Sazuna/UAT_keywords huggingface dataset:
Experimental and Computational Studies on the Physicochemical Behavior of Phosphine Induced by Reactions with H and D Atoms on Interstellar Ice Grains. Phosphine (PH3) is an important molecule in the chemistry of phosphorus (P)-bearing species in the interstellar medium. Interstellar PH3 is thought to primarily form on icy grains, where several surface processes may occur during and after its formation. To better understand the physicochemical behavior of PH3 on icy grains in dense molecular clouds, we performed experimental and computational studies on the reactions of phosphine with H and D atoms at low temperatures. We found that phosphine and its deuterated isotopologue PD3 are released into the gas phase from icy surfaces (porous amorphous, compact amorphous, and crystalline ice) via chemical desorption. Even though the effective desorption cross section did not vary between the different icy surfaces, the desorption fraction was smallest for porous amorphous ice. We confirmed that, at 10 K on icy surfaces, H-D substitution reactions of PH3 and D-H substitution reactions of PD3 occurred following reactions with D and H atoms, respectively. Because the activation barrier for the abstraction of H or D atoms from phosphine is ~1500 K, quantum tunneling should play a role at low temperatures. Under the present experimental conditions, the H-D substitution reaction of PH3 was slightly slower than the D-H substitution reaction of PD3. Therefore, the rates of the H-D and D-H substitution reactions should not be constrained by tunneling reactions but rather by other elementary processes such as atom diffusion on ice. Our experimental results suggest the possible presence of a deuterated phosphine isotopologue (PH2D) in PH3-rich interstellar environments.

Keywords: Pre-biotic astrochemistry, Interstellar dust processes, Dense interstellar clouds, Astrochemistry
A Blueprint for the Milky Way's Stellar Populations. III. Spatial Distributions and Population Fractions of Local Halo Stars. We analyze the observed spatial, chemical and dynamical distributions of local metal-poor stars, based on photometrically derived metallicity and distance estimates along with proper motions from the Gaia mission. Along the Galactic prime meridian, we identify stellar populations with distinct properties in the metallicity versus rotational velocity space, including Gaia Sausage/Enceladus (GSE), the metal-weak thick disk (MWTD), and the Splash (sometimes referred to as the "in situ" halo). We model the observed phase-space distributions using Gaussian mixtures and refine their positions and fractional contributions as a function of distances from the Galactic plane ( $| Z| $ ) and the Galactic center ( ${R}_{\mathrm{GC}}$ ), providing a global perspective of the major stellar populations in the local halo. Within the sample volume ( $| Z| \lt 6\,\mathrm{kpc}$ ), stars associated with GSE exhibit a larger proportion of metal-poor stars at greater ${R}_{\mathrm{GC}}$ ( ${\rm{\Delta }}\langle [\mathrm{Fe}/{\rm{H}}]\rangle /{\rm{\Delta }}{R}_{\mathrm{GC}}=-0.05\pm 0.02\,\mathrm{dex}\,{\mathrm{kpc}}^{-1}$ ). This observed trend, along with a mild anticorrelation of the mean rotational velocity with metallicity ( ${\rm{\Delta }}\langle {v}_{\phi }\rangle /{\rm{\Delta }}\langle [\mathrm{Fe}/{\rm{H}}]\rangle \sim -10\ \mathrm{km}\,{{\rm{s}}}^{-1}\,{\mathrm{dex}}^{-1}$ ), implies that more metal-rich stars in the inner region of the GSE progenitor were gradually stripped away, while the prograde orbit of the merger at infall became radialized by dynamical friction. The metal-rich GSE stars are causally disconnected from the Splash structure, whose stars are mostly found on prograde orbits (≳94%) and exhibit a more centrally concentrated distribution than GSE. The MWTD exhibits a similar spatial distribution to the Splash, suggesting earlier dynamical heating of stars in the primordial disk of the Milky Way, possibly before the GSE merger.

