Sazuna/UAT_keywords huggingface dataset:
Discovery of Protoclusters at z ∼ 3.7 and 4.9: Embedded in Primordial Superclusters. We have carried out follow-up spectroscopy on three overdense regions of g- and r-dropout galaxies in the Canada-France-Hawaii Telescope Legacy Survey Deep Fields, finding two new protoclusters at z = 4.898 and 3.721 and a possible protocluster at z = 3.834. The z = 3.721 protocluster overlaps with a previously identified protocluster at z = 3.675. The redshift separation between these two protoclusters is Δz = 0.05, which is slightly larger than the size of typical protoclusters. Therefore, if they are not the progenitors of a &gt;1015 M⊙ halo, they would grow into closely located independent halos like a supercluster. The other protocluster at z = 4.898 is also surrounded by smaller galaxy groups. These systems including protoclusters and neighboring groups are regarded as the early phase of superclusters. We quantify the spatial distribution of member galaxies of the protoclusters at z = 3.675 and 3.721 by fitting triaxial ellipsoids, finding a tentative difference: one has a pancake-like shape, while the other is filamentary. This could indicate that these two protoclusters are in different stages of formation. We investigate the relation between redshift and the velocity dispersion of protoclusters, including other protoclusters from the literature, in order to compare their dynamical states. Although there is no significant systematic trend in the velocity dispersions of protoclusters with redshift, the distribution is skewed to higher velocity dispersion over the redshift range of z = 2-6. This could be interpreted as two phases of cluster formation, one dominated by the steady accretion of galaxies and the other by the merging between group-size halos, perhaps depending on the surrounding large-scale environments.

Keywords: High-redshift galaxy clusters, Lyman-break galaxies, Galaxy environments
Rapid Postshock Cooling and Pressure-driven Shell-phase Evolution of the Galactic Halo SNR G70.0-21.5. The large, faint supernova remnant (SNR) G70.0-21.5 is believed to be the result of a Type Ia supernova some 90,000 yr ago at a distance of ∼1 kpc based on the Gaia proper motion and parallax of an unusual white dwarf. We have obtained narrow passband optical images and high-resolution spectroscopy to determine shock speeds of 70 to 110 km s-1. The shock itself is unusual in that the sharp Hα filaments arise from a very thin postshock zone where preshock neutral atoms are rapidly excited and ionized. Combining the shock speed with the remnant's estimated age, distance, and diameter, we investigate the SNR evolution in the post-Sedov phase. One-dimensional models that ignore such factors as magnetic fields, cosmic rays, and thermal conduction are marginally consistent with the observations.

Keywords: Supernova remnants, Shocks
PUSHing Core-collapse Supernovae to Explosions in Spherical Symmetry. IV. Explodability, Remnant Properties, and Nucleosynthesis Yields of Low-metallicity Stars. In this fourth paper of the series, we use the parameterized, spherically symmetric explosion method PUSH to perform a systematic study of two sets of nonrotating stellar progenitor models. Our study includes pre-explosion models with metallicities Z = 0 and Z = Z⊙ × 10-4 and covers a progenitor mass range from 11 to 75 M⊙. We present and discuss the explosion properties of all models and predict remnant (neutron star or black hole) mass distributions within this approach. We also perform systematic nucleosynthesis studies and predict detailed isotopic yields as a function of the progenitor mass and metallicity. We present a comparison of our nucleosynthesis results with observationally derived 56Ni ejecta from normal core-collapse supernovae (CCSNe) and with iron-group abundances for metal-poor star HD 84937. Overall, our results for explosion energies, remnant mass distribution, 56Ni mass, and iron-group yields are consistent with observations of normal CCSNe. We find that stellar progenitors at low and zero metallicity are more prone to black hole formation than those at solar metallicity, which allows for the formation of black holes in the mass range observed by LIGO/VIRGO.

