. These stars also appear to have hotter kinematics. At the lowest metallicities ([Fe/H] ≲ -2), the majority of stars (69%) belong to this kinematically offset diffuse population. Comparison to simulations suggests that the diffuse component was stripped from the Sagittarius progenitor at earlier epochs, and therefore resided at larger radius on average than the colder metal-rich component. We speculate that this kinematically diffuse, low-metallicity population is the stellar halo of the Sagittarius progenitor system.

Keywords: Tidal disruption, Dwarf galaxies, Sagittarius dwarf spheroidal galaxy, Milky Way Galaxy
High-resolution Infrared Spectroscopy of Hot Molecular Gas in AFGL 2591 and AFGL 2136: Accretion in the Inner Regions of Disks around Massive Young Stellar Objects. We have performed a high-resolution 4-13 μm spectral survey of the hot molecular gas associated with the massive protostars AFGL 2591 and AFGL 2136, utilizing the Echelon Cross Echelle Spectrograph (EXES) on board the Stratospheric Observatory for Infrared Astronomy, and the iSHELL instrument and Texas EchelonCross Echelle Spectrograph (TEXES) on the NASA Infrared Telescope Facility (IRTF). Here we present the results of this survey with analysis of CO, HCN, C2H2, NH3, and CS, deriving the physical conditions for each species. Also from the IRTF, iSHELL data at 3 μm for AFGL 2591 are presented that show HCN and C2H2 in emission. In the EXES and TEXES data, all species are detected in absorption, and temperatures and abundances are found to be high (600 K and 10-6, respectively). Differences of up to an order of magnitude in the abundances of transitions that trace the same ground-state level are measured for HCN and C2H2. The mid-infrared continuum is known to originate in a disk, hence we attribute the infrared absorption to arise in the photosphere of the disk. As absorption lines require an outwardly decreasing temperature gradient, we conclude that the disk is heated in the midplane by viscous heating due to accretion. We attribute the near-IR emission lines to scattering by molecules in the upper layers of the disk photosphere. The absorption lines trace the disk properties at 50 au where high-temperature gas-phase chemistry is taking place. Abundances are consistent with chemical models of the inner disk of Herbig disks.

Keywords: Interstellar line absorption, Star forming regions, Chemical abundances, Astrochemistry, Infrared astronomy, Star formation, Astrophysical processes
Heating Rates for Protons and Electrons in Polar Coronal Holes: Empirical Constraints from the Ultraviolet Coronagraph Spectrometer. Ultraviolet spectroscopy of the extended solar corona is a powerful tool for measuring the properties of protons, electrons, and heavy ions in the accelerating solar wind. The large coronal holes that expand up from the north and south poles at solar minimum are low-density collisionless regions in which it is possible to detect departures from one-fluid thermal equilibrium. An accurate characterization of these departures is helpful in identifying the kinetic processes ultimately responsible for coronal heating. In this paper, Ultraviolet Coronagraph Spectrometer (UVCS) measurements of the H I Lyα line are analyzed to constrain values for the solar wind speed, electron density, electron temperature, proton temperature (parallel and perpendicular to the magnetic field), and Alfvén-wave amplitude. The analysis procedure involves creating a large, randomized ensemble of empirical models, simulating their Lyα profiles, and building posterior probability distributions for only the models that agree with the UVCS data. The resulting temperatures do not exhibit a great deal of radial variation between heliocentric distances of 1.4 and 4 solar radii. Typical values for the electron, parallel proton, and perpendicular proton temperatures are 1.2, 1.8, and 1.9 MK, respectively. Resulting values for the "nonthermal" Alfvén wave amplitude show evidence for weak dissipation, with a total energy-loss rate that agrees well with an independently derived total heating rate for the protons and electrons. The moderate Alfvén-wave amplitudes appear to resolve some tension in the literature between competing claims of both higher (undamped) and lower (heavily damped) values.

