Sazuna/UAT_keywords huggingface dataset:
What Causes Faint Solar Coronal Jets from Emerging Flux Regions in Coronal Holes?. Using EUV images and line-of-sight magnetograms from Solar Dynamics Observatory, we examine eight emerging bipolar magnetic regions (BMRs) in central-disk coronal holes for whether the emerging magnetic arch made any noticeable coronal jets directly, via reconnection with ambient open field as modeled by Yokoyama &amp; Shibata. During emergence, each BMR produced no obvious EUV coronal jet of normal brightness, but each produced one or more faint EUV coronal jets that are discernible in AIA 193 &amp;angst; images. The spires of these jets are much fainter and usually narrower than for typical EUV jets that have been observed to be produced by minifilament eruptions in quiet regions and coronal holes. For each of 26 faint jets from the eight emerging BMRs, we examine whether the faint spire was evidently made a la Yokoyama &amp; Shibata. We find that (1) 16 of these faint spires evidently originate from sites of converging opposite-polarity magnetic flux and show base brightenings like those in minifilament-eruption-driven coronal jets, (2) the 10 other faint spires maybe were made by a burst of the external-magnetic-arcade-building reconnection of the emerging magnetic arch with the ambient open field, with reconnection directly driven by the arch's emergence, but (3) none were unambiguously made by such emergence-driven reconnection. Thus, for these eight emerging BMRs, the observations indicate that emergence-driven external reconnection of the emerging magnetic arch with ambient open field at most produces a jet spire that is much fainter than in previously reported, much more obvious coronal jets driven by minifilament eruptions.

Keywords: Solar corona, Solar magnetic fields, Solar magnetic reconnection, Solar filament eruptions
When Are LIGO/Virgo's Big Black Hole Mergers?. We study the evolution of the binary black hole (BBH) mass distribution across cosmic time. The second gravitational-wave transient catalog (GWTC-2) from LIGO/Virgo contains BBH events out to redshifts z ∼ 1, with component masses in the range ∼5-80 M⊙. In this catalog, the biggest BBHs, with m1 ≳ 45 M⊙, are only found at the highest redshifts, z ≳ 0.4. We ask whether the absence of high-mass observations at low redshift indicates that the mass distribution evolves: the biggest BBHs only merge at high redshift, and cease merging at low redshift. Modeling the BBH primary-mass spectrum as a power law with a sharp maximum mass cutoff (TRUNCATED model), we find that the cutoff increases with redshift (&gt; 99.9% credibility). An abrupt cutoff in the mass spectrum is expected from (pulsational) pair-instability supernova simulations; however, GWTC-2 is only consistent with a TRUNCATED mass model if the location of the cutoff increases from ${45}_{-5}^{+13}\,{M}_{\odot }$ at z &lt; 0.4 to ${80}_{-13}^{+16}\,{M}_{\odot }$ at z &gt; 0.4. Alternatively, if the primary-mass spectrum has a break in the power law (BROKEN POWER LAW) at ${38}_{-8}^{+15}\,{M}_{\odot }$ , rather than a sharp cutoff, the data are consistent with a nonevolving mass distribution. In this case, the overall rate of mergers, at all masses, increases with redshift. Future observations will distinguish between a sharp mass cutoff that evolves with redshift and a nonevolving mass distribution with a gradual taper, such as a BROKEN POWER LAW. After ∼100 BBH merger observations, a continued absence of high-mass, low-redshift events would provide a clear signature that the mass distribution evolves with redshift.

Keywords: Massive stars, Stellar mass black holes, Astrostatistics, Gravitational wave astronomy, Stellar remnants, Astrophysical black holes
The String Theory Swampland in the Euclid, Square Kilometer Array, and Vera Rubin Observatory Era. This article aims to draw the attention of astronomers to the ability of future cosmological surveys to put constraints on string theory. The fact that "quantum gravity" might be constrained by large-scale astrophysical observations is a remarkable fact that has recently concentrated a great amount of interest. In this work, we focus on future observatories and investigate their capability to put string theory, which is sometimes said to be "unfalsifiable," under serious pressure. We show that the combined analysis of the Square Kilometer Array, Euclid, and the Vera Rubin observatory—together with Planck results—could substantially improve the current limits on the relevant string swampland parameter. In particular, our analysis leads to a nearly model-independent prospective upper bound on the quintessence potential, $| V^{\prime} | /V\lt 0.16$ , in strong contradiction of the so-called de Sitter conjecture. Some lines of improvements for the very long run are also drawn, together with generic prospective results, underscoring the efficiency of this approach. The conjectures used in this work are discussed pedagogically, together with the cosmological models chosen in the analysis.