Keywords: Neutron stars, Hydrodynamical simulations, Explosive nucleosynthesis, Black holes, Core-collapse supernovae, Nucleosynthesis, Stellar abundances, Supernova remnants, Astrophysical fluid dynamics, Supernova dynamics
Star-forming Clumps in Local Luminous Infrared Galaxies. We present HST narrowband near-infrared imaging of Paα and Paβ emission of 48 local luminous infrared galaxies (LIRGs) from the Great Observatories All-Sky LIRG Survey. These data allow us to measure the properties of 810 spatially resolved star-forming regions (59 nuclei and 751 extranuclear clumps) and directly compare their properties to those found in both local and high-redshift star-forming galaxies. We find that in LIRGs the star-forming clumps have radii ranging from ∼90 to 900 pc and star formation rates (SFRs) of ∼1 × 10-3 to 10 M⊙ yr-1, with median values for extranuclear clumps of 170 pc and 0.03 M⊙ yr-1. The detected star-forming clumps are young, with a median stellar age of 8.7 Myr, and have a median stellar mass of 5 × 105 M⊙. The SFRs span the range of those found in normal local star-forming galaxies to those found in high-redshift star-forming galaxies at z = 1-3. The luminosity function of the LIRG clumps has a flatter slope than found in lower-luminosity, star-forming galaxies, indicating a relative excess of luminous star-forming clumps. In order to predict the possible range of star-forming histories and gas fractions, we compare the star-forming clumps to those measured in the MassiveFIRE high-resolution cosmological simulation. The star-forming clumps in MassiveFIRE cover the same range of SFRs and sizes found in the local LIRGs and have total gas fractions that extend from 10% to 90%. If local LIRGs are similar to these simulated galaxies, we expect that future observations with ALMA will find a large range of gas fractions, and corresponding star formation efficiencies, among the star-forming clumps in LIRGs.

Keywords: Star forming regions, Interacting galaxies, Luminous infrared galaxies
Time-varying Extinction, Polarization, and Colors of Type Ia Supernovae due to Rotational Disruption of Dust Grains. Observations toward type Ia supernovae (SNe Ia) frequently report an unusually low total-to-selective extinction ratio (RV &lt; 2) and a small peak wavelength of polarization (λmax &lt; 0.4 μm). Hoang et al. proposed that the dominance of small grains near SNe Ia due to RAdiative Torque Disruption (RATD) can explain the puzzle. To test this scenario, we model the dust extinction and polarization of SNe Ia, accounting for grain disruption and alignment by radiative torques and different grain tensile strengths from ${S}_{\max }={10}^{7}\mbox{--}{10}^{10}\,\mathrm{erg}\,{\mathrm{cm}}^{-3}$ . We find that RV decreases from ∼3.1 to ∼1.5 after disruption time tdisr &lt; 40 days for clouds at a distance d &lt; 4 pc from SNe Ia. We then calculate the observed lightcurves of SNe Ia and find that their colors change with time, due to varying dust extinction. The peak wavelength λmax also decreases from ∼0.55 to ∼0.15 μm over an alignment time of talign &lt; 10 days, due to the enhanced alignment of small grains. By fitting the theoretical polarization with the Serkowski law characterized by the K and λmax parameters, we find that K increases when large grains are disrupted by RATD, which is consistent with the unusual K versus λmax relationship of SNe Ia. Nevertheless, an accurate measurement of K and λmax is challenging, due to atmospheric effects and potential contamination of polarization by Rayleigh scattering by circumstellar matter. Our results demonstrate the importance of RATD for time-dependent extinction, polarization, and colors of SNe Ia.

Keywords: Interstellar dust, Astrosphere interstellar medium interactions, Core-collapse supernovae, Interstellar dust extinction, Starlight polarization, Type Ia supernovae, Interstellar dust processes, Supernovae
Covariant Radiative Transfer for Black Hole Spacetimes. It has now become possible to study directly, via numerical simulation, the evolution of relativistic, radiation-dominated flows around compact objects. With this in mind we set out explicitly covariant forms of the radiative transfer equation that are suitable for numerical integration in curved spacetime or flat spacetime in curvilinear coordinates. Our work builds on and summarizes in consistent form earlier work by Lindquist, Thorne, Morita &amp; Kaneko, and others. We give explicitly the basic equations in spherical polar coordinates for Minkowski space and the Kerr spacetime in Kerr-Schild coordinates.

