Sazuna/UAT_keywords huggingface dataset:
Laboratory Formation and Photochemistry of Fullerene/Anthracene Cluster Cations. Besides buckminsterfullerene (C60), other fullerenes and their derivatives may also reside in space. In this work, we study the formation and photodissociation processes of astronomically relevant fullerene/anthracene (C14H10) cluster cations in the gas phase. Experiments are carried out using a quadrupole ion trap in combination with time-of-flight mass spectrometry. The results show that fullerene (C60 and C70)/anthracene (i.e., [(C14H10) n C60]+ and [(C14H10) n C70]+), fullerene (C56 and C58)/anthracene (i.e., [(C14H10) n C56]+ and [(C14H10) n C58]+), and fullerene (C66 and C68)/anthracene (i.e., [(C14H10) n C66]+ and [(C14H10) n C68]+) cluster cations, are formed in the gas phase through an ion-molecule reaction pathway. With irradiation, all the fullerene/anthracene cluster cations dissociate into monoanthracene and fullerene species without dehydrogenation. The structure of newly formed fullerene/anthracene cluster cations and the bonding energy for these reaction pathways are investigated with quantum chemistry calculations. Our results provide a growth route toward large fullerene derivatives in a bottom-up process and insight into their photoevolution behavior in the interstellar medium, and clearly, when conditions are favorable, fullerene/polycyclic aromatic hydrocarbon clusters can form efficiently. In addition, these clusters (from 80 to 154 atoms or ∼2 nm in size) offer a good model for understanding the physical-chemical processes involved in the formation and evolution of carbon dust grains in space, and provide candidates of interest for the diffuse interstellar bands that could motivate spectroscopic studies.

Keywords: Interstellar molecules, Laboratory astrophysics, Experimental techniques, Astrochemistry, Interstellar medium, Interstellar dust processes
Observation of All Pre- and Post-reconnection Structures Involved in Three-dimensional Reconnection Geometries in Solar Eruptions. We report on observations of the two newly identified reconnection geometries involving erupting flux ropes. In 3D, a flux rope can reconnect either with a surrounding coronal arcade (recently named “ar-rf” reconnection) or with itself (“rr-rf” reconnection), and both kinds of reconnection create a new flux-rope field line and a flare loop. For the first time, we identify all four constituents of both reconnections in a solar eruptive event, the filament eruption of 2011 June 7 observed by Solar Dynamics Observatory/Atmospheric Imaging Assembly. The ar-rf reconnection manifests itself as shift of one leg of the filament by more than 25″ northward. At its previous location, a flare arcade is formed, while the new location of the filament leg previously corresponded to a footpoint of a coronal loop in 171 Å. In addition, the evolution of the flare ribbon hooks is also consistent with the occurrence of ar-rf reconnection as predicted by MHD simulations. Specifically, the growing hook sweeps footpoints of preeruptive coronal arcades, and these locations become inside the hook. Furthermore, the rr-rf reconnection occurs during the peak phase above the flare arcade, in an apparently X-type geometry involving a pair of converging bright filament strands in the erupting filament. A new flare loop forms near the leg of one of the strands, while a bright blob, representing a remnant of the same strand, is seen ascending into the erupting filament. All together, these observations vindicate recent predictions of the 3D standard solar-flare model.