Keywords: Cosmology, Quintessence, Dark energy
The HETDEX Survey: The Lyα Escape Fraction from 3D-HST Emission-Line Galaxies at z ∼ 2. In this work, we measure the Lyα escape fraction of 935 [O III]-emitting galaxies between 1.9 &lt; z &lt; 2.35 by comparing stacked spectra from the Hubble Space Telescope/WFC3's near-IR grism to corresponding stacks from the Hobby-Eberly Telescope Dark Energy Experiment's Internal Data Release 2. By measuring the stacks' Hβ to Lyα ratios, we determine the Lyα escape fraction as a function of stellar mass, star-formation rate, internal reddening, size, and [O III]/Hβ ratio. We show that the escape fraction of Lyα correlates with a number of parameters, such as galaxy size, star-formation rate, and nebular excitation. However, we also demonstrate that most of these relations are indirect, and that the primary variables controlling the escape of Lyα are likely to be stellar mass and internal extinction. Overall, the escape of Lyα declines from ≳16% in galaxies with $\mathrm{log}M/{M}_{\odot }\lesssim 9$ to ≲1% for systems with $\mathrm{log}M/{M}_{\odot }\gtrsim 10$ , with the sample's mean escape fraction being ${6.0}_{-0.5 \% }^{+0.6 \% }$ .

Keywords: Galaxy formation, Observational cosmology, High-redshift galaxies, Galaxy evolution
Dependence of Solar Wind Proton Temperature on the Polarization Properties of Alfvénic Fluctuations at Ion-kinetic Scales. We use fluctuating magnetic helicity to investigate the polarization properties of Alfvénic fluctuations at ion-kinetic scales in the solar wind as a function of βp, the ratio of proton thermal pressure to magnetic pressure, and θvB, the angle between the proton flow and local mean magnetic field, B0. Using almost 15 yr of Wind observations, we separate the contributions to helicity from fluctuations with wavevectors, k, quasi-parallel and oblique to B0, finding that the helicity of Alfvénic fluctuations is consistent with predictions from linear Vlasov theory. This result suggests that the nonlinear turbulent fluctuations at these scales share at least some polarization properties with Alfvén waves. We also investigate the dependence of proton temperature in the βp-θvB plane to probe for possible signatures of turbulent dissipation, finding that it correlates with θvB. The proton temperature parallel to B0 is higher in the parameter space where we measure the helicity of right-handed Alfvénic fluctuations, and the temperature perpendicular to B0 is higher where we measure left-handed fluctuations. This finding is inconsistent with the general assumption that by sampling different θvB in the solar wind we can analyze the dependence of the turbulence distribution on θkB, the angle between k and B0. After ruling out both instrumental and expansion effects, we conclude that our results provide new evidence for the importance of local kinetic processes that depend on θvB in determining proton temperature in the solar wind.

Keywords: Space plasmas, Heliosphere, Plasma physics, Interplanetary turbulence, The Sun, Solar wind, Alfven waves, Magnetic fields
Matching Globular Cluster Models to Observations. As ancient, gravitationally bound stellar populations, globular clusters represent abundant, vibrant laboratories, characterized by high frequencies of dynamical interactions, coupled to complex stellar evolution. Using surface brightness and velocity dispersion profiles from the literature, we fit 59 Milky Way globular clusters to dynamical models from the CMC Cluster Catalog. Without performing any interpolation, and without any directed effort to fit any particular cluster, 26 globular clusters are well matched by at least one of our models. We discuss in particular the core-collapsed clusters NGC 6293, NGC 6397, NGC 6681, and NGC 6624, and the non-core-collapsed clusters NGC 288, NGC 4372, and NGC 5897. As NGC 6624 lacks well-fitting snapshots on the main CMC Cluster Catalog, we run six additional models in order to refine the fit. We calculate metrics for mass segregation, explore the production of compact object sources such as millisecond pulsars, cataclysmic variables, low-mass X-ray binaries, and stellar-mass black holes, finding reasonable agreement with observations. In addition, closely mimicking observational cuts, we extract the binary fraction from our models, finding good agreement, except in the dense core regions of core-collapsed clusters. Accompanying this paper are a number of python methods for examining the publicly accessible CMC Cluster Catalog, as well as any other models generated using CMC.

