Sazuna/UAT_keywords huggingface dataset:
Constraining the Fluctuating Gunn-Peterson Approximation using Lyα Forest Tomography at z = 2. The fluctuating Gunn-Peterson approximation (FGPA) is a commonly used method to generate mock Lyα forest absorption skewers at Cosmic Noon (z ≳ 2) from the matter density field of N-body simulations without running expensive hydrodynamical simulations. Motivated by recent developments in 3D intergalactic medium (IGM) tomography observations as well as matter density field reconstruction techniques applied to galaxy redshift samples at z ~ 2, we examine the possibility of observationally testing FGPA by directly examining the relationship between Lyα transmission and the underlying matter density field. Specifically, we analyze the EAGLE, Illustris, IllustrisTNG, and Nyx cosmological hydrodynamic simulations that were run with different codes and sub-grid models. While the FGPA is an excellent description of the IGM in lower-density regions, the slope of the transmission-density distribution at higher densities is significantly affected by feedback processes causing the FGPA to break down in that regime. Even without added feedback, we find significant deviations caused by hydrodynamical effects arising from nonlinear structure growth. We then proceed to make comparisons using realistic mock data assuming the sightline sampling and spectral properties of the recent CLAMATO survey, and find that it would be challenging to discern between the FGPA and hydrodynamical models with current data sets. However, the improved sightline sampling from future extremely large telescopes or large volumes from multiplexed spectroscopic surveys such as Subaru PFS should allow for stringent tests of the FGPA, and make it possible to detect the effect of galaxy feedback on the IGM.

Keywords: Hydrodynamical simulations, Lyman alpha forest, Intergalactic medium
Cross-scale Correlations in Imbalanced Solar Wind Turbulence: Parker Solar Probe Observations. Based on Parker Solar Probe observations, this paper investigates the proton temperature, bulk speed, proton-scale magnetic helicity, and spectral index in the parameter space of (P  I , σ  c ), where P  I  is the magnetic energy density and σ  c  is the normalized cross helicity at proton inertial scales. Various correlations between these parameters are discussed and their relations are explored. These correlations indicate the following: (1) the turbulence with a larger P  I  is characterized by a higher σ  c ; (2) a larger P  I  corresponds to a higher proton temperature, faster bulk speed, and steeper proton-scale magnetic spectrum; (3) a higher σ  c  accounts for higher proton-scale magnetic helicity. In particular, the P  I  has the largest correlation coefficient (CC) of 0.85 with proton temperature and has a considerably large CC of 0.70 with a proton-scale spectral index. The σ  c  has a moderate CC of 0.52 with magnetic helicity in the low β  p  case (β  p  &lt; 0.6), where β  p  is the ratio of plasma to magnetic pressure. The correlation between σ  c  and P  I  is considerable with a CC exceeding 0.6 in the low β  p  case and tends to be negligible when β  p  approaches 1.5. These findings could be understood by the recently discovered "helicity barrier" effect and underline the importance of the generalized helicity invariant in low β  p  collisionless plasma for understanding imbalanced solar wind turbulence.

Keywords: Space plasmas, Plasma physics, Interplanetary turbulence, Solar coronal heating, Solar wind
Milky Way Zero-point Calibration of the JAGB Method: Using Thermally Pulsing AGB Stars in Galactic Open Clusters. We present a new calibration of the J-band absolute magnitude of the JAGB method based on thermally pulsing AGB stars that are members of Milky Way open clusters, having distances and reddenings, independently compiled and published by Marigo. A total 17 of these photometrically selected J-Branch AGB stars give M  J  = -6.40 mag with a scatter of ±0.40 mag, and 1σ on the mean of ±0.10 mag. Combining the Milky Way field carbon star calibration of Lee with this determination gives a weighted average of M  J (MW) = -6.19 ± 0.04 mag (error on the mean). This value is statistically indistinguishable from the value determined for this population of distance indicators in the LMC and SMC, giving further evidence that JAGB stars are extremely reliable distance indicators of high luminosity and universal applicability. Combining the zero-points for JAGB stars in these three systems, a value of M  J  = -6.20 ± 0.01 (stat) ±0.04 (sys) mag becomes our best current estimate of the JAGB zero-point and its associated errors. Finally, we note that no evidence is found for any statistically significant dependence of this zero-point on metallicity.

