Sazuna/UAT_keywords huggingface dataset:
FLEET: A Redshift-agnostic Machine Learning Pipeline to Rapidly Identify Hydrogen-poor Superluminous Supernovae. Over the past decade wide-field optical time-domain surveys have increased the discovery rate of transients to the point that ≲10% are being spectroscopically classified. Despite this, these surveys have enabled the discovery of new and rare types of transients, most notably the class of hydrogen-poor superluminous supernovae (SLSN-I), with about 150 events confirmed to date. Here we present a machine-learning classification algorithm targeted at rapid identification of a pure sample of SLSN-I to enable spectroscopic and multiwavelength follow-up. This algorithm is part of the Finding Luminous and Exotic Extragalactic Transients (FLEET) observational strategy. It utilizes both light-curve and contextual information, but without the need for a redshift, to assign each newly discovered transient a probability of being a SLSN-I. This classifier can achieve a maximum purity of about 85% (with 20% completeness) when observing a selection of SLSN-I candidates. Additionally, we present two alternative classifiers that use either redshifts or complete light curves and can achieve an even higher purity and completeness. At the current discovery rate, the FLEET algorithm can provide about 20 SLSN-I candidates per year for spectroscopic follow-up with 85% purity; with the Legacy Survey of Space and Time we anticipate this will rise to more than $\sim {10}^{3}$ events per year.

Keywords: Surveys, Supernovae, Core-collapse supernovae
The SOFIA Massive (SOMA) Star Formation Survey. III. From Intermediate- to High-mass Protostars. We present $\sim 10\mbox{--}40\,\mu {\rm{m}}$ SOFIA-FORCAST images of 14 intermediate-mass protostar candidates as part of the SOFIA Massive (SOMA) Star Formation Survey. We build spectral energy distributions, also using archival Spitzer, Herschel, and IRAS data. We then fit the spectral energy distributions with radiative transfer models of Zhang &amp; Tan, based on turbulent core accretion theory, to estimate key protostellar properties. With the addition of these intermediate-mass sources, based on average properties derived from SED fitting, SOMA protostars span luminosities from $\sim {10}^{2}\,\mathrm{to}\,{10}^{6}\ {L}_{\odot }$, current protostellar masses from $\sim 0.5\,{\rm{t}}{\rm{o}}\,35\,{M}_{\odot }$, and ambient clump mass surface densities, ${{\rm{\Sigma }}}_{\mathrm{cl}}$ , from $0.1\,\mathrm{to}\,{\rm{g}}\,{\mathrm{cm}}^{-2}$. A wide range of evolutionary states of the individual protostars and of the protocluster environments is also probed. We have also considered about 50 protostars identified in infrared dark clouds that are expected to be at the earliest stages of their evolution. With this global sample, most of the evolutionary stages of high- and intermediate-mass protostars are probed. The best-fitting models show no evidence that a threshold value of the protocluster clump mass surface density is required to form protostars up to $\sim 25\ {M}_{\odot }$. However, to form more massive protostars, there is tentative evidence that ${{\rm{\Sigma }}}_{\mathrm{cl}}$ needs to be $\gtrsim 1\,{\rm{g}}\,{\mathrm{cm}}^{-2}$. We discuss how this is consistent with expectations from core accretion models that include internal feedback from the forming massive star.

Keywords: Jets, Massive stars, Star formation, Infrared sources, Interstellar medium
Morphological and Rotation Structures of Circumgalactic Mg II Gas in the EAGLE Simulation and the Dependence on Galaxy Properties. Low-ionization-state Mg II gas has been extensively studied in quasar sightline observations to understand the cool, ∼104 K gas in the circumgalactic medium. Motivated by recent observations showing that the Mg II gas around low-redshift galaxies has significant angular momentum, we use the high-resolution EAGLE cosmological simulation to analyze the morphological and rotation structures of the z ≈ 0.3 circumgalactic Mg II gas and examine how they change with the host galaxy properties. Around star-forming galaxies, we find that the Mg II gas has an axisymmetric instead of a spherical distribution, and the axis of symmetry aligns with that of the Mg II gas rotation. A similar rotating structure is less commonly found in the small sample of simulated quiescent galaxies. We also examine how often Mg II gas around galaxies selected using a line-of-sight velocity cut includes gas physically outside of the virial radius (rvir). For example, we show that at an impact parameter of 100 pkpc, a ±500 km s-1 velocity cut around galaxies with stellar masses of 109-109.5 M⊙ (1010-1010.5 M⊙) selects Mg II gas beyond the virial radius 80% (6%) of the time. Because observers typically select Mg II gas around target galaxies using such a velocity cut, we discuss how this issue affects the study of circumgalactic Mg II gas properties, including the detection of corotation. While the corotating Mg II gas generally extends beyond 0.5rvir, the Mg II gas outside of the virial radius contaminates the corotation signal and makes observers less likely to conclude that gas at large impact parameters (e.g., ≳0.25rvir) is corotating.

