Sazuna/UAT_keywords huggingface dataset:
Systematic Investigation of Very-early-phase Spectra of Type Ia Supernovae. It has been widely accepted that Type Ia supernovae (SNe Ia) are thermonuclear explosions of a CO white dwarf. However, the natures of the progenitor system(s) and explosion mechanism(s) are still unclarified. Thanks to the recent development of transient observations, they are now frequently discovered shortly after the explosion, followed by rapid spectroscopic observations. In this study, by modeling very-early-phase spectra of SNe Ia, we try to constrain the explosion models of SNe Ia. By using the Monte Carlo radiation transfer code, TARDIS, we estimate the properties of their outermost ejecta. We find that the photospheric velocity of normal-velocity supernovae (NV SNe) in the first week is ~15,000 km s-1. The outer velocity, to which the carbon burning extends, spans the range between ~20,000 and 25,000 km s-1. The ejecta density of NV SNe also shows a large diversity. For high-velocity supernovae (HV SNe) and 1999aa-like SNe, the photospheric velocity is higher, ~20,000 km s-1. They have different photospheric densities, with HV SNe having higher densities than 1999aa-like SNe. For all these types, we show that the outermost composition is closely related to the outermost ejecta density; the carbon-burning layer and the unburnt carbon layer are found in the higher-density and lower-density objects, respectively. This finding suggests that there might be two sequences, the high-density and carbon-poor group (HV SNe and some NV SNe) and the low-density and carbon-rich group (1999aa-like and other NV SNe), which may be associated with different progenitor channels.

Keywords: Radiative transfer simulations, White dwarf stars, Type Ia supernovae
Impact of the Solar Activity on the Propagation of ICMEs: Simulations of Hydro, Magnetic and Median ICMEs at the Minimum and Maximum of Activity. The propagation of interplanetary coronal mass ejections (ICMEs) in the heliosphere is influenced by many physical phenomena, related to the internal structure of the ICME and its interaction with the ambient solar wind and magnetic field. As the solar magnetic field is modulated by the 11 yr dynamo cycle, our goal is to perform a theoretical exploratory study to assess the difference of propagation of an ICME in typical minimum and maximum activity backgrounds. We define a median representative CME at 0.1 au, using both observations and numerical simulations, and describe it using a spheromak model. We use the heliospheric propagator EUropean Heliospheric FORecasting Information Asset to inject the same ICME in two different background wind environments. We then study how the environment and the internal CME structure impact the propagation of the ICME toward Earth, by comparison with an unmagnetized CME. At minimum of activity, the structure of the heliosphere around the ecliptic causes the ICME to slow down, creating a delay with the polar parts of the ejecta. This delay is more important if the ICME is faster. At maximum of activity, a southern coronal hole causes a northward deflection. For these cases, we always find that the ICME at the maximum of activity arrives first, while the ICME at the minimum of activity is actually more geoeffective. The sign of the helicity of the ICME is also a crucial parameter, but at the minimum of activity only, since it affects the magnetic profile and the arrival time up to 8 hr.

Keywords: Solar cycle, Space weather, Solar wind, Solar coronal mass ejections
Impact of Pycnonuclear Fusion Uncertainties on the Cooling of Accreting Neutron Star Crusts. The observation of X-rays during quiescence from transiently accreting neutron stars provides unique clues about the nature of dense matter. This, however, requires extensive modeling of the crusts and matching the results to observations. The pycnonuclear fusion reaction rates implemented in these models are theoretically calculated by extending phenomenological expressions and have large uncertainties spanning many orders of magnitude. We present the first sensitivity studies of these pycnonuclear fusion reactions in realistic network calculations. We also couple the reaction network with the thermal evolution code dStar to further study their impact on the neutron star cooling curves in quiescence. Varying the pycnonuclear fusion reaction rates alters the depth at which nuclear heat is deposited although the total heating remains constant. The enhancement of the pycnonuclear fusion reaction rates leads to an overall shallower deposition of nuclear heat. The impurity factors are also altered depending on the type of ashes deposited on the crust. These total changes correspond to a variation of up to 9 eV in the modeled cooling curves. While this is not sufficient to explain the shallow heat source, it is comparable to the observational uncertainties and can still be important for modeling the neutron star crust.