Keywords: Carbon stars
The Effect of the Chromospheric Temperature on Coronal Heating. Recent observational and numerical studies show a variety of thermal structures in the solar chromosphere. Given that the thermal interplay across the transition region is a key to coronal heating, it is worth investigating how different thermal structures of the chromosphere yield different coronal properties. In this work, by MHD simulations of Alfvén-wave heating of coronal loops, we study how the coronal properties are affected by the chromospheric temperature. To this end, instead of solving the radiative transfer equation, we employ a simple radiative loss function so that the chromospheric temperature is easily tuned. When the chromosphere is hotter, because the chromosphere extends to a larger height, the coronal part of the magnetic loop becomes shorter, which enhances the conductive cooling. A larger loop length is therefore required to maintain the high-temperature corona against the thermal conduction. From our numerical simulations we derive a condition for the coronal formation with respect to the half loop length l loop in a simple form: ${l}_{\mathrm{loop}}\gt {{aT}}_{\min }+{l}_{\mathrm{th}}$ , where ${T}_{\min }$ is the minimum temperature in the atmosphere, and parameters a and l th have negative dependencies on the coronal field strength. Our conclusion is that the chromospheric temperature has a nonnegligible impact on coronal heating for loops with small lengths and weak coronal fields. In particular, the enhanced chromospheric heating could prevent the formation of the corona.

Keywords: Solar coronal loops, Solar corona, Magnetohydrodynamical simulations
Revisiting the Circumnuclear X-Ray Emission of NGC 2992 in a Historically Low State. The innermost region of the Seyfert galaxy NGC 2992 has long been suspected to be the location of intense AGN-host galaxy interaction, but photon pile up in previous high-resolution observations hampered the study of the soft X-ray excess and the interaction near its nucleus. We present an X-ray imaging and spectroscopic analysis of the circumnuclear (1″-3″) region of NGC 2992 using the zeroth-order image of a 135 ks grating observation obtained with Chandra, which captured the nucleus in a historically low flux state. Extended soft X-ray emission is detected in the circumnuclear region with an observed luminosity of L X ~ 7 × 1039 erg s-1. The majority of the previous, puzzling detection of soft excess could be associated with the outflow, indicated by the morphological correspondences between the soft X-ray emission and figure-eight-shaped radio bubbles. An anomalous narrow emission line with a centroid energy of ~4.97 keV is found. If attributed to redshifted highly ionized iron emission (e.g., Fe XXV), the required outflow velocity is ~0.23 c. An alternative explanation is that this line emission could be produced by the nuclear spallation of iron. We also find extended, asymmetric Fe Kα emission along the galactic disk, which could originate from reflection by cold gas on ~200 pc scale.

Keywords: Galactic winds, Seyfert galaxies, X-ray active galactic nuclei, Radio lobes
Direct Optimal Mapping for 21 cm Cosmology: A Demonstration with the Hydrogen Epoch of Reionization Array. Motivated by the desire for wide-field images with well-defined statistical properties for 21 cm cosmology, we implement an optimal mapping pipeline that computes a maximum likelihood estimator for the sky using the interferometric measurement equation. We demonstrate this "direct optimal mapping" with data from the Hydrogen Epoch of Reionization (HERA) Phase I observations. After validating the pipeline with simulated data, we develop a maximum likelihood figure-of-merit for comparing four sky models at 166 MHz with a bandwidth of 100 kHz. The HERA data agree with the GLEAM catalogs to &lt; 10%. After subtracting the GLEAM point sources, the HERA data discriminate between the different continuum sky models, providing most support for the model of Byrne et al. We report the computation cost for mapping the HERA Phase I data and project the computation for the HERA 320-antenna data; both are feasible with a modern server. The algorithm is broadly applicable to other interferometers and is valid for wide-field and noncoplanar arrays.

