Sazuna/UAT_keywords huggingface dataset:
Missing Giants: Predictions on Dust-obscured Galaxy Stellar Mass Assembly Throughout Cosmic Time. Due to their extremely dust-obscured nature, much uncertainty still exists surrounding the stellar mass growth and content in dusty, star-forming galaxies (DSFGs) at z &gt; 1. In this work, we present a numerical model built using empirical data on DSFGs to estimate their stellar mass contributions across the first ~10 Gyr of cosmic time. We generate a dust-obscured stellar mass function that extends beyond the mass limit of star-forming stellar mass functions in the literature, and predict that massive DSFGs constitute as much as 50%-100% of all star-forming galaxies with M ≥1011 M ⊙ at z &gt; 1. We predict the number density of massive DSFGs and find general agreement with observations, although more data is needed to narrow wide observational uncertainties. We forward-model mock massive DSFGs to their quiescent descendants and find remarkable agreement with observations from the literature demonstrating that, to first order, massive DSFGs are a sufficient ancestral population to describe the prevalence of massive quiescent galaxies at z &gt; 1. We predict that massive DSFGs and their descendants contribute as much as 25%-60% to the cosmic stellar mass density during the peak of cosmic star formation, and predict an intense epoch of population growth during the ~1 Gyr from z = 6 to 3 during which the majority of the most massive galaxies at high-z grow and then quench. Future studies seeking to understand massive galaxy growth and evolution in the early universe should strategize synergies with data from the latest observatories (e.g., JWST and the Atacama Large Millimeter/submillimeter Array) to better include the heavily dust-obscured galaxy population.

Keywords: High-redshift galaxies, Galaxy evolution, Luminous infrared galaxies
Searching for Radio Outflows from M31* with VLBI Observations. As one of the nearest and most dormant supermassive black holes (SMBHs), M31* provides a rare but promising opportunity for studying the physics of black hole accretion and feedback at the quiescent state. Previous Karl G. Jansky Very Large Array (VLA) observations with an arcsecond resolution have detected M31* as a compact radio source over centimeter wavelengths, but the steep radio spectrum suggests optically thin synchrotron radiation from an outflow driven by a hot accretion flow onto the SMBH. Aiming to probe the putative radio outflow, we conducted milliarcsecond-resolution very long baseline interferometric (VLBI) observations of M31* in 2016, primarily at 5 GHz and combining the Very Long Baseline Array, Tianma 65 m, and Shanghai 25 m radio telescopes. Despite the unprecedented simultaneous resolution and sensitivity achieved, no significant (≳3σ) signal is detected at the putative position of M31* given an rms level of 5.9 μJy beam-1, thus ruling out a pointlike source with a peak flux density comparable to that (~30 μJy beam-1) measured by the VLA observations taken in 2012. We disfavor the possibility that M31* has substantially faded since 2012, in view that a 2017 VLA observation successfully detected M31* at a historically high peak flux density (~75 μJy beam-1 at 6 GHz). Instead, the nondetection of the VLBI observations is best interpreted as the arcsecond-scale core being resolved out at the milliarcsecond scale, suggesting an intrinsic size of M31* at 5 GHz larger than ~300 times the Schwarzschild radius. Such extended radio emission may originate from a hot wind driven by the weakly accreting SMBH.

Keywords: Radio continuum emission, Low-luminosity active galactic nuclei, Andromeda Galaxy, Local Group
The Progenitors of Superluminous Type Ia Supernovae. Recent observations of type Ia supernovae (SNe Ia) have discovered a subclass of "super-Chandrasekhar" SNe Ia (SC SNe Ia) whose high luminosities and low ejecta velocities suggest that they originate from the explosions of white dwarfs (WDs) with masses that exceed the Chandrasekhar mass limit. Different models have been proposed to explain the progenitors of these explosions, including a "magnetized WD" model and a "WD merger" model. To test the robustness of these models, we conduct a 1D numerical parameter survey of WD explosions using these models as initial conditions. We follow the explosions using the hydrodynamics code Castro and then use the radiation transport code SuperNu to create light curves and spectra for the models. We find that while both classes of models fall within the range of SC SNe Ia observations on the light-curve width-luminosity relation, only the WD merger models reproduce the observed low ejecta velocities. The light curves of our merger models are more similar photometrically to observations than our magnetized models. Given this, we discuss possible explanations for the brightest SC SNe Ia observations that cannot be reproduced with our WD merger models. This study provides the basis for future SC SNe Ia observations and higher-dimensional numerical models.

