Sazuna/UAT_keywords huggingface dataset:
Anomalously Narrow Line Widths of Compact Massive Star-forming Galaxies at z ∼ 2.3: A Possible Inclination Bias in the Size-Mass Plane. Compact, massive star-forming galaxies at z ∼ 2.5 are thought to be building the central regions of giant elliptical galaxies today. However, a significant fraction of these objects were previously shown to have much smaller Hα line widths than expected. A possible interpretation is that Hα emission from their central regions, where the highest velocities are expected, is typically obscured by dust. Here we present Atacama Large Millimeter/submillimeter Array observations of the CO(3-2) emission line of three compact, massive galaxies with Hα line widths of FWHM(Hα) ∼ 125-260 km s-1 to test this hypothesis. Surprisingly, in all three galaxies, the CO line width is similar to the Hα line width: we find FWHM(CO) ∼ 165 km s-1 for all three galaxies whereas FWHM(CO) ∼ 450-700 km s-1 was expected from a simple virial estimator. These results show that the narrow Hα line widths of many compact massive star-forming galaxies are not due to preferential obscuration of the highest velocity gas. An alternative explanation for the narrow line widths is that the galaxies are disks that are viewed nearly face-on. We suggest that there may be an inclination bias in the size-mass plane, such that the apparent rest-frame optical sizes of face-on galaxies are smaller than those of edge-on galaxies. Although not conclusive, this hypothesis is supported by an observed anti-correlation between size and axis ratio of massive galaxies.

Keywords: Galaxy structure, Galaxy photometry, Galaxy kinematics, Submillimeter astronomy, Radio astronomy, High-redshift galaxies, Galaxy radii
Initial Characterization of Interstellar Comet 2I/2019 Q4 (Borisov). We present initial observations of the interstellar body 2I/(2019 Q4) Borisov taken to determine its nature prior to the perihelion in 2019 December. Images from the Nordic Optical Telescope show a prominent, morphologically stable dust coma and tail. The dust cross-section within 15,000 km of the nucleus averages 130 km2 (assuming geometric albedo 0.1) and increases by about 1% per day. If sustained, this rate indicates that the comet has been active for ∼100 days prior to the observations. Cometary activity thus started in 2019 June, at which time C/Borisov was at ∼4.5 au from the Sun, a typical distance for the onset of water ice sublimation in comets. The dust optical colors, B - V = 0.80 ± 0.05, V - R = 0.47 ± 0.03 and R- I = 0.49 ± 0.05, are identical to those of a sample of (solar system) long-period comets. The colors are similar to those of 1I/(2017 U1) ’Oumuamua, indicating a lack of the ultrared matter that is common in the Kuiper Belt, on both interstellar objects. The effective size of the dust particles is estimated as \overline{a} = 100 μm, based on the length of the dust tail and the 100 day lifetime. With this size, the ejected dust mass is of order 1.3 × 107 kg and the current dust mass loss rate ∼2 kg s-1. We set an upper limit to the nucleus radius using photometry at r  n  ≤3.8 km (again for albedo 0.1) and we use a statistical argument to show that the nucleus must be much smaller, likely a few hundred meters in radius.

Keywords: Comets
Spiral-wave Wind for the Blue Kilonova. The AT2017gfo kilonova (kN) counterpart of the binary neutron star merger event GW170817 was characterized by an early-time bright peak in optical and UV bands. Such blue kN is commonly interpreted as a signature of weak r-process nucleosynthesis in a fast expanding wind whose origin is currently debated. Numerical relativity simulations with microphysical equations of state, approximate neutrino transport, and turbulent viscosity reveal a new hydrodynamics-driven mechanism that can power the blue kN. Spiral density waves in the remnant generate a characteristic wind of mass ∼10-2 {M}⊙  and velocity ∼0.2 c. The ejected material has an electron fraction mostly distributed above 0.25 being partially reprocessed by hydrodynamic shocks in the expanding arms. The combination of dynamical ejecta and spiral-wave wind can account for solar system abundances of r-process elements and early-time observed light curves.