Keywords: Extragalactic astronomy, Hydrodynamical simulations, Circumgalactic medium
A Photoionized Accretion Disk around a Young High-mass Star. We present high spatial resolution (52 au) observations of the high-mass young stellar object (HMYSO) G345.4938+01.4677 made using the Atacama Large Millimeter/submillimeter Array. This O-type HMYSO is located at 2.38 kpc and is associated with a luminosity of 1.5 × 105 L⊙. We detect circumstellar emission from the H38β hydrogen recombination line showing a compact structure rotating perpendicularly to the previously detected radio jet. We interpret this emission as tracing a photoionized accretion disk around the HMYSO. While this disk-like structure seems currently too small to sustain continued accretion, the data present direct observational evidence of how disks can effectively survive the photoionization feedback from young high-mass stars. We also report the detection of a low-mass young stellar object in the vicinity of the HMYSO and suggest that it forms a high-mass and low-mass star binary system.

Keywords: Compact H II region, Massive stars, H I line emission, Star formation, Circumstellar disks
Constraining the Chemical Signatures and the Outburst Mechanism of the Class 0 Protostar HOPS 383. We present observations toward HOPS 383, the first known outbursting Class 0 protostar located within the Orion molecular cloud using the Atacama Large Millimeter/submillimeter Array (ALMA), Very Large Array (VLA), and Submillimeter Array (SMA). The SMA observations reveal envelope scale continuum and molecular line emission surrounding HOPS 383 at 0.85, 1.1, and 1.3 mm. The images show that HCO+ and H13CO+ peaks on or near the continuum, while N2H+ is reduced at the same position. This reflects the underlying chemistry where CO evaporating close to the protostar destroys N2H+ while forming HCO+. We also observe the molecular outflow traced by 12CO ( $J=2\to 1$ ) and ( $J=3\to 2$ ). A disk is resolved in the ALMA 0.87 mm dust continuum, orthogonal to the outflow direction, with an apparent radius of ∼62 au. Radiative transfer modeling of the continuum gives disk masses of 0.02 M☉ when fit to the ALMA visibilities. The models including VLA 8 mm data indicate that the disk mass could be up to a factor of 10 larger due to lower dust opacity at longer wavelengths. The disk temperature and surface density profiles from the modeling, and an assumed protostar mass of 0.5 M☉ suggest that the Toomre Q parameter &lt; 1 before the outburst, making gravitational instability a viable mechanism to explain outbursts at an early age if the disk is sufficiently massive.

Keywords: Interstellar molecules, Protostars, Circumstellar disks
A Significant Excess in Major Merger Rate for AGNs with the Highest Eddington Ratios at z &lt; 0.2. Observational studies are increasingly finding evidence against major mergers being the dominant mechanism responsible for triggering an active galactic nucleus (AGN). After studying the connection between major mergers and AGNs with the highest Eddington ratios at z = 2, we here expand our analysis to $z\lt 0.2$ , exploring the same AGN parameter space. Using ESO VLT/FORS2 $B-$ , $V-$ , and color images, we examine the morphologies of 17 galaxies hosting AGNs with Eddington ratios ${\lambda }_{\mathrm{edd}}\gt 0.3$ , and 25 mass- and redshift-matched control galaxies. To match the appearance of the two samples, we add synthetic point sources to the inactive comparison galaxies. The combined sample of AGN and inactive galaxies was independently ranked by 19 experts with respect to the degree of morphological distortion. We combine the resulting individual rankings into multiple overall rankings, from which we derive the respective major merger fractions of the two samples. With a best estimate of fm,agn = 0.41 ± 0.12 for the AGN host galaxies and fm,ina = 0.08 ± 0.06 for the inactive galaxies, our results imply that our AGN host galaxies have a significantly higher merger rate, regardless of the observed wavelength or applied methodology. We conclude that although major mergers are an essential mechanism to trigger local high Eddington ratio AGNs at $z\lt 0.2$ , the origin of $\gtrsim 50 \% $ of this specific AGN subpopulation still remains unclear.