Keywords: Aperture synthesis, Interferometers, H I line emission, Radio interferometry, Radio astronomy
The Stellar-mass Function of Long Gamma-Ray Burst Host Galaxies. Long gamma-ray bursts (GRBs) have been discussed as a potential tool to probe the cosmic star formation rate (SFR) for a long time. Some studies found an enhancement in the GRB rate relative to the galaxy-inferred SFR at high redshifts, which indicates that GRBs may not be good tracers of star formation. However, in these studies, the GRB rate measured at any redshift is an average over all galaxies at that epoch. A deep understanding of the connection between GRB production and environment also needs to characterize the population of GRB host galaxies directly. Based on a complete sample of GRB hosts, we constrain the stellar-mass function (SMF) of GRB hosts, and examine redshift evolution in the GRB host population. Our results confirm that a strong redshift evolution in energy (with an evolution index of $\delta ={2.47}_{-0.89}^{+0.73}$ ) or in density ( $\delta ={1.82}_{-0.59}^{+0.22}$ ) is needed in order to account for the observations. The GRB host SMF can be well described by the Schechter function with a power-law index ξ ≈ -1.10 and a break mass M  b,0 ≈ 4.9 × 1010 M ⊙, independent of the assumed evolutionary effects. This is the first formulation of the GRB host SMF. The observed discrepancy between the GRB rate and the galaxy-inferred SFR may also be explained by an evolving SMF.

Keywords: Stellar mass functions, Gamma-ray bursts, Star formation, Galaxies
A Volumetric Study of Flux Transfer Events at the Dayside Magnetopause. Localized magnetic reconnection at the dayside magnetopause leads to the production of Flux Transfer Events (FTEs). The magnetic fields within the FTEs exhibit complex helical flux-rope topologies. Leveraging the adaptive mesh refinement strategy, we perform a three-dimensional magnetohydrodynamic simulation of the magnetosphere of an Earth-like planet and study the evolution of these FTEs. For the first time, we detect and track the FTE structures in 3D and present a complete volumetric picture of FTE evolution. The temporal evolutions of thermodynamic quantities within the FTE volumes confirm that continuous reconnection is indeed the dominant cause of active FTE growth, as indicated by the deviation of the pressure-volume curves from an adiabatic profile. An investigation into the magnetic properties of the FTEs shows a rapid decrease in the perpendicular currents within the FTE volume, exhibiting the tendency of internal currents toward being field-aligned. An assessment of the validity of the linear force-free flux-rope model for such FTEs shows that the structures drift toward a constant-α state but continuous reconnection inhibits the attainment of a purely linear force-free configuration. Additionally, the fluxes enclosed by the selected FTEs are computed to range between 0.3 and 1.5 MWb. The FTE with the highest flux content constitutes ~1% of the net dayside open flux. These flux values are further compared against the estimates provided by the linear force-free flux-rope model. For the selected FTEs, the linear force-free model underestimated the flux content by up to 40%, owing to the continuous reconnected flux injection.

Keywords: Space plasmas, Planetary magnetospheres, Magnetohydrodynamical simulations
Thermal Evolution and Magnetic History of Rocky Planets. We present a thermal evolution model coupled with a Henyey solver to study the circumstances under which a rocky planet could potentially host a dynamo in its liquid iron core and/or magma ocean. We calculate the evolution of planet thermal profiles by solving the energy-balance equations for both the mantle and the core. We use a modified mixing length theory to model the convective heat flow in both the magma ocean and solid mantle. In addition, by including the Henyey solver, we self-consistently account for adjustments in the interior structure and heating (cooling) due to planet contraction (expansion). We evaluate whether a dynamo can operate using the critical magnetic Reynolds number. We run simulations to explore how the planet mass (M pl), core mass fraction (CMF), and equilibrium temperature (T eq) affect the evolution and lifetime of possible dynamo sources. We find that the T eq determines the solidification regime of the magma ocean, and only layers with melt fraction greater than a critical value of 0.4 may contribute to the dynamo source region in the magma ocean. We find that the mantle mass, determined by M pl and CMF, controls the thermal isolating effect on the iron core. In addition, we show that the liquid core lasts longer with increasing planet mass. For a core thermal conductivity of 40 Wm-1 K-1, the lifetime of the dynamo in the iron core is limited by the lifetime of the liquid core for 1 M ⊕ planets and by the lack of thermal convection for 3 M ⊕ planets.