Keywords: Neutron stars, Nucleosynthesis, R-process, Gravitational waves, Compact objects
Evolving LMXBs: CARB Magnetic Braking. The formation of low-mass X-ray binaries (LMXBs) is an ongoing challenge in stellar evolution. An important subset of LMXBs is the binary systems with a neutron star (NS) accretor. In NS LMXBs with nondegenerate donors, the mass transfer (MT) is mainly driven by magnetic braking (MB). The discrepancies between the observed MT rates and the theoretical models were known for a while. Theory predictions of the MT rates are too weak and differ by an order of magnitude or more. Recently, we showed that with the standard MB, it is not possible to find progenitor binary systems such that they could reproduce—at any time of their evolution—most of the observed persistent NS LMXBs. In this Letter we present a modified MB prescription, Convection And Rotation Boosted (CARB). CARB MB combines two recent improvements in understanding stellar magnetic fields and magnetized winds—the dependence of the magnetic field strength on the outer convective zone and the dependence of the Alfvèn radius on the donor’s rotation. Using this new MB prescription, we can reproduce the observed MT rates at the detected mass ratio and orbital period for all well-observed to-the-date Galactic persistent NS LMXBs. For the systems where the effective temperature of the donor stars is known, theory agrees with observations as well.

Keywords: Stellar evolutionary models, Binary stars, Stellar evolution
MESSENGER Observations of Giant Plasmoids in Mercury’s Magnetotail. Small-scale flux ropes, with estimated diameters of ∼500 km and that pass over the MESSENGER spacecraft on timescales of seconds or less, are a common feature in Mercury’s magnetosphere. These magnetic structures, sometimes referred to as plasmoids, are believed to form as a result of rapid transient reconnection in the cross-tail current sheet at Mercury and the other planets. Here we report the occurrence of unusually large plasmoids in Mercury’s magnetotail observed, by the MESSENGER spacecraft. These plasmoids are remarkable for several reasons. Their spatial scales in the north-south direction exceed Mercury’s radius of 2440 km, and their time durations are comparable to or longer than the average Dungey cycle time of ∼200 s. They also have a more loop-like magnetic structure than the more common helical-like flux rope topology. These new MESSENGER observations suggest that Mercury’s magnetosphere can dissipate large quantities of magnetic flux and energy not only through the formation of a large number of small flux ropes, but also occasionally by the formation and release of a single giant plasmoid.

Keywords: Space plasmas, Solar magnetic reconnection, Plasma physics, Mercury (planet), Planetary magnetospheres, Magnetic fields
Bright Gamma-Ray Flares Observed in GRB 131108A. GRB 131108A is a bright long gamma-ray burst (GRB) detected by the Large Area Telescope and the Gamma-ray Burst Monitor on board the Fermi Gamma-ray Space Telescope. Dedicated temporal and spectral analyses reveal three γ-ray flares dominating above 100 MeV, which are not directly related to the prompt emission in the Gamma-ray Burst Monitor band (10 keV-10 MeV). The high-energy light curve of GRB 131108A (100 MeV-10 GeV) shows an unusual evolution: a steep decay, followed by three flares with an underlying emission, and then a long-lasting decay phase. The detailed analysis of the γ-ray flares finds that the three flares are 6-20 times brighter than the underlying emission and are similar to each other. The fluence of each flare, (1.6 ∼ 2.0) × 10-6 erg cm-2, is comparable to that of emission during the steep decay phase, 1.7 × 10-6 erg cm-2. The total fluence from three γ-ray flares is 5.3 × 10-6 erg cm-2. The three γ-ray flares show properties similar to the usual X-ray flares that are sharp flux increases, occurring in ∼50% of afterglows, in some cases well after the prompt emission. Also, the temporal and spectral indices during the early steep decay phase and the decaying phase of each flare show the consistency with a relation of the curvature effect (\hat{α } = 2 + \hat{β }), which is the first observational evidence of the high-latitude emission in the GeV energy band.

