Sazuna/UAT_keywords huggingface dataset:
Star Formation Histories of Ultra-faint Dwarf Galaxies: Environmental Differences between Magellanic and Non-Magellanic Satellites?. We present the color-magnitude diagrams and star formation histories (SFHs) of seven ultra-faint dwarf galaxies: Horologium 1, Hydra 2, Phoenix 2, Reticulum 2, Sagittarius 2, Triangulum 2, and Tucana 2, derived from high-precision Hubble Space Telescope photometry. We find that the SFH of each galaxy is consistent with them having created at least 80% of the stellar mass by z ~ 6. For all galaxies, we find quenching times older than 11.5 Gyr ago, compatible with the scenario in which reionization suppresses the star formation of small dark matter halos. However, our analysis also reveals some differences in the SFHs of candidate Magellanic Cloud satellites, i.e., galaxies that are likely satellites of the Large Magellanic Cloud and that entered the Milky Way potential only recently. Indeed, Magellanic satellites show quenching times about 600 Myr more recent with respect to those of other Milky Way satellites, on average, even though the respective timings are still compatible within the errors. This finding is consistent with theoretical models that suggest that satellites' SFHs may depend on their host environment at early times, although we caution that within the error bars all galaxies in our sample are consistent with being quenched at a single epoch. * Based on observations obtained with the NASA/ESA Hubble Space Telescope at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy under NASA Contract NAS 5-26555.

Keywords: Local Group, Galaxy dynamics, Dwarf galaxies, Galaxy stellar content, Galaxy kinematics, Galaxy evolution, Star formation, Magellanic Clouds
On the Large Apparent Black Hole Spin-orbit Misalignment Angle in GW200115. GW200115 is one of the first two confidently detected gravitational-wave events of neutron star-black hole mergers. An interesting property of this merger is that the black hole, if spinning rapidly, has its spin axis negatively aligned (with a misalignment angle &gt;90°) with the binary orbital angular momentum vector. Although such a large spin-orbit misalignment angle naturally points toward a dynamical origin, the measured neutron star-black hole merger rate exceeds theoretical predictions of the dynamical formation channel. In the canonical isolated binary formation scenario, the immediate progenitor of GW200115 is likely to be a binary consisting of a black hole and a helium star, with the latter forming a neutron star during a supernova explosion. Since the black hole is generally expected to spin along the pre-supernova binary orbital angular momentum axis, a large neutron star natal kick is required to produce the observed misalignment angle. Using simple kinematic arguments, we find that a misalignment angle &gt;90° in GW200115-like systems implies a kick velocity ~600 km s-1 and a kick direction within ≈30° of the pre-supernova orbital plane. We discuss different interpretations of the large apparent black hole spin-orbit misalignment angle, including a nonspinning black hole.

Keywords: Stellar mass black holes, Neutron stars, Supernovae, Gravitational waves
Asymmetric H I 21 cm Lines of Fast Radio Burst Hosts: Connection with Galaxy Interaction. Fast radio bursts (FRBs) are enigmatic transients with very short radio emission. Their nature is still widely debated. I provide the first analysis of atomic gas properties of a small sample of FRB hosts to constrain their nature. H I observations exist for NGC 3252, the host of FRB 181030A, M81, the host of FRB 200120E, and the Milky Way, the host of FRB 200428. I report three observables: (i) all three FRB hosts are interacting galaxies; (ii) the H I spectra of both FRB hosts with such data available are highly asymmetric, several standard deviations above the general population of galaxies; (iii) two FRB hosts have normal atomic gas properties and one is strongly deficient in atomic gas. This indicates that nearby and repeating FRBs are connected with a recent enhancement of star formation due to interaction. This supports fast FRB channels, for example, a massive star with a short delay time so that interaction signatures giving rise to the birth of the progenitor are still visible. Long gamma-ray burst (GRB) and broad-lined type Ic supernova (SN) hosts exhibit much more symmetric spectra, even though they were claimed to experience gas inflow from the intergalactic medium. The difference can be explained by the interactions experienced by FRB hosts being more disruptive than these gas inflows, or by the mass effect, with GRB/SN hosts at lower masses having less organized gas motions, so with H I lines closer to a symmetrical Gaussian. This also suggests that the emission mechanisms of FRBs and GRBs are different.

