Sazuna/UAT_keywords huggingface dataset:
Physical Conditions in Shocked Interstellar Gas Interacting with the Supernova Remnant IC 443. We present the results of a detailed investigation into the physical conditions in interstellar material interacting with the supernova remnant (SNR) IC 443. Our analysis is based on a comprehensive examination of high-resolution far-ultraviolet spectra obtained with the Space Telescope Imaging Spectrograph onboard the Hubble Space Telescope of two stars behind IC 443. One of our targets (HD 43582) probes gas along the entire line of sight through the SNR, while the other (HD 254755) samples material located ahead of the primary supernova shock front. We identify low-velocity quiescent gas in both directions and find that the densities and temperatures in these components are typical of diffuse atomic and molecular clouds. Numerous high-velocity components are observed in the absorption profiles of neutral and singly ionized atomic species toward HD 43582. These components exhibit a combination of greatly enhanced thermal pressures and significantly reduced dust-grain depletions. We interpret this material as cooling gas in a recombination zone far downstream from shocks driven into neutral gas clumps. The pressures derived for a group of ionized gas components at high positive velocity toward HD 43582 are lower than those of the other shocked components, pointing to pressure inhomogeneities across the remnant. A strong, very high velocity component near -620 km s-1 is seen in the absorption profiles of highly ionized species toward HD 43582. The velocity of this material is consistent with the range of shock velocities implied by observations of soft thermal X-ray emission from IC 443. Moderately high velocity gas toward HD 254755 may represent shocked material from a separate foreground SNR. * Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.

Keywords: Interstellar molecules, Interstellar abundances, Supernova remnants, Diffuse interstellar clouds
Testing General Relativity with the Stellar-mass Black Hole in LMC X-1 Using the Continuum-fitting Method. The iron-line and continuum-fitting methods are currently the two leading techniques for measuring black-hole spins with electromagnetic radiation. They can be naturally extended for probing the spacetime geometry around black holes and testing general relativity in the strong field regime. In the past couple of years, there has been significant work to use the iron-line method to test the nature of black holes. Here we use the continuum-fitting method and we show its capability of constraining the spacetime geometry around black holes by analyzing 17 Rossi X-ray Timing Explorer data of the X-ray binary LMC X-1.

Keywords: X-ray astronomy, Kerr metric, Astrophysical black holes
Depth of Jupiter's Zonal Flow under the "Shallow-wind" Assumption. In this article, the depth of Jupiter's zonal flow in the molecular-hydrogen region is for the first time explored in the context of the so-called "shallow-wind" scenario, which means the internal zonal circulation is kinematically different from the fast atmospheric jet stream. A gravitationally constrained zonal flow of typical speed $O(1)\,{\rm{m}}\,{{\rm{s}}}^{-1}$ is adopted. The zonal flow is examined in the semiconducting region for its MHD interaction with Jupiter's main magnetic field and the resulting ohmic dissipation. Our calculations indicate that the zonal flow in Jupiter might be permitted to reach downward to the radial location at $r=0.937{R}_{J}$ , deeper than previous estimations obtained by assuming the fast cloud-top zonal wind extended straightforward into Jupiter's interior. On the other hand, it is also concluded that Jupiter's zonal flow likely cannot penetrate any deeper to where electrical conductivity is greater than $O(10)\,{\rm{S}}\,{{\rm{m}}}^{-1}$ ; though, fluid motion might be slow under the "shallow-wind" model assumption.