Keywords: Milky Way formation, Stellar populations, Stellar abundances, Milky Way dynamics, Milky Way stellar halo, Milky Way evolution, Milky Way Galaxy
Numerical Models of Externally Irradiated Herbig-Haro Objects. We use 3D radiation-hydrodynamic simulations to study the effects of an external photoionization source on the structure of a Herbig-Haro (HH) jet launched from a young stellar object. Different ionizing photon rates are considered as well as a time-dependent ejection velocity and density. From our numerical results, synthetic Hα emission maps are computed in order to study how the external ionizing source affects the observed morphology of the jet and counterjet. We find that, as expected, the outflow has jet/counterjet and side-to-side asymmetries (with brighter Hα emission toward the external photoionizing source). We find that, for a variable ejection velocity, jet morphologies similar to different observed externally irradiated jets can be straightforwardly obtained. Models of jets with a variable ejection density (and constant outflow velocity) produce morphologies that are not seen in observed HH jets and are, therefore, not justified by the presently available observations.

Keywords: Herbig-Haro objects, Computational methods, Stellar jets, Interstellar medium
Toward a More Complex Understanding of Natal Super Star Clusters with Multiwavelength Observations. Henize 2-10 (He 2-10) is a nearby (D = 9 Mpc) starbursting blue compact dwarf galaxy that boasts a high star formation rate and a low-luminosity active galactic nucleus. He 2-10 is also one of the first galaxies in which embedded super star clusters (SSCs) were discovered. SSCs are massive, compact star clusters that will impact their host galaxies dramatically when their massive stars evolve. Here, we discuss radio, submillimeter, and infrared observations of He 2-10 from 1.87 μm to 6 cm in high angular resolution (~0.3″), which allows us to disentangle individual clusters from aggregate complexes as identified at lower resolution. These results indicate the importance of spatial resolution to characterize SSCs, as low resolution studies of SSCs average over aggregate complexes that may host SSCs at different stages of evolution. We explore the thermal, nonthermal, and dust emission associated with the clusters along with dense molecular tracers to construct a holistic review of the natal SSCs that have yet to dramatically disrupt their parent molecular clouds. We assess the production rate of ionizing photons, extinction, total mass, and the star formation efficiency (SFE) associated with the clusters. Notably, we find that the SFE for the some of the natal clusters is high (&gt;70%), which suggests that these clusters could remain bound even after the gas is dispersed from the system from stellar feedback mechanisms. If they remain bound, these SSCs could survive to become objects indistinguishable from globular clusters.

Keywords: Blue compact dwarf galaxies, Star formation, Interstellar medium, H II regions, Galaxies, Star clusters
How Negative Energy and Kelvin-Helmholtz Instabilities Grow by Longitudinal Waves in Solar Atmospheric Jets. We model the propagation of slow magnetoacoustic body waves in solar jets in the course of negative energy wave excitation in the context of magnetohydrodynamic theory. Explicit approximate expressions are provided for the dispersion relation of slow body waves, providing insight into the influence of the steady flow speed, radiative cooling, and plasma-β at a glance. Analytic expressions are provided regarding critical speeds in the presence of backward waves, negative energy wave speeds, and instabilities. The buildup of the Kelvin-Helmholtz instability above the negative energy wave instability is expressed through analytic expressions that provide insight into the interplay of equilibrium conditions and dispersive effects as they affect the instability growth rate of slow body waves at various altitudes. As slow magnetoacoustic waves propagate with the same speed in the long-wavelength limit, slow body kink waves experience stronger dispersion than sausage waves. Backward waves are also probable at lower steady flow speeds for medium wavelengths when the jet hosts slow body kink waves that provide greater domains for dissipative processes. Slow body sausage waves grow faster while nearing the long-wavelength limit, while the internal plasma-β decreases the instability growth rate. The seismological aspect is that energy transfer to the external medium is observed on various timescales. The observational aspect is that slow body kink waves may exist at higher altitudes as energy has already been extracted to the external medium due to negative energy unstable slow body sausage waves in earlier stages contributing toward coronal heating.

Keywords: Magnetohydrodynamics, Solar coronal waves, Magnetic fields
Search for Neutrinos in Coincidence with Gravitational Wave Events from the LIGO-Virgo O3a Observing Run with the Super-Kamiokande Detector. The Super-Kamiokande detector can be used to search for neutrinos in time coincidence with gravitational waves detected by the LIGO-Virgo Collaboration (LVC). Both low-energy (7-100 MeV) and high-energy (0.1-105 GeV) samples were analyzed in order to cover a very wide neutrino spectrum. Follow-ups of 36 (out of 39) gravitational waves reported in the GWTC-2 catalog were examined; no significant excess above the background was observed, with 10 (24) observed neutrinos compared with 4.8 (25.0) expected events in the high-energy (low-energy) samples. A statistical approach was used to compute the significance of potential coincidences. For each observation, p-values were estimated using neutrino direction and LVC sky map; the most significant event (GW190602_175927) is associated with a post-trial p-value of 7.8% (1.4σ). Additionally, flux limits were computed independently for each sample and by combining the samples. The energy emitted as neutrinos by the identified gravitational wave sources was constrained, both for given flavors and for all flavors assuming equipartition between the different flavors, independently for each trigger and by combining sources of the same nature.