Keywords: Gamma-ray bursts, Interstellar atomic gas, Spiral galaxies, H I line emission, Radio bursts, Galaxy groups, Interacting galaxies, Radio transient sources
Some First Stars Were Red: Detecting Signatures of Massive Population III Formation through Long-term Stochastic Color Variations. Identifying stars formed in pristine environments (Population III) within the first billion years is vital to uncovering the earliest growth and chemical evolution of galaxies. Population III galaxies, however, are typically expected to be too faint and too few in number to be detectable by forthcoming instruments without extremely long integration times and/or extreme lensing. In an environment, however, where star formation is suppressed until a halo crosses the atomic-cooling limit (e.g., by a modest Lyman-Werner flux, high baryonic streaming velocities, and/or dynamical heating effects), primordial halos can form substantially more numerous and more massive stars. Some of these stars will in turn be accreting more rapidly than they can thermally relax at any given time. Using high-resolution cosmological zoom-in simulations of massive star formation in high-z halos, we find that such rapidly accreting stars produce prominent spectral features that would be detectable by the James Webb Space Telescope. The rapid-accretion episodes within the halo lead to stochastic reprocessing of 0%-20% of the total stellar emission into the rest-frame optical over long timescales, a unique signature which may allow deep observations to identify such objects out to z ~ 10-13 using mid- and wide-band NIRCam colors alone.

Keywords: Early universe, Population III stars, Primordial galaxies
Energy and Waiting Time Distributions of FRB 121102 Observed by FAST. The energy and waiting time distributions are important properties for understanding the physical mechanism of repeating fast radio bursts (FRBs). Recently, the Five-hundred-meter Aperture Spherical radio Telescope (FAST; Nan et al. 2011; Li et al. 2018) detected the largest burst sample of FRB 121102, containing 1652 bursts Li et al. (2021a) We use this sample to investigate the energy and waiting time distributions. The energy count distribution dN/dE at the high-energy range (&gt;1038 erg) can be fitted with a single power-law function with an index of -{1.86}_{-0.02}^{+0.02}$ , while the distribution at the low-energy range deviates from the power-law function. An interesting result of Li et al. (2021a) is that there is an apparent temporal gap between early bursts (occurring before MJD 58740) and late bursts (occurring after MJD 58740). We find that the energy distributions of high-energy bursts at different epochs are inconsistent. The power-law index is -{1.70}_{-0.03}^{+0.03}$ for early bursts and -{2.60}_{-0.14}^{+0.15}$ for late bursts. For bursts observed in a single day, a linear repetition pattern is found. We use the Weibull function to fit the distribution of waiting time of consecutive bursts. The shape parameter k={0.72}_{-0.01}^{+0.01}$ and the event rate r={736.43}_{-28.90}^{+26.55}$ day-1 are derived. If the waiting times with δt &lt; 28 s are excluded, the burst behavior can be described by a Poisson process. The best-fitting values of k are slightly different for low-energy (E &lt; 1.58 × 1038 erg) and high-energy (E &gt; 1.58 × 1038 erg) bursts.

Keywords: Radio bursts, Radio transient sources
Morphological Transition of the Compact Radio Lobe in 3C 84 via the Strong Jet-Cloud Collision. We report multiepoch very long baseline interferometric observations of the compact radio lobe in the radio galaxy 3C 84 (NGC 1275) during 2016-2020. The image sequence of 3C 84 reveals that the hotspot in the radio lobe showed the 1 year long frustration in 2017 within a compact region of about 0.07 pc, suggesting a strong collision between the jet and a compact dense cloud with an estimated average density of about (4-6) × 105 cm-3. Although the hotspot and the radio lobe began to move south again after its breakout, the radio lobe showed a morphological transition from an FR II- to FR I-class radio lobe and its radio flux became fainter. This is the first detection of the dynamical feedback from the cloud to the jet where the cloud located on the jet axis significantly interferes with the jet propagation and evolution at the central 1 pc region in the active galactic nucleus.