Keywords: Solar flares, Solar magnetic reconnection, Solar extreme ultraviolet emission, Solar coronal loops, Solar corona, Solar coronal mass ejections, Solar x-ray flares, Solar filament eruptions, Magnetohydrodynamical simulations
Pulsational Pair-instability Supernovae. I. Pre-collapse Evolution and Pulsational Mass Ejection. We calculate the evolution of massive stars, which undergo pulsational pair-instability (PPI) when the O-rich core is formed. The evolution from the main sequence through the onset of PPI is calculated for stars with initial masses of 80-140 M ⊙ and metallicities of Z = 10-3-1.0 Z ⊙. Because of mass loss, Z ≤ 0.5 Z ⊙ is necessary for stars to form He cores massive enough (i.e., mass &gt;40 M ⊙) to undergo PPI. The hydrodynamical phase of evolution from PPI through the beginning of Fe-core collapse is calculated for He cores with masses of 40-62 M ⊙ and Z = 0. During PPI, electron-positron pair production causes a rapid contraction of the O-rich core, which triggers explosive O-burning and a pulsation of the core. We study the mass dependence of the pulsation dynamics, thermodynamics, and nucleosynthesis. The pulsations are stronger for more massive He cores and result in a large amount of mass ejection such as 3-13 M ⊙ for 40-62 M ⊙ He cores. These He cores eventually undergo Fe-core collapse. The 64 M ⊙ He core undergoes complete disruption and becomes a pair-instability supernova. The H-free circumstellar matter ejected around these He cores is massive enough to explain the observed light curve of Type I (H-free) superluminous supernovae with circumstellar interaction. We also note that the mass ejection sets the maximum mass of black holes (BHs) to be ∼50 M ⊙, which is consistent with the masses of BHs recently detected by VIRGO and aLIGO.

Keywords: Massive stars, Black holes, Circumstellar masers, Stellar mass loss
A Data-driven Model of Nucleosynthesis with Chemical Tagging in a Lower-dimensional Latent Space. Chemical tagging seeks to identify unique star formation sites from present-day stellar abundances. Previous techniques have treated each abundance dimension as being statistically independent, despite theoretical expectations that many elements can be produced by more than one nucleosynthetic process. In this work, we introduce a data-driven model of nucleosynthesis, where a set of latent factors (e.g., nucleosynthetic yields) contribute to all stars with different scores and clustering (e.g., chemical tagging) is modeled by a mixture of multivariate Gaussians in a lower-dimensional latent space. We use an exact method to simultaneously estimate the factor scores for each star, the partial assignment of each star to each cluster, and the latent factors common to all stars, even in the presence of missing data entries. We use an information-theoretic Bayesian principle to estimate the number of latent factors and clusters. Using the second Galah data release, we find that six latent factors are preferred to explain N = 2566 stars with 17 chemical abundances. We identify the rapid- and slow neutron-capture processes, as well as latent factors consistent with Fe-peak and α-element production, and another where K and Zn dominate. When we consider N ∼ 160,000 stars with missing abundances, we find another seven factors, as well as 16 components in latent space. Despite these components showing separation in chemistry, which is explained through different yield contributions, none show significant structure in their positions or motions. We argue that more data and joint priors on cluster membership that are constrained by dynamical models are necessary to realize chemical tagging at a galactic-scale. We release accompanying software that scales well with the available data, allowing for the model’s parameters to be optimized in seconds given a fixed number of latent factors, components, and ∼107 abundance measurements.

Keywords: Bayesian statistics, Chemical abundances, Galaxy chemical evolution
ALMA Reveals a Gas-rich, Maximum Starburst in the Hyperluminous, Dust-obscured Quasar W0533-3401 at z ∼ 2.9. We present ALMA observations and multiwavelength spectral energy distribution analysis in a Wide-field Infrared Survey Explorer-selected, hyperluminous dust-obscured quasar W0533-3401 at z = 2.9. We derive the physical properties of each of its components, such as molecular gas, stars, dust, and the central supermassive black hole (SMBH). Both the dust continuum at 3 mm and the CO (3{--}2) line are detected. The derived molecular gas mass M gas = 8.4 × 1010 M ⊙ and its fraction f gas = 0.7 suggest that W0533-3401 is gas-rich. The star formation rate (SFR) has been estimated to be ∼3000-7000 M ⊙ yr-1 by using different methods. The high values of SFR and specific SFR suggest that W0533-3401 is a maximum starburst. The corresponding gas depletion timescales are very short (t depl ∼ 12-28 Myr). The CO (3{--}2) emission line is marginally resolved and has a velocity gradient, which is possibly due to a rotating gas disk, gas outflow, or merger. Finally, we infer the black hole mass growth rate of W0533-3401 ({\dot{M}}BH}=49 M ⊙ yr-1), which suggests a rapid growth of the central SMBH. The observed black hole to stellar mass ratio M BH/M ⋆ of W0533-3401, which is dependent on the adopted Eddington ratio, is over one order of magnitude higher than the local value, and is evolving toward the evolutionary trend of unobscured quasars. Our results are consistent with the scenario that W0533-3401, with both a gas-rich maximum starburst and a rapid black hole growth, is experiencing a short transition phase toward an unobscured quasar.