Keywords: Hydrodynamical simulations, Hydrodynamics, White dwarf stars, Type Ia supernovae, Radiative transfer simulations, Supernovae, Astronomical simulations
Period-Luminosity Relations for Galactic Classical Cepheids in the Sloan Bands. We present the first period-luminosity (PL) and period-Wesenheit (PW) relations in the Sloan-Pan-STARRS g  P1 r  P1 i  P1 bands for classical fundamental-mode Cepheids in the Milky Way. We used a relatively modest number of 76 stars for the PL and 84-85 stars for the PW relations calibration. The data for the project were collected with the network of 40 cm telescopes of the Las Cumbres Observatory, and Gaia Data Release 3 parallaxes were used for the calculations. These gri-band PL and PW relations calibrations will be a useful tool for distance determinations in the era of large sky surveys using the Sloan photometric system, especially with the near-future start of the Large Synoptic Survey of Space and Time. * Based on data from the Las Cumbres Observatory.

Keywords: Pulsating variable stars, Distance indicators, Cepheid variable stars, Sloan photometry, Milky Way Galaxy
How Magnetic Reconnection May Affect the Coherence of Interplanetary Coronal Mass Ejections. On 2020 April 19-20, a solar ejection was seen by spacecraft in a radial alignment that included Solar Orbiter and Wind. The ejection contained a magnetic flux rope where magnetic field and plasma parameters were well correlated between spacecraft. This structure is called an "unperturbed magnetic flux rope" (UMFR). Ahead of the UMFR is a portion of the ejection (not sheath) that is referred to as "upstream" (US). We focus on the US and inquire why the correlation is so much weaker there. Specifically, we analyze data collected by Solar Orbiter at 0.81 au and Wind at L1. We show that a plausible cause for the lack of coherence in the US is a combination of front erosion and internal reconnection occurring there. Front erosion is inferred from an analysis of azimuthal magnetic flux balance in the UMFR. In the present case, we contend that the US, rather than the UMFR, is the source of the eroded field lines. The presence of erosion is supported further by a direct comparison of the magnetic field data at both spacecraft that shows, in particular, a massive shrinkage of the front portion of the US. Internal reconnection is also happening at thin current sheets inside the US. Strong nonradial flows are reconfiguring the structure. As a result of these reconnection processes, a whole section of the US is disrupted and field lines move down the flanks of the ejection and out of view of Wind.

Keywords: Solar wind, Interplanetary magnetic fields, Solar coronal mass ejections
The Advanced Spectral Library: The Evolution of Chromospheric Wind Characteristics from Noncoronal to Hybrid Giant Stars. The Hubble Space Telescope (HST)/Space Telescope Imaging Spectrograph treasury program Advanced Spectral Library enables investigations of the characteristics and dynamics of the wind and chromosphere of cool stars using high-quality spectral data. This paper shows how the wind features change with spectral class when transferring across the Linsky-Haisch dividing line by comparing the noncoronal M3.5 giant γ Cru with the K5 hybrid γ Dra. We compare the presence of high-ionization diagnostics in the two objects in addition to the prominent wind spectrum in predominantly singly ionized species. We study the intrinsic strength and variation of the numerous Fe II profiles observed in the near-ultraviolet HST spectrum that are sensitive to the wind opacity, turbulence, and flow velocity. The Fe II relative strengths and wavelength shifts between the absorption and emission components reflect the acceleration of the wind from the base of the chromosphere. Furthermore, we have modeled the wind spectra using the SEI code to derive terminal velocities, wind acceleration, and mass-loss rates. Our results indicate that the chromosphere is denser when moving toward the hybrid objects. The derived average mass-loss rates in the two objects are similar but with a significantly greater terminal wind velocity and acceleration in the hybrid star. We present the analysis of the outflowing wind characteristics when transitioning from the cool noncoronal objects toward the warmer objects with chromospheric emission from a hotter environment. * This material is based upon work supported by NASA under award No. 80GSFC21M0002.