Keywords: Radiative magnetohydrodynamics, Radiative transfer, Black holes
Tidally Excited Oscillations in Heartbeat Binary Stars: Pulsation Phases and Mode Identification. Tidal forces in eccentric binary stars known as heartbeat stars excite detectable oscillations that shed light on the processes of tidal synchronization and circularization. We examine the pulsation phases of tidally excited oscillations (TEOs) in heartbeat binary systems. The target list includes four published heartbeat binaries and four additional systems observed by Kepler. To the first order, the pulsation phases of TEOs can be explained by the geometric effect of the dominant l = 2, m = 0, or ±2 modes assuming pulsations are adiabatic. We found that this simple theoretical interpretation can account for more than half of the systems on the list, assuming their spin and orbit axes are aligned. We do find significant deviations from the adiabatic predictions for some other systems, especially for the misaligned binary KIC 8164262. The deviations can potentially help to probe the nonadiabaticity of pulsation modes as well as resonances in the tidal forcing.

Keywords: Close binary stars, Stellar oscillations, Stellar interiors
Predictions of Cosmic Microwave Background Foreground Dust Polarization Using Velocity Gradients. Observations of fluctuations in the cosmic microwave background provide information about primordial inhomogeneities in the universe. However, the B-mode polarization of the inflationary gravitational wave is contaminated by the Galactic foreground polarized radiation arising from dust aligned by interstellar magnetic fields. To trace magnetic fields, we use the Velocity Gradient Technique (VGT), which employs modern understanding of the nature of magnetohydrodynamic turbulent motions. In this paper, we combine the VGT with Principal Component Analysis (PCA) to improve the accuracy of magnetic field tracing. We apply the VGT-PCA to the high-resolution neutral hydrogen data from the GALFA-H I survey to predict the polarization of dust. We report that the predicted directions of dust polarization provide good correspondence with those reported by Planck 353 GHz, with the alignment measure between the two ≃0.79 ± 0.01. We show that our results statistically agree with the Planck polarization in terms of magnetic field tracing. We find that the variation of dust emission efficiency across the sky is small. Using our maps of predicted polarization, we calculate the ratio of the E- and B-modes, and show that BB/EE ≃ 0.53 ± 0.10, which is similar to the result from Planck polarization.

Keywords: Interstellar magnetic fields, Cosmic microwave background radiation, Interstellar medium
Thermal Evolution of Neo-neutron Stars. I. Envelopes, Eddington Luminosity Phase, and Implications for GW170817. A neo-neutron star is a hot neutron star that has just become transparent to neutrinos. In a core-collapse supernova or accretion-induced collapse of a white dwarf, the neo-neutron star phase directly follows the proto-neutron star phase, about 30-60 s after the initial collapse. It will also be present in a binary neutron star merger in the case where the "born-again" hot massive compact star does not immediately collapse into a black hole. Eddington or even super-Eddington luminosities are present for some time. A neo-neutron star produced in a core-collapse supernova is not directly observable, but the one produced by a binary merger, likely associated with an off-axis short gamma-ray burst, may be observable for some time as well as when produced in the accretion-induced collapse of a white dwarf. We present a first step in the study of this neo-neutron star phase in a spherically symmetric configuration, thus ignoring fast rotation and also ignoring the effect of strong magnetic fields. We put particular emphasis on determining how long the star can sustain a near-Eddington luminosity and also show the importance of positrons and contraction energy during the neo-neutron star phase. We finally discuss the observational prospects for neutron star mergers triggered by LIGO and for accretion-induced collapse transients.

Keywords: Neutron stars, Type II supernovae, Gamma-ray bursts, X-ray point sources
Surveying the Giant H II Regions of the Milky Way with SOFIA. II. M17. We present our second set of results from our mid-infrared imaging survey of Milky Way giant H II regions. We used the FORCAST instrument on the Stratospheric Observatory For Infrared Astronomy (SOFIA) to obtain 20 and 37 μm images of the central ∼10' × 10' area of M17. We investigate the small- and large-scale properties of M17 using our data in conjunction with previous multiwavelength observations. The spectral energy distributions of individual compact sources were constructed with Spitzer-IRAC, SOFIA-FORCAST, and Herschel-PACS photometry data and fitted with massive young stellar object (MYSO) models. Seven sources were found to match the criteria for being MYSO candidates, four of which are identified here for the first time, and the stellar mass of the most massive object, UC 1, is determined to be 64 M⊙. We resolve the extended mid-infrared emission from the KW object and suggest that the angle of this extended emission is influenced by outflow. It is shown that IRS 5 decreases in brightness as a function of wavelength from the mid- to far-infrared and has several other indicators that point to it being an intermediate-mass Class II object and not an MYSO. We find that the large-scale appearance of emission in M17 at 20 μm is significantly affected by contamination from the [S III] emission line from the ionized gas of the giant H II region. Finally, a number of potential evolutionary tracers yield a consistent picture suggesting that the southern bar of M17 is likely younger than the northern bar.

