Sazuna/UAT_keywords huggingface dataset:
GRB 140423A: A Case of Stellar Wind to Interstellar Medium Transition in the Afterglow. We present very early ground-based optical follow-up observations of gamma-ray burst (GRB) 140423A, which was discovered by the Swift/Burst Alert Telescope (BAT) and by the Fermi/Gamma-Ray Burst Monitor. Its broadband afterglow was monitored by the Swift/X-Ray Telescope and ground-based optical telescopes from T0 + 70.96 s to 4.8 days after the Swift/BAT trigger. This is one more case of a prompt optical emission observation. The temporal and spectral joint fits of the multiwavelength light curves of GRB 140423A reveal that achromatic behavior is consistent with the external shock model, including a transition from a stellar wind to the interstellar medium (ISM) and energy injection. In terms of the optical light curves, there is an onset bump in the early afterglow with a rising index ${\alpha }_{{\rm{O}},{\rm{I}}}=-0.59\pm 0.04$ (peaking at ${t}_{\mathrm{peak}}-{T}_{0}\approx 206$ s). It then decays with a steep index ${\alpha }_{{\rm{O}},\mathrm{II}}=1.78\pm 0.03$ , and shows a steeper to flatter "transition" with ${\alpha }_{{\rm{O}},\mathrm{III}}=1.13\pm 0.03$ at around T0 + 5000 s. The observed X-ray afterglow reflects achromatic behavior, as does the optical light curve. There is no obvious evolution of the spectral energy distribution between the X-ray and optical afterglows, with an average value of the photon index ${\rm{\Gamma }}\approx 1.95$ . This "transition" is consistent with an external shock model having the circumburst medium transition from a wind to the ISM, by introducing a long-lasting energy injection with a Lorentz factor stratification of the ejecta. The best parameters from Monte Carlo Markov Chain fitting are ${E}_{{\rm{K}},\mathrm{iso}}\approx 2.14\times {10}^{55}$ erg, ${{\rm{\Gamma }}}_{0}\approx 162$ , ${\varepsilon }_{e}\approx 0.02$ , ${\varepsilon }_{B}\approx 1.7\times {10}^{-6}$ , ${A}_{* }\approx 1.0$ , ${R}_{t}\approx 4.1\times {10}^{17}$ cm, $n\approx 11.0\,\,{\mathrm{cm}}^{-3}$ , ${L}_{0}\approx 3.1\times {10}^{52}\,\mathrm{erg}\ {{\rm{s}}}^{-1}$ , $k\approx 1.98$ , $s\,\approx 1.54$ , and ${\theta }_{j}\gt 0.3\,\mathrm{rad}$ .

Keywords: Gamma-ray bursts, Non-thermal radiation sources
Black Hole Genealogy: Identifying Hierarchical Mergers with Gravitational Waves. In dense stellar environments, the merger products of binary black hole mergers may undergo additional mergers. These hierarchical mergers are naturally expected to have higher masses than the first generation of black holes made from stars. The components of hierarchical mergers are expected to have significant characteristic spins, imprinted by the orbital angular momentum of the previous mergers. However, since the population properties of first-generation black holes are uncertain, it is difficult to know if any given merger is first-generation or hierarchical. We use observations of gravitational waves to reconstruct the binary black hole mass and spin spectrum of a population including the possibility of hierarchical mergers. We employ a phenomenological model that captures the properties of merging binary black holes from simulations of globular clusters. Inspired by recent work on the formation of low-spin black holes, we include a zero-spin subpopulation. We analyze binary black holes from LIGO and Virgo's first two observing runs, and find that this catalog is consistent with having no hierarchical mergers. We find that the most massive system in this catalog, GW170729, is mostly likely a first-generation merger, having a 4% probability of being a hierarchical merger assuming a 5 × 105M⊙ globular cluster mass. Using our model, we find that 99% of first-generation black holes in coalescing binaries have masses below $44$ M⊙, and the fraction of binaries with near-zero component spins is less than $0.16$ (90% probability). Upcoming observations will determine if hierarchical mergers are a common source of gravitational waves.