Keywords: Late-type supergiant stars, Stellar atmospheres, Stellar mass loss
Cerium Features in Kilonova Near-infrared Spectra: Implication from a Chemically Peculiar Star. Observations of the kilonova from the neutron star merger event GW170817 opened a way to study r-process nucleosynthesis directly using neutron star mergers. It is, however, challenging to identify individual elements in kilonova spectra due to a lack of complete atomic data, in particular at near-infrared (NIR) wavelengths. In this paper, we demonstrate that spectra of chemically peculiar stars with enhanced heavy-element abundances can provide us with an excellent astrophysical laboratory for kilonova spectra. We show that the photosphere of the late B-type, chemically peculiar star HR 465 has similar lanthanide abundances and ionization degrees with those in the line-forming region in a kilonova at ~2.5 days after the merger. The NIR spectrum of HR 465 taken with Subaru/IRD indicates that Ce III lines give the strongest absorption feature around 16000 Å and there are no other comparably strong transitions around these lines. The Ce III lines nicely match with the broad absorption feature at 14500 Å observed in GW170817 with a blueshift of v = 0.1 c, which supports recent identification of this feature as Ce III by Domoto et al.

Keywords: Neutron stars, R-process, Stellar spectral lines, Transient sources
X-Ray Properties of Optically Variable Low-mass AGN Candidates. We present an X-ray analysis of 14 nearby (z &lt; 0.044) active galactic nuclei (AGNs) in low-mass galaxies (M * ≲ 5 × 109 M ☉) selected based on their optical variability. Comparing and contrasting different AGN selection techniques in low-mass galaxies is essential for obtaining an accurate estimate of the active fraction in this regime. We use both new and archival observations from the Chandra X-ray Observatory to search for X-ray point sources consistent with AGNs. Four objects have detected nuclear X-ray emission with luminosities ranging from L 0.5-7 ≈ 3 × 1040 to 9 × 1042 erg s-1 with two more marginal detections. All of the detected galaxies have luminosities exceeding those anticipated from X-ray binaries, and all sources are nuclear, suggesting the X-ray emission in most sources is due to an AGN. These observations demonstrate the success of variability at identifying AGNs in low-mass galaxies. We also explore emission-line diagnostics and discuss the differences in the results of these methods for AGN selection, in particular regarding low-mass and low-metallicity systems.

Keywords: Dwarf galaxies, Active galactic nuclei, Time domain astronomy, X-ray active galactic nuclei
Runaway and Hypervelocity Stars from Compact Object Encounters in Globular Clusters. The dense environments in the cores of globular clusters (GCs) facilitate many strong dynamical encounters among stellar objects. These encounters have been shown to be capable of ejecting stars from the host GC, whereupon they become runaway stars, or hypervelocity stars (HVSs) if unbound to the galactic potential. We study high-speed stellar ejecta originating from GCs by using Monte Carlo N-body models, in particular focusing on binary–single encounters involving compact objects. We pair our model-discriminated populations with observational catalogs of Milky Way GCs (MWGCs) to compose a present-day Galactic population of stellar ejecta. We find that these kinds of encounters can accelerate stars to velocities in excess of 2000 km s‑1, to speeds beyond the previously predicted limits for ejecta from star-only encounters and in the same regime of Galactic center ejections. However, the same ejections can only account for 1.5%–20% of the total population of stellar runaways, and only 0.0001%–1% of HVS, with similar relative rates found for runaway white dwarfs. We also provide credible regions for ejecta from 149 MWGCs, which we hope will be useful as supplementary evidence when pairing runaway stars with origin GCs.

Keywords: Globular star clusters, Hypervelocity stars, Runaway stars, Stellar dynamics
The First Instrumentally Documented Fall of an Iron Meteorite: Orbit and Possible Origin. A bright fireball observed on 2020 November 7, over Scandinavia, produced the first iron meteorite with a well-determined pre-atmospheric trajectory. We calculated the orbit of this meteoroid and found that it demonstrates no close affinity with the orbit of any known asteroid. We found that the meteoroid (or its parent body) most probably entered the near-Earth orbit from the main asteroid belt via either ν 6 secular resonance with Saturn (89%) or 3:1 mean-motion resonance with Jupiter (11%). The long YORP timescale of the meteoroid suggests that it could have been produced in the main asteroid belt and survived the journey to the near-Earth orbit.