Keywords: Globular star clusters, X-ray binary stars, Binary stars, Stellar mass black holes, Stellar dynamics, Computational methods, Cataclysmic variable stars
Benchmarking Dust Emission Models in M101. We present a comparative study of four physical dust models and two single-temperature modified blackbody models by fitting them to the resolved WISE, Spitzer, and Herschel photometry of M101 (NGC 5457). Using identical data and a grid-based fitting technique, we compare the resulting dust and radiation field properties derived from the models. We find that the dust mass yielded by the different models can vary by up to a factor of 3 (factor of 1.4 between physical models only), although the fits have similar quality. Despite differences in their definition of the carriers of the mid-IR aromatic features, all physical models show the same spatial variations for the abundance of that grain population. Using the well-determined metallicity gradient in M101 and resolved gas maps, we calculate an approximate upper limit on the dust mass as a function of radius. All physical dust models are found to exceed this maximum estimate over some range of galactocentric radii. We show that renormalizing the models to match the same Milky Way high-latitude cirrus spectrum and abundance constraints can reduce the dust mass differences between models and bring the total dust mass below the maximum estimate at all radii.

Keywords: Interstellar dust, Gas-to-dust ratio, Dust continuum emission, Spectral energy distribution, Metallicity
Detectable Data-driven Features in the Primordial Scalar Power Spectrum. In this work we explore the power of future large-scale surveys to constrain possible deviations from the standard single-field slow-roll inflationary scenario. Specifically, we parameterize possible fluctuations around the almost scale-invariant primordial scalar power spectrum in a model-independent way. We then use their imprints on the simulated matter distribution, as observed by the galaxy clustering and weak lensing probes of Euclid and the Square Kilometer Array, to construct the best constrainable patterns of fluctuations. For comparison, we make similar forecasts for a futuristic CMB-S4-like survey. The modes are found to have similar, yet shifted, patterns, with increasing number of wiggles as the mode number increases. The forecasted constraints are tightest for cosmic microwave background anisotropies and galaxy clustering, depending on the details of the specifications of the survey. As case studies, we explore how two greatly different physically motivated patterns of primordial power spectrum are reconstructed by the proposed modes. We propose a figure of merit based on the amount of information delivered by the modes to truncate the mode hierarchy, which is automatically generated by the analysis.

Keywords: Origin of the universe, Computational astronomy, Cosmic microwave background radiation, Large-scale structure of the universe
Neutron Tunneling: A New Mechanism to Power Explosive Phenomena in Neutron Stars, Magnetars, and Neutron Star Mergers. Neutron tunneling between neutron-rich nuclei in inhomogeneous dense matter encountered in neutron star crusts can release enormous energy on a short timescale to power explosive phenomena in neutron stars. In this work, we clarify aspects of this process that can occur in the outer regions of neutron stars when oscillations or cataclysmic events increase the ambient density. We use a time-dependent Hartree-Fock-Bogoliubov formalism to determine the rate of neutron diffusion and find that large amounts of energy can be released rapidly. The roles of nuclear binding, two-body interaction, and pairing in neutron diffusion times are investigated. We consider a one-dimensional quantum diffusion model and extend our analysis to study the impact of diffusion in three dimensions. We find that these novel neutron transfer reactions can generate energy in the amount of ≃ 1040-1044 erg under suitable conditions and assumptions.