Keywords: AGN host galaxies, Supermassive black holes, Quasars, Active galactic nuclei, Galaxy mergers, Galaxy evolution
Discriminating between Neutron Stars and Black Holes with Imperfect Knowledge of the Maximum Neutron Star Mass. Although gravitational-wave signals from exceptional low-mass compact binary coalescences, like GW170817, may carry matter signatures that differentiate the source from a binary black hole system, only one out of every eight events detected by the current Advanced LIGO and Virgo observatories are likely to have signal-to-noise ratios large enough to measure matter effects, even if they are present. Nonetheless, the systems' component masses will generally be constrained precisely. Constructing an explicit mixture model for the total rate density of merging compact objects, we develop a hierarchical Bayesian analysis to classify gravitational-wave sources according to the posterior odds that their component masses are drawn from different subpopulations. Accounting for current uncertainty in the maximum neutron star mass and adopting a power-law mass distribution with or without a mass gap and either random or mass-ratio-dependent pairing, we examine two recent events from the LIGO-Virgo Collaboration's third observing run, GW190425 and GW190814. For population models with no overlap between the neutron star and black hole mass distributions, we typically find that there is a $\gtrsim 70 \% $ chance, depending on the exact population model, that GW190425 was a binary neutron star merger rather than a neutron-star-black-hole merger. On the other hand, we find that there is a $\lesssim 6 \% $ chance that GW190814 involved a slowly spinning neutron star, regardless of our assumed population model.

Keywords: Neutron stars, Gravitational waves, Compact objects, Black holes
The Role of Parametric Instabilities in Turbulence Generation and Proton Heating: Hybrid Simulations of Parallel-propagating Alfvén Waves. Large-amplitude Alfvén waves tend to be unstable to parametric instabilities that result in a decay process of the initial wave into different daughter waves depending upon the amplitude of the fluctuations and the plasma beta. The propagation angle with respect to the mean magnetic field of the daughter waves plays an important role in determining the type of decay. In this paper, we revisit this problem by means of multidimensional hybrid simulations. In particular, we study the decay and the subsequent nonlinear evolution of large-amplitude Alfvén waves by investigating the saturation mechanism of the instability and its final nonlinear state reached for different wave amplitudes and plasma beta conditions. As opposed to one-dimensional simulations where the Decay instability is suppressed for increasing plasma beta values, we find that the decay process in multidimensions persists at large values of the plasma beta via the filamentation/magnetosonic decay instabilities. In general, the decay process acts as a trigger both to develop a perpendicular turbulent cascade and to enhance mean field-aligned wave-particle interactions. We find indeed that the saturated state is characterized by a turbulent plasma displaying a field-aligned beam at the Alfvén speed and increased temperatures that we ascribe to the Landau resonance and pitch-angle scattering in phase space.

Keywords: Space plasmas, Interplanetary turbulence, Solar wind, Interplanetary particle acceleration, Alfven waves
Characterizing the Evolved Stellar Population in the Galactic Foreground. I. Bolometric Magnitudes, Spatial Distribution and Period-Luminosity Relations. Radio campaigns using maser stellar beacons have provided crucial information to characterize Galactic stellar populations. Currently, the Bulge Asymmetries and Dynamical Evolution (BAaDE) project is surveying infrared (IR) color-selected targets for SiO masers. This provides a sample of evolved stars that can be used to study the inner, optically obscured Galaxy using line-of-sight velocities and possibly very long baseline interferometry proper motions. In order to use the BAaDE sample for kinematic studies, the stellar population should be characterized. In this study, the BAaDE targets have been cross-matched with IR (2MASS) and optical (Gaia) samples. By exploring the synergies of this cross-match together with Gaia parallaxes and extinction maps, the local (d &lt; 2 kpc) asymptotic giant branch (AGB) stars can be characterized. We have defined a BAaDE-Gaia sample of 20,111 sources resulting from cross-matching BAaDE targets with IR and optical surveys. From this sample, a local sample of 1812 evolved stars with accurate parallax measurements, confirmed evolved stellar evolution stage, and within 2 kpc distance around the Sun was selected, for which absolute (bolometric) magnitudes are estimated. The evolved stellar population with Gaia counterparts that are variable seems to be predominantly associated with AGB stars with moderate luminosity ( ${1500}_{-500}^{+3000}\ {L}_{\odot }$ ) and periods between 250 and 1250 days.