Keywords: Fireballs, Asteroids, Meteoroids, Iron meteorites, Celestial mechanics, Meteors, Meteorites, Astronomical simulations
Inverse MultiView. II. Microarcsecond Trigonometric Parallaxes for Southern Hemisphere 6.7 GHz Methanol Masers G232.62+00.99 and G323.74-00.26. We present the first results from the Southern Hemisphere Parallax Interferometric Radio Astrometry Legacy Survey: 10 μas accurate parallaxes and proper motions for two Southern Hemisphere 6.7 GHz methanol masers obtained using the inverse MultiView calibration method. Using an array of radio telescopes in Australia and New Zealand, we measured trigonometric parallaxes and proper motions for the masers associated with the star formation region G232.62+00.99 of π = 0.610 ± 0.011 mas, μ  x  = -2.266 ± 0.021 mas yr-1, and μ  y  = 2.249 ± 0.049 mas yr-1, which implies its distance to be d = 1.637 ± 0.029 kpc. These measurements represent an improvement in accuracy by more than a factor of 3 over the previous measurements obtained through Very Long Baseline Array observations of the 12 GHz methanol masers associated with this region. We also measure the trigonometric parallax and proper motion for G323.74-00.26 as π = 0.364 ± 0.009 mas, μ  x  = -3.239 ± 0.025 mas yr-1, and μ  y  = - 3.976 ± 0.039 mas yr-1, which implies a distance of d = 2.747 ± 0.068 kpc. These are the most accurate measurements of trigonometric parallax obtained for 6.7 GHz class II methanol masers to date. We confirm that G232.62+00.99 is in the Local Arm and find that G323.74-00.26 is in the Scutum-Centaurus arm. We also investigate the structure and internal dynamics of both masers.

Keywords: Very long baseline interferometry, Radio astrometry, Astrophysical masers
The Inner 2 pc of Sagittarius A*: Simulations of the Circumnuclear Disk and Multiphase Gas Accretion in the Galactic Center. The inner few parsecs of the Milky Way's Galactic center contain the central accreting supermassive black hole, over a million stars, and multiple large gaseous structures. In the past, the structures at these length scales have generally been modeled independently of each other. It is consequently not well understood how these complex features interact with each other, nor how gas flows between the outer few parsecs and the inner subarcsecond region (1″ ≈ 0.04 pc). In this work, we present hydrodynamic simulations of the inner few parsecs of the Galactic center that, for the first time, combine a realistic treatment of stellar winds and the circumnuclear disk (CND) as they interact with the gravitational potential of the nuclear star cluster and Sagittarius A*. We observe interactions of the stellar winds with the inner edge of the CND, which leads to the growth of instabilities, induced accretion of cool gas from the inner edge of the disk, and the eventual formation of a small accretion disk of ~104-105 K within r ~ 0.1 pc. The formation of an inner disk qualitatively agrees with observations. This disk grows in radial extent and mass with time on ≳10 kyr timescales, with a growth rate of $M\propto {t}_{\mathrm{kyr}}^{3.5}$ . We discuss additional physical mechanisms not yet included in this work that can improve our model.

Keywords: Galaxy circumnuclear disk, Stellar winds, Galactic center
Properties of the Turbulence and Topology in a Turbulent Magnetic Reconnection. Magnetic reconnection is a crucial process responsible for energy conversion and particle acceleration in space, astrophysical, and laboratory plasmas. Turbulence and magnetic reconnection can be mutually driven, but the underlying nature of energy dissipation, intrinsic turbulence waves, and magnetic field topologies in turbulent magnetic reconnection is still poorly understood. Here, using advanced multi-spacecraft mission and innovative methods, we provide a few new perspectives to investigate the properties of the turbulence and topology in a turbulent magnetic reconnection in the magnetotail. Our results reveal that in turbulent magnetic reconnection: (1) cyclotron resonance, an important mechanism of energy dissipation, is more effective in the core region of the reconnection than in the outflow regions; (2) energy is deposited in the form of kinetic Alfvén waves (KAWs) and fast/slow waves, with KAWs corresponding to low-frequency (ion cyclotron scale) and fast/slow waves corresponding to high-frequency (low-hybrid scale); and (3) the number of spiral nulls (O-lines) were about 3.6 times more than radial ones (X-lines), and three-dimensional structures were about 8 times more prevalent than two-dimensional ones. These findings should help us better unravel the dynamics of turbulent magnetic reconnection.