Keywords: Starburst galaxies, Quasars, Active galaxies, Galaxy evolution, High-redshift galaxies
Supernova 2014C: Ongoing Interaction with Extended Circumstellar Material with Silicate Dust. Supernova (SN) 2014C is unique: a seemingly typical hydrogen-poor SN that started to interact with a dense, hydrogen-rich circumstellar medium (CSM) ∼100 days post-explosion. The delayed interaction suggests a detached CSM shell, unlike in a typical SN IIn where the CSM is much closer and the interaction commences earlier post-explosion, indicating a different mass-loss history. We present infrared observations of SN 2014C 1-5 yr post-explosion, including uncommon 9.7 μm imaging with COMICS on the Subaru telescope. Spectroscopy shows the intermediate-width He I 1.083 μm emission from the interacting region up to the latest epoch 1639 days post-explosion. The last Spitzer/IRAC photometry at 1920 days confirms ongoing CSM interaction. The 1-10 μm spectral energy distributions (SEDs) can be explained by a dust model with a mixture of 62% carbonaceous and 38% silicate dust, pointing to a chemically inhomogeneous CSM. The inference of silicate dust is the first among interacting SNe. An SED model with purely carbonaceous CSM dust, while possible, requires more than 0.22 M ☉ of dust, an order of magnitude larger than what has been observed in any SNe at this epoch. The light curve beyond 500 days is well fit by an interaction model with a wind-driven CSM and a mass-loss rate of ∼10-3 M ☉ yr-1, which presents an additional CSM density component exterior to the constant-density shell reported previously in the literature. SN 2014C could originate in a binary system, similar to RY Scuti, which would explain the observed chemical and density profile inhomogeneity in the CSM.

Keywords: Core-collapse supernovae, Stellar mass loss
Precise Mass Determination of SPT-CL J2106-5844, the Most Massive Cluster at z &gt; 1. We present a detailed high-resolution weak-lensing study of SPT-CL J2106-5844 at z = 1.132, claimed to be the most massive system discovered at z &gt; 1 in the South Pole Telescope Sunyaev-Zel’dovich survey. Based on the deep imaging data from the Advanced Camera for Surveys and Wide Field Camera 3 on board the Hubble Space Telescope, we find that the cluster mass distribution is asymmetric, composed of a main clump and a subclump ∼640 kpc west thereof. The central clump is further resolved into two smaller northwestern and southeastern substructures separated by ∼150 kpc. We show that this rather complex mass distribution is more consistent with the cluster galaxy distribution than a unimodal distribution as previously presented. The northwestern substructure coincides with the brightest cluster galaxy and the X-ray peak while the southeastern one agrees with the location of the peak in number density. These morphological features and the comparison with the X-ray emission suggest that the cluster might be a merging system. We estimate the virial mass of the cluster to be {M}200c=({10.4}-3.0+3.3+/- 1.0)× {10}14 {M}⊙ , where the second error bar is the systematic uncertainty. Our result confirms that the cluster SPT-CL J2106-5844 is indeed the most massive cluster at z &gt; 1 known to date. We demonstrate the robustness of this mass estimate by performing a number of tests with different assumptions on the centroids, mass-concentration relations, and sample variance.

