Sazuna/UAT_keywords huggingface dataset:
Type IIP Supernova Progenitors. II. Stellar Mass and Obscuration by the Dust in the Circumstellar Medium. It has been well established from a variety of observations that red supergiants (RSGs) lose a lot of mass in stellar wind. Dust that has formed in this emitted gas over a few decades before core-collapse can lead to substantial extinction and obscure the intrinsic luminosity of the progenitor RSG. This may lead to a difficulty in determining the range of progenitor masses that lead to the different classes of supernovae. Even nearby, well-studied supernovae with pre-explosion observations, such as SN 2013ej, may suffer from this uncertainty in the progenitor mass. We explore here two different masses proposed for its progenitor. We compute their pre-supernova characteristics using Modules for Experiments in Stellar Astrophysics. We show that a non-rotating star with an initial mass of 26 M⊙ would require a considerable amount of circumstellar medium (AV ∼ 3) to obscure its high luminosity given the observed pre-explosion magnitudes detected by the Hubble Space Telescope (HST). Such a high value of visual extinction appears to be inconsistent with that derived for SN 2013ej as well as SN 2003gd in the same host galaxy, M74. In contrast, the evolutionary models of a lower mass (13 M⊙) star are easily accommodated within the observed HST magnitudes. Some of the 26 M⊙ simulations show luminosity variation in the last few years, which could be discriminated by high-cadence and multiband monitoring of supernova candidates in nearby galaxies. We demonstrate that our calculations are well resolved with adequate zoning and evolutionary time steps.

Keywords: Stellar interiors, Core-collapse supernovae, Type II supernovae, Massive stars, Stellar evolutionary models, Stellar mass loss, Computational methods, Supergiant stars, Hertzsprung Russell diagram, Circumstellar dust
A Convective Dredge-up Model as the Origin of Hydrogen in DBA White Dwarfs. We revisit the problem of the formation of DB white dwarfs, as well as the origin of hydrogen in DBA stars, using a new set of envelope model calculations with stratified and mixed hydrogen/helium compositions. We first describe an approximate model to simulate the so-called convective dilution process, where a thin, superficial hydrogen radiative layer is gradually eroded by the underlying and more massive convective helium envelope, thus transforming a DA white dwarf into a DB star. We show that this convective dilution process is able to account for the large increase in the number of DB white dwarfs below Teff ∼ 20,000 K, but that the residual hydrogen abundances expected from this process are still orders of magnitude lower than those observed in DBA white dwarfs. Scenarios involving the accretion of hydrogen from the interstellar medium or other external bodies have often been invoked to explain these overabundances of hydrogen. In this paper, we describe a new paradigm where hydrogen, initially diluted within the thick stellar envelope, is still present and slowly diffuses upward in the deeper layers of a Teff ∼ 20,000 K white dwarf. When the convective dilution process occurs, the bottom of the mixed H/He convection zone sinks deep into the star, resulting in large amounts of hydrogen being dredged up to the stellar surface, a phenomenon similar to that invoked in the context of DQ white dwarfs.

Keywords: Fundamental parameters of stars, Stellar abundances, White dwarf stars, Stellar evolution
Testing the Prediction of Fuzzy Dark Matter Theory in the Milky Way Center. The fuzzy dark matter model (FDM; also known as quantum wave dark matter model) argues that light bosons with a mass of $\sim {10}^{-22}\,\mathrm{eV}$ are a possible candidate for dark matter in the universe. One of the most important predictions of FDM is the formation of a soliton core instead of a density cusp at the center of galaxies. If FDM is the correct theory of dark matter, then the predicted soliton core can help form the Central Molecular Zone (CMZ) in the Milky Way. We present high-resolution hydrodynamical simulations of gas flow patterns to constrain the properties of the soliton core based on a realistic Milky Way potential. We find that a dense center is required to form a reasonable CMZ. The size and kinematics of the CMZ offer a relatively strong constraint on the inner enclosed mass profile of the Galaxy. If a soliton core is not considered, a compact nuclear bulge alone with a radially varying mass-to-light ratio can match the observed size and kinematics of the CMZ. A soliton core model with a mass of $\approx 4.0\times {10}^{8}\,{M}_{\odot }$ and a core radius of $\approx 0.05\,\mathrm{kpc}$ , together with a less massive nuclear bulge with a constant mass-to-light ratio, also agrees nicely with the current data. Such an FDM soliton core corresponds to a boson mass of $(\sim 2\mbox{--}7)\times {10}^{-22}\,\mathrm{eV}$ , which could be further constrained by the improved determination of the mass-to-light ratio in the Galactic center.