Keywords: Neutron stars, Soft gamma-ray repeaters, Gamma-ray sources
Mapping the Galactic Disk with the LAMOST and Gaia Red Clump Sample. VII. The Stellar Disk Structure Revealed by the Mono-abundance Populations. Using a sample of 96,201 primary red clump stars selected from the LAMOST and Gaia surveys, we investigate the stellar structure of the Galactic disk. The sample stars show two separated sequences of high-[α/Fe] and low-[α/Fe] in the [α/Fe]-[Fe/H] plane. We divide the sample stars into five mono-abundance populations (MAPs) with different ranges of [α/Fe] and [Fe/H], named as the high-[α/Fe], high-[α/Fe] and high-[Fe/H], low-[Fe/H], solar, high-[Fe/H] MAPs, respectively. We present the stellar number density distributions in the R-Z plane, and the scale heights and scale lengths of the individual MAPs by fitting their vertical and radial density profiles. The vertical profiles, the variation trend of scale height with the Galactocentric radius, indicate that there is a clear disk flare in the outer disk both for the low-[α/Fe] and the high-[α/Fe] MAPs. While the radial surface-density profiles show a peak radius of 7 kpc and 8 kpc for the high-[α/Fe] and low-[α/Fe] MAPs, respectively. We also investigate the correlation between the mean rotation velocity and metallicity of the individual MAPs, and find that the mean rotation velocities are well separated and show different trends between the high-[α/Fe] and the low-[α/Fe] MAPs. Finally, we discuss the character of the high-[α/Fe] and high-[Fe/H] MAP and find that it is more similar to the high-[α/Fe] MAP either in the radial and vertical density profiles or in the rotation velocity.

Keywords: Galaxy disks, Galaxy structure, Galaxy evolution, Galaxy abundances
Puffed-up Edges of Planet-opened Gaps in Protoplanetary Disks. I. Hydrodynamic Simulations. Dust gaps and rings appear ubiquitous in bright protoplanetary disks. Disk-planet interaction with dust trapping at the edges of planet-induced gaps is one plausible explanation. However, the sharpness of some observed dust rings indicate that sub-millimeter-sized dust grains have settled to a thin layer in some systems. We test whether or not such dust around gas gaps opened by planets can remain settled by performing three-dimensional, dust-plus-gas simulations of protoplanetary disks with an embedded planet. We find planets massive enough to open gas gaps stir small, sub-millimeter-sized dust grains to high disk elevations at the gap edges, where the dust scale height can reach ∼70% of the gas scale height. We attribute this dust "puff up" to the planet-induced meridional gas flows previously identified by Fung &amp; Chiang and others. We thus emphasize the importance of explicit 3D simulations to obtain the vertical distribution of sub-millimeter-sized grains around gas gaps opened by massive planets. We caution that the gas-gap-opening planet interpretation of well-defined dust rings is only self-consistent with large grains exceeding millimeter size.

Keywords: Interstellar dust, Hydrodynamical simulations, Protoplanetary disks, Planet formation
K-band High-resolution Spectroscopy of Embedded High-mass Protostars. A classical paradox in high-mass star formation is that powerful radiation pressure can halt accretion, preventing further growth of a central star. Disk accretion has been proposed to solve this problem, but the disks and the accretion process in high-mass star formation are poorly understood. We executed high-resolution (R = 35,000-70,000) iSHELL spectroscopy in K-band for 11 high-mass protostars. Br-γ emission was observed toward eight sources, and the line profiles for most of these sources are similar to those of low-mass PMS stars. Using an empirical relationship between the Br-γ and accretion luminosities, we tentatively estimate disk accretion rates ranging from ≲10-8 and ∼10-4 M⊙ yr-1. These low-mass-accretion rates suggest that high-mass protostars gain more mass via episodic accretion as proposed for low-mass protostars. Given the detection limits, CO overtone emission (v = 2-0 and 3-1), likely associated with the inner disk region (r ≪ 100 au), was found toward two sources. This low-detection rate compared with Br-γ emission is consistent with previous observations. Ten out of the 11 sources show absorption at the v = 0-2 R(7) - R(14) CO R-branch. Most of them are either blueshifted or redshifted, indicating that the absorption is associated with an outflow or an inflow with a velocity of up to ∼50 km s-1. Our analysis indicates that the absorption layer is well thermalized (and therefore ${n}_{{{\rm{H}}}_{2}}\gtrsim {10}^{6}$ cm-3) at a single temperature of typically 100-200 K, and located within 200-600 au of the star.