Keywords: Gamma-ray bursts
The Formation of CME from Coupling Fan-spine Magnetic System: A Difficult Journey. We present the eruption of a mini-filament that caused a large-scale complicated coronal mass ejection (CME) on 2014 March 28, using the high-resolution observations taken by the Solar Dynamic Observatory. Three-dimensional coronal magnetic field extrapolated from the nonlinear force-free field code reveals that the magnetic environment of the eruption source region was a large fan-spine magnetic system that hosted another small fan-spine system under its fan, and the mini-filament was located under the fan structure of the small fan-spine system. Our analysis results suggest that the eruption of the mini-filament underwent three reconnection processes before the formation of the CME. First, the erupting filament triggered the null point reconnection in the small fan-spine system. During this stage, the sudden expansion of the spine field lines also excited a large-scale extreme-ultraviolet wave. Second, the spine field lines of the small fan-spine system were pushed up by the erupting filament and therefore further triggered the null point reconnection in the large fan-spine magnetic system. Third, during the second stage, magnetic reconnection also occurred between the two legs of the stretched confining field lines of the mini-filament. The present study suggests that the formation of the observed CME from the coupling fan-spine magnetic system was more complicated than previously thought, needing to undergo multistage magnetic reconnection processes in the low corona.

Keywords: Solar activity, Solar coronal waves, Magnetic fields, Solar filament eruptions
ALMA C II 158 μm Imaging of an H I-selected Major Merger at z ∼ 4. We present high spatial resolution (≈2 kpc) Atacama Large Millimeter/submillimeter Array (ALMA) observations of [C II] 158 μm and dust-continuum emission from a galaxy at z=3.7978 selected by its strong H I absorption (a damped Lyα absorber, DLA) against a background QSO. Our ALMA images reveal a pair of star-forming galaxies separated by ≈ 6 kpc (projected) undergoing a major merger. Between these galaxies is a third emission component with highly elevated (2×) [C II] 158 μm emission relative to the dust continuum, which is likely to arise from stripped gas associated with the merger. This merger of two otherwise-normal galaxies is not accompanied by enhanced star formation, contrary to mergers detected in most luminosity-selected samples. The DLA associated with the merger exhibits extreme kinematics, with a velocity width for the low-ionization metal lines of {{Δ }}{v}90≈ 470 {km} {{{s}}}-1, that spans the velocity spread revealed in the [C II] 158 μm emission. We propose that DLAs with high {{Δ }}{v}90 values are a signpost of major mergers in normal galaxies at high redshifts, and use the distribution of the velocity widths of metal lines in high-z DLAs to provide a rough estimate the fraction of z &gt; 3 galaxies that are undergoing a major merger.

Keywords: Damped Lyman-alpha systems, Galaxy mergers, Quasar absorption line spectroscopy
Laboratory Experiments on the Motion of Dense Dust Clouds in Protoplanetary Disks. In laboratory experiments, we study the motion of levitated, sedimenting clouds of submillimeter grains at low ambient pressure and at high solid-to-gas ratios ɛ. The experiments show a collective behavior of particles, i.e., grains in clouds settle faster than an isolated grain. In collective particle clouds, the sedimentation velocity linearly depends on ɛ and linearly depends on the particle closeness C. However, collective behavior only sets in at a critical value ɛ crit that linearly increases with the experiment Stokes number St. For St &lt; 0.003 particles always behave collectively. For large Stokes numbers, large solid-to-gas ratios are needed to trigger collective behavior, e.g., ɛ crit = 0.04 at St = 0.01. Applied to protoplanetary disks, particles in dense environments will settle faster. In balance with upward gas motions (turbulent diffusion, convection) the thickness of the midplane particle layer will be smaller than calculated based on individual grains, especially for dust. For pebbles, large solid-to-gas ratios are needed to trigger instabilities based on back-reaction.

Keywords: Planetary system formation, Laboratory astrophysics, Protoplanetary disks, Planet formation
Frequency of Coronal Mass Ejection Impacts with Early Terrestrial Planets and Exoplanets around Active Solar-like Stars. Energetic flares and associated coronal mass ejections (CMEs) from young magnetically active solar-like stars can play a critical role in setting conditions for atmospheric escape as well as penetration of accelerated particles into their atmospheres that promotes formation of biologically relevant molecules. We have used the observationally reconstructed magnetic field of the 0.7 Gyr young Sun’s twin, k 1 Ceti, to study the effects of CME deflections in the magnetic corona of the young Sun and their effects on the impact frequency on the early Venus, Earth, and Mars. We find that the coronal magnetic field deflects the CMEs toward the astrospheric current sheet. This effect suggests that CMEs tend to propagate within a small cone about the ecliptic plane increasing the impact frequency of CMEs with planetary magnetospheres near this plane to ∼30% or by a factor of 6 as compared to previous estimate by Airapetian et al. Our model has important implications for the rise of prebiotic chemistry on early terrestrial planets as well as terrestrial-type exoplanets around young G-K dwarfs.