Keywords: Compact H II region, Massive stars, Star forming regions, Infrared astronomy, Star formation, Interstellar medium, Infrared sources, Protostars, H II regions
Model-independent Distance Calibration and Curvature Measurement Using Quasars and Cosmic Chronometers. We present a new model-independent method to determine spatial curvature and to mitigate the circularity problem affecting the use of quasars as distance indicators. Cosmic-chronometer measurements are used to construct the curvature-dependent luminosity distance ${D}_{L}^{\mathrm{cal}}({{\rm{\Omega }}}_{K},z)$ using a polynomial fit. Based on the reconstructed ${D}_{L}^{\mathrm{cal}}({{\rm{\Omega }}}_{K},z)$ and the known ultraviolet versus X-ray luminosity correlation of quasars, we simultaneously place limits on the curvature parameter ΩK and the parameters characterizing the luminosity correlation function. This model-independent analysis suggests that a mildly closed universe ( ${{\rm{\Omega }}}_{K}=-0.918\pm 0.429$ ) is preferred at the 2.1σ level. With the calibrated luminosity correlation, we build a new data set consisting of 1598 quasar distance moduli, and use these calibrated measurements to test and compare the standard ΛCDM model and the Rh = ct universe. Both models account for the data very well, though the optimized flat ΛCDM model has one more free parameter than Rh = ct, and is penalized more heavily by the Bayes Information Criterion. We find that Rh = ct is slightly favored over ΛCDM with a likelihood of ∼57.7% versus 42.3%.

Keywords: Cosmological models, Cosmological parameters, Quasars, Observational cosmology, Distance indicators
CME-induced Thermodynamic Changes in the Corona as Inferred from Fe XI and Fe XIV Emission Observations during the 2017 August 21 Total Solar Eclipse. We present the first remote sensing observations of the impact from a Coronal Mass Ejection (CME) on the thermodynamic properties of the solar corona between 1 and 3 R⊙. Measurements of the Fe XI (789.2 nm) and Fe XIV (530.3 nm) emission were acquired with identical narrow-bandpass imagers at three observing sites during the 2017 August 21 Total Solar Eclipse (TSE). Additional continuum imagers were used to observe K+F corona scattering, which is critical for the diagnostics presented here. The total distance between sites along the path of totality was 1400 km, corresponding to a difference of 28 minutes between the times of totality at the first and last site. These observations were used to measure the Fe XI and Fe XIV emission relative to continuum scattering, as well as the relative abundance of Fe10+ and Fe13+ from the line ratio. The electron temperature (Te) was then computed via theoretical ionization abundance values. We find that the range of Te is (1.1-1.2) × 106 K in coronal holes and (1.2-1.4) × 106 K in streamers. Statistically significant changes of Te occurred throughout much of the corona between the sites as a result of serendipitous CME activity prior to the eclipse. These results underscore the unique advantage of multi-site and multi-wavelength TSE observations for probing the dynamic and thermodynamic properties of the corona over an uninterrupted distance range from 1 to 3 R⊙.

Keywords: Solar coronal transients, Solar K corona, Total eclipses, Solar E corona, Solar eclipses, Solar abundances, Solar coronal mass ejection shocks, Solar F corona, Solar coronal mass ejections, Solar coronal holes, Solar coronal streamers, Solar particle emission
Characterizing the Uncertainty in Cluster Magnetic Fields Derived from Rotation Measures. Magnetic fields play vital roles in intracluster media (ICMs), but estimating their strengths and distributions from observations is a major challenge. Faraday rotation measures (RMs) are widely applied to this task, so it is critical to understand inherent uncertainties in RM analysis. In this paper, we seek to characterize those uncertainties given the types of information available today, independent of the specific technique used. We conduct synthetic RM observations through the ICM of a galaxy cluster drawn from a magnetohydrodynamic cosmological simulation in which the magnetic field is known. We analyze the synthetic RM observations using an analytical formalism based on commonly used model assumptions, allowing us to relate model physical variables to outcome uncertainties. Despite the simplicity of some assumptions, and unknown physical parameters, we are able to extract an approximate magnitude of the central magnetic field within an apparently irreducible uncertain factor of ≈3. Principal, largely irreducible, uncertainties come from the unknown depth along the line of sight of embedded polarized sources, the lack of robust coherence lengths from area-constrained polarization sampling, and the unknown scaling between ICM electron density and magnetic field strength. The RM-estimated central magnetic field strengths span more than an order of magnitude including the full range of synthetic experiments.