Keywords: Magnetohydrodynamics, Gravitation, Planetary atmospheres, Jupiter, Magnetic fields
Dynamical Evolution of Cosmic Supermassive Binary Black Holes and Their Gravitational-wave Radiation. We investigate the evolution of supermassive binary black holes (BBHs) in galaxies with realistic property distributions and the gravitational-wave (GW) radiation from the cosmic population of these BBHs. We incorporate a comprehensive treatment of the dynamical interactions of the BBHs with their environments by including the effects of galaxy triaxial shapes and inner stellar distributions, and generate a large number of BBH evolution tracks. By combining these BBH evolution tracks, galaxy mass functions, galaxy merger rates, and supermassive black hole-host galaxy relations into our model, we obtain statistical distributions of surviving BBHs, BBH coalescence rates, the strength of their GW radiation, and the stochastic GW background (GWB) contributed by the cosmic BBH population. About ∼1%-3% (or $\sim 10 \% $ ) of supermassive BHs at nearby galactic centers are expected to be binaries with mass ratio $\gt 1/3$ (or $\gt 1/100$ ). The characteristic strain amplitude of the GWB at frequency $1\,{\mathrm{yr}}^{-1}$ is estimated to be $\sim {2.0}_{-0.8}^{+1.4}\times {10}^{-16}$ , and the upper bound of its results obtained with the different BH-host galaxy relations can be up to $5.4\times {10}^{-16}$ , which await testing by future experiments (e.g., the Square Kilometer Array, FAST, Next-Generation Very Large Array). The turnover frequency of the GWB spectrum is at $\sim 0.25\,\mathrm{nHz}$ . The uncertainties on the above estimates and prospects for detecting individual sources are also discussed. The application of the cosmic BBH population to the Laser Interferometer Space Antenna (LISA) band provides a lower limit to the detection rate of BBHs by LISA, $\sim 0.9\,{\mathrm{yr}}^{-1}$ .

Keywords: Astrodynamics, Supermassive black holes, Cosmological evolution, Galaxy dynamics, Galaxy nuclei, Gravitational wave astronomy, Galaxy mergers, Gravitational waves
Using Stereoscopic Observations of Cometary Plasma Tails to Infer Solar Wind Speed. Detection of the solar wind speed near the Sun is significant in understanding the heating and acceleration of the solar wind. Cometary plasma tails have long been used as natural probes for solar wind speed; previous solar wind speed estimates via plasma tails, however, were based on comet images from a single viewpoint, and the projection effect may influence the result. Using stereoscopic observations from the Solar Terrestrial Relations Observatory and the Solar and Heliospheric Observatory, we three-dimensionally reconstruct the plasma tails of three comets C/2012 S1 (ISON), C/2010 E6, and C/2011 W3 (Lovejoy) and infer the ambient solar wind speed. The first comet is located between 3.5 and 6 solar radii (Rs) away from the Sun at high latitudes; the estimated solar wind speed is about 300-500 km s-1. The second comet is located within 10 Rs and about 20° away from the ecliptic; the estimated solar wind speed is about 200-320 km s-1. The third comet is also located at low latitudes but farther (&gt;20 Rs) away from the Sun; the estimated solar wind speed is about 100-600 km s-1. For comets near the ecliptic, our results are close to those predicted by MHD models, whereas for the comet at high latitudes, the deviation between our estimate and the model results is notable. This consistency and difference could be used to constrain and improve solar wind models. We will seek opportunities to apply the method to comet 322P, whose tail may sweep the Parker Solar Probe.

Keywords: Comet tails, Solar wind
Electronic Spectroscopy of {He}@{{C}}_{60}(+) for Astrochemical Consideration. The electronic spectrum of the endohedral fullerene $\mathrm{He}@{{\rm{C}}}_{60}^{+}$ observed by messenger spectroscopy in a cryogenic ion trap is presented. The role played by the messenger tag in the adopted experimental method is evaluated by recording spectra of $\mathrm{He}@{{\rm{C}}}_{60}^{+}-{\mathrm{He}}_{n}$ with n = 1-4. The results indicate a linear shift of ∼0.7 Å in the wavelengths allowing accurate gas phase values to be reported. The presence of the helium inside the cage shifts the absorption bands by 2-3 Å toward shorter wavelengths compared to ${{\rm{C}}}_{60}^{+}$ . The magnitude of this displacement will enable searches for the spectral signatures of this fullerene analogue in interstellar environments by absorption spectroscopy. The implications for potential astronomical detection are discussed.