Keywords: Radio continuum emission, Radio galaxies, Active galactic nuclei
Evidence of a Tidal-disruption Event in GSN 069 from the Abnormal Carbon and Nitrogen Abundance Ratio. GSN 069 is an ultra-soft X-ray active galactic nucleus that previously exhibited a huge X-ray outburst and a subsequent long-term decay. It has recently presented X-ray quasi-periodic eruptions (QPEs). We report the detection of strong nitrogen lines but weak or undetectable carbon lines in its far-ultraviolet spectrum. With a detailed photoionization model, we use the C IV/N IV] ratio and other ratios between nitrogen lines to constrain the [C/N] abundance of GSN 069 to be from -3.33 to -1.91. We argue that a partially disrupted red giant star can naturally explain the abnormal C/N abundance in the UV spectrum, while the surviving core orbiting the black hole might produce the QPEs.

Keywords: Active galaxies, Active galactic nuclei
New Multielement Isotopic Compositions of Presolar SiC Grains: Implications for Their Stellar Origins. We report NanoSIMS Si and Mg-Al isotopic data (and C, N, and Ti isotopic data, when available) for 85 submicron- to micron-sized presolar SiC grains from the CM2 Murchison meteorite, including 60 mainstream (MS), 8 AB1, 8 X, 7 AB2, and 2 Y grains. The MS and Y grain data demonstrate that (1) C and N contamination mainly appears as surface contamination, and sufficient presputtering is needed to expose a clean grain surface for obtaining intrinsic C and N signals, and (2) Mg and Al contamination appears as adjacent grains and rims, and high-resolution imaging and the choice of small regions of interest during data reduction together are effective in suppressing the contamination. Our results strongly indicate that previous studies of presolar SiC grains could have sampled differing degrees of contamination for C, N, Mg, and Al. Compared to the literature data, our new MS and Y grains are in better agreement with carbon star observations for both the C and N isotopic ratios. By comparing our new, tighter distributions of 12C/13C, 14N/15N, and initial 26Al/27Al ratios for MS and Y grains with FRUITY low-mass asymptotic giant branch (AGB) stellar models, we provide more stringent constraints on the occurrence of cool bottom processing and the production of 26Al in N-type carbon stars, which are classical AGB stars.

Keywords: Meteoroids, Stellar abundances, Circumstellar matter, Asymptotic giant branch stars, Meteors, Meteorites, Stellar nucleosynthesis
Probing the Chemical Complexity of Amines in the ISM: Detection of Vinylamine (C<SUB>2</SUB>H<SUB>3</SUB>NH<SUB>2</SUB>) and Tentative Detection of Ethylamine (C<SUB>2</SUB>H<SUB>5</SUB>NH<SUB>2</SUB>). Amines, particularly primary amines (R-NH2), are closely related to the primordial synthesis of amino acids since they share the same structural backbone. However, only a limited number of amines has been identified in the interstellar medium, which prevents us from studying their chemistry as well as their relation to prebiotic species that could lead to the emergence of life. In this Letter, we report the first interstellar detection of vinylamine (C2H3NH2) and tentative detection of ethylamine (C2H5NH2) toward the Galactic center cloud G+0.693-0.027. The derived abundance with respect to H2 is (3.3 ± 0.4) × 10-10 and (1.9 ± 0.5) × 10-10, respectively. The inferred abundance ratios of C2H3NH2 and C2H5NH2 with respect to methylamine (CH3NH2) are ~0.02 and ~0.008, respectively. The derived abundance of C2H3NH2, C2H5NH2, and several other NH2-bearing species are compared to those obtained toward high-mass and low-mass star-forming regions. Based on recent chemical and laboratory studies, possible chemical routes for the interstellar synthesis of C2H3NH2 and C2H5NH2 are discussed.