Keywords: Neutron stars, X-ray transient sources, Degenerate matter, Nuclear astrophysics
An ALMA Glimpse of Dense Molecular Filaments Associated with High-mass Protostellar Systems in the Large Magellanic Cloud. Recent millimeter/submillimeter facilities have revealed the physical properties of filamentary molecular clouds in relation to high-mass star formation. A uniform survey of the nearest, face-on star-forming galaxy, the Large Magellanic Cloud (LMC), complements the Galactic knowledge. We present ALMA survey data with a spatial resolution of ~0.1 pc in the 0.87 mm continuum and HCO+ (4-3) emission toward 30 protostellar objects with luminosities of 104-105.5 L ⊙ in the LMC. The spatial distributions of the HCO+ (4-3) line and thermal dust emission are well correlated, indicating that the line effectively traces dense, filamentary gas with an H2 volume density of ≳105 cm-3 and a line mass of ~103-104 M ⊙ pc-1. Furthermore, we obtain an increase in the velocity line widths of filamentary clouds, which follows a power-law dependence on their H2 column densities with an exponent of ~0.5. This trend is consistent with observations toward filamentary clouds in nearby star-forming regions within ≲1 kpc from us and suggests enhanced internal turbulence within the filaments due to surrounding gas accretion. Among the 30 sources, we find that 14 are associated with hub-filamentary structures, and these complex structures predominantly appear in protostellar luminosities exceeding ~5 × 104 L ⊙. The hub-filament systems tend to appear in the latest stages of their natal cloud evolution, often linked to prominent H II regions and numerous stellar clusters. Our preliminary statistics suggest that the massive filaments accompanied by hub-type complex features may be a necessary intermediate product in forming extremely luminous high-mass stellar systems capable of ultimately dispersing the parent cloud.

Keywords: Local Group, Molecular clouds, Large Magellanic Cloud, Star formation, Interstellar medium, Protostars
Moving Corona and the Line Profile of the Relativistic Broad Iron Emission Line. Iron fluorescence emission lines from X-ray binaries and active galactic nuclei are important diagnostic tools for studying the physical processes near the event horizon of both the stellar-mass black holes in X-ray binaries and the supermassive black holes in active galactic nuclei. In this work, we investigate the line profile of the relativistic broad iron lines from the cool accretion disk of a black hole due to the asymmetric illumination of a moving corona, which moves away from the disk with a relativistic velocity. Both the off-axis location and the radial velocity of the moving corona are considered. Our results clearly show that the illumination and the line profile are dependent on the position and velocity of the corona, since the disk region below the corona receives more flux, which is the most important factor affecting the line profiles. As expected, if the corona is close to the receding part of the rotating disk, the red peak is enhanced, while the blue peak is weakened in the broad line profile, and the central energy of the emission line is low. Conversely, if the corona is close to the approaching part of the disk, the blue peak is strong and the central energy of the emission line is high, even higher than the intrinsic energy of the emission line. Due to the beaming effect of the moving corona, the corona with high velocity illuminates the outer region of the disk, which leads to the red peak disappearing and there being only one blue peak in the profile of the emission line.

Keywords: Black hole physics, X-ray binary stars, High energy astrophysics
Excitation and Ionization Properties of Star-forming Galaxies at z = 2.0-9.3 with JWST/NIRSpec. We utilize medium-resolution JWST/NIRSpec observations of 164 galaxies at z = 2.0-9.3 from the Cosmic Evolution Early Release Science (CEERS) survey to investigate the evolution of the excitation and ionization properties of galaxies at high redshifts. Our results represent the first statistical constraints on the evolution of the [O III]/Hβ versus [N II]/Hα, [S II]/Hα, and [O I]/Hα "BPT" diagrams at z &gt; 2.7, and the first analysis of the O32 versus R23 diagram at z &gt; 4 with a large sample. We divide the sample into five redshift bins containing 30-40 galaxies each. The subsamples at z ~ 2.3, z ~ 3.3, and z ~ 4.5 are representative of the main-sequence star-forming galaxy population at these redshifts, while the z ~ 5.6 and z ~ 7.5 samples are likely biased toward high specific star formation rate, due to selection effects. Using composite spectra, we find that each subsample at z = 2.0-6.5 falls on the same excitation sequence in the [N II] and [S II] BPT diagrams and the O32-R23 diagram on average, and is offset from the sequences followed by z = 0 H II regions in the same diagrams. The direction of these offsets are consistent with high-redshift star-forming galaxies uniformly having harder ionizing spectra than typical local galaxies at fixed nebular metallicity. The similarity of the average line ratios suggests that the ionization conditions of the interstellar medium do not strongly evolve between z ~ 2 and z ~ 6. Overall, the rest-optical line ratios suggest the z = 2.7-9.3 CEERS/NIRSpec galaxies at log(M */M ⊙) ~ 7.5-10 have high degrees of ionization and moderately low oxygen abundances (~0.1-0.3 Z ⊙), but are not extremely metal-poor (&lt;0.1 Z ⊙) even at z &gt; 6.5.