Keywords: Interstellar molecules, Diffuse interstellar bands, Molecular spectroscopy
A Mean Density of 112 M<SUB>☉</SUB> pc<SUP>-3</SUP> for Central Molecular Zone Clumps—Evidences for Shear-enabled Pressure Equilibrium in the Galactic Center. We carry out a systematic study of the density structure of gas in the Central Molecular Zone (CMZ) in the Galactic center by extracting clumps from the APEX Telescope Large Area Survey of the Galaxy survey at 870 μm. We find that the clumps follow a scaling of m = ρ0r3, which corresponds to a characteristic density of ${n}_{{{\rm{H}}}_{2}}=1.6\times {10}^{3}\,{\mathrm{cm}}^{-3}$ (ρ0 = 112 M☉ pc-3) with a variation of ≍0.5 dex, where we assumed a gas-to-dust mass ratio of 100. This characteristic density can be interpreted as the result of thermal pressure equilibrium between the molecular gas and the warm ambient interstellar medium. Such an equilibrium can plausibly be established since shear has approximately the same strength as self-gravity. Our findings may explain the fact that star formation in the CMZ is highly inefficient compared to the rest of the Milky Way disk. We also identify a population of clumps whose densities are two orders of magnitudes higher in the vicinity of the Sgr B2 region, which we propose are produced by collisions between the clumps of lower densities. For these collisions to occur, processes such as compressive tides probably have created the appropriate condition by assembling the clumps together.

Keywords: Galactic center, Star formation, Gravitational collapse, Interstellar medium, Tidal interaction
Unveiling the Importance of Magnetic Fields in the Evolution of Dense Clumps Formed at the Waist of Bipolar H II Regions: A Case Study of Sh 2-201 with JCMT SCUBA-2/POL-2. We present the properties of magnetic fields (B fields) in two clumps (clump 1 and clump 2), located at the waist of the bipolar H II region Sh 2-201, based on James Clerk Maxwell Telescope SCUBA-2/POL-2 observations of 850 μm polarized dust emission. We find that B fields in the direction of the clumps are bent and compressed, showing bow-like morphologies, which we attribute to the feedback effect of the H II region on the surface of the clumps. Using the modified Davis-Chandrasekhar-Fermi method, we estimate B-field strengths of 266 and 65 μG for clump 1 and clump 2, respectively. From virial analyses and critical mass ratio estimates, we argue that clump 1 is gravitationally bound and could be undergoing collapse, whereas clump 2 is unbound and stable. We hypothesize that the interplay of the thermal pressure imparted by the H II region, the B-field morphologies, and the various internal pressures of the clumps (such as magnetic, turbulent, and gas thermal pressures) has the following consequences: (a) formation of clumps at the waist of the H II region; (b) progressive compression and enhancement of the B fields in the clumps; (c) stronger B fields that will shield the clumps from erosion by the H II region and cause pressure equilibrium between the clumps and the H II region, thereby allowing expanding ionization fronts to blow away from the filament ridge, forming bipolar H II regions; and (d) stronger B fields and turbulence that will be able to stabilize the clumps. A study of a larger sample of bipolar H II regions would help to determine whether our hypotheses are widely applicable.

Keywords: Stellar feedback, Magnetic fields, Interstellar magnetic fields, Dust continuum emission, Star formation, Submillimeter astronomy, H II regions
The ALMA Spectroscopic Survey in the HUDF: Deep 1.2 mm Continuum Number Counts. We present the results from the 1.2 mm continuum image obtained as part of the Atacama Large Millimeter/submillimeter Array Spectroscopic Survey in the Hubble Ultra Deep Field. The 1.2 mm continuum image has a size of 2.9 (4.2) arcmin2 within a primary beam response of 50% (10%) and an rms value of $9.3\,\mu \mathrm{Jy}\,{\mathrm{beam}}^{-1}$ . We detect 35 sources at high significance (Fidelity ≥0.5); 32 have well-characterized near-infrared Hubble Space Telescope counterparts. We estimate the 1.2 mm number counts to flux levels of $\lt 30\,\mu \mathrm{Jy}$ in two different ways: we first use the detected sources to constrain the number counts and find a significant flattening of the counts below Sν ∼ 0.1 mJy. In a second approach, we constrain the number counts using a probability of deflection statistics (P(D)) analysis. For this latter approach, we describe new methods to accurately measure the noise in interferometric imaging (employing jackknifing in the cube and in the visibility plane). This independent measurement confirms the flattening of the number counts. Our analysis of the differential number counts shows that we are detecting ∼93% (∼100% if we include the lower fidelity detections) of the total continuum dust emission associated with galaxies in the Hubble Ultra Deep Field. The ancillary data allow us to study the dependence of the 1.2 mm number counts on redshift (z = 0-4), galaxy dust mass ( ${M}_{\mathrm{dust}}={10}^{7}\mbox{--}{10}^{9}{M}_{\odot }$ ), stellar mass ( ${M}_{* }={10}^{9}\mbox{--}{10}^{12}{M}_{\odot }$ ), and star formation rate ( $\mathrm{SFR}=1-1000\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ ). In an accompanying paper we show that the number counts are crucial to constrain galaxy evolution models and the understanding of star-forming galaxies at high redshift.