Keywords: Neutron stars, Black holes, High energy astrophysics, Neutrino astronomy, Transient sources, Gravitational wave astronomy, Compact objects
Prior Probability Distributions of Neutron Star Crust Models. To make best use of multifaceted astronomical and nuclear data sets, probability distributions of neutron star models that can be used to propagate errors consistently from one domain to another are required. We take steps toward a consistent model for this purpose, highlight where model inconsistencies occur, and assess the resulting model uncertainty. Using two distributions of nuclear symmetry energy parameters-one uniform, the other based on pure neutron matter theory-we prepare two ensembles of neutron star inner crust models. We use an extended Skyrme energy density functional within a compressible liquid drop model (CLDM). We fit the surface parameters of the CLDM to quantum 3D Hartree-Fock calculations of crustal nuclei. All models predict that more than 50% of the crust by mass and 15% of the crust by thickness comprises pasta with medians of around 62% and 30%, respectively. We also present 68% and 95% ranges for the crust composition as a function of density. We examine the relationships between crust-core boundary and pasta transition properties, the thickness of the pasta layers, the symmetry energy at saturation and subsaturation densities, and the neutron skins of 208Pb and 48Ca. We quantify the correlations using the maximal information coefficient, which can effectively characterize nonlinear relationships. Future measurements of neutron skins, information from nuclear masses and giant resonances, and theoretical constraints on PNM will be able to place constraints on the location of the pasta and crust-core boundaries and the amount of pasta in the crust.

Keywords: Neutron stars, Nuclear astrophysics, Pulsars
Search for Long-duration Gravitational-wave Signals Associated with Magnetar Giant Flares. Magnetar giant flares are rare and highly energetic phenomena observed in the transient sky whose emission mechanisms are still not fully understood. Depending on the nature of the excited modes of the magnetar, they are also expected to emit gravitational waves (GWs), which may bring unique information about the dynamics of the excitation. A few magnetar giant flares have been proposed to be associated with short gamma-ray bursts. In this paper we use a new gravitational-wave search algorithm to revisit the possible emission of GWs from four magnetar giant flares within 5 Mpc. While no gravitational-wave signals were observed, we discuss the future prospects of detecting signals with more sensitive gravitational-wave detectors. In particular, we show that galactic magnetar giant flares that emit at least 1% of their electromagnetic energy as GWs could be detected during the planned observing run of the LIGO and Virgo detectors at design sensitivity, with even better prospects for third-generation detectors.

Keywords: Magnetars, Gamma-ray bursts, Gravitational waves
Gas-phase Formation of Cationic Fullerene/Amino Acid Clusters: Evidence for the "Magic Number" Chemical Reactivity of Fullerene Cations. An experimental and theoretical investigation on the chemical reactivity of fullerene cations (Cn+, n = [36, 60]) with amino acid molecules (e.g., isoleucine, C6H13NO2) is performed. The results show that, in the gas phase, fullerene cations can react with amino acid molecules to form fullerene/amino acid cluster cations with high efficiency. The formation rate constants for the ion-molecule collision reactions between fullerene cations and isoleucine are estimated under the pseudo-first-order reaction condition. We find the formation rate constants increase gradually with a declining C-atom number of fullerene cations (Cn+, n = [46, 60]), and depict a plateau in the reactivity for smaller fullerene cations (Cn+, n = [36, 44]). More importantly, by comparing to its neighbor fullerenes, the magic number of C-atom counts (54, 58) that process with enhanced chemical reactivity are determined. We also obtained the molecular structures and binding energies for the fullerene-monoisoleucine adducts by quantum chemical calculations, which give a good explanation for the magic number chemical reactivity and the enhanced chemical reactivity of smaller fullerene cations. We infer that our results demonstrate the importance of ion-molecule reactions to the formation of large and complex fullerene-amino acid derivatives in the ISM. The high reactivity of fullerene species may indicate that amino acid molecules or other related prebiotic compounds can accrete on small interstellar carbon dust grains.