Keywords: Cosmology, Galactic center, Galaxy dynamics, Interstellar medium, Barred spiral galaxies, Astrophysical fluid dynamics, Dark matter, Milky Way Galaxy
Measurement of Void Bias Using Separate Universe Simulations. Cosmic voids are biased tracers of the large-scale structure of the universe. Separate universe simulations (SUS) enable accurate measurements of this biasing relation by implementing the peak-background split (PBS). In this work, we apply the SUS technique to measure the void bias parameters. We confirm that the PBS argument works well for underdense tracers. The response of the void size distribution depends on the void radius. For voids larger (smaller) than the size at the peak of the distribution, the void abundance responds negatively (positively) to a long wavelength mode. The linear bias from the SUS is in good agreement with the cross power spectrum measurement on large scales. Using the SUS, we have detected the quadratic void bias for the first time in simulations. We find that b2 is negative when the magnitude of b1 is small, and that it becomes positive and increases rapidly when $| {b}_{1}| $ increases. We compare the results from voids identified in the halo density field with those from the dark matter distribution, and find that the results are qualitatively similar, but the biases generally shift to the larger voids sizes.

Keywords: Cosmology, Dark matter distribution, Large-scale structure of the universe, Voids, Cosmic web
Luminous Lyα Emitters with Very Blue UV-continuum Slopes at Redshift 5.7 ≤ z ≤ 6.6. We study six luminous Lyα emitters (LAEs) with very blue rest-frame UV continua at 5.7 ≤ z ≤ 6.6. These LAEs have previous Hubble Space Telescope (HST) and Spitzer IRAC observations. Combining our newly acquired HST images, we find that their UV-continuum slopes β are in a range of -3.4 ≤ β ≤ -2.6. Unlike previous, tentative detections of β ≃ -3 in photometrically selected, low-luminosity galaxies, our LAEs are spectroscopically confirmed and luminous (MUV &lt; -20 mag). We model their broadband spectral energy distributions (SEDs), and find that two β ≃ -2.6 ± 0.2 galaxies can be well fitted with young and dust-free stellar populations. However, it becomes increasingly difficult to fit bluer galaxies. We explore further interpretations by including the non-zero LyC escape fraction fesc, very low metallicities, and/or active galactic nucleus contributions. Assuming fesc ≃ 0.2, we achieve the bluest slopes β ≃ -2.7 when nebular emission is considered. This can nearly explain the SEDs of two galaxies with β ≃ -2.8 and -2.9 (σβ = 0.15). Larger fesc values and very low metallicities are not favored by the strong nebular line emission (evidenced by the IRAC flux) or the observed (IRAC 1 - IRAC 2) color. Finally, we find that the β ≃ -2.9 galaxy can potentially be well explained by the combination of a very young population with a high fesc (≥0.5) and an old, dusty population. We are not able to produce two β ≃ -3.4 ± 0.4 galaxies. Future deep spectroscopic observations are needed to fully understand these galaxies.

Keywords: Lyman-alpha galaxies, High-redshift galaxies, Galaxy properties
A Unified Framework for X-shaped Radio Galaxies. We propose a radically different picture for X-shaped radio galaxies compared with existing models as transition objects between cold-mode accreting, low-spinning retrograde black holes and low-spinning prograde black holes. This model explains their smaller average black hole masses; their general aversion for cluster compared with isolated environments; the negligible difference in spectral index between primary and secondary jets, despite a time difference in their formation; their absence among the most powerful radio quasars and radio galaxies; and their connection to the elusive Fanaroff-Riley I quasar class, among others. The key to their formation is cold gas accretion onto Schwarzschild black holes.