Keywords: Periodic variable stars, Surveys, Solar neighborhood, Galaxy stellar content, Asymptotic giant branch stars, Astrometry
Significant Suppression of Star Formation in Radio-quiet AGN Host Galaxies with Kiloparsec-scale Radio Structures. We conducted 22 GHz 1″ Jansky Very Large Array imaging of 100 radio-quiet X-ray-selected active galactic nuclei (AGN) from the Swift-Burst Array Telescope (Swift-BAT) survey. We find AGN-driven kiloparsec-scale radio structures inconsistent with pure star formation in 11 AGN. The host galaxies of these AGN lie significantly below the star-forming main sequence, indicating suppressed star formation. While these radio structures tend to be physically small compared to the host galaxy, the global star formation rate of the host is affected. We evaluate the energetics of the radio structures interpreted first as immature radio jets, and then as consequences of an AGN-driven radiative outflow, and compare them to two criteria for successful feedback: the ability to remove the CO-derived molecular gas mass from the galaxy gravitational potential and the kinetic energy transfer to molecular clouds leading to vcloud &gt; σ*. In most cases, the jet interpretation is insufficient to provide the energy necessary to cause the star formation suppression. Conversely, the wind interpretation provides ample energy in all but one case. We conclude that it is more likely that the observed suppression of star formation in the global host galaxy is due to interstellar medium interactions of a radiative outflow, rather than a small-scale radio jet.

Keywords: Galactic winds, Radio jets, Star formation, Active galactic nuclei, Galaxy winds
Detection of Opposite Magnetic Polarity in a Light Bridge: Its Emergence and Cancellation in Association with LB Fan-shaped Jets. Light bridges (LBs) are relatively bright structures that divide sunspot umbrae into two or more parts. Chromospheric LBs are known to be associated with various activities including fan-shaped jet-like ejections and brightenings. Although magnetic reconnection is frequently suggested to be responsible for such activities, not many studies present firm evidence to support the scenario. We carry out magnetic field measurements and imaging spectroscopy of an LB where fan-shaped jet-like ejections occur with co-spatial brightenings at their footpoints. We study LB fine structure and magnetic field changes using TiO images, Near-InfraRed Imaging Spectropolarimeter, and Hα data taken by the 1.6 m Goode Solar Telescope. We detect magnetic flux emergence in the LB that is of opposite polarity to that of the sunspot. The new magnetic flux cancels with the pre-existing flux at a rate of 5.6 × 1018 Mx hr-1. Both the recurrent jet-like ejections and their base brightenings are initiated at the vicinity of the magnetic flux cancellation, and show apparent horizontal extension along the LB at a projected speed of up to $18.4$ km s-1 to form a fan-shaped appearance. Based on these observations, we suggest that the fan-shaped ejections may have resulted from slipping reconnection between the new flux emerging in the LB and the ambient sunspot field.

Keywords: Solar activity, Solar magnetic fields, Solar chromosphere, Solar photosphere
The TeV Gamma-Ray Luminosity of the Milky Way and the Contribution of H.E.S.S. Unresolved Sources to Very High Energy Diffuse Emission. H.E.S.S. has recently completed the first systematic survey of the Galactic plane in the TeV energy domain. We analyze the flux, latitude, and longitude distributions of γ-ray sources observed by H.E.S.S. in order to infer the properties of the Galactic TeV source population. We show that the total Milky Way luminosity in the 1-100 TeV energy range is ${L}_{\mathrm{MW}}={1.7}_{-0.4}^{+0.5}\times {10}^{37}\,\mathrm{erg}\,{{\rm{s}}}^{-1}$ . Evaluating the cumulative flux expected at Earth by the considered population, we show that H.E.S.S. unresolved sources provide a relevant contribution to the diffuse Galactic emission. Finally, in the hypothesis that the majority of bright sources detected by H.E.S.S. are powered by pulsar activity, like, e.g., pulsar wind nebulae or TeV halos, we estimate the main properties of the pulsar population.