Keywords: Galaxy clusters, Intracluster medium, Polarimetry, Extragalactic magnetic fields
Prospects for Life on Temperate Planets around Brown Dwarfs. There is growing evidence that brown dwarfs may be comparable to main-sequence stars in terms of their abundance. In this paper, we explore the prospects for the existence of life on Earth-like planets around brown dwarfs. We consider the following factors: (I) the length of time that planets can exist in the temporally shifting habitable zone, (II) the minimum photon fluxes necessary for oxygenic photosynthesis, and (III) the lower limits on the fluxes of ultraviolet radiation to drive prebiotic reactions ostensibly necessary for the origin of life. By taking these effects into consideration, we find that it is unlikely for brown dwarfs with masses ≲30 MJ to host habitable planets over geologically significant timescales. We also briefly discuss some of the major biosignatures that might arise on these planets, assess the likelihood of their detection, and highlight some avenues for further study.

Keywords: Brown dwarfs, Exoplanet evolution, Astrobiology, Biosignatures, Habitable zone, Habitable planets
A New Microquasar Candidate in M83. Microquasars are neutron star or black hole X-ray binaries with jets. These jets can create bubbles of hot plasma shock ionized that can masquerade as peculiar supernova remnants (SNRs) in extragalactic surveys. To see if this is the case in the well-studied spiral galaxy M83, where one microquasar candidate (M83-MQ1) has already been identified, we studied the properties of nine SNR candidates, selected because of their elongated or irregular morphology, from the set of previously identified SNRs in that galaxy. Using multiwavelength data from Chandra, the Hubble Space Telescope, Gemini, and the Australia Telescope Compact Array, we found that at least six of our nine sources are best interpreted as SNRs. For one source, we do not have enough observational data to explain its linear morphology. Another source shows a nebular optical spectrum dominated by photoionization by O stars, but its excess [Fe II] and radio luminosity suggest a possible hidden SNR. Finally, one source (S2) shows an elongated structure of ionized gas, two radio sources along that line, and an accretion-powered X-ray source in between them (the Chandra source L14-139). While S2 could be a chance alignment of multiple SNRs and one X-ray binary, it seems more likely that it is a single physical structure powered by the jet from the accreting compact object. In the latter case, the size and luminosity of S2 suggest a kinetic power of ∼1040 erg s-1, in the same class as the most powerful microquasars in the local universe (e.g., S26 in NGC 7793 and SS 433 in our own Galaxy).

Keywords: X-ray binary stars, Jets, Spiral galaxies, Supernova remnants, Interstellar medium
Local Regimes of Turbulence in 3D Magnetic Reconnection. The process of magnetic reconnection when studied in nature or when modeled in 3D simulations differs in one key way from the standard 2D paradigmatic cartoon: it is accompanied by many fluctuations in the electromagnetic fields and plasma properties. We developed a diagnostics to study the spectrum of fluctuations in the various regions around a reconnection site. We define the regions in terms of the local value of the flux function that determines the distance from the reconnection site, with positive values in the outflow and negative values in the inflow. We find that fluctuations belong to two very different regimes depending on the local plasma beta (defined as the ratio of plasma and magnetic pressures). The first regime develops in the reconnection outflows where beta is high and it is characterized by a strong link between plasma and electromagnetic fluctuations, leading to momentum and energy exchanges via anomalous viscosity and resistivity. But there is a second, low-beta regime: it develops in the inflow and in the region around the separatrix surfaces, including the reconnection electron diffusion region itself. It is remarkable that this low-beta plasma, where the magnetic pressure dominates, remains laminar even though the electromagnetic fields are turbulent.

Keywords: Space plasmas, Geomagnetic fields, Solar magnetic reconnection, Plasma physics, Interplanetary turbulence, Plasma astrophysics, Interplanetary magnetic fields, Solar-terrestrial interactions