Keywords: Interstellar molecules, Galactic center, Chemical abundances, Pre-biotic astrochemistry
OSSOS Finds an Exponential Cutoff in the Size Distribution of the Cold Classical Kuiper Belt. The cold main classical Kuiper Belt consists of the nonresonant small solar system bodies with low orbital inclinations and orbital semimajor axes between 42.4 and 47.7 au. These objects likely formed in situ, and the population has experienced minimal collisional modification since formation. Using the Outer Solar System Origins Survey ensemble sample and characterization, combined with constraints from deeper surveys and supported by evidence from the Minor Planet Center catalog and the Deep Ecliptic Survey, we determine the absolute magnitude Hr distribution of the cold classical belt from Hr ≃ 5 to 12 (roughly diameters of 400-20 km). We conclude that the cold population's Hr distribution exhibits an exponential cutoff at large sizes. Exponential cutoffs at large sizes are not a natural outcome of pairwise particle accretion, but exponentially tapered power-law size distributions are a feature of numerical simulations of planetesimal formation via a streaming instability. Our observation of an exponential cutoff agrees with previous observational inferences that no large objects (D ≳ 400 km) exist in the cold population. We note that the asymptotic slope of the Hr distribution is consistent with α ~ 0.4. This asymptotic slope is also found in streaming instability modeling of planetesimal formation and is thus not necessarily associated with achieving collisional equilibrium. Studies of the trans-Neptunian region are providing the parameters that will enable future streaming-instability studies to determine the initial conditions of planetesimal formation in the ≈45 au region of the Sun's protoplanetary disk.

Keywords: Kuiper belt, Classical Kuiper belt objects, Trans-Neptunian objects
Onset of Plasmoid Reconnection during Magnetorotational Instability. The evolution of current sheets in accretion flows undergoing magnetorotational instability (MRI) is examined through two- and three-dimensional numerical modeling of the resistive MHD equations in global cylindrical geometry. With an initial uniform magnetic field aligned in the vertical (z) direction, MRI produces radially extended toroidal (azimuthal) current sheets. In both 2D and 3D when axisymmetric modes dominate, these current sheets attract each other and merge in the poloidal (rz) plane, driving magnetic reconnection when the Lundquist number S &gt; 3 × 102, making it a possible source of plasmoids (closed magnetic loops) in accretion disks. At high Lundquist numbers in the 2D regime, starting at S = 5 × 103, self-consistent MRI-generated current sheets become thin and subject to plasmoid instability, and therefore spontaneous magnetic reconnection. When nonaxisymmetric 3D modes dominate, turbulence makes the azimuthal current sheets more unstable and stretch vertically. Toroidally extended vertical current sheets in the inner region, as well as larger 3D magnetic islands in the outer regions of the disks are also formed. These findings have strong ramifications for astrophysical disks as potential sources of plasmoids that could cause local heating, particle acceleration, and high energy EM radiation.

Keywords: Magnetic fields, Plasma astrophysics, Magnetohydrodynamical simulations
Development of a Deep Learning Model for Inversion of Rotational Coronagraphic Images Into 3D Electron Density. We present, for the first time, a deep learning model that returns the three-dimensional (3D) coronal electron density from coronagraphic images. The intensity of coronagraphic observations arises from the Thomson scattering of photospheric light by the coronal electrons. We use MHD numerical simulations to obtain realistic 3D electron density and construct error-free training sets consisting of input (observation) and target (electron density) images. In the training sets, the input images are directly synthesized from the target 3D electron density by applying the Thomson scattering theory. The input and target images are in the form of latitude-longitude maps given at a radius, often referred to as synoptic maps. Using synoptic maps reduces a tomographic method to an image translation problem. We use pix2pixHD, one of the well-established supervised image translation methods and develop models for six selected heights: 2.0, 2.2, 2.5, 4.0, 6.0, and 12.0 solar radii. All six models have similar performance and the mean absolute percent error of the generated density images is less than 7% with respect to the ground-truth simulated data sets.

Keywords: Coronagraphic imaging, Solar corona, Neural networks
Relation of Microstreams in the Polar Solar Wind to Switchbacks and Coronal X-Ray Jets. Ulysses data obtained at high solar latitudes during periods of minimum solar activity in 1994 and 2007 are examined to determine the relation between velocity structures called microstreams and folds in the magnetic field called switchbacks. A high correlation is found. The possibility of velocity peaks in microstreams originating from coronal X-ray jets is reexamined; we now suggest that microstreams are the consequence of the alternation of patches of switchbacks and quiet periods, where the switchbacks could be generated by minifilament/flux rope eruptions that cause coronal jets.