Keywords: Solar analogs, Earth (planet), Exoplanet astronomy, Magnetic variable stars, Stellar coronal mass ejections, Stellar coronae, Magnetic fields
Nonlinear Rossby Wave-Wave and Wave-Mean Flow Theory for Long-term Solar Cycle Modulations. The Schwabe cycle of solar activity exhibits modulations and frequency fluctuations on slow timescales of centuries and millennia. Plausible physical explanations for the cause of these long-term variations of the solar cycle are still elusive, with possible theories including stochasticity of the alpha effect and fluctuations of the differential rotation. It has been suggested recently in the literature that there exists a possible relation between the spatiotemporal structure of the solar cycle and the nonlinear dynamics of magnetohydrodynamic (MHD) Rossby waves at the solar tachocline, including both wave-wave and wave-mean flow interactions. Here we extend the nonlinear theory of MHD Rossby waves presented in a previous article to take into account long-term modulation effects due to a recently discovered mechanism that allows significant energy transfers throughout different wave triads: the precession resonance mechanism. We have found a large number of Rossby-Hauwirtz wave triads whose frequency mismatches are compatible with the solar cycle frequency. Consequently, by analyzing the reduced dynamics of two triads coupled with a single mode (five-wave system), we have demonstrated that in the amplitude regime in which precession resonance occurs, the energy transfer throughout the system yields significant long-term modulations on the main ∼11 yr period associated with intratriad energy exchanges. We further show that such modulations display an inverse relationship between the characteristic wave amplitude and the period of intratriad energy exchanges, which is consistent with the Waldmeier law for the solar cycle. In the presence of a constant forcing and dissipation, the five-wave system in the precession resonance regime exhibits irregular amplitude fluctuations, with some periods resembling the grand minimum states.

Keywords: Solar activity, Magnetohydrodynamics, Maunder minimum
High-frequency Wave Propagation Along a Spicule Observed by CLASP. The Chromospheric Lyman-Alpha Spectro-Polarimeter (CLASP) sounding rocket experiment, launched in 2015 September, observed the hydrogen Lyα line (121.6 nm) in an unprecedented high temporal cadence of 0.3 s. CLASP performed sit-and-stare observations of the quiet Sun near the limb for 5 minutes with a slit perpendicular to the limb and successfully captured an off-limb spicule evolving along the slit. The Lyα line is well suited for investigating how spicules affect the corona because it is sensitive to higher temperatures than other chromospheric lines, owing to its large optical thickness. We found high-frequency oscillations of the Doppler velocity with periods of 20-50 s and low-frequency oscillation of periods of ∼240 s on the spicule. From a wavelet analysis of the time sequence data of the Doppler velocity, in the early phase of the spicule evolution, we found that waves with a period of ∼30 s and a velocity amplitude of 2-3 km s-1 propagated upward along the spicule with a phase velocity of ∼470 km s-1. In contrast, in the later phase, possible downward and standing waves with smaller velocity amplitudes were also observed. The high-frequency waves observed in the early phase of the spicule evolution would be related with the dynamics and the formation of the spicules. Our analysis enabled us to identify the upward, downward, and standing waves along the spicule and to obtain the velocity amplitude of each wave directly from the Doppler velocity for the first time. We evaluated the energy flux by the upward-propagating waves along the spicule, and discussed the impact to the coronal heating.

Keywords: Solar spicules, Solar chromosphere, Alfven waves, Solar transition region
A Statistical Approach to Planetesimal Condensate Composition beyond the Snowline Based on the Carbon-to-oxygen Ratio. The ratio between carbon and oxygen is regarded as an important driver of circumstellar and planetary chemistry, which can be used as a parameter to estimate the fractionation among refractory and volatile portions of a planet. From this motivation, nearly 500 stars including some with planets discovered around them are investigated. The relation between the C/O ratio and fractions of icy and refractory species is traced for planetesimals expected to form in their protostellar disks. It is found that low C/O ratios lead to planets rich in ice, but poor in organic and other refractory materials. With increasing C/O ratios, the ice fraction diminishes, where organics increase and other refractory materials dominate. Apart from that, the carbon portion incorporated in the solid phase and the redox state of the environment are altered to analyze their influence on bulk formation for generated planets. Under zero solid carbon contribution, ice formation decreases and refractory formation increases with increasing C/O ratio. When the carbon contribution is considered to be entirely in the solid phase, refractory materials are not significantly affected by the increasing C/O ratio while ice may even disappear. For reducing conditions, the C/O ratio is not an obstacle for ice formation no matter how high it is. Under oxidizing conditions, however, water is not found where the C/O ratio is greater than 0.8. Bulk densities are also calculated according to alternative scenarios along with compositional distributions, and results are compared to solar system objects. This study, therefore, exemplifies how a simple correlation can be drawn between stellar chemistry, redox state, and planetesimal composition.