Keywords: Gravitational wave astronomy, Hierarchical models, Gravitational wave sources, Astrophysical black holes
Galaxy Zoo Builder: Four-component Photometric Decomposition of Spiral Galaxies Guided by Citizen Science. Multicomponent modeling of galaxies is a valuable tool in the effort to quantitatively understand galaxy evolution, yet the use of the technique is plagued by issues of convergence, model selection, and parameter degeneracies. These issues limit its application over large samples to the simplest models, with complex models being applied only to very small samples. We attempt to resolve this dilemma of "quantity or quality" by developing a novel framework, built inside the Zooniverse citizen-science platform, to enable the crowdsourcing of model creation for Sloan Digital Sky Survey galaxies. We have applied the method, including a final algorithmic optimization step, on a test sample of 198 galaxies, and examine the robustness of this new method. We also compare it to automated fitting pipelines, demonstrating that it is possible to consistently recover accurate models that either show good agreement with, or improve on, prior work. We conclude that citizen science is a promising technique for modeling images of complex galaxies, and release our catalog of models.

Keywords: Barred spiral galaxies, Disk galaxies, Galaxy classification systems, Spiral galaxies
The Origin of Elements from Carbon to Uranium. To reach a deeper understanding of the origin of elements in the periodic table, we construct Galactic chemical evolution (GCE) models for all stable elements from C (A = 12) to U (A = 238) from first principles, i.e., using theoretical nucleosynthesis yields and event rates of all chemical enrichment sources. This enables us to predict the origin of elements as a function of time and environment. In the solar neighborhood, we find that stars with initial masses of M &gt; 30M⊙ can become failed supernovae if there is a significant contribution from hypernovae (HNe) at M ∼ 20-50M⊙. The contribution to GCE from super-asymptotic giant branch (AGB) stars (with M ∼ 8-10M⊙ at solar metallicity) is negligible, unless hybrid white dwarfs from low-mass super-AGB stars explode as so-called Type Iax supernovae, or high-mass super-AGB stars explode as electron-capture supernovae (ECSNe). Among neutron-capture elements, the observed abundances of the second (Ba) and third (Pb) peak elements are well reproduced with our updated yields of the slow neutron-capture process (s-process) from AGB stars. The first peak elements (Sr, Y, Zr) are sufficiently produced by ECSNe together with AGB stars. Neutron star mergers can produce rapid neutron-capture process (r-process) elements up to Th and U, but the timescales are too long to explain observations at low metallicities. The observed evolutionary trends, such as for Eu, can well be explained if ∼3% of 25-50M⊙ HNe are magneto-rotational supernovae producing r-process elements. Along with the solar neighborhood, we also predict the evolutionary trends in the halo, bulge, and thick disk for future comparison with Galactic archeology surveys.

Keywords: Isotopic abundances, Core-collapse supernovae, Nucleosynthesis, Galaxy chemical evolution, Stellar abundances, Chemical abundances, Stellar physics, Galaxy abundances, Asymptotic giant branch stars, Type Ia supernovae, Galaxy evolution, Milky Way Galaxy
Protostellar Collapse: Regulation of the Angular Momentum and Onset of an Ionic Precursor. Through the magnetic braking and the launching of protostellar outflows, magnetic fields play a major role in the regulation of angular momentum in star formation, which directly impacts the formation and evolution of protoplanetary disks and binary systems. The aim of this paper is to quantify those phenomena in the presence of nonideal magnetohydrodynamics effects, namely, the ohmic and ambipolar diffusion. We perform three-dimensional simulations of protostellar collapses varying the mass of the prestellar dense core, the thermal support (the α ratio), and the dust grain size distribution. The mass mostly influences the magnetic braking in the pseudo-disk, while the thermal support impacts the accretion rate and hence the properties of the disk. Removing the grains smaller than 0.1 μm in the Mathis-Rumpl-Nordsieck distribution enhances the ambipolar diffusion coefficient. Similar to previous studies, we find that this change in the distribution reduces the magnetic braking with an impact on the disk. The outflow is also significantly weakened. In either case, the magnetic braking largely dominates the outflow as a process to remove the angular momentum from the disk. Finally, we report a large ionic precursor to the outflow with velocities of several km s-1, which may be observable.