Keywords: Emission line galaxies, High-redshift galaxies, Galaxy evolution, Ionization
The Formation of Star-forming Disks in the TNG50 Simulation. We investigate the disk formation process in the TNG50 simulation, examining the profiles of SFR surface density (ΣSFR), gas inflow and outflow, and the evolution of the angular momentum of inflowing gas particles. The TNG50 galaxies tend to have larger star-forming disks, and they also show larger deviations from exponential profiles in ΣSFR when compared to real galaxies in the Mapping Nearby Galaxies at APO survey. The stellar surface density of TNG50 galaxies show good exponential profiles, which is found to be the result of strong radial migration of stars over time. However, this strong radial migration of stars in the simulation produces flatter age profiles in TNG50 disks compared to observed galaxies. The star formation in the simulated galaxies is sustained by a net gas inflow, and this gas inflow is the primary driver for the cosmic evolution of star formation, as expected from simple gas-regulator models of galaxies. There is no evidence for any significant loss of angular momentum for the gas particles after they are accreted on to the galaxy, which may account for the large disk sizes in the TNG50 simulation. Adding viscous processes to the disks, such as the magnetic stresses from magnetorotational instability proposed by Wang &amp; Lilly, will likely reduce the sizes of the simulated disks and the tension with the sizes of real galaxies, and this may produce more realistic exponential profiles.

Keywords: Galaxy disks, Star formation, Magnetohydrodynamical simulations
Revisiting X-Ray-bright Optically Normal Galaxies with the Chandra Source Catalog. X-ray bright optically normal galaxies (XBONGs) are galaxies with X-ray luminosities consistent with those of active galactic nuclei (AGNs) but no evidence of AGN optical emission lines. Crossmatching the Chandra Source Catalog version 2 with the Sloan Digital Sky Survey sample of spectroscopically classified galaxies, we have identified 817 XBONG candidates with L X &gt; 1042 erg s-1 and X-ray to optical flux ratio F XO &gt; 0.1. Comparisons with Wide-field Infrared Survey Explorer colors and near-IR, optical, UV, and radio luminosities show that the loci of XBONGs are in-between those of control samples of normal galaxies and quasars and are consistent with low-luminosity quasars. We find that 43% of the XBONG sample have X-ray colors suggesting N H &gt; 1022 cm-2, double the fraction in the QSO sample, suggesting that a large fraction of XBONG are highly obscured AGNs. However, ~50% of the XBONGs are not obscured and have X-ray colors harder than those of normal galaxies. Some of these XBONGs have spatially extended X-ray emission. These characteristics suggest that they may be unidentified galaxy groups and clusters. Using the X-ray luminosity functions of QSOs, galaxies, groups and clusters, we estimate the approximate fraction of extended XBONGs to be &lt;20%. We also assess the approximate fraction of XBONGs whose AGN signatures are diluted by stellar light of host galaxies to be ~30%, based on their redshift and deviation from the extrapolation of the QSO L X-L  r  relation.