Keywords: Surveys, Infrared sources, Millimeter astronomy, Galaxies
Large-format X-Ray Reflection Grating Operated in an Echelle-like Mounting. We report on resolving power measurements of an X-ray reflection grating designed for use in an astronomical soft X-ray spectrograph. The grating was patterned via electron-beam lithography (EBL) to have fanned grooves to match the convergence of an illuminating beam. Grating measurements were conducted in an echelle-like mounting, which yields access to high diffraction orders in the soft X-ray bandpass (0.2-2.0 keV). By comparing the zeroth-order line-spread function to the telescope focus, we find evidence for minimal broadening (&lt;1″) introduced by the figure of the grating. In addition, we fit for the spectral resolution (R = λ/Δλ) intrinsic to this grating using a Bayesian Markov Chain Monte Carlo approach. Using an ensemble fitting technique, we find that the grating resolution R exceeds 2200 (3σ lower bound). This current grating resolution meets the performance required for a notional soft X-ray grating spectroscopy mission measuring hot baryonic material in the extended halos of galaxies. Using ray-trace simulations, we identify a geometric aberration resulting from path length differences across the width of the grating as a limiting factor in assessing the resolution of these gratings and discuss methods for placing better constraints on the inherent resolution of X-ray astronomical reflection gratings fabricated using EBL.

Keywords: Astronomical techniques, Bayesian statistics, Astronomical instrumentation, Spectroscopy
The Beautiful Mess in Abell 2255. We present LOFAR observations of one of the most spectacular objects in the radio sky: Abell 2255. This is a nearby (z = 0.0806) merging galaxy cluster hosting one of the first radio halos ever detected in the intracluster medium (ICM). The deep LOFAR images at 144 MHz of the central ∼10 Mpc2 region show a plethora of emission on different scales, from tens of kiloparsecs to above megaparsec sizes. In this work, we focus on the innermost region of the cluster. Among the numerous interesting features observed, we discover remarkable bright and filamentary structures embedded in the radio halo. We incorporate archival WSRT 1.2 GHz data to study the spectral properties of the diffuse synchrotron emission and find a very complex spectral index distribution in the halo spanning a wide range of values. We combine the radio data with Chandra observations to investigate the connection between the thermal and nonthermal components by quantitatively comparing the radio and X-ray surface brightness and the spectral index of the radio emission with the thermodynamical quantities of the ICM. Despite the multitude of structures observed in the radio halo, we find that the X-ray and radio emission are overall well correlated. The fact that the steepest spectrum emission is located in the cluster center and traces regions with high entropy possibly suggests the presence of seed particles injected by radio galaxies that are spread in the ICM by the turbulence generating the extended radio halo.

Keywords: Galaxy clusters, X-ray astronomy, Extragalactic radio sources, Extended radiation sources, Non-thermal radiation sources, Intracluster medium, Tailed radio galaxies, Abell clusters, Radio interferometry, Radio astronomy
On the AGN Nature of Two UV-bright Sources at z<SUB>spec</SUB> ∼ 5.5 in the CANDELS Fields: An Update on the AGN Space Density at M<SUB>1450</SUB> ∼ -22.5. It is widespread opinion that hydrogen reionization is mainly driven by primeval star-forming galaxies, with high-z active galactic nuclei (AGNs) having a minor role. Recent observations, however, challenge this notion, indicating a number of issues related to a galaxy-driven reionization scenario. We provide here an updated assessment of the space density of relatively faint (M1450 ∼ -22.5) AGNs at zspec ∼ 5.5 in order to improve the estimate of the photoionization rate contribution from accreting supermassive black holes. Exploiting deep UV rest-frame ground-based spectra collected at the Very Large Telescope on the CANDELS/GOODS-South field and deep Chandra X-ray images in the CANDELS/GOODS-North and EGS areas, we find two relatively bright (M1450 ∼ -22.5) AGNs at zspec ∼ 5.5. We derive an AGN space density of Φ = 1.29 × 10-6 cMpc-3 at z ∼ 5.5 and M1450 ∼ -22.5 by simply dividing their observed number by the cosmological volume in the range 5.0 &lt; z &lt; 6.1. Our estimate does not consider corrections for incompleteness; therefore, it represents a lower limit, although uncertainties due to cosmic variance can still be significant. This value supports a high space density of AGNs at z &gt; 5, in contrast with previous claims mostly based on standard color selection, possibly affected by significant incompleteness. Our estimate for the AGN photoionization rate at z ∼ 5.5 is in agreement with the observed values at similar redshifts, which are needed to keep the intergalactic medium highly ionized. Upcoming James Webb Space Telescope and giant ground-based telescopes observations will improve the study of high-z AGNs and their contribution to the reionization of the universe.