Keywords: Interstellar dust, Magnetohydrodynamics, Star formation, Protoplanetary disks, Gravitational collapse, Magnetic fields
Revisiting the Magnetic Field of the L183 Starless Core. We present observations of linear polarization from dust thermal emission at 850 μm toward the starless cloud L183. These data were obtained at the James Clerk Maxwell Telescope (JCMT) using the SCUBA-2 camera in conjunction with its polarimeter POL-2. Polarized dust emission traces the plane-of-sky magnetic field structure in the cloud, thus allowing us to investigate the role of magnetic fields in the formation and evolution of its starless core. To interpret these measurements, we first calculate the dust temperature and column density in L183 by fitting the spectral energy distribution obtained by combining data from the JCMT and the Herschel space observatory. We used the Davis-Chandrasekhar-Fermi technique to measure the magnetic field strength in five subregions of the cloud, and we find values ranging from ∼120 ± 18 μG to ∼270 ± 64 μG in agreement with previous studies. Combined with an average hydrogen column density ( ${N}_{{{\rm{H}}}_{2}}$ ) of ∼1.5 × 1022 cm-2 in the cloud, we also find that all five subregions are magnetically subcritical. These results indicate that the magnetic field in L183 is sufficiently strong to oppose the gravitational collapse of the cloud.

Keywords: Starlight polarization, Magnetic fields, Interstellar medium
Secular Gravitational Instability of Drifting Dust in Protoplanetary Disks: Formation of Dusty Rings without Significant Gas Substructures. Secular gravitational instability (GI) is one promising mechanism for creating annular substructures and planetesimals in protoplanetary disks. We perform numerical simulations of secular GI in a radially extended disk with inwardly drifting dust grains. The results show that, even in the presence of dust diffusion, dust rings form via secular GI while the dust grains are moving inward, and the dust surface density increases by a factor of 10. Once secular GI develops into a nonlinear regime, the total mass of the resultant rings can be a significant fraction of the dust disk mass. In this way, a large amount of drifting dust grains can be collected in the dusty rings and stored for planetesimal formation. In contrast to the emergence of remarkable dust substructures, secular GI does not create significant gas substructures. This result indicates that observations of a gas density profile near the disk midplane enable us to distinguish the mechanisms for creating the annular substructures in the observed disks. The resultant rings start decaying once they enter the inner region stable to secular GI. Because the ring-gap contrast smoothly decreases, it seems possible that the rings are observed even in the stable region. We also discuss the likely outcome of the nonlinear growth and indicate the possibility that a significantly developed region of secular GI may appear as a gap-like substructure in dust continuum emission as dust growth into larger solid bodies and planetesimal formation reduce the total emissivity.

Keywords: Protoplanetary disks
A Census of Sub-kiloparsec Resolution Metallicity Gradients in Star-forming Galaxies at Cosmic Noon from HST Slitless Spectroscopy. We present the hitherto largest sample of gas-phase metallicity radial gradients measured at sub-kpc resolution in star-forming galaxies in the redshift range of z ∈ [1.2, 2.3]. These measurements are enabled by the synergy of slitless spectroscopy from the Hubble Space Telescope near-infrared channels and the lensing magnification from foreground galaxy clusters. Our sample consists of 76 galaxies with stellar mass ranging from 107 to 1010 ${M}_{\odot }$ , an instantaneous star formation rate in the range of [1, 100] ${M}_{\odot }$ yr-1, and global metallicity $[\tfrac{1}{12},2]$ of solar. At a 2σ confidence level, 15/76 galaxies in our sample show negative radial gradients, whereas 7/76 show inverted gradients. Combining ours and all other metallicity gradients obtained at a similar resolution currently available in the literature, we measure a negative mass dependence of Δlog(O/H)/ ${\rm{\Delta }}r\,[\mathrm{dex}\,{\mathrm{kpc}}^{-1}]$ = (-0.020 ± 0.007) + (-0.016 ± 0.008) $\mathrm{log}({M}_{* }/{10}^{9.4}\,{M}_{\odot })$ , with the intrinsic scatter being σ = 0.060 ± 0.006 over 4 orders of magnitude in stellar mass. Our result is consistent with strong feedback, not secular processes, being the primary governor of the chemostructural evolution of star-forming galaxies during the disk mass assembly at cosmic noon. We also find that the intrinsic scatter of metallicity gradients increases with decreasing stellar mass and increasing specific star formation rate. This increase in the intrinsic scatter is likely caused by the combined effect of cold-mode gas accretion and merger-induced starbursts, with the latter more predominant in the dwarf mass regime of ${M}_{* }\lesssim {10}^{9}\,{M}_{\odot }$ .