Keywords: Weak gravitational lensing, Galaxy clusters, High-redshift galaxy clusters, Gravitational lensing, Dark matter
Modeling Energetic Particle Acceleration and Transport in a Solar Wind Region with Contracting and Reconnecting Small-scale Flux Ropes at Earth Orbit. New analytical steady-state and time-dependent solutions for the acceleration of energetic particles by contracting and reconnecting small-scale flux ropes (SMFRs) in the solar wind are presented. For this purpose, a telegrapher-type Parker transport equation was derived from the existing underlying focused transport equation. The solutions unify all SMFR acceleration mechanisms present in the transport equation, showing that SMFR acceleration by the reconnection electric field in the mixed-derivative transport term is constrained by and requires the presence of second-order Fermi SMFR acceleration. We explore the potential of these solutions in reproducing energetic proton flux enhancements and spectral evolution between ∼50 keV and 5 MeV in dynamic SMFR regions near large-scale reconnecting current sheets in the solar wind at Earth orbit. It is shown that second-order Fermi SMFR acceleration involving the variance in SMFR compression and incompressible parallel shear flow and confirmed that first-order SMFR Fermi acceleration, due to mean SMFR compression (successfully used before in data fits), are both workable options in reproducing observed flux amplification factors when using reasonable SMFR parameters. However, the predicted substantial quantitative differences in the spatial evolution of the accelerated spectra through the SMFR region might provide a way to distinguish between first- and second-order Fermi SMFR acceleration in observations. It is concluded that more detailed data analysis of SMFR parameters in SMFR acceleration events is needed before the relative role of first- and second-order SMFR acceleration mechanisms can be determined.

Keywords: Solar energetic particles, Solar magnetic fields, Solar wind, Solar magnetic reconnection
Nature and Origins of Rich Complexes of C IV Associated Absorption Lines. Rich complexes of associated absorption lines (AALs) in quasar spectra provide unique information about gaseous infall, outflows, and feedback processes in quasar environments. We study five quasars at redshifts z ~ 3.1-4.4 with AAL complexes containing from 7 to 18 C IV λ1548, 1551 systems in high-resolution spectra. These complexes span velocity ranges ≲3600 km s-1 within ≲8200 km s-1 of the quasar redshifts. All are highly ionized with no measurable low-ionization ions like Si II or C II, and all appear to form in the quasar/host galaxy environments based on evidence for line locking, partial covering of the background light source, strong N V absorption, and/or roughly solar metallicities, and on the implausibility of such complexes forming in unrelated intervening galaxies. Most of the lines in all five complexes identify high-speed quasar-driven outflows at velocity shifts v≲ -1000 km s-1. Four of the complexes also have lines at smaller blueshifted velocities that might form in ambient interstellar clouds, low-speed outflows, or at feedback interfaces in the host galaxies where high-speed winds impact and shred interstellar clouds. The partial covering we measure in some of the high-speed outflow lines require small absorbing clouds with characteristic sizes ≲1 pc or ≲0.01 pc. The short survival times of these clouds require locations very close to the quasars, or cloud creation in situ at larger distances perhaps via feedback/cloud-shredding processes. The AAL complex in one quasar, J1008+3623, includes unusually narrow C IV systems at redshifted velocities 350≲ v≲ 640 km s-1 that are excellent candidates for gaseous infall toward the quasar, e.g., “cold-mode” accretion or a gravitationally bound galactic fountain.

Keywords: Galaxy evolution, Quasar absorption line spectroscopy, Quasars
The Interaction between the Supernova Remnant W41 and the Filamentary Infrared Dark Cloud G23.33-0.30. G23.33-0.30 is a 600 M ⊙ infrared dark molecular filament that exhibits large NH3 velocity dispersions (σ ∼ 8 km s-1) and bright, narrow NH3(3, 3) line emission. We have probed G23.33-0.30 at the &lt; 0.1 pc scale and confirmed that the narrow NH3(3, 3) line is emitted by four rare NH3(3, 3) masers, which are excited by a large-scale shock impacting the filament. G23.33-0.30 also displays a velocity gradient along its length, a velocity discontinuity across its width, shock-tracing SiO(5-4) emission extended throughout the filament, and broad turbulent line widths in NH3(1, 1) through (6, 6), CS(5-4), and SiO(5-4), as well as an increased NH3 rotational temperature (T rot) and velocity dispersion (σ) associated with the shocked, blueshifted component. The correlations among T rot, σ, and V LSR imply that the shock is accelerating, heating, and adding turbulent energy to the filament gas. Given G23.33-0.30's location within the giant molecular cloud G23.0-0.4, we speculate that the shock and NH3(3, 3) masers originated from the supernova remnant (SNR) W41, which exhibits additional evidence of an interaction with G23.0-0.4. We have also detected the 1.3 mm dust continuum emission from at least three embedded molecular cores associated with G23.33-0.30. Although the cores have moderate gas masses (M = 7-10 M ⊙), their large virial parameters (α = 4-9) suggest that they will not collapse to form stars. The turbulent line widths of the (α &gt; 1) cores may indicate negative feedback due to the SNR shock.