Keywords: Surveys, Reionization, X-ray active galactic nuclei, Active galactic nuclei
Self-consistent Semianalytic Modeling of Feedback during Primordial Star Formation and Reionization. We present a new semianalytic model of the formation of the first stars. Our method takes dark matter halo merger trees (including three-dimensional spatial information) from cosmological N-body simulations as input and applies analytic prescriptions to compute both the Population III and metal-enriched star formation histories. We have developed a novel method to accurately compute the major feedback processes affecting Population III star formation: H2 photodissociation from Lyman-Werner (LW) radiation, suppression of star formation due to inhomogeneous reionization, and metal enrichment via supernova winds. Our method utilizes a grid-based approach relying on fast Fourier transforms to rapidly track the LW intensity, ionization fraction, and metallicity in three dimensions throughout the simulation box. We present simulations for a wide range of astrophysical model parameters from z ≈ 30 to 6. Initially long-range LW feedback and local metal enrichment and reionization feedback dominate. However, for z ≲ 15 we find that the star formation rate density (SFRD) of Population III stars is impacted by the combination of external metal enrichment (metals from one halo polluting other pristine halos) and inhomogeneous reionization. We find that the interplay of these processes is particularly important for the Population III SFRD at z ≲ 10. Reionization feedback delays star formation long enough for metal bubbles to reach halos that would otherwise form Population III stars. Including these effects can lead to more than an order-of-magnitude decrease in the Population III SFRD at z = 6 compared to LW feedback alone.

Keywords: Cosmology, Population III stars, High-redshift galaxies
Properties of Neutron Stars Described by a Relativistic Ab Initio Model. Properties of neutron stars are investigated by an available relativistic ab initio method, the relativistic Brueckner-Hartree-Fock (RBHF) model, with the latest high-precision, relativistic charge-dependent potentials, pvCD-Bonn A, B, C. The neutron star matter is solved within the beta equilibrium and charge neutrality conditions in the framework of the RBHF model. Compared to the conventional treatment, where the chemical potential of leptons was approximately represented by the symmetry energy of nuclear matter, the equation of state of neutron star matter in the present self-consistent calculation with pvCD-Bonn B has a striking difference above the baryon number density nb = 0.55 fm-3. However, these differences influence the global properties of neutron stars only about 1% to 2%. Then, three two-body potentials pvCD-Bonn A, B, C, with different tensor components, are systematically applied in the RBHF model to calculate the properties of neutron stars. It is found that the maximum masses of neutron stars are around 2.21-2.30 M⊙, and the corresponding radii are R = 11.18-11.72 km. The radii of a 1.4 M⊙ neutron star are predicated as R1.4 = 12.34-12.91 km, and their dimensionless tidal deformabilities are Λ1.4 = 485-626. Furthermore, the direct URCA process in neutron star cooling will happen from nb = 0.414 to 0.530 fm-3 with the proton fractions Yp = 0.136-0.138. All of the results obtained from the RBHF model only with two-body pvCD-Bonn potentials completely satisfy various constraints from recent astronomical observations of massive neutron stars, gravitational wave detection (GW170817), and simultaneous mass-radius measurement.

Keywords: Neutron stars, Neutron star cores, Gravitational waves, Nuclear physics