Keywords: Galaxy formation, Strong gravitational lensing, Dwarf galaxies, Galaxy abundances, Galaxy evolution, High-redshift galaxies
REQUIEM-2D Methodology: Spatially Resolved Stellar Populations of Massive Lensed Quiescent Galaxies from Hubble Space Telescope 2D Grism Spectroscopy. We present a novel Bayesian methodology to jointly model photometry and deep Hubble Space Telescope 2D grism spectroscopy of high-redshift galaxies. Our requiem2d code measures both unresolved and resolved stellar populations, ages, and star formation histories (SFHs) for the ongoing REsolving QUIEscent Magnified (REQUIEM) Galaxies Survey, which targets strong gravitationally lensed quiescent galaxies at z ∼ 2. We test the accuracy of requiem2d using a simulated sample of massive galaxies at z ∼ 2 from the Illustris cosmological simulation and find that we recover the general trends in SFH and median stellar ages. We further present a pilot study for the REQUIEM Galaxies Survey: MRG-S0851, a quintuply imaged, massive ( $\mathrm{log}{M}_{* }/{M}_{\odot }=11.02\pm 0.04$ ) red galaxy at z = 1.883 ± 0.001. With an estimated gravitational magnification of $\mu ={5.7}_{-0.2}^{+0.4}$ , we sample the stellar populations on 0.6 kpc physical size bins. The global mass-weighted median age is constrained to be ${1.8}_{-0.2}^{+0.3}$ Gyr, and our spatially resolved analysis reveals that MRG-S0851 has a flat age gradient in the inner 3 kpc core after taking into account the subtle effects of dust and metallicity on age measurements, favoring an early formation scenario. The analysis for the full REQUIEM-2D sample will be presented in a forthcoming paper with a beta release of the requiem2d code.

Keywords: Galaxy formation, Strong gravitational lensing, Galaxy stellar content, Galaxy quenching, High-redshift galaxies
A Stacking Search for Gamma-Ray Emission from Nearby Flare Stars and the Periodic Source TVLM 513-46546. So far, the Sun is the only isolated main-sequence star detected in gamma-rays, particularly during powerful flares. Young ultracool dwarfs are far more active so they are also plausible gamma-ray sources. We performed a spatial stack of 97 of the nearest X-ray and radio flare stars to search for GeV emission using nearly 12 yr of data from the Fermi Gamma-ray Space Telescope. The stacked residual maps showed no significant signal. Modeling the upper limits indicates a peak stellar flux at least a factor of 7 below the noise level. We also analyze the phase-folded light curve of the rapidly rotating radio star TVLM 513-46546, report a tentative (TS = 30) pulsed signal, and refine its period. We examine the possibility of a false-positive signal by analyzing nearby Fermi catalog sources and test fields, and by repeating the analysis using different periods. No other periodic signals are found, despite clear detections of the catalog sources, and the TS value for TVLM 513 increases systematically to the optimal period. The putative gamma-ray signal is nearly in phase with the optical peak, and out of phase with the radio pulses by 0.4 ± 0.05 rotations. These results argue for emission from relativistic protons streaming down flux tubes toward the photospheric active regions. The protons colliding with the atmosphere create neutral pions that decay into gamma-ray photons. This would be the first detection of a normal, isolated star in gamma-rays, and the strongest evidence yet for proton acceleration in stellar magnetospheres.

Keywords: Stellar flares
The Strength of the Dynamical Spiral Perturbation in the Galactic Disk. The mean Galactocentric radial velocities $\langle {v}_{R}\rangle (R,\varphi )$ of luminous red giant stars within the midplane of the Milky Way reveal a spiral signature, which could plausibly reflect the response to a nonaxisymmetric perturbation of the gravitational potential in the Galactic disk. We apply a simple steady-state toy model of a logarithmic spiral to interpret these observations, and find a good qualitative and quantitative match. Presuming that the amplitude of the gravitational potential perturbation is proportionate to that in the disk's surface mass density, we estimate the surface mass density amplitude to be ${{\rm{\Sigma }}}_{\max }({R}_{\odot })\approx 5.5\,{M}_{\odot }\,{\mathrm{pc}}^{-2}$ at the solar radius when choosing a fixed pattern speed of ${{\rm{\Omega }}}_{{\rm{p}}}=12\,\mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{kpc}}^{-1}$ . Combined with the local disk density, this implies a surface mass density contrast between the arm and inter-arm regions of approximately ±10% at the solar radius, with an increase toward larger radii. Our model constrains the pitch angle of the dynamical spiral arms to be approximately 12°.