Keywords: Interplanetary turbulence, Space plasmas, Spectral index
Real-time Likelihood Methods for Improved γ-Ray Transient Detection and Localization. We present a maximum-likelihood (ML) algorithm that is fast enough to detect γ-ray transients in real time on low-performance processors often used for space applications. We validate the routine with simulations and find that, relative to algorithms based on excess counts, the ML method is nearly twice as sensitive, allowing detection of 240%-280% more short γ-ray bursts. We characterize a reference implementation of the code, estimating its computational complexity and benchmarking it on a range of processors. We exercise the reference implementation on archival data from the Fermi Gamma-ray Burst Monitor (GBM), verifying the sensitivity improvements. In particular, we show that the ML algorithm would have detected GRB 170817A even if it had been nearly 4 times fainter. We present an ad hoc but effective scheme for discriminating transients associated with background variations. We show that the onboard localizations generated by ML are accurate, but that refined off-line localizations require a detector response matrix with about 10 times finer resolution than is the current practice. Increasing the resolution of the GBM response matrix could substantially reduce the few-degree systematic uncertainty observed in the localizations of bright bursts.

Keywords: Gamma-ray bursts, Likelihood ratio test, Gamma-ray detectors, Gamma-ray telescopes, Gamma-ray astronomy, Maximum likelihood estimation, Algorithms
Peculiar Spectral Evolution of the Type I Supernova 2019eix: A Possible Double Detonation from a Helium Shell on a Sub-Chandrasekhar-mass White Dwarf. We present photometric and spectroscopic data for the nearby Type I supernova (SN Ia) 2019eix (originally classified as an SN Ic), from the day of its discovery up to 100 days after maximum brightness. Before maximum light, SN 2019eix resembles a typical SN Ic, albeit lacking the usual O I feature. Its light curve is similar to the typical SN Ic with decline rates (ΔM 15,V  = 0.84) and absolute magnitude M  V  = -18.35. However, after maximum light, this SN has unusual spectroscopic features, a large degree of line blending, significant line blanketing in the blue (λ &lt; 5000 Å), and strong Ca II absorption features during and after peak brightness. These unusual spectral features are similar to models of subluminous thermonuclear explosions, specifically double-detonation models of SNe Ia. Photometrically, SN 2019eix appears to be somewhat brighter with slower decline rates than other double-detonation candidates. We modeled the spectra using the radiative-transfer code TARDIS using SN 1994I (an SN Ic) as a base model to see whether we could reproduce the unusual features of SN 2019eix and found them to be consistent with the exception of the O I feature. We also compared SN 2019eix with double-detonation models and found them to best match the observations of SN 2019eix, but failed to reproduce its full photometric and spectroscopic evolution.

Keywords: Supernovae
Active Galactic Nuclei Feedback in SDSS-IV MaNGA: AGNs Have Suppressed Central Star Formation Rates. Despite the importance of feedback from active galactic nuclei (AGNs) in models of galaxy evolution, observational constraints on the influence of AGN feedback on star formation remain weak. To this end, we have compared the star formation trends of 279 low-redshift AGN galaxies with 558 inactive control galaxies using integral field unit spectroscopy from the Sloan Digital Sky Survey-IV Mapping Nearby Galaxies at Apache Point Observatory survey. With a Gaussian-process-based methodology, we reconstruct nonparametric star formation histories in spatially resolved spaxels covering the face of each galaxy. Based on the galaxy-wide star formation rates (SFRs) alone, we find no obvious signatures of AGN feedback. However, the AGN galaxies have significantly suppressed central (kiloparsec-scale) SFRs, lying up to a factor of 2 below those of the control galaxies, providing direct observational evidence of AGN feedback suppressing star formation. The suppression of central SFRs in the AGN galaxies began in the central regions ~6 Gyr ago (redshift z ~ 0.7), taking place over a few gigayears. A small subset of the AGN galaxies were rapidly driven to quiescence shortly before being observed (in the last 500 Myr), potentially indicating instances of AGN-driven feedback. More frequently, however, star formation continues in the AGN galaxies, with suppression primarily in the central regions. This is suggestive of a picture in which integrated (gigayear-timescale) AGN feedback can significantly affect central star formation, but may be inefficient in driving galaxy-wide quenching in low-redshift galaxies, instead leaving them in the green valley.

Keywords: AGN host galaxies, Galaxy quenching, Active galactic nuclei, Galaxy evolution