Keywords: X-ray astronomy, Classification, Active galactic nuclei, X-ray surveys, X-ray sources, Galaxy groups, Galaxies
NeutralUniverseMachine: An Empirical Model for the Evolution of H I and H<SUB>2</SUB> Gas in the Universe. Accurately modeling the cold gas content in the universe is challenging for current theoretical models. We propose a new empirical model NeutralUniverseMachine for the evolution of H I and H2 gas along with dark matter halos based on the UniverseMachine catalog. It is able to accurately describe the observed H I and H2 mass functions, molecular-to-atomic ratio, H I-halo mass relation, H I/H2-stellar mass relations at z ~ 0, as well as the evolution of cosmic gas densities ρ H I and ${\rho }_{{{\rm{H}}}_{2}}$ at 0 &lt; z &lt; 6. The predictions from our model include the following: (i) There is weak evolution of H I mass function at 0 &lt; z &lt; 3, but the evolution of H2 mass function is much stronger at the massive end. (ii) The average H I and H2 masses at a given stellar mass decrease by around 1 dex since z = 3 for the star-forming galaxies, but the evolution for the quenched galaxies is much weaker. (iii) Star-forming galaxies have a varying H I depletion time τ H I from 0.1-10 Gyr, and the dependence of τ H I on stellar mass and redshift is much stronger than those of the H2 depletion time. The quenched galaxies have a much longer gas depletion time and weaker redshift evolution. (iv) The cosmic baryon density associated with galaxies is dominated by stars at z &lt; 1.2 and mainly contributed by H I gas at higher redshifts. (v) The H I bias gradually increases with the redshift from 0.69 to 2.33 at 0 &lt; z &lt; 3 and is consistent with recent H I intensity mapping experiments.

Keywords: Galaxy dark matter halos, Molecular gas, Theoretical models, H I line emission, Star formation, Cold neutral medium, Galaxy evolution, Circumgalactic medium, Baryon density
Magnetohydrodynamic Shocks Revisited: Magnetically Constraining the Upstream Solar Wind Condition. Magnetohydrodynamic (MHD) shocks are commonly found in various space and astrophysical systems. One often encounters the problem that only the magnetic field data are available when studying interplanetary shocks and planetary bow shocks in the solar system, and not the plasma data due to instrumental and/or telemetry limitations. We aim to reveal the mathematical structure of the MHD Rankine-Hugoniot relation under the condition that magnetic field changes across the shock are known, which can be devised into a diagnosis tool to constrain the shock parameters. The perturbative solution is already known for the Rankine-Hugoniot equation. The solution is combined with the condition of the de Hoffmann-Teller frame for the vanishing convective electric field, and we obtain a two-dimensional matrix equation for the density jump and the Alfvén Mach number. The lesson is that the shock parameters (density jump and Alfvén Mach number) are analytically obtained by inverting the MHD Rankine-Hugoniot equation under the condition that the plasma beta is either a priori set or known. Further numerical studies indicate that the presented shock jump estimation works particularly well for quasi-perpendicular shocks. Moreover, a test case with the Earth bow shock crossing data supports our theoretical development. The presented method opens the door to determining or constraining the shock parameters even if the data are limited to the magnetic field only.

Keywords: Magnetohydrodynamics
Neutral Atomic and Molecular Clouds and Star Formation in the Outer Carina Arm. We present a comprehensive investigation of H I (super)clouds, molecular clouds (MCs), and star formation in the Carina spiral arm of the outer Galaxy. Utilizing HI4PI and CfA CO survey data, we identify H I clouds and MCs based on the (l, v LSR) locations of the Carina arm. We analyzed 26 H I clouds and 48 MCs. Most of the identified H I clouds are superclouds, with masses exceeding 106 M ⊙. We find that 15 of these superclouds have associated MC(s) with M H I ≳ 106 M ⊙ and ${{\rm{\Sigma }}}_{{\rm{H}}\,{\rm\small{I}}+{{\rm{H}}}_{2}}\gtrsim $ 50 M ⊙ pc-2. Our virial equilibrium analysis suggests that these CO-bright H I clouds are gravitationally bound or marginally bound. We report an anticorrelation between molecular mass fractions and Galactocentric distances, and a correlation with total gas surface densities. Nine CO-bright H I superclouds are associated with H II regions, indicating ongoing star formation. We confirm the regular spacing of H I superclouds along the spiral arm, which is likely due to some underlying physical process, such as gravitational instabilities. We observe a strong spatial correlation between H II regions and MCs, with some offsets between MCs and local H I column density peaks. Our study reveals that, in the context of H I superclouds, the star formation rate surface density is independent of H I and total gas surface densities but positively correlates with molecular gas surface density. This finding is consistent with both extragalactic studies of the resolved Kennicutt-Schmidt relation and local giant molecular clouds study of Lada et al. (2013), emphasizing the crucial role of molecular gas in regulating star formation processes.