Keywords: Exoplanet structure, Exoplanet evolution, Magnetic fields, Extrasolar rocky planets
The Synchrotron Low-energy Spectrum Arising from the Cooling of Electrons in Gamma-Ray Bursts. This work is a continuation of a previous effort (Panaitescu) to study the cooling of relativistic electrons through radiation (synchrotron and self-Compton) emission and adiabatic losses, with application to the spectra and light curves of the synchrotron gamma-ray burst (GRB) produced by such cooling electrons. Here, we derive the low-energy slope β LE of a GRB pulse-integrated spectrum and quantify the implications of the measured distribution of β LE. Radiative processes that produce soft integrated spectra can accommodate the harder slopes measured by CGRO/BATSE and Fermi/GBM only if the magnetic field lifetime t  B  is shorter than the time during which the typical GRB electrons cool to radiate below 1-10 keV, which is less than (at most) 10 radiative cooling timescales t rad of the typical GRB electron. In this case, there is a one-to-one correspondence between t  B  and β LE. To account for low-energy slopes β LE &gt; -3/4, the adiabatic electron-cooling requires a similar restriction on t  B . In this case, the diversity of slopes arises mostly from how the electron-injection rate varies with time (temporal power-law injection rates yield power-law low-energy GRB spectra) and not from the magnetic field timescale.

Keywords: Gamma-ray bursts, Non-thermal radiation sources, Plasma astrophysics, Radiative processes
TIC 114936199: A Quadruple Star System with a 12 Day Outer-orbit Eclipse. We report the discovery with TESS of a remarkable quadruple star system with a 2+1+1 configuration. The two unique characteristics of this system are that (i) the inner eclipsing binary (stars Aa and Ab) eclipses the star in the outermost orbit (star C), and (ii) these outer fourth-body eclipses last for ~12 days, the longest of any such system known. The three orbital periods are ~3.3 days, ~51 days, and ~2100 days. The extremely long duration of the outer eclipses is due to the fact that star B slows binary A down on the sky relative to star C. We combine TESS photometric data, ground-based photometric observations, eclipse timing points, radial velocity measurements, the composite spectral energy distribution, and stellar isochrones in a spectrophotodynamical analysis to deduce all of the basic properties of the four stars (mass, radius, T eff, and age), as well as the orbital parameters for all three orbits. The four masses are M Aa = 0.382 M ⊙, M Ab = 0.300 M ⊙, M B = 0.540 M ⊙, and M C = 0.615 M ⊙, with a typical uncertainty of 0.015 M ⊙.

Keywords: Eclipsing binary stars, Multiple stars
HST UV Spectroscopy of the Planet-hosting T Tauri Star PDS 70. We summarize Hubble Space Telescope (HST) UV observations of the weak-lined T Tauri star (wTTS) PDS 70 obtained with the Space Telescope Imaging Spectrograph. These observations provide the first far-UV (FUV) and near-UV (NUV) spectra of PDS 70. Ground-based observations have so far revealed two formative giant planets orbiting in a wide gap in its circumstellar disk. Both the star and young planets are thought to still be accreting. The HST spectra provide new insight into physical conditions in the star's outer atmosphere and circumstellar environment. The spectra are dominated by chromospheric and transition-region emission lines with maximum formation temperatures log T = 4.5-5.2 K. Stellar continuum emission is present in the NUV but we find no significant FUV continuum, as could arise from accretion shocks. Several fluorescent FUV H2 emission lines are present, a surprising result since H2 lines are usually undetected in wTTS. The H2 lines likely originate in irradiated circumstellar gas that could serve as a reservoir for the star's waning accretion. A previously established correlation between C IV line luminosity and accretion rate yields ${\dot{M}}_{\mathrm{acc}}\sim {10}^{-10}\,{M}_{\odot }\,{\mathrm{yr}}^{-1}$ , consistent with previous estimates. Atacama Large Millimeter/submillimeter Array disk gas models imply strong absorption of stellar X-ray and UV (XUV) radiation near the star, effectively shielding the planets. Inner disk gas is exposed to ongoing photoevaporation by XUV radiation and the disk is nearing the end of its expected lifetime, making PDS 70 an important example of a young planet-hosting star in the late stage of accretion.