Keywords: Radio galaxies
Fast and Wide CMEs without Observed &gt;20 MeV Protons. Statistical studies have found a close association between large solar energetic particle (SEP) events and fast and wide coronal mass ejections (CMEs). However, not all fast and wide CMEs have an associated SEP event. From the Coordinated Data Analysis Web catalog of CMEs observed by the Solar and Heliospheric Observatory (SOHO) between 2009 January 1 and 2014 September 30, we select fast (plane-of-sky speed &gt;1000 km s-1) and wide (plane-of-sky angular width &gt;120°) CMEs and determine whether &gt;20 MeV protons were detected by either SOHO or the Solar TErrestrial RElations Observatory (STEREO-A or STEREO-B). Among the 123 selected CMEs, only 11 did not produce a &gt;20 MeV proton intensity increase at any of the three spacecraft. We use multispacecraft coronagraph observations to reevaluate the speeds and widths of the CMEs. The 11 CMEs without observed &gt;20 MeV protons tend to be in the narrow and slow end of the distribution of the selected CMEs. We consider several factors that might play a role in the nonobservation of high-energy particles in these events, including (1) the ambiguous determination of the CME parameters, (2) the inefficiency of the particle sources to produce &gt;20 MeV protons, (3) the lack of magnetic connection between particle sources and any spacecraft, and (4) the lack of particles accelerated and released during the parent solar eruptions. Whereas the extent of the high Mach number regions formed in front of the CME is limited, the characteristic that seems to distinguish those fast and wide CMEs that lack observed &gt;20 MeV protons is a deficit in the release of particles during the solar eruptions.

Keywords: Solar energetic particles, Solar coronal mass ejection shocks, Solar particle emission, Solar coronal mass ejections
Quiescent Galaxies 1.5 Billion Years after the Big Bang and Their Progenitors. We report two secure ( $z=3.775,4.012$ ) and one tentative (z ≈ 3.767) spectroscopic confirmations of massive and quiescent galaxies through K-band observations with Keck/MOSFIRE and Very Large Telescope/X-Shooter. The stellar continuum emission, absence of strong nebular emission lines, and lack of significant far-infrared detections confirm the passive nature of these objects, disfavoring the alternative solution of low-redshift dusty star-forming interlopers. We derive stellar masses of log(M⋆/M☉) ∼ 11 and ongoing star formation rates placing these galaxies ≳1-2 dex below the main sequence at their redshifts. The adopted parameterization of the star formation history suggests that these sources experienced a strong ( $\langle \mathrm{SFR}\rangle \sim 1200\mbox{--}3500$ M☉ yr-1) and short (∼50 Myr) burst of star formation, peaking ∼150-500 Myr before the time of observation, all properties reminiscent of the characteristics of submillimeter galaxies (SMGs) at z &gt; 4. We investigate this connection by comparing the comoving number densities and the properties of these two populations. We find a fair agreement only with the deepest submillimeter surveys detecting not only the most extreme starbursts but also more normal galaxies. We support these findings by further exploring the Illustris TNG cosmological simulation, retrieving populations of both fully quenched massive galaxies at z ∼ 3-4 and SMGs at z ∼ 4-5, with number densities and properties in agreement with the observations at z ∼ 3 but in increasing tension at higher redshift. Nevertheless, as suggested by the observations, not all of the progenitors of quiescent galaxies at these redshifts shine as bright SMGs in their past, and, similarly, not all bright SMGs quench by z ∼ 3, both fractions depending on the threshold assumed to define the SMGs themselves.

Keywords: Starburst galaxies, Galaxy stellar content, Star formation, Galaxy evolution, Elliptical galaxies, High-redshift galaxies
The Effect of Star-Disk Interactions on Highly Eccentric Stellar Orbits in Active Galactic Nuclei: A Disk Loss Cone and Implications for Stellar Tidal Disruption Events. Galactic center black holes appear to be nearly universally surrounded by dense stellar clusters. When these black holes go through an active accretion phase, the multiple components of the accretion disk, stellar cluster, and black hole system all coexist. We analyze the effect of drag forces on highly eccentric stellar orbits incurred as stars puncture through the disk plane. Disk crossings dissipate orbital energy, drawing eccentric stars into more circular orbits. For high surface density disks, such as those found around black holes accreting near the Eddington mass accretion limit, the magnitude of this energy dissipation can be larger than the mean scatterings that stars receive by two-body relaxation. One implication of this is the presence of a disk "loss cone" for highly eccentric stellar orbits where the dissipation from disk interaction outweighs scatter via two-body relaxation. The disk loss cone is larger than the tidal disruption loss cone for near-Eddington black hole accretion rates. Stellar orbits within the disk loss cone are lost from the overall cluster as stellar orbits are circularized and stars are potentially ablated by their high-velocity impacts with the disk. We find, however, that the presence of the disk loss cone has a minimal effect on the overall rate of stellar tidal disruptions. Stars are still efficiently fed to the black hole from more-distant stellar orbits that receive large-enough per-orbit scatter to jump over the disk loss cone and end up tidally disrupted.