Keywords: Supernova remnants, Infrared dark clouds
Mapping Metallicity Variations across Nearby Galaxy Disks. The distribution of metals within a galaxy traces the baryon cycle and the buildup of galactic disks, but the detailed gas phase metallicity distribution remains poorly sampled. We have determined the gas phase oxygen abundances for 7138 H II regions across the disks of eight nearby galaxies using Very Large Telescope/Multi Unit Spectroscopic Explorer (MUSE) optical integral field spectroscopy as part of the PHANGS-MUSE survey. After removing the first-order radial gradients present in each galaxy, we look at the statistics of the metallicity offset (∆O/H) and explore azimuthal variations. Across each galaxy, we find low (σ = 0.03-0.05 dex) scatter at any given radius, indicative of efficient mixing. We compare physical parameters for those H II regions that are 1σ outliers toward both enhanced and reduced abundances. Regions with enhanced abundances have high ionization parameter, higher Hα luminosity, lower Hα velocity dispersion, younger star clusters, and associated molecular gas clouds showing higher molecular gas densities. This indicates recent star formation has locally enriched the material. Regions with reduced abundances show increased Hα velocity dispersions, suggestive of mixing introducing more pristine material. We observe subtle azimuthal variations in half of the sample, but cannot always cleanly associate this with the spiral pattern. Regions with enhanced and reduced abundances are found distributed throughout the disk, and in half of our galaxies we can identify subsections of spiral arms with clearly associated metallicity gradients. This suggests spiral arms play a role in organizing and mixing the interstellar medium.

Keywords: Spiral galaxies, Disk galaxies, Chemical abundances, Galaxy abundances, H II regions, Metallicity
A Hybrid Approach Toward Simulating Reionization: Coupling Ray Tracing with Excursion Sets. This paper introduces a new method of generating 21 cm maps that is based on ideas from ray tracing and excursion sets. In this method, photons generated in each grid cell are computed using the excursion set ideas while their propagation is accounted for by ray tracing. The method requires the overdensity field over a grid as a starting point. Then the usual reionization parameters, minimum mass of collapsed halos (M min), number of ionizing photons deposited in the intergalactic medium per collapsed baryon (n ion), and ratio of ionization rate to recombination rate (represented through n rec) are used. Thus, this is a hybrid method that utilizes the results of theoretically motivated excursion sets and combines them with the computationally intensive procedure of ray tracing. As the method integrates simple principles of both the approaches, it is expected to yield precise and fast estimates of the power spectrum on the scales of interest (0.1 Mpc-1 ≲ k ≲ 1.0 Mpc-1).

Keywords: Cosmology, Cosmological models, Large-scale structure of the universe
Stellar Pulsation and the Production of Dust and Molecules in Galactic Carbon Stars. New infrared spectra of 33 Galactic carbon stars from FORCAST on SOFIA reveal strong connections between stellar pulsations and the dust and molecular chemistry in their circumstellar shells. A sharp boundary in overall dust content, which predominantly measures the amount of amorphous carbon, separates the semiregular and Mira variables, with the semiregulars showing little dust in their spectra and the Miras showing more. In semiregulars, the contribution from SiC dust increases rapidly as the overall dust content grows, but in Miras, the SiC dust feature grows weaker as more dust is added. A similar dichotomy is found with the absorption band from CS at ∼7.3 μm, which is generally limited to semiregular variables. Observationally, these differences make it straightforward to distinguish semiregular and Mira variables spectroscopically without the need for long-term photometric observations or knowledge of their distances. The rapid onset of strong SiC emission in Galactic carbon stars in semiregular variables points to a different dust-condensation process before strong pulsations take over. The break in the production of amorphous carbon between semiregulars and Miras seen in the Galactic sample is also evident in Magellanic carbon stars, linking strong pulsations in carbon stars to the strong mass-loss rates which will end their lives as stars across a wide range of metallicities.

Keywords: Circumstellar matter, Carbon stars, Long period variable stars, Spectroscopy