Keywords: Space plasmas, Solar ultraviolet emission, Solar wind, Alfven waves, Spectroscopy, Solar coronal holes
Vanadium Abundance Derivations in 255 Metal-poor Stars. We present vanadium (V) abundances for 255 metal-poor stars derived from high-resolution optical spectra from the Magellan Inamori Kyocera Echelle spectrograph on the Magellan Telescopes at Las Campanas Observatory, the Robert G. Tull Coudé Spectrograph on the Harlan J. Smith Telescope at McDonald Observatory, and the High Resolution Spectrograph on the Hobby-Eberly Telescope at McDonald Observatory. We use updated V I and V II atomic transition data from recent laboratory studies, and we increase the number of lines examined (from one to four lines of V I, and from two to seven lines of V II). As a result, we reduce the V abundance uncertainties for most stars by more than 20% and expand the number of stars with V detections from 204 to 255. In the metallicity range -4.0 &lt; [Fe/H] &lt; -1.0, we calculate the mean ratios [V I/Fe I] = -0.10 ± 0.01 (σ = 0.16) from 128 stars with ≥2 V I lines detected, [V II/Fe II] = +0.13 ± 0.01 (σ = 0.16) from 220 stars with ≥2 V II lines detected, and [V II/V I] = +0.25 ± 0.01 (σ = 0.15) from 119 stars. We suspect that this offset is due to departures from local thermodynamic equilibrium, and we recommend using [V II/Fe II], which is enhanced relative to the solar ratio, as a better representation of [V/Fe]. We provide more extensive evidence for abundance correlations detected previously among scandium, titanium, and vanadium, and we identify no systematic effects in the analysis that can explain these correlations. * This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile, and The McDonald Observatory of The University of Texas at Austin. The Hobby-Eberly Telescope is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen.

Keywords: Population II stars, Stellar abundances, Nucleosynthesis
Some Die Filthy Rich: The Diverse Molecular Gas Contents of Post-starburst Galaxies Probed by Dust Absorption. Quenched post-starburst galaxies (QPSBs) are a rare but important class of galaxies that show signs of rapid cessation or recent rejuvenation of star formation. A recent observation shows that about half of QPSBs have large amounts of cold gas. This molecular CO sample is, however, too small and is not without limitations. Our work aims to verify previous results by applying a new method to study a uniformly selected sample, more than 10 times larger. In particular, we present detailed analysis of Hα/Hβ ratios of face-on QPSBs at z = 0.02-0.15 and with ${M}_{\star }={10}^{10}-{10}^{11}\,{M}_{\odot }$ . We interpret the Hα/Hβ ratios by applying our recent gas mass calibration, which is based on non-PSB galaxies but predicts gas masses that are consistent with CO observations of ∼100 PSBs. We estimate the molecular gas by either using PSBs with well-measured Hα/Hβ ratios or measuring them from stacked spectra. Our analysis reveals that QPSBs have a wide range of Hα/Hβ ratios and molecular gas fractions that overlap with the typical gas fractions of star-forming or quiescent galaxies: Hα/Hβ ≍ 3-8 and ${f}_{{{\rm{H}}}_{2}}\approx 1 \% \mbox{--}20 \% $ with median ${f}_{{{\rm{H}}}_{2}}\approx 4 \% \mbox{--}6 \% $ , which correspond to ${M}_{{{\rm{H}}}_{2}}\approx (1\mbox{--}3)\times {10}^{9}\,{M}_{\odot }$ . Our results indicate that large reservoirs of cold gas are still present in significant numbers of QPSBs and that they arguably were not removed or destroyed by feedback from active galactic nuclei.

Keywords: Interstellar molecules, Starburst galaxies, AGN host galaxies, Interstellar dust extinction, Seyfert galaxies, Galaxy evolution, Interstellar medium
Constraints on Dynamical Dark Energy Models from the Abundance of Massive Galaxies at High Redshifts. We compare the maximal abundance of massive systems predicted in different dynamical dark energy (DDE) models at high redshifts z ≈ 4-7 with the measured abundance of the most massive galaxies observed to be already in place at such redshifts. The aim is to derive constraints for the evolution of the dark energy equation-of-state parameter w that are complementary to existing probes. We adopt the standard parameterization for the DDE evolution in terms of the local value w0 and of the lookback time derivative of the equation of state wa. We derive constraints on combinations of (w0, wa) in the different DDE models by using three independent probes: (i) the observed stellar mass function of massive objects at z ≥ 6 derived from the CANDELS survey; (ii) the estimated volume density of massive halos derived from the observation of massive, star-forming galaxies detected in the submillimeter range at z ≈ 4; (iii) the rareness of the most massive system (with an estimated gas mass exceeding 3 × 1011 M⊙) observed to be in place at z ≈ 7, a far-infrared-luminous object recently detected in the South Pole Telescope survey. Finally, we show that the combination of our results from the three above probes excludes a sizable fraction of the DDE parameter space wa ≳ -3/4 - (w0 + 3/2) presently allowed (or even favored) by existing probes.