Keywords: Supermassive black holes, Active galactic nuclei, Star clusters
Ion-neutral Interactions and Nonequilibrium Ionization in the Solar Chromosphere. The thermal structure of the chromosphere is regulated through a complex interaction of various heating processes, radiative cooling, and the ionization degree of the plasma. Here, we study the impact on the thermal properties of the chromosphere when including the combined action of nonequilibrium ionization (NEI) of hydrogen and helium and ion-neutral interaction effects. We have performed a 2.5D radiative magnetohydrodynamic simulation using the Bifrost code. This model includes ion-neutral interaction effects by solving the generalized Ohm' s law (GOL) as well as NEI for hydrogen and helium. The GOL equation includes ambipolar diffusion and the Hall term. We compare this simulation with another simulation that computes the ionization in local thermodynamic equilibrium (LTE) including ion-neutral interaction effects. Our numerical models reveal substantial thermal differences in magneto-acoustic shocks, the wake behind the shocks, spicules, low-lying magnetic loops, and the transition region. In particular, we find that heating through ambipolar diffusion in shock wakes is substantially less efficient, while in the shock fronts themselves it is more efficient, under NEI conditions than when assuming LTE.

Keywords: Radiative magnetohydrodynamics, Magnetohydrodynamical simulations, Solar spicules, Solar magnetic fields, Solar chromospheric heating, Solar chromosphere
The GBT Diffuse Ionized Gas Survey: Tracing the Diffuse Ionized Gas around the Giant Hii Region W43. The Green Bank Telescope Diffuse Ionized Gas Survey (GDIGS) is a fully sampled radio recombination line (RRL) survey of the inner Galaxy at C-band (4-8 GHz). We average together ∼15 Hnα RRLs within the receiver bandpass to improve the spectral signal-to-noise ratio. The average beam size for the RRL observations at these frequencies is ∼2'. We grid these data to have spatial and velocity spacings of 30″ and 0.5 $\mathrm{km}\,{{\rm{s}}}^{-1}$ , respectively. Here we discuss the first RRL data from GDIGS: a 6 deg2 area surrounding the Galactic H II region complex W43. We attempt to create a map devoid of emission from discrete H II regions and detect RRL emission from the diffuse ionized gas (DIG) across nearly the entire mapped area. We estimate the intensity of the DIG emission by a simple empirical model, taking only the H II region locations, angular sizes, and RRL intensities into account. The DIG emission is predominantly found at two distinct velocities: ∼40 and ∼100 $\mathrm{km}\,{{\rm{s}}}^{-1}$ . While the 100 $\mathrm{km}\,{{\rm{s}}}^{-1}$ component is associated with W43 at a distance of ∼6 kpc, the origin of the 40 $\mathrm{km}\,{{\rm{s}}}^{-1}$ component is less clear. Since the distribution of the 40 $\mathrm{km}\,{{\rm{s}}}^{-1}$ emission cannot be adequately explained by ionizing sources at the same velocity, we hypothesize that the plasma at the two velocity components is interacting, placing the 40 $\mathrm{km}\,{{\rm{s}}}^{-1}$ DIG at a similar distance as the 100 $\mathrm{km}\,{{\rm{s}}}^{-1}$ emission. We find a correlation between dust temperature and integrated RRL intensity, suggesting that the same radiation field that heats the dust also maintains the ionization of the DIG.

Keywords: Galactic radio sources, Surveys, Interstellar abundances, Photodissociation regions, Warm ionized medium, H II regions, Interstellar medium, Radio astronomy
The Original Anisotropy of TeV Cosmic Rays in the Local Interstellar Medium. This paper presents the original anisotropy that TeV cosmic rays (CRs) have in the local interstellar medium. This anisotropy is obtained using a method of flux mapping with the Liouville theorem and a magnetohydrodynamic (MHD) heliosphere model of the electromagnetic field to remove the particle propagation effects hidden in the measurements made by the Tibet ASγ experiment at Earth. The original interstellar anisotropy turns out to be almost a pure dipole, which results from a diffusion flow of CRs escaping along the local interstellar magnetic field into the northern Galactic halo. The observed anisotropy maps at Earth appear quite complex because the heliosphere distorts the dipole anisotropy, generating a significant amount of high-order multipoles, while interstellar magnetic field fluctuations contribute to some weak anisotropy on small angular scales. It is found that the density gradient of these CRs points approximately toward Vela in the Local Bubble, providing experimental evidence to show that the local supernova is making a special contribution to the TeV CRs we see at Earth. This special contribution will keep growing in the future tens of thousand years. The original anisotropy also reveals that the CRs spread from the source primarily along the interstellar magnetic field, while experiencing a nearly isotropic pitch-angle scattering process caused by interstellar turbulence.