Keywords: Solar system, Protoplanetary disks
Carnegie Supernova Project-II: Near-infrared Spectroscopic Diversity of Type II Supernovae. We present 81 near-infrared (NIR) spectra of 30 Type II supernovae (SNe II) from the Carnegie Supernova Project-II (CSP-II), the largest such data set published to date. We identify a number of NIR features and characterize their evolution over time. The NIR spectroscopic properties of SNe II fall into two distinct groups. This classification is first based on the strength of the He I λ1.083 μm absorption during the plateau phase; SNe II are either significantly above (spectroscopically strong) or below 50 Å (spectroscopically weak) in pseudo equivalent width. However, between the two groups other properties, such as the timing of CO formation and the presence of Sr II, are also observed. Most surprisingly, the distinct weak and strong NIR spectroscopic classes correspond to SNe II with slow and fast declining light curves, respectively. These two photometric groups match the modern nomenclature of SNe IIP, which show a long duration plateau, and IIL, which have a linear declining light curve. Including NIR spectra previously published, 18 out of 19 SNe II follow this slow declining-spectroscopically weak and fast declining-spectroscopically strong correspondence. This is in apparent contradiction to the recent findings in the optical that slow and fast decliners show a continuous distribution of properties. The weak SNe II show a high-velocity component of helium that may be caused by a thermal excitation from a reverse shock created by the outer ejecta interacting with the red supergiant wind, but the origin of the observed dichotomy is not understood. Further studies are crucial in determining whether the apparent differences in the NIR are due to distinct physical processes or a gap in the current data set.

Keywords: Spectroscopy, Core-collapse supernovae, Near infrared astronomy
The COS CGM Compendium. III. Metallicity and Physical Properties of the Cool Circumgalactic Medium at z ≲ 1. We characterize the metallicities and physical properties of cool, photoionized gas in a sample of 152 z ≲ 1 strong Lyα forest systems (SLFSs, absorbers with 15 &lt; log N H I  &lt; 16.2). The sample is drawn from our Cosmic Origins Spectrograph (COS) circumgalactic medium compendium (CCC), an ultraviolet survey of H I-selected circumgalactic gas around z ≲ 1 galaxies that targets 261 absorbers with 15 &lt; log N H I  &lt; 19. We show that the metallicity probability distribution function of the SLFSs at z ≲ 1 is unimodal, skewed to low metallicities with a mean and median of [X/H] = -1.47 and -1.18 dex. Very metal-poor gas with [X/H] &lt; -1.4 represents about half of the population of absorbers with 15 &lt; log N H I  ≲ 18, while it is rare at higher N H I . Thus, there are important reservoirs of primitive (though not pristine) diffuse ionized gas around z ≲ 1 galaxies. The photoionized gas around z ≲ 1 galaxies is highly inhomogeneous based on the wide range of metallicities observed (-3 ≲ [X/H] ≲ +0.4) and the fact that there are large metallicity variations (factors of 2 to 25) for most of the closely spaced absorbers (∆v ≲ 300 km s-1) along the same sightlines. These absorbers show a complex evolution with redshift and H I column density, and we identify subtle cosmic evolution effects that affect the interpretation of metallicity distributions and comparison with other absorber samples. We discuss the physical conditions and cosmic baryon and metal budgets of the CCC absorbers. Finally, we compare the CCC results to recent cosmological zoom simulations and explore the origins of the 15 &lt; log N H I  &lt; 19 absorbers within the Evolution and Assembly of GaLaxies and their Environments (EAGLE) high-resolution simulations.

Keywords: Galaxy environments, Metallicity, Quasar absorption line spectroscopy, Circumgalactic medium