Keywords: Solar corona, Fast solar wind
Two Sites of r-process Production Assessed on the Basis of the Age-tagged Abundances of Solar Twins. Solar twins, i.e., stars that are nearly identical to the Sun, including their metallicities, in the solar vicinity show ages widely distributed from 0 to 10 Gyr. This fact matches the orbital history of solar twins in the new paradigm of galactic dynamics, in which stars radially move on the disk when they encounter transient spiral arms. This finding suggests that older twins were born closer to the Galactic center and traveled a longer distance to reach their present location, according to the hypothesis that chemical enrichment occurs more quickly and that solar metallicity is attained on a shorter timescale with a decreasing Galactocentric distance (RGC). We show that abundance patterns covering a wide range of heavy elements for solar twins sharing similar ages are identical and that their variation among different age groups can be understood on the basis of the age-RGC connection within the framework of Galactic chemical evolution. This study identifies the Galactic bulge as the birthplace of the oldest solar twins. Based on this scheme, we find that the relation between [r-process/Fe] and RGC for the inner Galactic region is incompatible with the hypothesis of a sole site for r-process production, that is, neutron star mergers, whose delay time distribution could be approximated by the power-law form (∝ tn). Alternatively, this relation suggests the presence of two distinct sites for r-process production: short-lived massive stars, ending with specific core-collapse supernovae, and neutron star mergers that are heavily inclined to emerge with longer delay times, as represented by n = 0-0.5.

Keywords: Galaxy chemical evolution, Galactic archaeology, Galaxy dynamics, Galactic bulge, Solar abundances, Milky Way disk
Mapping the 3D Kinematical Structure of the Gas Disk of HD 169142. The disk around HD 169142 has been suggested to host multiple embedded planets due to the range of structures observed in the dust distributions. We analyze archival Atacama Large (sub-) Millimetre Array observations of 12CO (2-1), 13CO (2-1), and C18O (2-1) to search for large-scale kinematic structures associated with other embedded planets in the outer disk. At 125 au, we identify a coherent flow from the disk surface to the midplane, traced by all three CO isotopologues, and interpret it as a meridional flow potentially driven by an embedded planet. We use changes in the rotation speed of the gas to characterize the physical structure across this region, finding that at 125 au the CO emission traces regions of increased gas pressure, despite being at a surface density minimum. Developing a simple analytical model, we demonstrate that the physical structure of the gap can have non-trivial responses to changes in the surface density, consistent both with previous thermo-chemical models and the conditions inferred observationally. Applying this technique to a range of sources will allow us to directly confront theoretical models of gap-opening in protoplanetary disks.

Keywords: Submillimeter astronomy, Planetary-disk interactions, Protoplanetary disks
Split Peas in a Pod: Intra-system Uniformity of Super-Earths and Sub-Neptunes. The planets within compact multiplanet systems tend to have similar sizes, masses, and orbital period ratios, like "peas in a pod." This pattern was detected when considering planets with radii between 1 and 4 R⊕. However, these same planets show a bimodal radius distribution, with few planets between 1.5 and 2 R⊕. The smaller "super-Earths" are consistent with being stripped rocky cores, while the larger "sub-Neptunes" likely have gaseous H/He envelopes. Given these distinct structures, it is worthwhile to test for intra-system uniformity separately within each category of planets. Here, we find that the tendency for intra-system uniformity is twice as strong when considering planets within the same size category than it is when combining all planets together. The sub-Neptunes tend to be ${1.7}_{-0.3}^{+0.6}$ times larger than the super-Earths in the same system, corresponding to an envelope mass fraction of about 2.6% for a 5 M⊕ planet. For the sub-Neptunes, the low-metallicity stars are found to have planets with more equal sizes, with modest statistical significance (p ~ 0.005). There is also a modest (~2σ) tendency for wider-orbiting planets to be larger, even within the same size category.

Keywords: Mini Neptunes, Super Earths, Exoplanet systems, Exoplanets