Keywords: Polycyclic aromatic hydrocarbons, Astrochemistry, Molecular physics, Interstellar medium, Interstellar dust processes
KMTNet Nearby Galaxy Survey. III. Deficient Hα Flux in the Extended Disks of Spiral Galaxies. We perform a deep, wide-field imaging survey of nearby galaxies using Hα and broadband filters to investigate the characteristics of star formation in galaxies. Motivated by the finding that star formation rates (SFRs) derived from Hα fluxes in dwarf galaxies are systematically lower than those inferred from far-ultraviolet (FUV) fluxes, we attempt to determine whether the same trend exists in the extended disks of two star-forming galaxies. We perform spatially resolved photometry using grid-shaped apertures to measure the FUV and Hα fluxes of star-forming regions. We also perform spectral energy distribution (SED) fittings using 11 photometric data points (FUV-to-MIR), including data from the literature, to estimate the local properties such as internal attenuation of individual star-forming clumps. Comparing SFRFUV and SFRHα, which are converted from the Hα and FUV fluxes corrected for the local properties, we find that SFRHα/SFRFUV tend to decrease as the SFR decreases. We evaluate possible causes of this discrepancy between the two SFRs by restricting parameters in the SED fitting and conclude that deficient Hα fluxes in the extended disks of galaxies are tightly correlated with recent starbursts. The strong and short starburst, which has been rapidly suppressed over the last 10 Myr, seems to induce a significant discrepancy between the SFRHα and SFRFUV. In addition, the recent bursts in the extended disks of galaxies appear to have occurred azimuth-symmetrically, implying that these were likely triggered by gas accretion or internal processes rather than external perturbation.

Keywords: Galaxy properties, Photometry, Star formation, Galaxies
The Hot Circumgalactic Medium of the Milky Way: Evidence for Supervirial, Virial, and Subvirial Temperatures; Nonsolar Chemical Composition; and Nonthermal Line Broadening. For the first time, we present the simultaneous detection and characterization of three distinct phases at &gt;105 K in z = 0 absorption using deep Chandra observations toward Mrk 421. The extraordinarily high signal-to-noise ratio (≥60) of the spectra has allowed us to detect a hot phase of the Milky Way circumgalactic medium (CGM) at ${3.2}_{-0.5}^{+1.5}\times $ 107 K coexisting with a warm-hot phase at 1.5 ± 0.1 × 106 K and a warm phase at 3.0 ± 0.4 × 105 K. The warm-hot phase is at the virial temperature of the Galaxy, and the warm phase may have cooled from the warm-hot phase, but the supervirial hot phase remains a mystery. We find that [C/O] in the warm and warm-hot phases, [Mg/O] in the warm-hot phase, and [Ne/O] in the hot phase are supersolar, and the hot and the warm-hot phases are α-enhanced. Nonthermal line broadening is evident in the warm-hot and the hot phases, and it dominates the total line broadening. Our results indicate that the &gt;105 K CGM is a complex ecosystem. It provides insights on the thermal and chemical history of the Milky Way CGM and theories of galaxy evolution.