Keywords: Interstellar clouds
Crossing the Rubicon of Reionization with z   5 QSOs. One of the key open questions in cosmology is the nature of sources that completed cosmological hydrogen reionization at z ~ 5.2. High-z primeval galaxies have been long considered the main drivers of reionization, with a minor role played by high-z active galactic nuclei (AGN). However, in order to confirm this scenario, it is fundamental to measure the photoionization rate produced by active SMBHs close to the Epoch of Reionization. Given the pivotal role played by spectroscopically complete observations of high-z QSOs, in this paper we present the first results of the RUBICON (Reionizing the Universe with Bright Cosmological Nuclei) survey. It consists of a color-selected sample of bona fide z ~ 5 QSO candidates from the Hyper Suprime-Cam Subaru Strategic Survey. Our QSO candidates have been validated both by photometric redshifts based on spectral energy distribution fitting and by spectroscopic redshifts, confirming that they lie at 4.5 &lt; z spec &lt; 5.2. A relatively high space density of QSOs (Φ ~ 1.4 × 10-8 c Mpc-3) is thus confirmed at z ~ 5 and M 1450 ~ -27, consistent with a pure density evolution of the AGN luminosity function from z = 4 to z = 5, with a mild density evolution rate of 0.25 dex. This indicates that AGN could play a nonnegligible role in cosmic reionization. The Rubicon of reionization has been crossed.

Keywords: Quasars, Surveys, Observational cosmology, Reionization, Catalogs
Identification of Bubble Nebulae around NGC 55 ULX-1 with MUSE Observations. Using the Multi Unit Spectroscopic Explorer (MUSE) instrument on the Very Large Telescope, we identified three bubble nebulae (denoted as A, B, and C) around an ultraluminous X-ray source (ULX) in NGC 55. Bubble A shows a regular elliptical shape surrounding the ULX, with a morphology similar to the canonical ULX bubble around NGC 1313 X-2. It is most likely inflated by the ULX disk wind with a mechanical power close to 1039 erg s-1. Bubble B lies 11″ away from the ULX on the sky plane and is not contiguous to Bubble A. It displays a bow-shock-like morphology, and is likely driven by a collimated dark jet from the ULX with a mechanical power of about 3 × 1038 erg s-1. If this scenario is correct, we predict that Bubble B should present radio emission with a flux of about 1-102 μJy at 5 GHz. Bubble C appears within Bubble A, with a velocity and velocity dispersion distinct from the rest of Bubble A. Its nature is unclear and could be part of Bubble A as a result of low local density. The optical counterpart of ULX-1 exhibits broad Hα, consistent with emission from a hot disk wind.

Keywords: Accretion, Ultraluminous x-ray sources, Superbubbles, Emission nebulae
Using Tianwen-1 Differential One-way Range Signals to Probe Corotating Interaction Regions: Case Studies. The study reports the first detection of corotating interaction regions (CIRs) in the solar wind by the differential one-way range (DOR) signals transmitted by Tianwen-1. Differential phase delay is calculated for the DOR signals. Variations of the total electron content (TEC) along the signal path between Tianwen-1 and the ground stations are then derived from changes in the differential phase delay. Large TEC variations are found for 2021 February 11, 18, and 19 even after the influence from the Earth's ionosphere has been removed. In situ solar wind measurements and the corresponding simulation results further show that the TEC variations are caused by the CIRs that passed through the signal path on these days. The study demonstrates that CIR structures can be probed using deep-space spacecraft range signals. Such measurements can be used to constrain global solar wind forecast models.

Keywords: Deep space probes, Solar wind, Remote sensing, Corotating streams, Radio astronomy
Energetic Neutral Atoms from Solar Energetic Particles due to Shocks: Inclusion of Upstream Particles. Many aspects of solar energetic particles are not well understood, including their acceleration mechanism. There has been recent interest in the potential of energetic neutral atoms (ENAs) as remote probes of solar energetic particles (SEPs) and their acceleration. The single accidental observation (in physical units) has been modeled as accelerated by a coronal mass ejection (CME)-driven shock by several authors, all of whom have assumed that the upstream component of the shock can be ignored. In this article, we relax this assumption and model the flux of ENAs at 1 au due to a CME-driven shock with an upstream component. We show the effect of varying parameters of the shock acceleration model, specifically α, the exponent of the power law in momentum of the mean free path, and η, a measure of the relative turbulence level. The main result is that including the upstream component significantly increases the flux at 1 au for typically assumed parameters in the energy range of the STEREO observation. We also derive the form of the ENA transport equation that we used in this study. These results enable a better understanding of potential observations of ENAs due to SEPs.

Keywords: Solar energetic particles