Keywords: Dark energy, Galaxy evolution, Cosmological parameters
A Universal Fundamental Plane and the M<SUB>dyn</SUB>-M<SUB>⋆</SUB> Relation for Galaxies with CALIFA and MaNGA. We use the stellar kinematics for 2458 galaxies from the MaNGA survey to explore a universal fundamental plane (UFP) described by the equation $\mathrm{log}({{\rm{\Upsilon }}}_{e})=\mathrm{log}({S}_{0.5}^{2})-\mathrm{log}({I}_{e})-\mathrm{log}({R}_{e})+C$ , defined by the logarithms of effective radius, Re; the surface brightness within Re, Ie; the dynamical mass-to-light ratio within Re, Ye; and the total velocity parameter at Re, ${S}_{K}^{2}={{KV}}_{{R}_{e}}^{2}+{\sigma }_{{\star }_{e}}^{2}$ , where ${V}_{{R}_{e}}$ is the rotation velocity and ${\sigma }_{{\star }_{e}}$ is the velocity dispersion. The surface brightness is within Re, Ie, and the dynamical mass-to-light ratio is within Re, ϒe. We use sophisticated Schwarzschild dynamical models for a subsample of 300 galaxies from the CALIFA survey to calibrate the universal fundamental plane. This calibration allows us to propose both (i) a parameterization to estimate the difficult-to-measure averaged dynamical mass-to-light ratio within Re, ${{\rm{\Upsilon }}}_{e}^{\mathrm{fit}}$ , once the internal kinematics, surface brightness, and effective radius are known; and (ii) a new, more robust dynamical mass proxy consistent with dynamical models within 0.09 dex. We reproduce the relation between the dynamical mass and the stellar mass in the inner regions of galaxies with lower scatter. We use the estimated ${{\rm{\Upsilon }}}_{e}^{\mathrm{fit}}$ from our analysis to explore the UFP with the MaNGA data set. We find that all galaxies, from spheroids to disks, follow the UFP with a scatter significantly smaller (0.05 dex) than the one reported for the fundamental plane (∼0.09 dex) and comparable with Tully-Fisher studies (∼0.05 dex), but for a wider range of galaxy types. We also confirm that spheroidal and spiral galaxies follow the same M⋆-S0.5 scaling relation, with lower scatter than the ${M}_{\star }\mbox{--}{V}_{{R}_{e}}$ and ${M}_{\star }\mbox{--}{\sigma }_{{\star }_{e}}$ ones, which is in agreement with previous studies found in the literature.

Keywords: Galaxies, Late-type galaxies, Scaling relations, Galaxy kinematics, Early-type galaxies
Mass Estimation of Galaxy Clusters with Deep Learning. I. Sunyaev-Zel'dovich Effect. We present a new application of deep learning to infer the masses of galaxy clusters directly from images of the microwave sky. Effectively, this is a novel approach to determining the scaling relation between a cluster's Sunyaev-Zel'dovich (SZ) effect signal and mass. The deep-learning algorithm used is mResUNet, which is a modified feed-forward deep-learning algorithm that broadly combines residual learning, convolution layers with different dilation rates, image regression activation, and a U-Net framework. We train and test the deep-learning model using simulated images of the microwave sky that include signals from the cosmic microwave background, dusty and radio galaxies, and instrumental noise as well as the cluster's own SZ signal. The simulated cluster sample covers the mass range 1 × 1014 M⊙ &lt; M200c &lt; 8 × 1014 M⊙ at z = 0.7. The trained model estimates the cluster masses with a 1σ uncertainty ΔM/M ≤ 0.2, consistent with the input scatter on the SZ signal of 20%. We verify that the model works for realistic SZ profiles even when trained on azimuthally symmetric SZ profiles by using the Magneticum hydrodynamical simulations.

Keywords: Galaxy clusters, Sky surveys, Large-scale structure of the universe, Convolutional neural networks, Cosmic microwave background radiation, Sunyaev-Zeldovich effect