Keywords: X-ray astronomy, Galaxy formation, Milky Way formation, Galaxy chemical evolution, Quasar absorption line spectroscopy, Hot ionized medium, Milky Way Galaxy physics, Interstellar absorption, Galaxy evolution, Circumgalactic medium, Milky Way evolution, Milky Way Galaxy
The SAMI Galaxy Survey: Detection of Environmental Dependence of Galaxy Spin in Observations and Simulations Using Marked Correlation Functions. The existence of a kinematic morphology-density relation remains uncertain, and instead stellar mass appears the more dominant driver of galaxy kinematics. We investigate the dependence of the stellar spin parameter proxy ${\lambda }_{{R}_{e}}$ on environment using a marked cross-correlation method with data from the Sydney Australian Astronomical Observatory Multi-object Integral-field Spectrograph (SAMI) Galaxy Survey. Our sample contains 710 galaxies with spatially resolved stellar velocity and velocity dispersion measurements. By utilizing the highly complete spectroscopic data from the Galaxy and Mass Assembly Survey, we calculate marked cross-correlation functions for SAMI galaxies using a pair count estimator and marks based on stellar mass and ${\lambda }_{{R}_{e}}$ . We detect an anticorrelation of stellar kinematics with environment at the 3.2σ level, such that galaxies with low ${\lambda }_{{R}_{e}}$ values are preferably located in denser galaxy environments. However, a significant correlation between stellar mass and environment is also found (correlation at 2.4σ), as found in previous works. We compare these results to mock observations from the cosmological Evolution and Assembly of Galaxies and their Environments (EAGLE) simulations, where we find a similar significant ${\lambda }_{{R}_{{\rm{e}}}}$ anticorrelation with environment, and a mass and environment correlation. We demonstrate that the environmental correlation of ${\lambda }_{{R}_{{\rm{e}}}}$ is not caused by the mass-environment relation. The significant relationship between ${\lambda }_{{R}_{{\rm{e}}}}$ and environment remains when we exclude slow rotators. The signals in SAMI and EAGLE are strongest on small scales (10-100 kpc) as expected from galaxy interactions and mergers. Our work demonstrates that the technique of marked correlation functions is an effective tool for detecting the relationship between ${\lambda }_{{R}_{{\rm{e}}}}$ and environment.

Keywords: Galaxy clusters, Galaxy environments, Galaxy kinematics, Redshift surveys, Two-point correlation function
The JCMT BISTRO Survey: An 850/450 μm Polarization Study of NGC 2071IR in Orion B. We present the results of simultaneous 450 μm and 850 μm polarization observations toward the massive star-forming region NGC 2071IR, a target of the BISTRO (B-fields in STar-forming Region Observations) Survey, using the POL-2 polarimeter and SCUBA-2 camera mounted on the James Clerk Maxwell Telescope. We find a pinched magnetic field morphology in the central dense core region, which could be due to a rotating toroidal disklike structure and a bipolar outflow originating from the central young stellar object IRS 3. Using the modified Davis-Chandrasekhar-Fermi method, we obtain a plane-of-sky magnetic field strength of 563 ± 421 μG in the central ~0.12 pc region from 850 μm polarization data. The corresponding magnetic energy density of 2.04 × 10-8 erg cm-3 is comparable to the turbulent and gravitational energy densities in the region. We find that the magnetic field direction is very well aligned with the whole of the IRS 3 bipolar outflow structure. We find that the median value of polarization fractions is 3.0% at 450 μm in the central 3' region, which is larger than the median value of 1.2% at 850 μm. The trend could be due to the better alignment of warmer dust in the strong radiation environment. We also find that polarization fractions decrease with intensity at both wavelengths, with slopes, determined by fitting a Rician noise model of 0.59 ± 0.03 at 450 μm and 0.36 ± 0.04 at 850 μm, respectively. We think that the shallow slope at 850 μm is due to grain alignment at the center being assisted by strong radiation from the central young stellar objects.

Keywords: Interstellar magnetic fields, Star forming regions, Polarimetry, Interstellar medium
Using Cosmic Rays Detected by HST as Geophysical Markers. I. Detection and Characterization of Cosmic Rays. The Hubble Space Telescope (HST) has been operational for over 30 years, and throughout that time it has been bombarded by high-energy charged particles colloquially referred to as cosmic rays. In this paper, we present a comprehensive study of more than 1.2 billion cosmic rays observed with HST using a custom-written Python package, HSTcosmicrays, that is available to the astronomical community. We analyzed 75,908 dark calibration files taken as part of routine calibration programs for five different CCD imagers with operational coverage of Solar Cycle 23 and 24. We observe the expected modulation of galactic cosmic rays by solar activity. We model the observed energy-loss distributions to derive an estimate of 534 ± 117 MeV for the kinetic energy of the typical cosmic ray impacting HST. For the three imagers with the largest nonuniformity in thickness, we independently confirm the overall structure produced by fringing analyses by analyzing cosmic ray strikes across the detector field of view. We analyze STIS/CCD observations taken as HST crosses over the South Atlantic Anomaly and find a peak cosmic ray particle flux of ~1100 particle s-1 cm-2. We find strong evidence for two spatially confined regions over North America and Australia that exhibit increased cosmic ray particle fluxes at the 5σ level.

Keywords: Galactic cosmic rays, Hubble Space Telescope, Geomagnetic fields, Cosmic rays