Keywords: Gamma-ray sources, High energy astrophysics, Pulsars
Observations of the Onset of Complex Organic Molecule Formation in Interstellar Ices. Isolated dense molecular cores are investigated to study the onset of complex organic molecule formation in interstellar ice. Sampling three cores with ongoing formation of low-mass stars (B59, B335, and L483) and one starless core (L694-2), we sample lines of sight to nine background stars and five young stellar objects (YSOs; AK ∼ 0.5-4.7). Spectra of these stars from 2 to 5 μm with NASA's Infrared Telescope Facility (IRTF) simultaneously display signatures from the cores of H2O (3.0 μm), CH3OH (C-H stretching mode, 3.53 μm), and CO (4.67 μm) ices. The CO ice is traced by nine stars, in which five show a long-wavelength wing due to a mixture of CO with polar ice (COr), presumably CH3OH. Two of these sightlines also show independent detections of CH3OH. For these we find the ratio of the CH3OH:COr is 0.55 ± 0.06 and 0.73 ± 0.07 from L483 and L694-2, respectively. The detections of both CO and CH3OH for the first time through lines of sight toward background stars observationally constrains the conversion of CO into CH3OH ice. Along the lines of sight, most of the CO exists in the gas phase and ≤15% of the CO is frozen out. However, CH3OH ice is abundant with respect to CO (∼50%) and exists mainly as a CH3OH-rich CO ice layer. Only a small fraction of the lines of sight contains CH3OH ice, presumably those with the highest density. The high conversion of CO to CH3OH can explain the abundances of CH3OH ice found in later stage Class 1 low-mass YSO envelopes (CH3OH:COr ∼ 0.5-0.6). For high-mass YSOs and one Class 0 YSO, this ratio varies significantly, implying local variations can affect ice formation. The large CH3OH ice abundance indicates that the formation of complex organic molecules is likely during the prestellar phase in cold environments without higher energy particle interactions (e.g., cosmic rays).

Keywords: Interstellar molecules, Bok globules, Ice formation, Molecular clouds, Chemical abundances, Dense interstellar clouds, Astrochemistry, Star formation, Collapsing clouds
Hinode/EIS Measurements of Active-region Magnetic Fields. The present work illustrates the potential of a new diagnostic technique that allows the measurement of the coronal magnetic field strength in solar active regions by utilizing a handful of bright Fe X and Fe XI lines commonly observed by the high-resolution Hinode/EUV Imaging Spectrometer (EIS). The importance of this new diagnostic technique is twofold: (1) the coronal magnetic field is probably the most important quantity in coronal physics, being at the heart of the processes regulating space weather and the properties of the solar corona, and (2) this technique can be applied to the existing EIS archive spanning from 2007 to 2020, including more than one full solar cycle and covering a large number of active regions, flares, and even coronal mass ejections. This new diagnostic technique opens the door to a whole new field of studies, complementing the magnetic field measurements from the upcoming DKIST and UCoMP ground-based observatories, and extending our reach to active regions observed on the disk and until now only sampled by radio measurements. In this work, we present a few examples of the application of this technique to EIS observations taken at different times during the EIS mission, and we discuss its current limitations and the steps to improve its accuracy. We also present a list of EIS observing sequences whose data include all of the lines necessary for the application of this diagnostic technique, to help the solar community navigate the immense set of EIS data and to find observations suitable for measuring the coronal magnetic field.

Keywords: Solar corona, Solar magnetic fields
Electromagnetic Emission Produced by Three-wave Interactions in a Plasma with Continuously Injected Counterstreaming Electron Beams. Three-wave interactions between Langmuir and electromagnetic waves in plasma with unstable electron flows are believed to be the main cause of type II and III solar radio emissions. The narrow band of type II bursts requires assuming that this radiation is generated in some local regions of shock fronts traveling in the solar corona, where the specific conditions for the enhancement of electromagnetic emissions near the plasma frequency harmonics are created. The reason for such enhancement at the second harmonic may be the formation of counterstreaming electron beams. There are different opinions in the literature on whether the second harmonic electromagnetic emission in the presence of an additional beam can be efficient enough to markedly dominate emissions produced by a single beam. In the present paper, we carry out particle-in-cell simulations of the collision of two symmetric electron beams in plasma with open boundary conditions and show that the efficiency of beam-to-radiation power conversion can be significantly increased compared to models with periodic boundary conditions and reach the level of a few percent if three-wave interactions with electromagnetic waves near the second harmonic of the plasma frequency becomes available for the most unstable, oblique, beam-driven modes.

Keywords: Radio bursts, Solar radio emission, Plasma physics