Keywords: Stellar kinematics, Galaxy structure, Milky Way dynamics, Stellar parallax, Spiral arms, Milky Way disk, Spiral pitch angle, Stellar distance
Diffusive Hydrogenation Reactions of CO Embedded in Amorphous Solid Water at Elevated Temperatures ∼70 K. The surface processes on interstellar dust grains have an important role in the chemical evolution in molecular clouds. Hydrogenation reactions on ice surfaces have been extensively investigated and are known to proceed at low temperatures mostly below 20 K. In contrast, information about the chemical processes of molecules within an ice mantle is lacking. In this work, we investigated diffusive hydrogenation reactions of carbon monoxide (CO) embedded in amorphous solid water (ASW) as a model case and discovered that the hydrogenation of CO efficiently proceeds to yield H2CO and CH3OH even above 20 K when CO is buried beneath ASW. The experimental results suggest that hydrogen atoms diffuse through the cracks of ASW and have a sufficient residence time to react with embedded CO. The hydrogenation reactions occurred even at temperatures up to ∼70 K. Cracks collapse at elevated temperatures but the occurrence of hydrogenation reactions means that the cracks would not completely disappear and remain large enough for penetration by hydrogen atoms. Considering the hydrogen-atom fluence in the laboratory and molecular clouds, we suggest that the penetration of hydrogen and its reactions within the ice mantle occur in astrophysical environments.

Keywords: Interstellar molecules, Interstellar dust, Laboratory astrophysics, Molecular clouds, Dense interstellar clouds, Astrochemistry
Formation of Interstellar Complex Polycyclic Aromatic Hydrocarbons: Insights from Molecular Dynamics Simulations of Dehydrogenated Benzene. Small organic molecules are thought to provide building blocks for the formation of complex interstellar polycyclic aromatic hydrocarbons (PAHs). However, the underlying chemical mechanisms remain unclear, particularly concerning the role of interstellar dust. Using molecular dynamics, we simulate the chemical reaction between dehydrogenated benzene molecules in the gas phase or on the surface of an onion-like carbon nanoparticle (NP). The reaction leads to the formation of PAHs of complex structures. The size of the formed molecules is found to roughly increase with increasing temperature up to 800 K, and to be correlated with the level of dehydrogenation. Morphology analysis features the formation of large rings that contain up to 32 carbon atom at high temperature. Density functional theory (DFT) calculations are performed to search the fundamental energetic reaction pathways. The DFT results quantitatively confirm the correlation between the reactivity and the dehydrogenation level, and the formation of stable C-8 rings. Moreover, the nanostructures formed on the NP surface point to a possible layer-by-layer formation mechanism for interstellar fullerene and carbon onions.

Keywords: Interstellar molecules, Polycyclic aromatic hydrocarbons, Astrochemistry, Interstellar medium
X-Ray Observations of a [C II]-bright, z = 6.59 Quasar/Companion System. We present deep Chandra observations of PSO J231.6576-20.8335, a quasar at redshift z = 6.59 with a nearby (∼8 proper kpc) companion galaxy. The Atacama Large Millimeter/submillimeter Array observed both the quasar and companion to be bright in [C II], and the system has significant extended Lyα emission around the quasar, suggesting that a galaxy merger is ongoing. Unlike previous studies of two similar systems, and despite observing the system with Chandra for 140 ks, we do not detect the companion in X-rays. The quasar itself is detected, but only ${13.3}_{-3.7}^{+4.8}$ net counts are observed. From a basic spectral analysis, the X-ray spectrum of the quasar is soft (hardness ratio of ${ \mathcal H }{ \mathcal R }=-{0.60}_{-0.27}^{+0.17}$ , power-law index of ${\rm{\Gamma }}={2.6}_{-0.9}^{+1.0}$ ), which results in a rest-frame X-ray luminosity comparable to other bright quasars ( ${L}_{2\mbox{--}10}={1.09}_{-0.70}^{+2.20}\times {10}^{45}\ \mathrm{erg}\ {{\rm{s}}}^{-1}$ ) despite the faint observed X-ray flux. We highlight two possible interpretations of this result: the quasar has a steep value of Γ—potentially related to observed ongoing Eddington accretion—thereby pushing much of the emission out of our observed band, or the quasar has a more normal spectrum (Γ ∼ 2) but is therefore less X-ray luminous ( ${L}_{2\mbox{--}10}\sim 0.6\times {10}^{45}\ \mathrm{erg}\ {{\rm{s}}}^{-1}$ ).

Keywords: X-ray astronomy, Quasar-galaxy pairs, Quasars, X-ray quasars, Galaxy mergers