Keywords: Ultraviolet astronomy, Pre-main sequence stars, Weak-line T Tauri stars
The Relative Importance of Thermal Gas, Radiation, and Magnetic Pressures around Star-forming Regions in Normal Galaxies and Dusty Starbursts. In this paper, an investigation on the relative importance of the thermal gas, radiation, and (minimum-energy) magnetic pressures around ≈200 star-forming regions in a sample of nearby normal and luminous infrared galaxies is presented. Given the range of galaxy distances, pressure estimates are made on spatial scales spanning ~0.1-3 kpc. The ratio of thermal gas-to-radiation pressures does not appear to significantly depend on star formation rate surface density (ΣSFR), but exhibits a steady decrease with increasing physical size of the aperture over which the quantities are measured. The ratio of magnetic-to-radiation pressures appears to be relatively flat as a function of ΣSFR and similar in value for both nuclear and extranuclear regions, but, unlike the ratio of thermal gas-to-radiation pressures, exhibits a steady increase with increasing aperture size. Furthermore, it seems that the magnetic pressure is typically weaker than the radiation pressure on subkiloparsec scales, and only starts to play a significant role on few-kiloparsec scales. When the internal pressure terms are summed, their ratio to the (ΣSFR-inferred) kiloparsec-scale dynamical equilibrium pressure estimates is roughly constant. Consequently, it appears that the physical area of the galaxy disk, and not necessarily environment (e.g., nuclear versus extranuclear regions) or star formation activity, may play the dominant role in determining which pressure term is most active around star-forming regions. These results are consistent with a scenario in which a combination of processes acting primarily on different physical scales work collectively to regulate the star formation process in galaxy disks.

Keywords: Stellar feedback, Disk galaxies, Star forming regions, Luminous infrared galaxies, Star formation, Galaxy evolution, Dust continuum emission, Radio continuum emission, Magnetic fields, Galaxies, Extragalactic magnetic fields
Large Sunspot Groups and Great Magnetic Storms: Magnetic Suppression of CMEs. A solar spot group with a large area is not a requirement for a great magnetic storm. Nearly half (14/30) of all storms with a minimum Dst value ≤-300 nT from 1932-2014 originated in spot groups with corrected areas ≤1000 millionths of a solar hemisphere (μsh) on the day of the associated eruption. Over the same interval, spot groups with area 3000-4000 μsh were ~250 times more likely to give rise to a great storm than those with areas from 100-1000 μsh, with the high percentage of great storms originating in small spot groups attributed primarily to the much higher occurrence frequency of such groups. Above ~3500 μsh, the ability of a spot group to produce a great storm appears to drop abruptly. For the 1932-2014 interval, we find that for the 71 days when a spot group had a measured daily area of 3000-3500 μsh, five great storms were observed versus none for the 67 times when a group spot with an area from 3500 to ~6000 μsh was observed on the Sun. This is consistent with recent studies indicating that large spot groups on the Sun and stars can suppress coronal mass ejections.

Keywords: Solar flares, Sunspot groups, Space weather, Solar active regions, Solar filament eruptions, Solar coronal mass ejections, Solar activity, Solar-terrestrial interactions
Combined Effects of f(R) Gravity and Massive Neutrinos on the Turnaround Radii of Dark Matter Halos. We present a new statistics based on the turnaround radii of cluster halos to break the dark sector degeneracy between the ΛCDM model and the alternative ones with f(R) gravity and massive neutrinos (ν) characterized by the strength of the fifth force, ∣f  R0∣, and the total neutrino mass, M  ν . Analyzing the Rockstar halo catalogs at the present epoch from the DUSTGRAIN-pathfinder N-body simulations performed for four different cosmologies, namely, ΛCDM (∣f  R0∣ = 0, ∑m  ν  = 0.0 eV), fR6 (∣f  R0∣ = 10-6, ∑m  ν  = 0.0 eV), fR6+0.06 eV(∣f  R0∣ = 10-6, ∑m  ν  = 0.06 eV), and fR5+0.15 eV(∣f  R0∣ = 10-5, ∑m  ν  = 0.15 eV), which are known to yield very similar conventional statistics to one another. For each model, we select those cluster halos that do not neighbor any other larger halos in their bound zones and construct their bound-zone peculiar velocity profiles at z = 0. Then, we determine the radial distance of each selected halo at which the bound-zone velocity becomes equal to the recession speed of the Hubble flow as its turnaround radius, and evaluate the cumulative probability distribution of the ratios of the turnaround radii to the virial counterparts, P(r  t /r  v  ≥ α). The degeneracy between the fR6 and fR5+0.15 eV models is found to be readily broken by the 10σ ΔP  difference in the value of P(α = 4), while the 3.2σ ΔP  difference between the ΛCDM and fR6+0.06 eV models is detected in the value of P(α = 8.5). It is also found that the four models yield smaller differences in P(α) at higher redshifts.

Keywords: Cosmological models, Large-scale structure of the universe