Keywords: Infrared astronomy, Stellar accretion disks, Star formation
Fast Magnetic Reconnection Structures in Poynting Flux-dominated Jets. The ubiquitous relativistic jet phenomena associated with black holes play a major role in high and very-high-energy (VHE) astrophysics. In particular, observations have demonstrated that blazars show VHE emission with time variability from days to minutes (in the gigaelectronvolt and teraelectronvolt bands), implying very compact emission regions. The real mechanism of the particle acceleration process responsible for this emission is still being debated, but magnetic reconnection has lately been discussed as a strong potential candidate. In this work, we present the results of three-dimensional special relativistic magnetohydrodynamic simulations of the development of reconnection events driven by turbulence induced by current-driven kink instability along a relativistic jet. We have performed a systematic identification of all reconnection regions in the system, characterizing their local magnetic field topology and quantifying the reconnection rates. We obtained average rates of 0.051 ± 0.026 (in units of Alfvén speed), which are comparable to the predictions of the theory of turbulence-induced fast reconnection. A detailed statistical analysis also demonstrated that the fast reconnection events follow a log-normal distribution, which is a signature of its turbulent origin. To probe the robustness of our method, we have applied our results to the blazar Mrk 421. Building a synthetic light curve from the integrated magnetic reconnection power, we evaluated the time variability from a power spectral density analysis, obtaining good agreement with observations in the gigaelectronvolt band. This suggests that turbulent fast magnetic reconnection can be a possible process behind the high-energy emission variability phenomena observed in blazars.

Keywords: Magnetohydrodynamics, High energy astrophysics, Special relativity, Plasma astrophysics, Relativistic jets, Magnetohydrodynamical simulations
Ionization Instability Driven Outbursts in SXTs. We study the hydrogen ionization instability mechanism in the context of low-mass X-ray binaries with a black hole as a central object. We make numerical calculations of the predicted outbursts' light curves and compare them to the data observed by X-ray satellites. The comparison to the data is done for five sources observed by RXTE/ASM (XTE J1550-564, 4U 1630-472, XTE J1859+226, GX 339-4, XTE J1818-245) and one source observed by MAXI (MAXI J1659-152). The aim of this paper is to show that the hydrogen ionization instability operating in an accretion disk is responsible for the shape of outbursts observed in low-mass X-ray binaries. From the data fitting process, we put tight constraints on global source parameters such as black hole mass and disk accretion rate. The influence of chemical composition on the overall analysis is also shown. In the case of each outburst, we found the overall bolometric light curve shape that qualitatively matches the data. We were able to model the main outburst and secondary reflare often seen in the data, the latter one caused by the presence of metals in disk gas. In the case of 4U 1630-472, we analyzed two outbursts, which allowed us to put tight constraints on the black hole mass of 4 ± 0.5M⊙ and on the accretion rate of ${2}_{-0.2}^{+1.4}\times {10}^{-8}{M}_{\odot }$ yr-1.

Keywords: Accretion, Stellar accretion disks, Transient sources, Ionization, Low-mass x-ray binary stars
The Luminosity Function of Bright QSOs at z ∼ 4 and Implications for the Cosmic Ionizing Background. Based on results by recent surveys, the number of bright quasars at redshifts z &gt; 3 is being constantly revised upward. The current consensus is that at bright magnitudes (M1450 ≤ -27) the number densities of such sources could have been underestimated by a factor of 30%-40%. In the framework of the QUBRICS survey, we identified 58 bright QSOs at 3.6 ≤ z ≤ 4.2, with magnitudes ipsf ≤ 18, in an area of 12400 deg2. The uniqueness of our survey is underlined by the fact that it allows us, for the first time, to extend the sampled absolute magnitude range up to M1450 = -29.5. We derived a bright-end slope of β = -4.025 and a space density at &lt;M1450&gt; = -28.75 of 2.61 × 10-10 Mpc-3 comoving, after taking into account the estimated incompleteness of our observations. Taking into account the results of fainter surveys, active galactic nuclei (AGNs) brighter than M1450 = -23 could produce at least half of the ionizing emissivity at z ∼ 4. Considering a mean escape fraction of 0.7 for the QSO and AGN population, combined with a mean free path of 41.3 proper Mpc at z = 3.9, we derive a photoionization rate of ${\rm{Log}}({\rm{\Gamma }}\left[{{\rm{s}}}^{-1}\right])=-{12.17}_{-0.07}^{+0.13}$ , produced by AGNs at M1450 &lt; -18, that is, ∼100% of the measured ionizing background at z ∼ 4.

Keywords: Surveys, Cosmology, Quasars