Keywords: Galactic cosmic rays, Cosmic ray sources, Heliosphere
Investigating Overdensities around z &gt; 6 Galaxies through ALMA Observations of [C II]. We present a search for companion [C II] emitters to known luminous sources at 6 &lt; z &lt; 6.5 in deep, archival ALMA observations. The observations are deep enough to detect sources with ${L}_{[{\rm{C}}{\rm{II}}]}\sim {10}^{8}\ {L}_{\odot }$ at z ∼ 6. We identify three new robust line detections from a blind search of five deep fields centered on ultraluminous infrared galaxies and QSOs. We calculate the volume density of companions and find a relative overdensity of ${6}_{-3}^{+4}$ and ${86}_{-37}^{+60}$ when comparing to current observational constraints and theoretical predictions, respectively. These results suggest that the central sources may be highly biased tracers of mass in the early universe. We find these companion lines to have comparable properties to other known galaxies at the same epoch. All companions lie less than 650 km s-1 and between 25 and 60 kpc (projected) from their central source. To place these discoveries in context, we employ a mock galaxy catalog to estimate the luminosity function for [C II] during reionization and compare to our observations. The simulations support this result by showing a similar level of elevated counts found around such luminous [C II] sources.

Keywords: Quasar-galaxy pairs, Submillimeter astronomy, Reionization, High-redshift galaxies, Galaxies
Diagnosing the Stellar Population and Tidal Structure of the Blanco 1 Star Cluster. We present the stellar population, using Gaia DR2 parallax, kinematics, and photometry, of the young (∼100 Myr), nearby (∼230 pc) open cluster, Blanco 1. A total of 644 member candidates are identified via the unsupervised machine learning method StarGO to find the clustering in the five-dimensional position and proper motion parameter (X, Y, Z, ${\mu }_{\alpha }\cos \delta $ , μδ) space. Within the tidal radius of 10.0 ± 0.3 pc, there are 488 member candidates, 3 times more than those outside. A leading tail and a trailing tail, each of 50-60 pc in the Galactic plane, are found for the first time for this cluster, with stars further from the cluster center streaming away faster, manifest stellar stripping. Blanco 1 has a total detected mass of 285 ± 32 M⊙ with a mass function consistent with a slope of α = 1.35 ± 0.2 in the sense of ${dN}/{dm}\propto {m}^{-\alpha }$ , in the mass range of 0.25-2.51 M⊙, where N is the number of members and m is stellar mass. A minimum spanning tree (ΛMSR) analysis shows the cluster to be moderately mass segregated among the most massive members (≳1.4 M⊙), suggesting an early stage of dynamical disintegration.

Keywords: Stellar mass functions, Open star clusters, Stellar evolution
Variable Hα Emission in the Nebular Spectra of the Low-luminosity Type Ia SN2018cqj/ATLAS18qtd. We present optical photometry and spectroscopy of the Type Ia supernova SN2018cqj/ATLAS18qtd. The supernova exploded in an isolated region at ∼65 kpc from the S0 galaxy IC 550 at z = 0.0165 (D ≈ 74 Mpc) and has a redshift consistent with a physical association to this galaxy. Multicolor photometry show that SN2018cqj/ATLAS18qtd is a low-luminosity ( ${M}_{{B}_{\max }}\approx -17.9$ mag), fast-declining Type Ia, with color stretch sBV ≈ 0.6 and B-band decline rate ∆m15(B) ≈ 1.77 mag. Two nebular-phase spectra obtained as part of the 100IAS survey at +193 and +307 days after peak show the clear detection of a narrow Hα line in emission that is resolved in the first spectrum with FWHM ≈ 1200 km s-1 and LHα ≈ 3.8 × 1037 erg s-1. The detection of a resolved Hα line with a declining luminosity is broadly consistent with recent models where hydrogen is stripped from the nondegenerate companion in a single-degenerate progenitor system. However, the amount of hydrogen consistent with the luminosities of the Hα line would be ∼10-3 M☉, which is significantly less than theoretical model predictions in the classical single-degenerate progenitor systems. SN2018cqj/ATLAS18qtd is the second low-luminosity, fast-declining SN Ia after SN2018fhw/ASASSN-18tb that shows narrow Hα in emission in its nebular-phase spectra.

Keywords: Transient sources, Type Ia supernovae, Supernovae, High energy astrophysics